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Difference between revisions of "Intuition Menus"

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= Intuition Menus =
 +
== Intuition Menus ==
   
−
Menus are command and option lists associated with an application window that the user can bring into view at any time. These lists provide the user with a simple way to access features of the application without having to remember or enter complex character-based command strings.
 +
Menus are command and option lists associated with an application window or gadget that the user can bring into view at any time. These lists provide the user with a simple way to access features of the application without having to remember or enter complex character-based command strings.
   
 
The Intuition menu system handles all of the menu display without intervention from the application. The program simply submits an initialized list of data structures to Intuition and waits for menu events.
  
The Intuition menu system handles all of the menu display without intervention from the application. The program simply submits an initialized list of data structures to Intuition and waits for menu events.
   
  +
There are three basic types of menu subsystems in Intuition:
−
This chapter shows how to set up menus that allow the user to choose from your program’s commands and options.
  
  +
# [[Intuition_Classic_Menus|Classic or Traditional Menus]]
  +
# [[Intuition_Menu_Class|BOOPSI Menu Class Menus]]
  +
# [[Intuition_Context_Menus|Context Menus]]
  +
  +
Programmers are urged to use the [[Intuition_Menu_Class|BOOPSI Menu Class Menus]] which should be able to cover a vast majority of their needs.
   
 
== About Menus ==
  
== About Menus ==
   
−
Intuition’s menu system provides applications with a convenient way to group together and display the commands and options available to the user. In most cases menus consist of a fixed list of text choices however this is not a requirement. Items in the menu list may be either graphic images or text, and the two types can be freely used together. The number of items in a menu can be changed if necessary.
 +
Intuition's menu systems provide applications with a convenient way to group together and display the commands and options available to the user. In most cases menus consist of a fixed list of text choices however this is not a requirement. Items in the menu list may be either graphic images or text, and the two types can be freely used together. The number of items in a menu can be changed if necessary.
   
 
=== Types of Menu Choices ===
  
=== Types of Menu Choices ===
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Menu choices represent either actions or attributes. Actions are analogous to verbs. An action is executed and then forgotten. Actions include such things as saving and printing files, calculating values and displaying information on the program.
  
Menu choices represent either actions or attributes. Actions are analogous to verbs. An action is executed and then forgotten. Actions include such things as saving and printing files, calculating values and displaying information on the program.
   
−
Attributes are analogous to adjectives. An attribute stays in effect until canceled. Attributes include such things as pen type, color, draw mode and numeric format.
 +
Attributes are analogous to adjectives. An attribute stays in effect until cancelled. Attributes include such things as pen type, color, draw mode and numeric format.
   
 
For instance, in a word processor, menus could be used to control the following types of features:
  
For instance, in a word processor, menus could be used to control the following types of features:
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* Current font and style (attributes).
  
* Current font and style (attributes).
   
−
Menus can be set up such that some attribute items are mutually exclusive (selecting an attribute cancels the effects of one or more other attributes). For example, a drawing or graphics package may only allow one color to be active at a time–selecting a color cancels the previous active color.
 +
Menus can be set up such that some attribute items are mutually exclusive (selecting an attribute cancels the effects of one or more other attributes). For example, a drawing or graphics package may only allow one color to be active at a time; selecting a color cancels the previous active color.
   
 
The program can also allow a number of attributes to be in effect at the same time. A common example of this appears in most word processing programs, where the text style may be bold, italic or underlined. Selecting bold does not rule out italic or underlined, in fact, all three may be active at the same time.
  
The program can also allow a number of attributes to be in effect at the same time. A common example of this appears in most word processing programs, where the text style may be bold, italic or underlined. Selecting bold does not rule out italic or underlined, in fact, all three may be active at the same time.
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=== The Menu System ===
  
=== The Menu System ===
   
  +
To activate the menu system, the user presses the menu button (the right mouse button). This most often displays the menu bar in the screen's title area. The menu bar displays a list of topics (called menus) that have menu items associated with them (see figure). The menu bar and menu items only remain visible while the menu button is held down.
   
  +
[[File:LibFig2-4.png|frame|center|Screen with Menu Bar Displayed]]
−  
−
To activate the menu system, the user presses the menu button (the right mouse button). This displays the menu bar in the screen’s title area. The menu bar displays a list of topics (called menus) that have menu items associated with them (see figure). The menu bar and menu items only remain visible while the menu button is held down.
  
−  
−
<sub>f</sub>igureFig<sub>2</sub>-4Screen with Menu Bar Displayed
  
   
 
When the mouse pointer is moved onto one of the menus in the menu bar, a list of menu items appears below the menu. The user can move the pointer within the list of menu items while holding down the menu button. A menu item will highlight when the pointer is over it and, if the item has a sub-item list, that list will be displayed.
  
When the mouse pointer is moved onto one of the menus in the menu bar, a list of menu items appears below the menu. The user can move the pointer within the list of menu items while holding down the menu button. A menu item will highlight when the pointer is over it and, if the item has a sub-item list, that list will be displayed.
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The specific menu that is displayed belongs to the active window. Changing the active window will change the menu bar and the choices available to the user.
  
The specific menu that is displayed belongs to the active window. Changing the active window will change the menu bar and the choices available to the user.
   
  +
Unlike some other systems, the Amiga has no "standard menu" that appears in every menu bar. In fact, a window or gadget need not have any menus at all, thus holding down the mouse menu button does not guarantee the appearance of a menu. Although there is no "standard menu", the AmigaOS development team does have a well-defined set of standards for menu design. These standards are covered in the [[User_Interface_Style_Guide|Amiga User Interface Style Guide]].
−  
−  
−
Unlike some other systems, the Amiga has no “standard menu” that appears in every menu bar. In fact, a window need not have any menus at all, thus holding down the mouse menu button does not guarantee the appearance of a menu bar. Although there is no “standard menu”, Commodore does have a well-defined set of standards for menu design. These standards are covered in ''The Amiga User Interface Style Guide''.
  
   
 
==== Selecting Menu Items ====
  
==== Selecting Menu Items ====
   
−
To select a single menu item, the user releases the menu button when the pointer is over the desired item. Intuition can notify your program whenever the user makes a menu selection by sending an IDCMP message to your window’s UserPort. Your application is then responsible for carrying out the action associated with the menu item selected. Action items lead to actions taken by the program while attribute items set values in the program for later reference.
 +
To select a single menu item, the user releases the menu button when the pointer is over the desired item. Intuition can notify your program whenever the user makes a menu selection by sending an IDCMP message to your window's UserPort. Your application is then responsible for carrying out the action associated with the menu item selected. Action items lead to actions taken by the program while attribute items set values in the program for later reference.
   
 
Menu selection is restricted to the most subordinate item. Top level menus are never selected. A menu item can be selected as long as it has no sub-items, and a sub-item may always be selected. (Of course, disabled menu items and sub-items cannot be selected.)
  
Menu selection is restricted to the most subordinate item. Top level menus are never selected. A menu item can be selected as long as it has no sub-items, and a sub-item may always be selected. (Of course, disabled menu items and sub-items cannot be selected.)
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==== Menu Item Imagery ====
  
==== Menu Item Imagery ====
   
  +
Menu items can be graphic images or text. There is no conceptual difference between menus that display text and menus that display images, in fact, the two techniques may be used together.
−  
−  
−
Menu items can be graphic images or text. There is no conceptual difference between menus that display text and menus that display images, in fact, the two techniques may be used together. The examples in this chapter use text based menus to avoid the extra code required to define images.
  
−  
−  
   
 
When the user positions the pointer over an item, the item can be highlighted through a variety of techniques. These techniques include a highlighted box around the selected item, complementing the entire item and replacing the item with an alternate image or alternate text.
  
When the user positions the pointer over an item, the item can be highlighted through a variety of techniques. These techniques include a highlighted box around the selected item, complementing the entire item and replacing the item with an alternate image or alternate text.
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Attribute items can have an image rendered next to them, usually a checkmark, to indicate whether they are in effect or not. The checkmark is positioned to the left of the item. If the checkmark is present, the attribute is on. If not, the attribute is off.
  
Attribute items can have an image rendered next to them, usually a checkmark, to indicate whether they are in effect or not. The checkmark is positioned to the left of the item. If the checkmark is present, the attribute is on. If not, the attribute is off.
   
  +
On the right side of menu items, command key alternatives may be displayed. Command key alternatives allow the user to make menu selections with the keyboard instead of the mouse. This is most often done by holding down the right Amiga key and then pressing the single character command key alternative listed next to the menu item. Command key alternatives appear as a fancy "A", followed by the single character command key.
   
  +
Menu items or whole menus may be enabled or disabled. Disabling an item prevents the user from selecting it. Disabled items are ghosted in order to distinguish them from enabled items.
   
  +
Menu help allows the application to be notified when the user presses the help key at the same time the menu system is activated. This allows applications to provide a help feature for every item in its menus. Menu help may be requested on any level of a menu.
−
On the right side of menu items, command key alternatives may be displayed. Command key alternatives allow the user to make menu selections with the keyboard instead of the mouse. This is done by holding down the right Amiga key and then pressing the single character command key alternative listed next to the menu item. Command key alternatives appear as a reverse video, fancy “A”, followed by the single character command key.
  
−  
−  
−  
−
Menu items or whole menus may be enabled or disabled. Disabling an item prevents the user from selecting it. Disabled items are ghosted (overwritten with a pattern of dots making the image less distinct) in order to distinguish them from enabled items.
  
−  
−
Menu help, a new feature of Release 2, allows the application to be notified when the user presses the help key at the same time the menu system is activated. This allows applications to provide a help feature for every item in its menus. Menu help may be requested on any level of a menu.
  
−  
−
=== Menu Limitations ===
  
−  
−
Menus are not layered so they lock the screen while they are displayed. While the screen is locked, applications cannot render graphics into that screen–any rendering will be suspended until the menus are no longer displayed.
  
−  
−
Menus can only display a limited number of choices. Each window may have up to 31 menus, each menu may have up to 63 items, and each item may have up to 31 sub-items.
  
−  
−
Menus always appear at the top of the screen and cannot be repositioned or sized by the user. Moving the pointer to the menu bar may be inconvenient or time consuming for the user. (This is why it is generally a good idea to provide keyboard alternatives for menu items.) If some application has a function that the user will be performing repeatedly, it may be better to use a series of gadgets in the window (or a separate window) rather than a menu item.
  
−  
−
==== Alternatives to Menus ====
  
−  
−
You may want to use a requester or a window as an alternative to menus. A requester can function as a “super menu” using gadgets to provide the commands and options of a menu but with fewer restrictions on their placement, size and layout. See the chapter entitled “Intuition Requesters and Alerts,” for more information.
  
   
  +
=== Alternatives to Menus ===
   
  +
You may want to use a requester or a window as an alternative to menus. A requester can function as a "super menu" using gadgets to provide the commands and options of a menu but with fewer restrictions on their placement, size and layout. See [[Intuition_Requesters|Intuition Requesters]] for more information.
   
 
A window, also, could be substituted for a menu where an application has special requirements. Unlike menus, windows allow layered operations so that commands and options can be presented without forcing all other window output in the active screen to halt.
  
A window, also, could be substituted for a menu where an application has special requirements. Unlike menus, windows allow layered operations so that commands and options can be presented without forcing all other window output in the active screen to halt.
   
−
Windows may be sized, positioned and depth arranged. This positioning flexibility allows the user to make other parts of the screen and other windows visible while they are entering data or selecting operations. The ability to access or view other data may be important in the user’s choice of actions or attributes. See the “Intuition Windows” chapter for more details.
 +
Windows may be sized, positioned and depth arranged. This positioning flexibility allows the user to make other parts of the screen and other windows visible while they are entering data or selecting operations. The ability to access or view other data may be important in the user's choice of actions or attributes. See [[Intuition_Windows|Intuition Windows]] for more details.
   
−
=== Setting Up Menus ===
  
−  
−
The application does not have to worry about handling the menu display. The menus are simply submitted to Intuition and the application waits for Intuition to send messages about the selection of menu items. These messages, along with the data in the menu structures, give the application all the information required for the processing of the user actions.
  
−  
−
Menus can be set up with the GadTools library on systems running Release 2 or a later version of the OS. Since GadTools makes menu set up easier and handles much of the detail work of menu processing (including adjusting to the current font selection), it should be used whenever possible.
  
−  
−
Under 1.3 (V34) and older versions of the OS, GadTools is not available. To set up menus that work with these older systems, you use the Menu and MenuItem structures. In general, for each menu in the menu bar, you declare one instance of the Menu structure. For each item or sub-item within a menu, you declare one instance of the MenuItem structure. Text-based menus like the kind used in this chapter require an additional IntuiText structure for each menu, menu item and sub-item. All these structures are defined in &lt;intuition/intuition.h&gt;.
  
−  
−
The data structures used for menus are linked together to form a list known as a ''menu strip''. For all the details of how the structures are linked and for listings of Menu and MenuItem, see the “Menu Structures” section later in this chapter.
  
−  
−
=== Submitting and Removing Menu Strips ===
  
−  
−  
−  
−
Once the application has set up the proper menu structures, linked them into a list and attached the list to a window, the menu system completely handles the menu display. The menu strip is submitted to Intuition and attached to the window by calling the function SetMenuStrip().
  
−  
−
<pre>BOOL SetMenuStrip( struct Window *window, struct Menu *menu );</pre>
  
−  
−  
−
SetMenuStrip()
  
−  
−
always returns TRUE. This function can also be used to attach a single menu strip to multiple windows by calling SetMenuStrip() for each window (see below).
  
−  
−
Any menu strip attached to a window must be removed before the window is closed. To remove the menu strip, call ClearMenuStrip().
  
−  
−
<pre>VOID ClearMenuStrip( struct Window *window );</pre>
  
−
The menu example below demonstrates how to use these functions with a simple menu strip.
  
−  
−
=== Simple Menu Example ===
  
−  
−
Menu concepts are explained in great detail later in this chapter; for now though it may be helpful to look at an example. Here is a very simple example of how to use the Intuition menu system. The example shows how to set up a menu strip consisting of a single menu with five menu items. The third menu item in the menu has two sub-items.
  
−  
−
The example works with all versions of the Amiga OS however it assumes that the Workbench screen is set up with the the Topaz 8 ROM font. If the font is different, the example will exit immediately since the layout of the menus depends on having a monospaced font with 8<math>\times</math>8 pixel characters.
  
−  
−  
−  
−
<pre>;/* simplemenu.c - Execute me to compile me with SAS C 5.10
  
−
LC -b1 -cfistq -v -y -j73 simplemenu.c
  
−
Blink FROM LIB:c.o,simplemenu.o TO simplemenu LIBRARY LIB:LC.lib,LIB:Amiga.lib
  
−
quit
  
−  
−
** simplemenu.c: how to use the menu system with a window under all OS versions.
  
−
*/
  
−
#define INTUI_V36_NAMES_ONLY
  
−  
−
#include &lt;exec/types.h&gt;
  
−
#include &lt;exec/memory.h&gt;
  
−
#include &lt;graphics/text.h&gt;
  
−
#include &lt;intuition/intuition.h&gt;
  
−
#include &lt;intuition/intuitionbase.h&gt;
  
−  
−
#include &lt;clib/exec_protos.h&gt;
  
−
#include &lt;clib/graphics_protos.h&gt;
  
−
#include &lt;clib/intuition_protos.h&gt;
  
−  
−
#include &lt;stdio.h&gt;
  
−
#include &lt;string.h&gt;
  
−  
−
#ifdef LATTICE
  
−
int CXBRK(void) { return(0); } /* Disable Lattice CTRL/C handling */
  
−
int chkabort(void) { return(0); } /* really */
  
−
#endif
  
−  
−
/* These values are based on the ROM font Topaz8. Adjust these */
  
−
/* values to correctly handle the screen's current font. */
  
−
#define MENWIDTH (56+8) /* Longest menu item name * font width */
  
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/* + 8 pixels for trim */
  
−
#define MENHEIGHT (10) /* Font height + 2 pixels */
  
−  
−
struct Library *GfxBase;
  
−
struct Library *IntuitionBase;
  
−  
−
/* To keep this example simple, we'll hard-code the font used for menu */
  
−
/* items. Algorithmic layout can be used to handle arbitrary fonts. */
  
−
/* Under Release 2, GadTools provides font-sensitive menu layout. */
  
−
/* Note that we still must handle fonts for the menu headers. */
  
−
struct TextAttr Topaz80 =
  
−
{
  
−
&quot;topaz.font&quot;, 8, 0, 0
  
−
};
  
−  
−
struct IntuiText menuIText[] =
  
−
{
  
−
{ 0, 1, JAM2, 0, 1, &amp;Topaz80, &quot;Open...&quot;, NULL },
  
−
{ 0, 1, JAM2, 0, 1, &amp;Topaz80, &quot;Save&quot;, NULL },
  
−
{ 0, 1, JAM2, 0, 1, &amp;Topaz80, &quot;Print \273&quot;, NULL },
  
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{ 0, 1, JAM2, 0, 1, &amp;Topaz80, &quot;Draft&quot;, NULL },
  
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{ 0, 1, JAM2, 0, 1, &amp;Topaz80, &quot;NLQ&quot;, NULL },
  
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{ 0, 1, JAM2, 0, 1, &amp;Topaz80, &quot;Quit&quot;, NULL }
  
−
};
  
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−
struct MenuItem submenu1[] =
  
−
{
  
−
{ /* Draft */
  
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&amp;submenu1[1], MENWIDTH-2, -2 , MENWIDTH, MENHEIGHT,
  
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ITEMTEXT | MENUTOGGLE | ITEMENABLED | HIGHCOMP,
  
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0, (APTR)&amp;menuIText[3], NULL, NULL, NULL, NULL
  
−
},
  
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{ /* NLQ */
  
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NULL, MENWIDTH-2, MENHEIGHT-2, MENWIDTH, MENHEIGHT,
  
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ITEMTEXT | MENUTOGGLE | ITEMENABLED | HIGHCOMP,
  
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0, (APTR)&amp;menuIText[4], NULL, NULL, NULL, NULL
  
−
}
  
−
};
  
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−
struct MenuItem menu1[] =
  
−
{
  
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{ /* Open... */
  
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&amp;menu1[1], 0, 0, MENWIDTH, MENHEIGHT,
  
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ITEMTEXT | MENUTOGGLE | ITEMENABLED | HIGHCOMP,
  
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0, (APTR)&amp;menuIText[0], NULL, NULL, NULL, NULL
  
−
},
  
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{ /* Save */
  
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&amp;menu1[2], 0, MENHEIGHT , MENWIDTH, MENHEIGHT,
  
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ITEMTEXT | MENUTOGGLE | ITEMENABLED | HIGHCOMP,
  
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0, (APTR)&amp;menuIText[1], NULL, NULL, NULL, NULL
  
−
},
  
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{ /* Print */
  
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&amp;menu1[3], 0, 2*MENHEIGHT , MENWIDTH, MENHEIGHT,
  
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ITEMTEXT | MENUTOGGLE | ITEMENABLED | HIGHCOMP,
  
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0, (APTR)&amp;menuIText[2], NULL, NULL, &amp;submenu1[0] , NULL
  
−
},
  
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{ /* Quit */
  
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NULL, 0, 3*MENHEIGHT , MENWIDTH, MENHEIGHT,
  
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ITEMTEXT | MENUTOGGLE | ITEMENABLED | HIGHCOMP,
  
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0, (APTR)&amp;menuIText[5], NULL, NULL, NULL, NULL
  
−
},
  
−
};
  
−  
−
/* We only use a single menu, but the code is generalizable to */
  
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/* more than one menu. */
  
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#define NUM_MENUS 1
  
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−
STRPTR menutitle[NUM_MENUS] = { &quot;Project&quot; };
  
−  
−
struct Menu menustrip[NUM_MENUS] =
  
−
{
  
−
{
  
−
NULL, /* Next Menu */
  
−
0, 0, /* LeftEdge, TopEdge, */
  
−
0, MENHEIGHT, /* Width, Height, */
  
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MENUENABLED, /* Flags */
  
−
NULL, /* Title */
  
−
&amp;menu1[0] /* First item */
  
−
}
  
−
};
  
−  
−
struct NewWindow mynewWindow =
  
−
{
  
−
40,40, 300,100, 0,1, IDCMP_CLOSEWINDOW | IDCMP_MENUPICK,
  
−
WFLG_DRAGBAR | WFLG_ACTIVATE | WFLG_CLOSEGADGET, NULL,NULL,
  
−
&quot;Menu Test Window&quot;, NULL,NULL,0,0,0,0,WBENCHSCREEN
  
−
};
  
−  
−
/* our function prototypes */
  
−
VOID handleWindow(struct Window *win, struct Menu *menuStrip);
  
−  
−
/* Main routine. */
  
−
/* */
  
−
VOID main(int argc, char **argv)
  
−
{
  
−
struct Window *win=NULL;
  
−
UWORD left, m;
  
−  
−
/* Open the Graphics Library */
  
−
GfxBase = OpenLibrary(&quot;graphics.library&quot;,33);
  
−
if (GfxBase)
  
−
{
  
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/* Open the Intuition Library */
  
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IntuitionBase = OpenLibrary(&quot;intuition.library&quot;, 33);
  
−
if (IntuitionBase)
  
−
{
  
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if ( win = OpenWindow(&amp;mynewWindow) )
  
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{
  
−
left = 2;
  
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for (m = 0; m &lt; NUM_MENUS; m++)
  
−
{
  
−
menustrip[m].LeftEdge = left;
  
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menustrip[m].MenuName = menutitle[m];
  
−
menustrip[m].Width = TextLength(&amp;win-&gt;WScreen-&gt;RastPort,
  
−
menutitle[m], strlen(menutitle[m])) + 8;
  
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left += menustrip[m].Width;
  
−
}
  
−
if (SetMenuStrip(win, menustrip))
  
−
{
  
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handleWindow(win, menustrip);
  
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ClearMenuStrip(win);
  
−
}
  
−
CloseWindow(win);
  
−
}
  
−
CloseLibrary(IntuitionBase);
  
−
}
  
−
CloseLibrary(GfxBase);
  
−
}
  
−
}
  
−  
−
/*
  
−
** Wait for the user to select the close gadget.
  
−
*/
  
−
VOID handleWindow(struct Window *win, struct Menu *menuStrip)
  
−
{
  
−
struct IntuiMessage *msg;
  
−
SHORT done;
  
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ULONG class;
  
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UWORD menuNumber;
  
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UWORD menuNum;
  
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UWORD itemNum;
  
−
UWORD subNum;
  
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struct MenuItem *item;
  
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−
done = FALSE;
  
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while (FALSE == done)
  
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{
  
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/* we only have one signal bit, so we do not have to check which
  
−
** bit broke the Wait().
  
−
*/
  
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Wait(1L &lt;&lt; win-&gt;UserPort-&gt;mp_SigBit);
  
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−
while ( (FALSE == done) &amp;&amp;
  
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(msg = (struct IntuiMessage *)GetMsg(win-&gt;UserPort)))
  
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{
  
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class = msg-&gt;Class;
  
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if(class == IDCMP_MENUPICK) menuNumber = msg-&gt;Code;
  
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−
switch (class)
  
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{
  
−
case IDCMP_CLOSEWINDOW:
  
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done = TRUE;
  
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break;
  
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case IDCMP_MENUPICK:
  
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while ((menuNumber != MENUNULL) &amp;&amp; (!done))
  
−
{
  
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item = ItemAddress(menuStrip, menuNumber);
  
−  
−
/* process this item
  
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** if there were no sub-items attached to that item,
  
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** SubNumber will equal NOSUB.
  
−
*/
  
−
menuNum = MENUNUM(menuNumber);
  
−
itemNum = ITEMNUM(menuNumber);
  
−
subNum = SUBNUM(menuNumber);
  
−  
−
/* Note that we are printing all values, even things
  
−
** like NOMENU, NOITEM and NOSUB. An application should
  
−
** check for these cases.
  
−
*/
  
−
printf(&quot;IDCMP_MENUPICK: menu %d, item %d, sub %d\n&quot;,
  
−
menuNum, itemNum, subNum);
  
−  
−
/* This one is the quit menu selection...
  
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** stop if we get it, and don't process any more.
  
−
*/
  
−
if ((menuNum == 0) &amp;&amp; (itemNum == 4))
  
−
done = TRUE;
  
−  
−
menuNumber = item-&gt;NextSelect;
  
−
}
  
−
break;
  
−
}
  
−
ReplyMsg((struct Message *)msg);
  
−
}
  
−
}
  
−
}</pre>
  
 
=== Disabling Menu Operations ===
  
=== Disabling Menu Operations ===
−  
−  
   
 
If an application does not use menus at all, it may set the WFLG_RMBTRAP flag, which allows the program to trap right mouse button events for its own use.
  
If an application does not use menus at all, it may set the WFLG_RMBTRAP flag, which allows the program to trap right mouse button events for its own use.
−  
−  
   
 
By setting the WFLG_RMBTRAP flag with the WA_Flags tag when the window is opened, the program indicates that it does not want any menu operations at all for the window. Whenever the user presses the right button while this window is active, the program will receive right button events as normal IDCMP_MOUSEBUTTONS events.
  
By setting the WFLG_RMBTRAP flag with the WA_Flags tag when the window is opened, the program indicates that it does not want any menu operations at all for the window. Whenever the user presses the right button while this window is active, the program will receive right button events as normal IDCMP_MOUSEBUTTONS events.
−  
−
=== Changing Menu Strips ===
  
−  
−  
−  
−
Direct changes to a menu strip attached to a window may be made only after the menu strip has been removed from the window. Use the ClearMenuStrip() function to remove the menu strip. It may be added back to the window after the changes are complete.
  
−  
−
Major changes include such things as adding or removing menus, items and sub-items; changing text or image data; and changing the placement of the data. These changes require the system to completely re-layout the menus.
  
−  
−  
−  
−
An additional function, ResetMenuStrip(), is available to let the application make small changes to the menus without the overhead of SetMenuStrip(). Only two things in the menu strip may be changed before a call to ResetMenuStrip(), they are: changing the CHECKED flag to turn checkmarks on or off, and changing the ITEMENABLED flag to enable/disable menus, items or sub-items.
  
−  
−
<pre>BOOL ResetMenuStrip( struct Window *window, struct Menu *menu );</pre>
  
−  
−  
−
ResetMenuStrip()
  
−  
−
is called in place of SetMenuStrip(), and may only be called on menus that were previously initialized with a call to SetMenuStrip(). As with SetMenuStrip(), the menu strip must be removed from the window before calling ResetMenuStrip(). Note that the window used in the ResetMenuStrip() call does not have to be the same window to which the menu was previously attached. The window, however, must be on a screen of the same mode to prevent the need for recalculating the layout of the menu.
  
−  
−  
−  
−
If the application wishes to attach a different menu strip to a window that already has an existing menu strip, the application must call ClearMenuStrip() before calling SetMenuStrip() with the new menu strip.
  
−  
−  
−  
−
The flow of events for menu operations should be:
  
−  
−
<ol>
  
−
<li><p>OpenWindowTagList()</p>
  
−
<p>.</p></li>
  
−
<li><p>SetMenuStrip()</p>
  
−
<p>.</p></li>
  
−
<li><p>Zero or more iterations of ClearMenuStrip() and SetMenuStrip() or ResetMenuStrip().</p></li>
  
−
<li><p>ClearMenuStrip()</p>
  
−
<p>.</p></li>
  
−
<li><p>CloseWindow()</p>
  
−
<p>.</p></li></ol>
  
−  
−
=== Sharing Menu Strips ===
  
−  
−  
−  
−
A single menu strip may be attached to multiple windows in an application by calling SetMenuStrip() for each window. All of the windows must be on the same screen for this to work. Since menus are always associated with the active window on a given screen, and since only one window may be active on a screen at a time, only one window may display the shared menu strip at any given time.
  
−  
−  
−  
−
When multiple windows share a single menu strip, they will all “see” the same state of the menus, that is, changes made to the menu strip from one window will still exist when a new window is activated. If the application wishes to share menu strips but to have a different flag and enabled status for each window, the program may watch IDCMP_ACTIVEWINDOW for the windows and modify the menu strip to match the active window’s requirements at that point. In addition, the application must also set IDCMP_MENUVERIFY to insure that the user can’t access the menus of a newly activated window before the application can process the IDCMP_ACTIVEWINDOW message.
  
−  
−  
−  
−
ResetMenuStrip()
  
−  
−
may also be used to set the menus for the multiple windows as long as SetMenuStrip() is used first to attach the menu strip to any one window and no major changes are made to the menu strip before the calls to ResetMenuStrip() on subsequent windows.
  
−  
−
=== Menu Selection Messages ===
  
−  
−  
−  
−
An input event is generated every time the user activates the menu system, either by pressing the mouse menu button or its keyboard equivalent (right Amiga Alt), or entering an appropriate command key sequence. The program receives a message of type IDCMP_MENUPICK detailing which menu items or sub-items were selected. Even if the user activates the menu system without selecting a menu item or sub-item, an event is generated.
  
−  
−
==== Multi-Selection of Menu Items ====
  
−  
−
Each activation of the menu system generates only a single event. The user may select none, one or many items using any of the selection techniques described above; still, only one event is sent.
  
−  
−  
−  
−
The program finds out whether or not multiple items have been chosen by examining the field called NextSelect in the MenuItem structure. The selected items are chained together through this field. This list is only valid until the user next activates the menu system, as the items are chained together through the actual MenuItem structures used in the menu system. If the user reselects an item, the NextSelect field of that item will be overwritten.
  
−  
−  
−  
−
In processing the menu events, the application should first take the appropriate action for the item selected by the user, then check the NextSelect field. If the number there is equal to the constant MENUNULL, there is no next selection. However, if it is not equal to MENUNULL, the user has selected another option after this one. The program should process the next item as well, by checking its NextSelect field, until it finds a NextSelect equal to MENUNULL.
  
−  
−
The following code fragment shows the correct way to process a menu event:
  
−  
−  
−  
−
<pre>struct IntuiMessage *msg;
  
−
struct Menu *menuStrip;
  
−
UWORD menuNumber;
  
−
struct MenuItem *item;
  
−  
−
menuNumber = msg-&gt;Code;
  
−  
−
while (menuNumber != MENUNULL)
  
−
{
  
−
item = ItemAddress(menuStrip, menuNumber);
  
−  
−
/* process this item */
  
−  
−
menuNumber = item-&gt;NextSelect;
  
−
}</pre>
  
−  
−  
−
Intuition specifies which item or sub-item was selected in the IDCMP_MENUPICK event by using a shorthand code known as a ''menu number''. Programs can locate the MenuItem structure that corresponds to a given menu number by using the ItemAddress() function. This function translates a menu number into a pointer to the MenuItem structure represented by the menu number.
  
−  
−
<pre>struct MenuItem *ItemAddress( struct Menu *menuStrip, ULONG menuNumber );</pre>
  
−  
−  
−
This allows the application to gain access to the MenuItem structure and to correctly process multi-select events. Again, when the user performs multiple selection, the program will receive only one message of class IDCMP_MENUPICK. For the program to behave correctly, it must pay attention to the NextSelect field of the MenuItem, which will lead to the other menu selections.
  
−  
−
There may be some cases in an application’s logical flow where the selection of a menu item voids any further menu processing. For instance, after processing a “quit” menu selection, the application will, in general, ignore all further menu selections.
  
−  
−
=== Menu Numbers ===
  
−  
−  
−  
−
The menu numbers Intuition provides in the IDCMP_MENUPICK messages, describe the ordinal position of the menu in the linked list of menus, the ordinal position of the menu item beneath that menu, and (if applicable) the ordinal position of the sub-item beneath that menu item. Ordinal means the successive number of the linked items, in this case, starting from 0.
  
−  
−
To determine which menus and menu items (sub-items are special cases of menu items) were selected, use the following macros:
  
−  
−  
−  
−
[h] Macros Used with Intuition Menus
  
−  
−
<table>
  
−
<tbody>
  
−
<tr class="odd">
  
−
<td align="left">MENUNUM(num)</td>
  
−
<td align="left">Extracts the ordinal menu number from num.</td>
  
−
</tr>
  
−
<tr class="even">
  
−
<td align="left">ITEMNUM(num)</td>
  
−
<td align="left">Extracts the ordinal item number from num.</td>
  
−
</tr>
  
−
<tr class="odd">
  
−
<td align="left">SUBNUM(num)</td>
  
−
<td align="left">Extracts the ordinal sub-item number from num.</td>
  
−
</tr>
  
−
</tbody>
  
−
</table>
  
−  
−  
−  
−
MENUNULL is the constant describing “no menu selection made.” Likewise, NOMENU, NOITEM, and NOSUB describe the conditions “no menu chosen,” “no item chosen” and “no sub-item chosen.”
  
−  
−
For example:
  
−  
−
<pre>if (menuNumber == MENUNULL)
  
−
/* no menu selection was made */ ;
  
−
else
  
−
{
  
−
/* if there were no sub-items attached to that item,
  
−
** SubNumber will equal NOSUB.
  
−
*/
  
−
menuNum = MENUNUM(menuNumber);
  
−
itemNum = ITEMNUM(menuNumber);
  
−
subNum = SUBNUM(menuNumber);
  
−
}</pre>
  
−  
−  
−
The menu number received by the program is always set to either MENUNULL or a valid menu selection. If the menu number represents a valid selection, it will always have at least a menu number and a menu item number. Users can never select the menu text itself, but they always select at least an item within a menu. Therefore, the program always gets at least the menu selected and the menu item selected. If the menu item selected has a sub-item, a sub-item number will also be received.
  
−  
−
Just as it is not possible to select an entry in the menu bar, it is not possible to select a menu item that has attached sub-items. The user must select one of the options in the sub-item list before the program hears about the action as a valid menu selection.
  
−  
−  
−  
−
<sub>b</sub>oxHelp Is Available.The restrictions on what can be selected do not apply to IDCMP_MENUHELP messages. Using menu help, a user can select any component of a menu, including the menu header itself.
  
−  
−
==== How Menu Numbers Really Work ====
  
−  
−
The following is a description of how menu numbers really work. It should clarify why there are some restrictions on the number of menu components Intuition allows. Programs should not rely on the information given here to access menu number information directly though. Always use the Intuition menu macros to handle menu numbers.
  
−  
−  
−  
−
For convenience you should use the menus supplied. For example, to extract the item number from the menu number, call the macro ITEMNUM(menu_number); to construct a menu number, call the macro FULLMENUNUM(menu, item, sub). See the section at the end of this chapter for a more complete description of the menu number macros.
  
−  
−
Menu numbers are 16-bit numbers with 5 bits used for the menu number, 6 bits used for the menu item number, and 5 bits used for the sub-item number. The three numbers only have meaning when used together to determine the position of the item or sub-item selected.
  
−  
−
[[File:LibMenuNum1.png]]
  
−  
−
The value "all bits on" means that no selection of this particular component was made. MENUNULL actually equals "no selection of any of the components was made" so MENUNULL always equals "all bits of all components on."
  
−  
−
For example, suppose that the program gets back the menu number (in hexadecimal) 0x0CA0. In binary that equals:
  
−  
−
[[File:LibMenuNum2.png]]
  
−  
−
Again, the application should not examine these numbers directly. Use the macros described above to ensure proper menu handling.
  
−  
−
=== Help Key Processing in Menus ===
  
−  
−  
−  
−
If the window is opened with the WA_MenuHelp tag, then user selection of the help key while menus are displayed will be detected. This tag is only available under V37 and later.
  
−  
−  
−  
−
When the user presses the Help key while using the menu system, the menu selection is terminated and an IDCMP_MENUHELP event is sent. The IDCMP_MENUHELP event is sent in place of the IDCMP_MENUPICK event, not in addition to it. IDCMP_MENUHELP never come as multi-select items, and the event terminates the menu processing session.
  
−  
−  
−  
−
The routine that handles the IDCMP_MENUHELP events must be very careful–it can receive menu information that is impossible under IDCMP_MENUPICK. IDCMP_MENUHELP events may be sent for any menu, item or sub-item in the menu strip, regardless of its state or position in the list. The program may receive events for items that are disabled or ghosted. IDCMP_MENUHELP events may send the menu header number alone, or the menu and item numbers, or all three components regardless of the items linked to the selected menu or item. This is done because it is reasonable for a user to request help in a disabled item or a menu header. If the user requests menu help on a disabled menu item or sub-item, try to explain to the user why that item is disabled and what steps are necessary to enable it. For instance, pressing help while a menu header is highlighted will trigger an IDCMP_MENUHELP event with a code that has a valid number for the menu, then NOITEM and NOSUB (IDCMP_MENUPICK would receive MENUNULL in this case.)
  
−  
−
The application should not take the action indicated by the IDCMP_MENUHELP event, it should provide the user with a description of the use or status of that menu. The application should never step through the NextSelect chain when it receives a IDCMP_MENUHELP event.
  
−  
−
=== Menu Layout ===
  
−  
−  
−  
−
The Amiga allows great flexibility in the specification of fonts for the display. Default fonts are chosen by the user to suit their particular requirements and display resolution. The application should, where possible, use one of the preferred fonts.
  
−  
−
If the application did not open its own screen and completely specify the font for that screen, it must perform dynamic menu layout. This is because the Menu structure does not specify font. The menu header always uses the screen font and the program should update the size and position of these items at runtime to reflect the font.
  
−  
−  
−  
−
The font for menu items may be specified in the MenuItem structure, allowing the programmer to hard code values for the font, size and position of these items. This is not recommended. A specific font, while ideal on one system, may be less than ideal on another display type. Use the preferred font wherever possible.
  
−  
−
If the application does its own menu layout, it must use great care to handle the font in the menu strip and the font in each item or sub-item. The code should also keep items from running off the edges of the screen.
  
−  
−  
−  
−
See the description of ItemFill in the section “MenuItem Structure” below for information on the positioning of multiple IntuiText or Image structures within the menu item.
  
−  
−
Applications should use the GadTools library menu layout routines whenever possible, rather than performing their own layout. See the chapter on the “GadTools Library” for more details.
  
−  
−
=== About Menu Item Boxes ===
  
−  
−
The item box is the rectangle containing the menu items or sub-items.
  
−  
−
The size and location of the item or sub-item boxes is not directly described by the application. Instead, the size is indirectly described by the placement of items and sub-items. When presented with a menu strip, Intuition first calculates the minimum size box required to hold the items. It then adjusts the box to ensure the menu display conforms to certain design philosophy constraints for items and sub-items.
  
−  
−
<sub>f</sub>igureFig<sub>6</sub>-2Example Item Box
  
−  
−
The item box must start no further right than the leftmost position of the menu header’s select box. It must end no further left than the rightmost position of the menu header’s select box. The top edge of each item box must overlap the screen’s title bar by one line. Each sub-item box must overlap its item’s select box somewhere.
  
−  
−
<sub>b</sub>oxAlways Overlap.If your application is designed to work on systems prior to V37, do not leave space between sub-items in a sub-item list. This may cause flickering as the pointer moves off one item into the gap between the items. Even a single line between the items may cause flickering. This flickering is eliminated starting with V37.
  
−  
−
<sub>f</sub>igureFig<sub>6</sub>-3Example Sub-item Box
  
−  
−
=== Attribute Items and the Checkmark ===
  
−  
−
Attribute items are items that have two states: selected and unselected. In the menu system, these items are often represented as items with checkmarks. If the checkmark is visible, then the item (or attribute) is selected. Otherwise, the attribute is not selected.
  
−  
−
Checkmarked items (attributes) may be toggle selected or mutually exclusive. Selecting a toggle selected item toggles its state–if it was selected, it will become unselected; and if it was unselected, it will become selected. Selecting a mutually exclusive item puts it in the selected state, while possibly clearing one or more other items, where it remains until it is cleared by the selection of some other item.
  
−  
−  
−  
−
A menu item is specified as a checkmark item by setting the CHECKIT flag in the Flags variable of the item’s MenuItem structure.
  
−  
−
The program can initialize the state of the checkmark (checked or not) by presetting the item’s CHECKED flag. If this flag is set when the menu strip is submitted to Intuition, then the item is considered selected and the checkmark will be drawn.
  
−  
−
The program can use the default Intuition checkmark or provide a custom checkmark for the menus. To use a custom checkmark, the application must provide a pointer to the image with the WA_Checkmark tag when the window is opened. See the chapter “Intuition Windows” for details about supplying a custom checkmark.
  
−  
−  
−  
−
The application must provide sufficient blank space at the left edge of the select box for the checkmark imagery. Constants are provided to standardize the space reserved in the menu for the checkmark. LOWCHECKWIDTH gives the amount of space required for checkmarks on low resolution screens and CHECKWIDTH gives space for all other screens.
  
−  
−  
−  
−
These constants specify the space required by the default checkmarks (with a bit of space for aesthetic purposes). If the image would normally be placed such that the LeftEdge of the image without the checkmark is 5, the image should start at 5 + CHECKWIDTH if CHECKIT is set. Also, the select box must be made CHECKWIDTH wider than it would be without the checkmark. It is generally accepted on the Amiga that only checkmarked items should be indented by the size of the checkmark, other items are left justified within their column.
  
−  
−
=== Toggle Selection ===
  
−  
−  
−  
−
Some of the checkmarked menu items may be of the toggle select type. Each time the user accesses such an item, it changes state, selected or unselected. To make an attribute item toggle select, set both the CHECKIT and the MENUTOGGLE flags for that menu item. Of course, the CHECKED flag may be preset to the desired initial state.
  
−  
−
=== Mutual Exclusion ===
  
−  
−
Mutual exclusion allows the selection of an item to cause other items to become unselected.
  
−  
−  
−  
−
For example, for a list of menu items describing the available sizes for a font, the selection of any size could unselect all other sizes. Use the MutualExclude variable in the MenuItem structure to specify other menu items to be excluded when the user selects an item. Exclusion also depends upon the CHECKED and CHECKIT flags of the MenuItem, as explained below.
  
−  
−
<ul>
  
−
<li><p>If CHECKED is not set, then this item is available to be selected. If the user selects this item, the CHECKED flag is set and the checkmark will be drawn to the left of the item.</p>
  
−
<p></p></li>
  
−
<li><p>If the item selected has bits set in the MutualExclude field, the CHECKED flag is examined in the excluded items. If any item is currently CHECKED, its checkmark is erased, and its CHECKED flag is cleared.</p>
  
−
<p></p></li>
  
−
<li><p>Mutual exclusion pertains only to items that have the CHECKIT flag set. Attempting to exclude items that do not have the CHECKIT flag set has no effect.</p></li></ul>
  
−  
−
<sub>b</sub>oxKeep track of deselected items.It is up to the program to track internally which excluded items have been deselected. See the section “Enabling and Disabling Menus and Menu Items” below for more information.
  
−  
−
In the MutualExclude field, bit 0 refers to the first item in the item list, bit 1 to the second, bit 2 to the third, and so on.
  
−  
−
In the text style example described above, selecting plain excludes any other style. The MutualExclude fields of the four items would look like this:
  
−  
−
[h]
  
−  
−
<table>
  
−
<tbody>
  
−
<tr class="odd">
  
−
<td align="left">Plain</td>
  
−
<td align="left">0xFFFE</td>
  
−
</tr>
  
−
<tr class="even">
  
−
<td align="left">Bold</td>
  
−
<td align="left">0x0001</td>
  
−
</tr>
  
−
<tr class="odd">
  
−
<td align="left">Italic</td>
  
−
<td align="left">0x0001</td>
  
−
</tr>
  
−
<tr class="even">
  
−
<td align="left">Underline</td>
  
−
<td align="left">0x0001</td>
  
−
</tr>
  
−
</tbody>
  
−
</table>
  
−  
−
“Plain” is the first item on the list. It excludes all items except the first one. All of the other items exclude only the first item, so that bold, underlined text may be selected, while bold, plain text may not.
  
−  
−
=== Managing the State of Checkmarks ===
  
−  
−
To correctly handle checkmarked menu items, from time to time the application will need to read the CHECKED bit of its CHECKIT MenuItems. It is not adequate to infer which items are checked by tracking what their state must have become. There are several reasons for this (although it’s not important to understand the details; just the implication):
  
−  
−
* Using multi-selection of menus, the user can toggle the state of a MENUTOGGLE item several times, yet the application will receive only a single IDCMP_MENUPICK event, and that item will only appear once in the NextSelect chain.
  
−
* When the user selects a mutually exclusive menu item, the IDCMP_MENUPICK event refers to that item, but Intuition doesn’t notify your application of other items that may have been deselected through mutual exclusion.
  
−
* Prior to V36, unusually complex multi-selection operations could orphan menu selections. That is to say, some items that were selected may not even appear on the NextSelect chain. If such an item had a checkmark, the state of that checkmark could nevertheless have changed.
  
−
* For complex multi-selection operations, the NextSelect chain will not be in select-order (a side-effect of the fact that the same MenuItem cannot appear twice in the same NextSelect chain combined with the fix to the orphaning problems mentioned above). With certain mutual exclusion arrangements, it is impossible to predict the state of the checkmarks.
  
−
* If the user begins multi-selection in the menus and hits several checkmarked items, but then presses the help key, the application will receive an IDCMP_MENUHELP message. No IDCMP_MENUPICK message will have been sent. Thus, some checkmark changes could have gone unnoticed by the application.
  
−  
−
It is legal to examine the CHECKED state of a MenuItem while that MenuItem is still attached to a window. It is unnecessary to first call ClearMenuStrip().
  
−  
−
=== Command Key Sequences ===
  
−  
−  
−  
−
A command key sequence is an event generated when the user holds down one of the Amiga keys (the ones with the fancy A) and presses one of the normal alphanumeric keys at the same time. There are two different command or Amiga keys, commonly known as the left Amiga key and the right Amiga key.
  
−  
−
Menu command key sequences are combinations of the right Amiga key with any alphanumeric character, and may be used by any program. These sequences must be accessed through the menu system. Command key sequences using the left Amiga key cannot be associated with menu items.
  
−  
−
Menu command key sequences, like the menus themselves, are only available for a window while that window is active. Each window may control these keys by setting keyboard shortcuts in the menu item structures which make up the window’s menu strip.
  
−  
−
If the user presses a command key sequence that is associated with one of the menu items, Intuition will send the program an event that is identical to the event generated by selecting that menu item with the mouse. Many users would rather keep their hands on the keyboard than use the mouse to make a menu selection when accessing often repeated selections. Menu command key sequences allow the program to provide shortcuts to the user who prefers keyboard control.
  
−  
−  
−  
−
A command key sequence is associated with a menu item by setting the COMMSEQ flag in the Flags variable of the MenuItem structure and by placing the ASCII character (upper or lower case) that is to be associated with the sequence into the Command variable of the MenuItem structure.
  
−  
−
Command keys are not case sensitive and they do not repeat. Command keys are processed through the keymap so that they will continue to work even if the key value is remapped to another position. International key values are supported as long as they are accessible without using the Alt key (right-Amiga-Alt maps to the right mouse button on the mouse).
  
−  
−
<sub>f</sub>igureFig<sub>6</sub>-4Menu Items with Command Key Shortcuts
  
−  
−
When items have alternate key sequences, the menu boxes show a special Amiga key glyph rendered roughly one character span plus a few pixels from the right edge of the menu select box. The command key used with the Amiga key is displayed immediately to the right of the Amiga key image, at the rightmost edge of the menu select box (see figure).
  
−  
−  
−  
−
Space must be provided at the right edge of the select box for the Amiga key imagery and for the actual command character. Leave COMMWIDTH pixels on high resolution screens, and LOWCOMMWIDTH pixels on low resolution screens. The character’s width may be calculated with the graphics library TextLength() call. In general, each column of items should leave enough room for the widest command character plus the width of the Amiga key imagery.
  
−  
−
=== Enabling and Disabling Menus and Menu Items ===
  
−  
−  
−  
−
Disabling menu items makes them unavailable for selection by the user.
  
−  
−
Disabled menus and menu items are displayed in a ghosted fashion; that is, their imagery is overlaid with a faint pattern of dots, making it less distinct.
  
−  
−  
−  
−
Enabling or disabling a menu or menu item is always a safe procedure, whether or not the user is currently using the menus. Of course, by the time you have disabled the item, the user may have already selected it. Thus, the program may receive a IDCMP_MENUPICK message for that item, even though it considers the item disabled. The program should be prepared to handle this case and ignore items that it knows are already disabled. This implies that the program must track internally which items are enabled and which are disabled.
  
−  
−  
−  
−
The OffMenu() and OnMenu() functions may be used to enable or disable items while a menu strip is attached to the window.
  
−  
−  
−  
−
<pre>VOID OffMenu( struct Window *window, ULONG menuNumber );
  
−
VOID OnMenu( struct Window *window, ULONG menuNumber );</pre>
  
−
These routines check if the user is currently using the menus and whether the menus need to be redrawn to reflect the new states. If the menus are currently in use, these routines wait for the user to finish before proceeding.
  
−  
−  
−  
−
If the item component referenced by menuNumber equals NOITEM, the entire menu will be disabled or enabled. If the item component equates to an actual component number, then that item will be disabled or enabled. Use the macros defined below for the construction of menu numbers from their component parts.
  
−  
−
The program can enable or disable whole menus, just the menu items, or just single sub-items.
  
−  
−
* To enable or disable a whole menu, set the item component of the menu number to NOITEM. This will enable or disable all items and any sub-items for that menu.
  
−
* To enable or disable a single item and all sub-items attached to that item, set the item component of the menu number to the item’s ordinal number. If the item has a sub-item list, set the sub-item component of the menu number to NOSUB. If the item has no sub-item list, the sub-item component of the menu number is ignored.
  
−
* To enable or disable a single sub-item, set the item and sub-item components appropriately.
  
−  
−
It is also legal to remove the menu strip from each window that it is attached to (with ClearMenuStrip() ) change the ITEMENABLED or MENUENABLED flag of one or more Menu or MenuItem structures and add the menu back using ResetMenuStrip() (in V36 or higher) or SetMenuStrip() (in any version of the OS).
  
−  
−
=== Intercepting Normal Menu Operations ===
  
−  
−  
−  
−
IDCMP_MENUVERIFY gives the program the opportunity to react before menu operations take place and, optionally, to cancel menu operations. Menus may be completely disabled by removing the menu strip with a call to ClearMenuStrip().
  
−  
−
==== A Warning on the MENUSTATE Flag ====
  
−  
−  
−  
−
The MENUSTATE flag is set by Intuition in Window.Flags when the menus of that window are in use. Beware: in typical event driven programming, such a state variable is not on the same timetable as the application’s input message handling, and should not be used to draw profound conclusions in any program. Use IDCMP_MENUVERIFY to synchronize with the menu handling.
  
−  
−
==== Menu Verify ====
  
−  
−
Menu verify is one of the Intuition verification capabilities that allow an application to ensure that it is prepared for some action taken by Intuition before that action takes place. Through menu verify, Intuition allows all windows in a screen to verify that they are prepared for menu operations before the operations begin. In general, use menu verify if the program is doing something special to the display of a custom screen, and needs to be sure the operation has completed before menus are rendered.
  
−  
−  
−  
−
Any window can access the menu verify feature by setting the IDCMP_MENUVERIFY flag with the WA_IDCMP tag when opening the window. When menus are activated in a screen which contains at least one window with IDCMP_MENUVERFIY set, menu operations will not proceed until all windows with the menu verify flag set reply to the notification or until the last message times out. The specific menu verify protocol is described below.
  
−  
−  
−  
−
In any case, it is vital that the application know when menu operations terminate, for only then does it have control of the screen again. For the active window, this is typically detected by watching for an IDCMP_MENUPICK message. If the program cancels the menu operations (MENUCANCEL), then it will instead receive an IDCMP_MOUSEBUTTONS message with code equal to MENUUP. Inactive windows will always receive IDCMP_MOUSEBUTTONS message with code equal to MENUUP.
  
−  
−
The active window is given special menu verify treatment. It receives the menu verify message before any other window and has the option of canceling menu operations altogether. This could be used, for instance, to examine where the user has positioned the mouse when the right button was pressed. For example, the application may choose to allow normal menu operations to proceed only when the pointer is in the menu bar area. When the pointer is below the menu bar, then the application can choose to interpret the menu verify message as a right button event for some non-menu purpose.
  
−  
−  
−  
−
The program can tell if it is the active window for the verify event by examining the Code field of the IDCMP_MENUVERIFY message. If the Code field is equal to MENUWAITING, this window is not active and Intuition is simply waiting for verification that menu operations may continue. However, if the Code field is equal to MENUHOT, this window is active and it determines if menu operations should proceed.
  
−  
−  
−  
−
If it wishes menu operations to proceed, the active window should reply to the IDCMP_MENUVERIFY message without changing any values. To cancel the menu operation, change the code field of the message to MENUCANCEL before replying to the message.
  
−  
−
When the active window cancels the menu operation it will be sent an IDCMP_MOUSEBUTTONS message with code equal to MENUUP. In general, the window will not then receive an IDCMP_MENUPICK event as it cancelled the operation. However, the system should be prepared to handle an IDCMP_MENUPICK message with code equal to MENUNULL as one may be sent if the user releases the mouse button before the window replies to the message.
  
−  
−
The system takes no action on screen until the active window either replies to the menu verify event or the event times out. If the active window replies to the event in time and does not cancel the menu operation, Intuition will then move the screen title bar layer to the front, display the menu strip and notify all inactive menu verify windows of the operation. Layers will not be locked and the actual menus will not be swapped in until all these inactive windows reply to the message or time out. The inactive windows may not cancel the menu operation.
  
−  
−  
−  
−
If the user releases the menu button before the active window replies to the menu verify message, the menu operation will be cancelled and the active window will be sent an IDCMP_MOUSEBUTTONS message with code equal to MENUUP. When the active window finally replies to the message, it will receive an IDCMP_MENUPICK message with code equal to MENUNULL.
  
−  
−  
−  
−
If the event times out before the active window replies to the message, it will immediately be sent an IDCMP_MENUPICK message with code equal to MENUNULL. Then, when the user releases the menu button, the program will receive an IDCMP_MOUSEBUTTONS message with code equal to MENUUP.
  
−  
−
If an inactive window receives an IDCMP_MENUVERIFY message, it will always receive an IDCMP_MOUSEBUTTONS message with code equal to MENUUP when the menu operations are completed.
  
−  
−
<sub>b</sub>oxAbout Double-Menu Requesters.The processing described above becomes more complicated when double-menu requester processing is introduced. If an application chooses to use a double-menu requester in a window with IDCMP_MENUVERIFY set, it should be aware that odd message combinations are possible. For instance, it is possible to receive only an IDCMP_MENUVERIFY event with no following IDCMP_MOUSEBUTTONS event or IDCMP_MENUPICK event. Applications should avoid using double menu requesters if possible.
  
−  
−
==== Shortcuts and IDCMP_MENUVERIFY ====
  
−  
−
The idea behind IDCMP_MENUVERIFY is to synchronize the program with Intuition’s menu handling sessions. The motive was to allow a program to arbitrate access to a custom screen’s bitmap, so that Intuition would not render menus before the application was prepared for them.
  
−  
−  
−  
−
Some programs use IDCMP_MENUVERIFY to permit them to intercept the right mouse button for their own purposes. Other programs use it to delay menu operations while they recover from unusual events such as illegible colors of the screen or double buffering and related ViewPort operations.
  
−  
−  
−  
−
Menu shortcut keystrokes, for compatibility, also respect IDCMP_MENUVERIFY. They are always paired with an IDCMP_MENUPICK message so that the program knows the menu operation is over. This is true even if the menu event is cancelled.
  
−  
−
==== IDCMP_MENUVERIFY and Deadlock ====
  
−  
−  
−  
−
The program may call ModifyIDCMP() to turn IDCMP_MENUVERIFY and the other VERIFY IDCMP options off. It is important that this be done each and every time that the application is directly or indirectly waiting for Intuition, since Intuition may be waiting for the application, but not watching the window message port for IDCMP_MENUVERIFY events. The program cannot wait for a gadget or mouse event without checking also for any IDCMP_MENUVERIFY event messages that may require program response.
  
−  
−  
−  
−
The most common problem area is System Requesters (AutoRequest() and EasyRequest()). Before AutoRequest() and EasyRequest() return control to the application, Intuition must be free to run and accept a response from the user. If the user presses the menu button, Intuition will wait for the program to reply to the IDCMP_MENUVERIFY event and a deadlock results.
  
−  
−  
−  
−
Therefore, it is extremely important to use ModifyIDCMP() to turn off all verify messages before calling AutoRequest(), EasyRequest() or, directly or indirectly, AmigaDOS, since many error conditions in the DOS require user input in the form of an EasyRequest(). Indirect DOS calls include OpenLibrary(), OpenDevice(), and OpenDiskFont().
  
−  
−
Beginning with V36, all windows that have the IDCMP_MENUVERIFY bit set must respond to Intuition within a set time period, or the menu operation will time out and the menu action will be canceled. This prevents the deadlocks that were possible under previous versions of the operating system.
  
−  
−
== Menu Data Structures ==
  
−  
−
The specifications for the menu structures are given below. Menus are the headers that show in the menu bar, and MenuItems are the items and sub-items that can be chosen by the user.
  
−  
−
=== Menu Structure ===
  
−  
−  
−  
−
Here is the specification for a Menu structure:
  
−  
−
<pre>struct Menu
  
−
{
  
−
struct Menu *NextMenu;
  
−
WORD LeftEdge, TopEdge;
  
−
WORD Width, Height;
  
−
UWORD Flags;
  
−
BYTE *MenuName;
  
−
struct MenuItem *FirstItem;
  
−
WORD JazzX, JazzY, BeatX, BeatY;
  
−
};</pre>
  
−
The variables in the Menu structure have the following meanings:
  
−  
−  
−  
−
This variable points to the next Menu header in the list. The last Menu in the list should have a NextMenu value of NULL.
  
−  
−  
−  
−
These fields describe the select box of the header. Currently, any values supplied for TopEdge and Height are ignored by Intuition, which uses instead the screen’s TopBorder for the TopEdge and the height of the screen’s title bar for the Height.
  
−  
−
LeftEdge
  
−  
−
is relative to the LeftEdge of the screen plus the screen’s left border width, so if LeftEdge is 0, Intuition puts this header at the leftmost allowable position.
  
−  
−  
−  
−
The flag space is shared by the program and Intuition. The flags are:
  
−  
−  
−  
−
This flag is for Intuition’s use and indicates whether or not this Menu is currently enabled. Set this flag before submitting the menu strip to Intuition. If this flag is not set, the menu header and all menu items below it will be disabled, and the user will be able to view, but not select any of the items. After submitting the strip to Intuition, the disabled or enabled status may be changed by calling OnMenu() or OffMenu().
  
−  
−
This flag indicates whether or not this menu’s items are currently displayed to the user.
  
−  
−  
−  
−
This is a pointer to a NULL terminated character string that is printed on the screen’s title bar starting at the LeftEdge of this menu’s select box and at the TopEdge just below the screen title bar’s top border. The text is rendered in the screen’s font.
  
−  
−  
−  
−
This points to the first MenuItem structure in the linked list of this menu’s items.
  
−  
−  
−  
−
For internal use only.
  
−  
−
=== MenuItem Structure ===
  
−  
−  
−  
−
The MenuItem structure is used for both items and sub-items. There is no internal difference between items and sub-items, other than how they are linked into the menu strip. Items are linked directly to Menu structures through the FirstItem field, sub-items are linked to MenuItem structures through the SubItem field.
  
−  
−
Here is the specification:
  
−  
−
<pre>struct MenuItem
  
−
{
  
−
struct MenuItem *NextItem;
  
−
WORD LeftEdge, TopEdge;
  
−
WORD Width, Height;
  
−
UWORD Flags;
  
−
LONG MutualExclude;
  
−
APTR ItemFill;
  
−
APTR SelectFill;
  
−
BYTE Command;
  
−
struct MenuItem *SubItem;
  
−
UWORD NextSelect;
  
−
};</pre>
  
−
The fields have the following meanings:
  
−  
−
This field is a pointer to the next item in the list. The last item in the list should have a NextItem value of NULL.
  
−  
−  
−  
−
These fields describe the select box of the MenuItem. The LeftEdge is relative to the LeftEdge of the Menu. The TopEdge is relative to the topmost position Intuition allows. TopEdge is based on the way the user has the system configured–which font, which resolution, and so on. Use 0 for the topmost position.
  
−  
−
The flag space is shared by the program and Intuition. See “MenuItem Flags” below for a description of the flag bits.
  
−  
−  
−  
−
Use these bits to describe which of the other items, if any, are mutually excluded by this one. This long word refers to the items in the same menu as this one. A maximum of 32 items may be described by this variable, and they must be the first 32 items in the menu. This does not mean that there cannot be more than 32 items in any given menu, just that only the first 32 can be mutually excluded.
  
−  
−  
−  
−
This points to the data used in rendering this MenuItem. It can point to either an instance of an IntuiText structure with text for this MenuItem or an instance of an Image structure with image data. The program tells Intuition the type of data pointed to by this variable by setting or clearing the MenuItem flag bit ITEMTEXT. (See “MenuItem Flags” below for more details about ITEMTEXT.)
  
−  
−  
−  
−
Note that the IntuiText or Image data need not be simple imagery, either of them may consist of multiple objects of the same type chained together as described in the chapter “Intuition Images, Line Drawing and Text”. By chaining multiple IntuiText structures, the application may “fine tune” the positioning of text within each item. This is especially important for proportional fonts, where the width of the individual characters is not constant. This also allows items to have part of the text left justified and part right justified.
  
−  
−  
−  
−
If HIGHIMAGE is set in the Flags variable as the MenuItem highlighting mode, Intuition substitutes this alternate image or text for the original rendering described by ItemFill. The type of this structure must be the same as ItemFill. SelectFill can point to either an Image or an IntuiText, where the type is determined by the setting of the ITEMTEXT flag.
  
−  
−  
−  
−
This variable is storage for a single alphanumeric character to be used as the command key substitute for this menu item. The command key sequence will be rendered in the menu display to the right of the item’s select area, with a fancy, reverse-video A, followed by the command character. Case is ignored.
  
−  
−  
−  
−
If the flag COMMSEQ is set, the user can hold down the right Amiga key on the keyboard (to mimic using the right mouse menu button) and press the indicated key as a shortcut for using the mouse to select this item.
  
−  
−
If this item has a sub-item list, this variable should point to the MenuItem structure describing the first sub-item in the list.
  
−  
−
<sub>b</sub>oxThere Is No Such Thing as a Sub-sub-item.A sub-item cannot have a sub-item attached to it. If this MenuItem structure is not an item, this variable is ignored.
  
−  
−  
−  
−
This field is filled in by Intuition when this MenuItem is selected by the user. After an item has been selected by the user, the program should process the request and then check the NextSelect field. If the NextSelect field is equal to MENUNULL, no other items were selected; otherwise, there is another item to process. See “Menu Numbers and Menu Selection Messages” above for more information about user selections.
  
−  
−
=== MenuItem Flags ===
  
−  
−
Here are the flags that can be set by the application in the Flags field of the MenuItem structure:
  
−  
−  
−  
−
Set this flag to inform Intuition that this item is a checkmark item and should be preceded by a checkmark if the flag CHECKED is set.
  
−  
−  
−  
−
For an item with the CHECKIT flag set, set this bit to specify that the checkmark is displayed. After the menu strip is submitted to Intuition, it will maintain the CHECKED bit based on effects from other items’ mutual exclusions, or, for MENUTOGGLE items, from user accesses to this item.
  
−  
−  
−  
−
Set this flag if the representation of the item pointed to by the ItemFill field and, possibly, by SelectFill is text and points to an IntuiText structure. Clear this bit if the item is graphic and points to an Image structure.
  
−  
−  
−  
−
If this flag is set, this item has an equivalent command key sequence set in the Command field of the MenuItem structure.
  
−  
−  
−  
−
This flag is used in conjunction with the CHECKIT flag. If MENUTOGGLE is set, a checkmark that is turned on may be turned off by selecting the item. This allows the user to toggle between the checked and non-checked states by repeatedly selecting the item.
  
−  
−
This flag describes whether or not this item is currently enabled. If an item is not enabled, its image will be ghosted and the user will not be able to select it. If this item has sub-items, all of the sub-items are disabled when the item is disabled.
  
−  
−  
−  
−
Set this flag before submitting the menu strip to Intuition. Once the menu strip has been submitted to Intuition, enable or disable items by calling OnMenu() or OffMenu().
  
−  
−  
−  
−
An item can be highlighted when the user positions the pointer over the item. These bits describe what type of highlighting will be used, if any. One of the following bits must be set, according to the type of highlighting desired:
  
−  
−
This complements all of the bits contained by this item’s select box.
  
−  
−
This draws a box outside this item’s select box.
  
−  
−  
−  
−
This displays alternate imagery referenced in SelectFill. For alternate text, make sure that ITEMTEXT is set, and that the SelectFill field points to an IntuiText structure. For alternate image, ITEMTEXT must be cleared, and the SelectFill field must point to an Image structure.
  
−  
−
This specifies no highlighting.
  
−  
−
The following two flags are used by Intuition:
  
−  
−
Intuition sets this flag when this item’s sub-items are currently displayed to the user and clears it when they are not.
  
−  
−
Intuition sets this flag when this item is highlighted and clears it when the item is not highlighted.
  
−  
−
== A Menu Example ==
  
−  
−
This example shows how to implement menus. The menu code is simply part of the processing for Intuition messages as shown in the IDCMP example in the “Intuition Input and Output Methods” chapter. The example implements extended selection for menus, adaptation to fonts of different sizes, mutual exclusion and checkmarks.
  
−  
−
If possible, applications should use the menu layout routines available in the GadTools library, rather than doing the job themselves as this example does. See the “GadTools Library” chapter for more information.
  
−  
−  
−  
−
<pre>;/* menulayout.c - Execute me to compile me with SAS C 5.10
  
−
LC -b1 -cfistq -v -y -j73 menulayout.c
  
−
Blink FROM LIB:c.o,menulayout.o TO menulayout LIBRARY LIB:LC.lib,LIB:Amiga.lib
  
−
quit
  
−
** menulayout.c - Example showing how to do menu layout in general. This example
  
−
** also illustrates handling menu events, including IDCMP_MENUHELP events.
  
−
**
  
−
** Note that handling arbitrary fonts is fairly complex. Applications that require V37
  
−
** should use the simpler menu layout routines found in the GadTools library.
  
−
*/
  
−
#define INTUI_V36_NAMES_ONLY
  
−  
−
#include &lt;exec/types.h&gt;
  
−
#include &lt;intuition/intuition.h&gt;
  
−
#include &lt;intuition/intuitionbase.h&gt;
  
−
#include &lt;graphics/gfxbase.h&gt;
  
−
#include &lt;dos/dos.h&gt;
  
−
#include &lt;clib/exec_protos.h&gt;
  
−
#include &lt;clib/graphics_protos.h&gt;
  
−
#include &lt;clib/intuition_protos.h&gt;
  
−
#include &lt;stdlib.h&gt;
  
−
#include &lt;stdio.h&gt;
  
−
#include &lt;string.h&gt;
  
−  
−
#ifdef LATTICE
  
−
int CXBRK(void) { return(0); } /* Disable Lattice CTRL/C handling */
  
−
int chkabort(void) { return(0); } /* really */
  
−
#endif
  
−
/* Our function prototypes */
  
−
BOOL processMenus(USHORT selection, BOOL done);
  
−
BOOL handleIDCMP(struct Window *win);
  
−
USHORT MaxLength(struct RastPort *textRPort, struct MenuItem *first_item, USHORT char_size);
  
−
VOID setITextAttr(struct IntuiText *first_IText, struct TextAttr *textAttr);
  
−
VOID adjustItems(struct RastPort *textRPort, struct MenuItem *first_item, struct TextAttr *textAttr,
  
−
USHORT char_size, USHORT height, USHORT level, USHORT left_edge);
  
−
BOOL adjustMenus(struct Menu *first_menu, struct TextAttr *textAttr);
  
−
LONG doWindow(void);
  
−  
−
/* Settings Item IntuiText */
  
−
struct IntuiText SettText[] = {
  
−
{0,1,JAM2,2, 1, NULL, &quot;Sound...&quot;, NULL },
  
−
{0,1,JAM2,CHECKWIDTH,1, NULL, &quot; Auto Save&quot;, NULL },
  
−
{0,1,JAM2,CHECKWIDTH,1, NULL, &quot; Have Your Cake&quot;, NULL },
  
−
{0,1,JAM2,CHECKWIDTH,1, NULL, &quot; Eat It Too&quot;, NULL }
  
−
};
  
−  
−
struct MenuItem SettItem[] = {
  
−
{ /* &quot;Sound...&quot; */
  
−
&amp;SettItem[1], 0, 0, 0, 0, ITEMTEXT|ITEMENABLED|HIGHCOMP, 0,
  
−
(APTR)&amp;SettText[0], NULL, NULL, NULL, MENUNULL },
  
−
{ /* &quot;Auto Save&quot; (toggle-select, initially selected) */
  
−
&amp;SettItem[2], 0, 0, 0, 0, ITEMTEXT|ITEMENABLED|HIGHCOMP|CHECKIT|MENUTOGGLE|CHECKED, 0,
  
−
(APTR)&amp;SettText[1], NULL, NULL, NULL, MENUNULL },
  
−
{ /* &quot;Have Your Cake&quot; (initially selected, excludes &quot;Eat It Too&quot;) */
  
−
&amp;SettItem[3], 0, 0, 0, 0, ITEMTEXT|ITEMENABLED|HIGHCOMP|CHECKIT|CHECKED, 8,
  
−
(APTR)&amp;SettText[2], NULL, NULL, NULL, MENUNULL },
  
−
{ /* &quot;Eat It Too&quot; (excludes &quot;Have Your Cake&quot;) */
  
−
NULL, 0, 0, 0, 0, ITEMTEXT|ITEMENABLED|HIGHCOMP|CHECKIT, 4,
  
−
(APTR)&amp;SettText[3], NULL, NULL, NULL, MENUNULL }
  
−
};
  
−  
−
/* Edit Menu Item IntuiText */
  
−
struct IntuiText EditText[] = {
  
−
{0,1,JAM2,2,1, NULL, &quot;Cut&quot;, NULL },
  
−
{0,1,JAM2,2,1, NULL, &quot;Copy&quot;, NULL },
  
−
{0,1,JAM2,2,1, NULL, &quot;Paste&quot;, NULL },
  
−
{0,1,JAM2,2,1, NULL, &quot;Erase&quot;, NULL },
  
−
{0,1,JAM2,2,1, NULL, &quot;Undo&quot;, NULL }
  
−
};
  
−  
−
/* Edit Menu Items */
  
−
struct MenuItem EditItem[] = {
  
−
{ /* &quot;Cut&quot; (key-equivalent: 'X') */
  
−
&amp;EditItem[1], 0, 0, 0, 0, ITEMTEXT|COMMSEQ|ITEMENABLED|HIGHCOMP, 0,
  
−
(APTR)&amp;EditText[0], NULL, 'X', NULL, MENUNULL },
  
−
{ /* &quot;Copy&quot; (key-equivalent: 'C') */
  
−
&amp;EditItem[2], 0, 0, 0, 0, ITEMTEXT|COMMSEQ|ITEMENABLED|HIGHCOMP, 0,
  
−
(APTR)&amp;EditText[1], NULL, 'C', NULL, MENUNULL },
  
−
{ /* &quot;Paste&quot; (key-equivalent: 'V') */
  
−
&amp;EditItem[3], 0, 0, 0, 0, ITEMTEXT|COMMSEQ|ITEMENABLED|HIGHCOMP, 0,
  
−
(APTR)&amp;EditText[2], NULL, 'V', NULL, MENUNULL },
  
−
{ /* &quot;Erase&quot; (disabled) */
  
−
&amp;EditItem[4], 0, 0, 0, 0, ITEMTEXT|HIGHCOMP, 0,
  
−
(APTR)&amp;EditText[3], NULL, NULL, NULL, MENUNULL },
  
−
{ /* &quot;Undo&quot; MenuItem (key-equivalent: 'Z') */
  
−
NULL, 0, 0, 0, 0, ITEMTEXT|COMMSEQ|ITEMENABLED|HIGHCOMP, 0,
  
−
(APTR)&amp;EditText[4], NULL, 'Z', NULL, MENUNULL }
  
−
};
  
−  
−
/* IntuiText for the Print Sub-Items */
  
−
struct IntuiText PrtText[] = {
  
−
{0,1, JAM2,2,1, NULL, &quot;NLQ&quot;, NULL },
  
−
{0,1, JAM2,2,1, NULL, &quot;Draft&quot;, NULL }
  
−
};
  
−  
−
/* Print Sub-Items */
  
−
struct MenuItem PrtItem[] = {
  
−
{ /* &quot;NLQ&quot; */
  
−
&amp;PrtItem[1], 0, 0, 0, 0, ITEMTEXT|ITEMENABLED|HIGHCOMP, 0,
  
−
(APTR)&amp;PrtText[0], NULL, NULL, NULL, MENUNULL },
  
−
{ /* &quot;Draft&quot; */
  
−
NULL, 0, 0, 0, 0, ITEMTEXT|ITEMENABLED|HIGHCOMP, 0,
  
−
(APTR)&amp;PrtText[1], NULL, NULL, NULL, MENUNULL }
  
−
};
  
−
/* Uses the &gt;&gt; character to indicate a sub-menu item.
  
−
** This is \273 Octal, 0xBB Hex or Alt-0 from the Keyboard.
  
−
**
  
−
** NOTE that standard menus place this character at the right margin of the menu box.
  
−
** This may be done by using a second IntuiText structure for the single character,
  
−
** linking this IntuiText to the first one, and positioning the IntuiText so that the
  
−
** character appears at the right margin. GadTools library will provide the correct behavior.
  
−
*/
  
−  
−
/* Project Menu Item IntuiText */
  
−
struct IntuiText ProjText[] = {
  
−
{0,1, JAM2,2,1, NULL, &quot;New&quot;, NULL },
  
−
{0,1, JAM2,2,1, NULL, &quot;Open...&quot;, NULL },
  
−
{0,1, JAM2,2,1, NULL, &quot;Save&quot;, NULL },
  
−
{0,1, JAM2,2,1, NULL, &quot;Save As...&quot;, NULL },
  
−
{0,1, JAM2,2,1, NULL, &quot;Print \273&quot;, NULL },
  
−
{0,1, JAM2,2,1, NULL, &quot;About...&quot;, NULL },
  
−
{0,1, JAM2,2,1, NULL, &quot;Quit&quot;, NULL }
  
−
};
  
−  
−  
−
/* Project Menu Items */
  
−
struct MenuItem ProjItem[] = {
  
−
{ /* &quot;New&quot; (key-equivalent: 'N' */
  
−
&amp;ProjItem[1],0, 0, 0, 0, ITEMTEXT|COMMSEQ|ITEMENABLED|HIGHCOMP, 0,
  
−
(APTR)&amp;ProjText[0], NULL, 'N', NULL, MENUNULL },
  
−
{ /* &quot;Open...&quot; (key-equivalent: 'O') */
  
−
&amp;ProjItem[2],0, 0, 0, 0, ITEMTEXT|COMMSEQ|ITEMENABLED|HIGHCOMP, 0,
  
−
(APTR)&amp;ProjText[1], NULL, 'O', NULL, MENUNULL },
  
−
{ /* &quot;Save&quot; (key-equivalent: 'S') */
  
−
&amp;ProjItem[3],0, 0, 0, 0, ITEMTEXT|COMMSEQ|ITEMENABLED|HIGHCOMP, 0,
  
−
(APTR)&amp;ProjText[2], NULL, 'S', NULL, MENUNULL },
  
−
{ /* &quot;Save As...&quot; (key-equivalent: 'A') */
  
−
&amp;ProjItem[4],0, 0, 0, 0, ITEMTEXT|COMMSEQ|ITEMENABLED|HIGHCOMP, 0,
  
−
(APTR)&amp;ProjText[3], NULL, 'A', NULL, MENUNULL },
  
−
{ /* &quot;Print&quot; (has sub-menu) */
  
−
&amp;ProjItem[5],0, 0, 0, 0, ITEMTEXT|ITEMENABLED|HIGHCOMP, 0,
  
−
(APTR)&amp;ProjText[4], NULL, NULL, &amp;PrtItem[0], MENUNULL },
  
−
{ /* &quot;About...&quot; */
  
−
&amp;ProjItem[6],0, 0, 0, 0, ITEMTEXT|ITEMENABLED|HIGHCOMP, 0,
  
−
(APTR)&amp;ProjText[5], NULL, NULL, NULL, MENUNULL },
  
−
{ /* &quot;Quit&quot; (key-equivalent: 'Q' */
  
−
NULL, 0, 0, 0, 0, ITEMTEXT|COMMSEQ|ITEMENABLED|HIGHCOMP, 0,
  
−
(APTR)&amp;ProjText[6], NULL, 'Q', NULL, MENUNULL }
  
−
};
  
−  
−
/* Menu Titles */
  
−
struct Menu Menus[] = {
  
−
{&amp;Menus[1], 0, 0, 63, 0, MENUENABLED, &quot;Project&quot;, &amp;ProjItem[0]},
  
−
{&amp;Menus[2], 70, 0, 39, 0, MENUENABLED, &quot;Edit&quot;, &amp;EditItem[0]},
  
−
{NULL, 120, 0, 88, 0, MENUENABLED, &quot;Settings&quot;, &amp;SettItem[0]},
  
−
};
  
−  
−
/* A pointer to the first menu for easy reference */
  
−
struct Menu *FirstMenu = &amp;Menus[0];
  
−  
−
/* Window Text for Explanation of Program */
  
−
struct IntuiText WinText[] = {
  
−
{0, 0, JAM2, 0, 0, NULL, &quot;How to do a Menu&quot;, NULL},
  
−
{0, 0, JAM2, 0, 0, NULL, &quot;(with Style)&quot;, &amp;WinText[0]}
  
−
};
  
−  
−
/* Globals */
  
−
struct Library *IntuitionBase = NULL;
  
−
struct Library *GfxBase = NULL;
  
−  
−
/* open all of the required libraries. Note that we require
  
−
** Intuition V37, as the routine uses OpenWindowTags().
  
−
*/
  
−
VOID main(int argc, char **argv)
  
−
{
  
−
LONG returnValue;
  
−  
−
/* This gets set to RETURN_OK if everything goes well. */
  
−
returnValue = RETURN_FAIL;
  
−  
−
/* Open the Intuition Library */
  
−
IntuitionBase = OpenLibrary(&quot;intuition.library&quot;, 37);
  
−
if (IntuitionBase)
  
−
{
  
−
/* Open the Graphics Library */
  
−
GfxBase = (struct GfxBase *)OpenLibrary(&quot;graphics.library&quot;, 33);
  
−
if (GfxBase)
  
−
{
  
−
returnValue = doWindow();
  
−  
−
CloseLibrary(GfxBase);
  
−
}
  
−
CloseLibrary(IntuitionBase);
  
−
}
  
−
exit(returnValue);
  
−
}
  
−  
−
/* Open a window with some properly positioned text. Layout and set
  
−
** the menus, then process any events received. Cleanup when done.
  
−
*/
  
−  
−
LONG doWindow()
  
−
{
  
−
struct Window *window;
  
−
struct Screen *screen;
  
−
struct DrawInfo *drawinfo;
  
−
ULONG signalmask, signals;
  
−
ULONG win_width, alt_width, win_height;
  
−
LONG returnValue = RETURN_FAIL;
  
−
BOOL done = FALSE;
  
−  
−
if (screen = LockPubScreen(NULL))
  
−
{
  
−
if (drawinfo = GetScreenDrawInfo(screen))
  
−
{
  
−
/* get the colors for the window text */
  
−
WinText[0].FrontPen = WinText[1].FrontPen = drawinfo-&gt;dri_Pens[TEXTPEN];
  
−
WinText[0].BackPen = WinText[1].BackPen = drawinfo-&gt;dri_Pens[BACKGROUNDPEN];
  
−  
−
/* use the screen's font for the text */
  
−
WinText[0].ITextFont = WinText[1].ITextFont = screen-&gt;Font;
  
−  
−
/* calculate window size */
  
−
win_width = 100 + IntuiTextLength(&amp;(WinText[0]));
  
−
alt_width = 100 + IntuiTextLength(&amp;(WinText[1]));
  
−
if (win_width &lt; alt_width)
  
−
win_width = alt_width;
  
−
win_height = 1 + screen-&gt;WBorTop + screen-&gt;WBorBottom +
  
−
(screen-&gt;Font-&gt;ta_YSize * 5);
  
−  
−
/* calculate the correct positions for the text in the window */
  
−
WinText[0].LeftEdge = (win_width - IntuiTextLength(&amp;(WinText[0]))) &gt;&gt; 1;
  
−
WinText[0].TopEdge = 1 + screen-&gt;WBorTop + (2 * screen-&gt;Font-&gt;ta_YSize);
  
−
WinText[1].LeftEdge = (win_width - IntuiTextLength(&amp;(WinText[1]))) &gt;&gt; 1;
  
−
WinText[1].TopEdge = WinText[0].TopEdge + screen-&gt;Font-&gt;ta_YSize;
  
−  
−
/* Open the window */
  
−
window = OpenWindowTags(NULL,
  
−
WA_PubScreen, screen,
  
−
WA_IDCMP, IDCMP_MENUPICK | IDCMP_CLOSEWINDOW | IDCMP_MENUHELP,
  
−
WA_Flags, WFLG_DRAGBAR | WFLG_DEPTHGADGET | WFLG_CLOSEGADGET |
  
−
WFLG_ACTIVATE | WFLG_NOCAREREFRESH,
  
−
WA_Left, 10, WA_Top, screen-&gt;BarHeight + 1,
  
−
WA_Width, win_width, WA_Height, win_height,
  
−
WA_Title, &quot;Menu Example&quot;, WA_MenuHelp, TRUE,
  
−
TAG_END);
  
−  
−  
−  
−
if (window)
  
−
{
  
−
returnValue = RETURN_OK; /* program initialized ok */
  
−  
−
/* Give a brief explanation of the program */
  
−
PrintIText(window-&gt;RPort,&amp;WinText[1],0,0);
  
−  
−
/* Adjust the menu to conform to the font (TextAttr) */
  
−
adjustMenus(FirstMenu, window-&gt;WScreen-&gt;Font);
  
−  
−
/* attach the menu to the window */
  
−
SetMenuStrip(window, FirstMenu);
  
−  
−
/* Set up the signals that you want to hear about ... */
  
−
signalmask = 1L &lt;&lt; window-&gt;UserPort-&gt;mp_SigBit;
  
−  
−
/* And wait to hear from your signals */
  
−
while (!done)
  
−
{
  
−
signals = Wait(signalmask);
  
−
if (signals &amp; signalmask) done = handleIDCMP(window);
  
−
};
  
−  
−
/* clean up everything used here */
  
−
ClearMenuStrip(window);
  
−
CloseWindow(window);
  
−
}
  
−
FreeScreenDrawInfo(screen,drawinfo);
  
−
}
  
−
UnlockPubScreen(NULL,screen);
  
−
}
  
−
return(returnValue);
  
−
}
  
−  
−
/* print out what menu was selected. Properly handle the IDCMP_MENUHELP
  
−
** events. Set done to TRUE if quit is selected.
  
−
*/
  
−
BOOL processMenus(USHORT selection, BOOL done)
  
−
{
  
−
USHORT flags;
  
−
USHORT menuNum, itemNum, subNum;
  
−  
−
menuNum = MENUNUM(selection);
  
−
itemNum = ITEMNUM(selection);
  
−
subNum = SUBNUM(selection);
  
−  
−
/* when processing IDCMP_MENUHELP, you are not guaranteed
  
−
** to get a menu item.
  
−
*/
  
−
if (itemNum != NOITEM)
  
−
{
  
−
flags = ((struct MenuItem *)ItemAddress(FirstMenu,(LONG)selection))-&gt;Flags;
  
−
if (flags &amp; CHECKED)
  
−
printf(&quot;(Checked) &quot;);
  
−
}
  
−  
−
switch (menuNum)
  
−
{
  
−
case 0: /* Project Menu */
  
−
switch (itemNum)
  
−
{
  
−
case NOITEM: printf(&quot;Project Menu\n&quot;); break;
  
−
case 0: printf(&quot;New\n&quot;); break;
  
−
case 1: printf(&quot;Open\n&quot;); break;
  
−
case 2: printf(&quot;Save\n&quot;); break;
  
−
case 3: printf(&quot;Save As\n&quot;); break;
  
−
case 4: printf(&quot;Print &quot;);
  
−
switch (subNum)
  
−
{
  
−
case NOSUB: printf(&quot;Item\n&quot;); break;
  
−
case 0: printf(&quot;NLQ\n&quot;); break;
  
−
case 1: printf(&quot;Draft\n&quot;); break;
  
−
}
  
−
break;
  
−
case 5: printf(&quot;About\n&quot;); break;
  
−
case 6: printf(&quot;Quit\n&quot;); done = TRUE; break;
  
−
}
  
−
break;
  
−  
−  
−  
−  
−  
−
case 1: /* Edit Menu */
  
−
switch (itemNum) {
  
−
case NOITEM: printf(&quot;Edit Menu\n&quot;); break;
  
−
case 0: printf(&quot;Cut\n&quot;); break;
  
−
case 1: printf(&quot;Copy\n&quot;); break;
  
−
case 2: printf(&quot;Paste\n&quot;); break;
  
−
case 3: printf(&quot;Erase\n&quot;); break;
  
−
case 4: printf(&quot;Undo\n&quot;); break;
  
−
}
  
−
break;
  
−
case 2: /* Settings Menu */
  
−
switch (itemNum) {
  
−
case NOITEM: printf(&quot;Settings Menu\n&quot;); break;
  
−
case 0: printf(&quot;Sound\n&quot;); break;
  
−
case 1: printf(&quot;Auto Save\n&quot;); break;
  
−
case 2: printf(&quot;Have Your Cake\n&quot;); break;
  
−
case 3: printf(&quot;Eat It Too\n&quot;); break;
  
−
}
  
−
break;
  
−
case NOMENU: /* No menu selected, can happen with IDCMP_MENUHELP */
  
−
printf(&quot;no menu\n&quot;);
  
−
break;
  
−
}
  
−
return(done);
  
−
}
  
−  
−
/* Handle the IDCMP messages. Set done to TRUE if quit or closewindow is selected. */
  
−
BOOL handleIDCMP(struct Window *win)
  
−
{
  
−
BOOL done;
  
−
USHORT code, selection;
  
−
struct IntuiMessage *message = NULL;
  
−
ULONG class;
  
−  
−
done = FALSE;
  
−  
−
/* Examine pending messages */
  
−
while (message = (struct IntuiMessage *)GetMsg(win-&gt;UserPort)) {
  
−
class = message-&gt;Class;
  
−
code = message-&gt;Code;
  
−  
−
/* When we're through with a message, reply */
  
−
ReplyMsg((struct Message *)message);
  
−  
−
/* See what events occurred */
  
−
switch (class) {
  
−
case IDCMP_CLOSEWINDOW:
  
−
done = TRUE;
  
−
break;
  
−
case IDCMP_MENUHELP:
  
−
/*
  
−
** The routine that handles the menus for IDCMP_MENUHELP must be very careful
  
−
** it can receive menu information that is impossible under IDCMP_MENUPICK.
  
−
** For instance, the code value on a IDCMP_MENUHELP may have a valid number
  
−
** for the menu, then NOITEM and NOSUB. IDCMP_MENUPICK would get MENUNULL
  
−
** in this case. IDCMP_MENUHELP never come as multi-select items, and the
  
−
** event terminates the menu processing session.
  
−
**
  
−
** Note that I do not keep the return value from the processMenus() routine here--the
  
−
** application should not quit if the user selects &quot;help&quot; over the quit menu item.
  
−
*/
  
−
printf(&quot;IDCMP_MENUHELP: Help on &quot;);
  
−
processMenus(code,done);
  
−
break;
  
−
case IDCMP_MENUPICK:
  
−
for ( selection = code; selection != MENUNULL;
  
−
selection = (ItemAddress(FirstMenu,(LONG)selection))-&gt;NextSelect)
  
−
{
  
−
printf(&quot;IDCMP_MENUPICK: Selected &quot;);
  
−
done = processMenus(selection,done);
  
−
}
  
−
break;
  
−
}
  
−
}
  
−
return(done);
  
−
}
  
−
/* Steps thru each item to determine the maximum width of the strip */
  
−
USHORT MaxLength(struct RastPort *textRPort, struct MenuItem *first_item, USHORT char_size)
  
−
{
  
−
USHORT maxLength;
  
−
USHORT total_textlen;
  
−
struct MenuItem *cur_item;
  
−
struct IntuiText *itext;
  
−
USHORT extra_width;
  
−
USHORT maxCommCharWidth;
  
−
USHORT commCharWidth;
  
−  
−
extra_width = char_size; /* used as padding for each item. */
  
−  
−
/* Find the maximum length of a command character, if any.
  
−
** If found, it will be added to the extra_width field.
  
−
*/
  
−
maxCommCharWidth = 0;
  
−
for (cur_item = first_item; cur_item != NULL; cur_item = cur_item-&gt;NextItem)
  
−
{
  
−
if (cur_item-&gt;Flags &amp; COMMSEQ)
  
−
{
  
−
commCharWidth = TextLength(textRPort,&amp;(cur_item-&gt;Command),1);
  
−
if (commCharWidth &gt; maxCommCharWidth)
  
−
maxCommCharWidth = commCharWidth;
  
−
}
  
−
}
  
−  
−
/* if we found a command sequence, add it to the extra required space. Add
  
−
** space for the Amiga key glyph plus space for the command character. Note
  
−
** this only works for HIRES screens, for LORES, use LOWCOMMWIDTH.
  
−
*/
  
−
if (maxCommCharWidth &gt; 0)
  
−
extra_width += maxCommCharWidth + COMMWIDTH;
  
−  
−
/* Find the maximum length of the menu items, given the extra width calculated above. */
  
−
maxLength = 0;
  
−
for (cur_item = first_item; cur_item != NULL; cur_item = cur_item-&gt;NextItem)
  
−
{
  
−
itext = (struct IntuiText *)cur_item-&gt;ItemFill;
  
−
total_textlen = extra_width + itext-&gt;LeftEdge +
  
−
TextLength(textRPort, itext-&gt;IText, strlen(itext-&gt;IText));
  
−  
−
/* returns the greater of the two */
  
−
if (total_textlen &gt; maxLength)
  
−
maxLength = total_textlen;
  
−
}
  
−
return(maxLength);
  
−
}
  
−  
−
/* Set all IntuiText in a chain (they are linked through the NextText ** field) to the same font. */
  
−
VOID setITextAttr(struct IntuiText *first_IText, struct TextAttr *textAttr)
  
−
{
  
−
struct IntuiText *cur_IText;
  
−  
−
for (cur_IText = first_IText; cur_IText != NULL; cur_IText = cur_IText-&gt;NextText)
  
−
cur_IText-&gt;ITextFont = textAttr;
  
−
}
  
−  
−  
−
/* Adjust the MenuItems and SubItems */
  
−
VOID adjustItems(struct RastPort *textRPort, struct MenuItem *first_item,
  
−
struct TextAttr *textAttr, USHORT char_size, USHORT height,
  
−
USHORT level, USHORT left_edge)
  
−
{
  
−
register USHORT item_num;
  
−
struct MenuItem *cur_item;
  
−
USHORT strip_width, subitem_edge;
  
−  
−
if (first_item == NULL)
  
−
return;
  
−  
−
/* The width of this strip is the maximum length of its members. */
  
−
strip_width = MaxLength(textRPort, first_item, char_size);
  
−  
−  
−  
−
/* Position the items. */
  
−
for (cur_item = first_item, item_num = 0; cur_item != NULL; cur_item = cur_item-&gt;NextItem, item_num++)
  
−
{
  
−
cur_item-&gt;TopEdge = (item_num * height) - level;
  
−
cur_item-&gt;LeftEdge = left_edge;
  
−
cur_item-&gt;Width = strip_width;
  
−
cur_item-&gt;Height = height;
  
−  
−
/* place the sub_item 3/4 of the way over on the item. */
  
−
subitem_edge = strip_width - (strip_width &gt;&gt; 2);
  
−  
−
setITextAttr((struct IntuiText *)cur_item-&gt;ItemFill, textAttr);
  
−
adjustItems(textRPort,cur_item-&gt;SubItem,textAttr,char_size,height,1,subitem_edge);
  
−
}
  
−
}
  
−  
−  
−
/* The following routines adjust an entire menu system to conform to the specified fonts' width and
  
−
** height. Allows for Proportional Fonts. This is necessary for a clean look regardless of what the
  
−
** users preference in Fonts may be. Using these routines, you don't need to specify TopEdge,
  
−
** LeftEdge, Width or Height in the MenuItem structures.
  
−
**
  
−
** NOTE that this routine does not work for menus with images, but assumes that all menu items are
  
−
** rendered with IntuiText.
  
−
**
  
−
** This set of routines does NOT check/correct if the menu runs off
  
−
** the screen due to large fonts, too many items, lo-res screen.
  
−
*/
  
−
BOOL adjustMenus(struct Menu *first_menu, struct TextAttr *textAttr)
  
−
{
  
−
struct RastPort textrp = {0}; /* Temporary RastPort */
  
−
struct Menu *cur_menu;
  
−
struct TextFont *font; /* Font to use */
  
−
USHORT start, char_size, height;
  
−
BOOL returnValue = FALSE;
  
−  
−
/* open the font */
  
−
if (font = OpenFont(textAttr))
  
−
{
  
−
SetFont(&amp;textrp, font); /* Put font into temporary RastPort */
  
−  
−
char_size = TextLength(&amp;textrp, &quot;n&quot;, 1); /* Get the Width of the Font */
  
−  
−
/* To prevent crowding of the Amiga key when using COMMSEQ, don't allow the items to be less
  
−
** than 8 pixels high. Also, add an extra pixel for inter-line spacing.
  
−
*/
  
−
if (font-&gt;tf_YSize &gt; 8)
  
−
height = 1 + font-&gt;tf_YSize;
  
−
else
  
−
height = 1 + 8;
  
−  
−
start = 2; /* Set Starting Pixel */
  
−  
−
/* Step thru the menu structure and adjust it */
  
−
for (cur_menu = first_menu; cur_menu != NULL; cur_menu = cur_menu-&gt;NextMenu)
  
−
{
  
−
cur_menu-&gt;LeftEdge = start;
  
−
cur_menu-&gt;Width = char_size +
  
−
TextLength(&amp;textrp, cur_menu-&gt;MenuName, strlen(cur_menu-&gt;MenuName));
  
−
adjustItems(&amp;textrp, cur_menu-&gt;FirstItem, textAttr, char_size, height, 0, 0);
  
−
start += cur_menu-&gt;Width + char_size + char_size;
  
−
}
  
−
CloseFont(font); /* Close the Font */
  
−
returnValue = TRUE;
  
−
}
  
−
return(returnValue);
  
−
}</pre>
  
−
== Other Menu Macros ==
  
−  
−  
−  
−
The MENUNEM(), ITEMNUM() and SUBNUM() macros let an application break a menu number down into its component parts–the specific menu number, the item number and the sub-item number. (See the section on “Menu Numbers” earlier in this chapter for details.) Intuition also supplies macros that allow an application to construct a menu number given its components:
  
−  
−
Create a properly masked and shifted specific menu number.
  
−  
−
Create a properly masked and shifted item number.
  
−  
−
Create a properly masked and shifted sub-item number.
  
−  
−
Create a complete composite menu number from its components.
  
−  
−
== Function Reference ==
  
−  
−
The following are brief descriptions of the Intuition functions that relate to the use of Intuition menus. See the ''Amiga ROM Kernel Reference Manual: Includes and Autodocs'' for details on each function call.
  
−  
−  
−  
−
[h] Functions for Intuition Menus
  
−  
−
<table>
  
−
<thead>
  
−
<tr class="header">
  
−
<th align="left">'''Function'''</th>
  
−
<th align="left">'''Description'''</th>
  
−
</tr>
  
−
</thead>
  
−
<tbody>
  
−
<tr class="odd">
  
−
<td align="left">SetMenuStrip()</td>
  
−
<td align="left">Set a menu for an open window.</td>
  
−
</tr>
  
−
<tr class="even">
  
−
<td align="left">ClearMenuStrip()</td>
  
−
<td align="left">Clear the menu of an open window.</td>
  
−
</tr>
  
−
<tr class="odd">
  
−
<td align="left">ResetMenuStrip()</td>
  
−
<td align="left">Set a pre-calculated menu for an open window.</td>
  
−
</tr>
  
−
<tr class="even">
  
−
<td align="left">ItemAddress()</td>
  
−
<td align="left">Find the address of a menu item from its position.</td>
  
−
</tr>
  
−
<tr class="odd">
  
−
<td align="left">OffMenu()</td>
  
−
<td align="left">Disable a menu in a menu strip.</td>
  
−
</tr>
  
−
<tr class="even">
  
−
<td align="left">OnMenu()</td>
  
−
<td align="left">Enable a menu in a menu strip.</td>
  
−
</tr>
  
−
</tbody>
  
−
</table>
  

Latest revision as of 19:16, 9 July 2015

Intuition Menus

Menus are command and option lists associated with an application window or gadget that the user can bring into view at any time. These lists provide the user with a simple way to access features of the application without having to remember or enter complex character-based command strings.

The Intuition menu system handles all of the menu display without intervention from the application. The program simply submits an initialized list of data structures to Intuition and waits for menu events.

There are three basic types of menu subsystems in Intuition:

  1. Classic or Traditional Menus
  2. BOOPSI Menu Class Menus
  3. Context Menus

Programmers are urged to use the BOOPSI Menu Class Menus which should be able to cover a vast majority of their needs.

About Menus

Intuition's menu systems provide applications with a convenient way to group together and display the commands and options available to the user. In most cases menus consist of a fixed list of text choices however this is not a requirement. Items in the menu list may be either graphic images or text, and the two types can be freely used together. The number of items in a menu can be changed if necessary.

Types of Menu Choices

Menu choices represent either actions or attributes. Actions are analogous to verbs. An action is executed and then forgotten. Actions include such things as saving and printing files, calculating values and displaying information on the program.

Attributes are analogous to adjectives. An attribute stays in effect until cancelled. Attributes include such things as pen type, color, draw mode and numeric format.

For instance, in a word processor, menus could be used to control the following types of features:

  • File loading and saving (action).
  • Editing functions (action).
  • Formatting preferences (attributes).
  • Printing functions (action).
  • Current font and style (attributes).

Menus can be set up such that some attribute items are mutually exclusive (selecting an attribute cancels the effects of one or more other attributes). For example, a drawing or graphics package may only allow one color to be active at a time; selecting a color cancels the previous active color.

The program can also allow a number of attributes to be in effect at the same time. A common example of this appears in most word processing programs, where the text style may be bold, italic or underlined. Selecting bold does not rule out italic or underlined, in fact, all three may be active at the same time.

The Menu System

To activate the menu system, the user presses the menu button (the right mouse button). This most often displays the menu bar in the screen's title area. The menu bar displays a list of topics (called menus) that have menu items associated with them (see figure). The menu bar and menu items only remain visible while the menu button is held down.

Screen with Menu Bar Displayed

When the mouse pointer is moved onto one of the menus in the menu bar, a list of menu items appears below the menu. The user can move the pointer within the list of menu items while holding down the menu button. A menu item will highlight when the pointer is over it and, if the item has a sub-item list, that list will be displayed.

The specific menu that is displayed belongs to the active window. Changing the active window will change the menu bar and the choices available to the user.

Unlike some other systems, the Amiga has no "standard menu" that appears in every menu bar. In fact, a window or gadget need not have any menus at all, thus holding down the mouse menu button does not guarantee the appearance of a menu. Although there is no "standard menu", the AmigaOS development team does have a well-defined set of standards for menu design. These standards are covered in the Amiga User Interface Style Guide.

Selecting Menu Items

To select a single menu item, the user releases the menu button when the pointer is over the desired item. Intuition can notify your program whenever the user makes a menu selection by sending an IDCMP message to your window's UserPort. Your application is then responsible for carrying out the action associated with the menu item selected. Action items lead to actions taken by the program while attribute items set values in the program for later reference.

Menu selection is restricted to the most subordinate item. Top level menus are never selected. A menu item can be selected as long as it has no sub-items, and a sub-item may always be selected. (Of course, disabled menu items and sub-items cannot be selected.)

Intuition menus allow the user to select multiple items by:

  • Pressing and releasing the select button (left mouse button) without releasing the menu button. This selects the item and keeps the menus active so that other items may be selected.
  • Holding down both mouse buttons and sliding the pointer over several items. This is called drag selecting. All items highlighted while dragging are selected.

Drag selection, single selection with the select button and releasing the mouse button over an item can all be combined in a single operation. Any technique used to select a menu item is also available to select a menu sub-item.

Menu Item Imagery

Menu items can be graphic images or text. There is no conceptual difference between menus that display text and menus that display images, in fact, the two techniques may be used together.

When the user positions the pointer over an item, the item can be highlighted through a variety of techniques. These techniques include a highlighted box around the selected item, complementing the entire item and replacing the item with an alternate image or alternate text.

Attribute items can have an image rendered next to them, usually a checkmark, to indicate whether they are in effect or not. The checkmark is positioned to the left of the item. If the checkmark is present, the attribute is on. If not, the attribute is off.

On the right side of menu items, command key alternatives may be displayed. Command key alternatives allow the user to make menu selections with the keyboard instead of the mouse. This is most often done by holding down the right Amiga key and then pressing the single character command key alternative listed next to the menu item. Command key alternatives appear as a fancy "A", followed by the single character command key.

Menu items or whole menus may be enabled or disabled. Disabling an item prevents the user from selecting it. Disabled items are ghosted in order to distinguish them from enabled items.

Menu help allows the application to be notified when the user presses the help key at the same time the menu system is activated. This allows applications to provide a help feature for every item in its menus. Menu help may be requested on any level of a menu.

Alternatives to Menus

You may want to use a requester or a window as an alternative to menus. A requester can function as a "super menu" using gadgets to provide the commands and options of a menu but with fewer restrictions on their placement, size and layout. See Intuition Requesters for more information.

A window, also, could be substituted for a menu where an application has special requirements. Unlike menus, windows allow layered operations so that commands and options can be presented without forcing all other window output in the active screen to halt.

Windows may be sized, positioned and depth arranged. This positioning flexibility allows the user to make other parts of the screen and other windows visible while they are entering data or selecting operations. The ability to access or view other data may be important in the user's choice of actions or attributes. See Intuition Windows for more details.

Disabling Menu Operations

If an application does not use menus at all, it may set the WFLG_RMBTRAP flag, which allows the program to trap right mouse button events for its own use.

By setting the WFLG_RMBTRAP flag with the WA_Flags tag when the window is opened, the program indicates that it does not want any menu operations at all for the window. Whenever the user presses the right button while this window is active, the program will receive right button events as normal IDCMP_MOUSEBUTTONS events.

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