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	The Screeen Mode requester provides application writers with a convenient way to ask the user for their screen display preferences. You create an ASL screen mode requester the same way you create an ASL file requester or font requester; only the tags and structures used are different.		The Screeen Mode requester provides application writers with a convenient way to ask the user for their screen display preferences. You create an ASL screen mode requester the same way you create an ASL file requester or font requester; only the tags and structures used are different.

	<syntaxhighlight>		<syntaxhighlight lang="C" line>
	struct ScreenModeRequester {		struct ScreenModeRequester {
	ULONG sm_DisplayID; /* Display mode ID */		ULONG sm_DisplayID; /* Display mode ID */
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	Listed below is a simple program that displays the new ASL screen mode requester including depth, width and height gadgets.		Listed below is a simple program that displays the new ASL screen mode requester including depth, width and height gadgets.

	<syntaxhighlight>		<syntaxhighlight lang="C" line>
	/*		/*
	** aslsm.c		** aslsm.c

Steven Solie: /* Creating a Screen Mode Requester */

2014-04-25T15:01:43Z

Creating a Screen Mode Requester

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Steven Solie: Created page with "== Creating a Screen Mode Requester == The Screeen Mode requester provides application writers with a convenient way to ask the user for their screen display preferences. You..."

2014-04-25T14:35:47Z

Created page with "== Creating a Screen Mode Requester == The Screeen Mode requester provides application writers with a convenient way to ask the user for their screen display preferences. You..."

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== Creating a Screen Mode Requester ==

The Screeen Mode requester provides application writers with a convenient way to ask the user for their screen display preferences. You create an ASL screen mode requester the same way you create an ASL file requester or font requester; only the tags and structures used are different.

There are three main functions to call:

{| class="wikitable"
| AllocAslRequest() || Sets up the ScreenModeRequester structure you need.
|-
| AslRequest() || Displays the requester you have set up with AllocAslRequest().
|-
| FreeAslRequest() || Frees the ScreenModeRequester structure and other resources.
|}

The first step is to set up a ScreenModeRequester structure with the AllocAslRequest() function. The ScreenModeRequester structure is defined in <libraries/asl.h> as follows:

<syntaxhighlight>
struct ScreenModeRequester {
ULONG sm_DisplayID; /* Display mode ID */
ULONG sm_DisplayWidth; /* Width of display in pixels */
ULONG sm_DisplayHeight; /* Height of display in pixels */
UWORD sm_DisplayDepth; /* Number of bit-planes of display */
UWORD sm_OverscanType; /* Type of overscan of display */
BOOL sm_AutoScroll; /* Display should auto-scroll? */
ULONG sm_BitMapWidth; /* Used to create your own BitMap */
ULONG sm_BitMapHeight;
WORD sm_LeftEdge; /* Coordinates of requester on exit */
WORD sm_TopEdge;
WORD sm_Width;
WORD sm_Height;
BOOL sm_InfoOpened; /* Info window opened on exit? */
WORD sm_InfoLeftEdge; /* Last coordinates of Info window */
WORD sm_InfoTopEdge;
WORD sm_InfoWidth;
WORD sm_InfoHeight;
APTR sm_UserData; /* You can store your own data here */
};
</syntaxhighlight>

The fields in this structure will be filled in with information obtained from the user. This information can then be used in your application to create the type of screen that the user prefers.

Note that for most programs, the user's preferred screen mode can be determined from the Amiga's Preferences subsystem. You do not have to use a screen mode requester. Consider carefully whether it is more appropriate to use an ASL requester or to obtain the information directly from the settings in Overscan and ScreenMode Preferences.

Listed below is a simple program that displays the new ASL screen mode requester including depth, width and height gadgets.

<syntaxhighlight>
/*
** aslsm.c
*/

#include <exec/types.h>
#include <libraries/asl.h>
#include <utility/tagitem.h>

#define SMRTITLE "Simplest ScreenMode Requester"

struct AslIFace *IAsl;

int main(int argc, char **argv)
{

struct ScreenModeRequester *smr;
struct TagItem smrtags[5];

struct Library *AslBase = IExec->OpenLIbrary("asl.library", 50);
IAsl = (struct AslIFace*)IExec->GetInterface(AslBase, "main", 1, NULL);

if( IAsl != NULL)
{
smrtags[0].ti_Tag=ASLSM_TitleText;
smrtags[0].ti_Data=(ULONG)SMRTITLE;

smrtags[1].ti_Tag=ASLSM_DoWidth;
smrtags[1].ti_Data=TRUE;

smrtags[2].ti_Tag=ASLSM_DoHeight;
smrtags[2].ti_Data=TRUE;

smrtags[3].ti_Tag=ASLSM_DoDepth;
smrtags[3].ti_Data=TRUE;

smrtags[4].ti_Tag=TAG_END;

if( smr = (struct ScreenModeRequester *)
IAsl->AllocAslRequest(ASL_ScreenModeRequest, smrtags) )
{
if( IAsl->AslRequest(smr, 0L) )
{
IDOS->Printf("Display type: $%lx (see graphics/displayinfo.h)\n",
smr->sm_DisplayID);
IDOS->Printf("Display width: %ld, height: %ld, depth: %ld\n",
smr->sm_DisplayWidth, smr->sm_DisplayHeight,
smr->sm_DisplayDepth);
}
else
IDOS->Printf("User cancelled or error...\n");

IAsl->FreeAslRequest(smr);
}
}

IExec->DropInterface((struct Interface*)IAsl);
IExec->CloseLibrary(AslBase);

return 0;
}
</syntaxhighlight>

As with other ASL requesters, the attributes of the screen mode requester are established using tag items when AllocAslRequest() is called. These attributes can later be changed by using different tag items in the AslRequest() call.

For instance, in the example above, tag items are used to specify that the screen mode requester should include gadgets for setting the display height (ASLSM_DoHeight), width (ASLSM_DoWidth) and depth (ASLSM_DoDepth).

=== Screen Mode Requester Tags ===

Here's a brief summary of the tag items that apply only to the ASL screen mode requester. For a complete listing of all ASL tag items, refer to the ASL include files and Autodocs.

{| class="wikitable"
! Screen Mode Tag Name
! Used For
|-
| ASLSM_Window || Parent window
|-
| ASLSM_Screen || Screen to open on if no window
|-
| ASLSM_PubScreenName || Name of public screen
|-
| ASLSM_PrivateIDCMP || Allocate private IDCMP?
|-
| ASLSM_IntuiMsgFunc || Function to handle IntuiMessages
|-
| ASLSM_SleepWindow || Block input in ASLSM_Window?
|-
| ASLSM_UserData || What to put in sm_UserData
|-
| ASLSM_TextAttr || Text font to use for gadget text
|-
| ASLSM_Locale || Locale ASL should use for text
|-
| ASLSM_TitleText || Title of requester
|-
| ASLSM_PositiveText || Positive gadget text
|-
| ASLSM_NegativeText || Negative gadget text
|-
| ASLSM_InitialLeftEdge || Initial requester left coordinate
|-
| ASLSM_InitialTopEdge || Initial requester top coordinate
|-
| ASLSM_InitialWidth || Initial requester width
|-
| ASLSM_InitialHeight || Initial requester height
|-
| ASLSM_InitialDisplayID || Initial display mode id
|-
| ASLSM_InitialDisplayWidth || Initial display width
|-
| ASLSM_InitialDisplayHeight || Initial display height
|-
| ASLSM_InitialDisplayDepth || Initial display depth
|-
| ASLSM_InitialOverscanType || Initial type of overscan
|-
| ASLSM_InitialAutoScroll || Initial autoscroll setting
|-
| ASLSM_InitialInfoOpened || Info window initially opened?
|-
| ASLSM_InitialInfoLeftEdge || Initial Info window left coordinate
|-
| ASLSM_InitialInfoTopEdge || Initial Info window top coordinate
|-
| ASLSM_DoWidth || Display Width gadget?
|-
| ASLSM_DoHeight || Display Height gadget?
|-
| ASLSM_DoDepth || Display Depth gadget?
|-
| ASLSM_DoOverscanType || Display Overscan Type gadget?
|-
| ASLSM_DoAutoScroll || Display AutoScroll gadget?
|-
| ASLSM_PropertyFlags || Must have these Property flags
|-
| ASLSM_PropertyMask || Only these should be looked at
|-
| ASLSM_MinWidth || Minimum display width to allow
|-
| ASLSM_MaxWidth || Maximum display width to allow
|-
| ASLSM_MinHeight || Minimum display height to allow
|-
| ASLSM_MaxHeight || Maximum display height to allow
|-
| ASLSM_MinDepth || Minimum display depth
|-
| ASLSM_MaxDepth || Maximum display depth
|-
| ASLSM_FilterFunc || Function to filter mode id's
|-
| ASLSM_CustomSMList || Exec list of struct DisplayMode
|}

ASL Screen Mode Requester - Revision history

Costel Mincea: Text replacement - "" to ""

Steven Solie: /* Creating a Screen Mode Requester */

Steven Solie: Created page with "== Creating a Screen Mode Requester == The Screeen Mode requester provides application writers with a convenient way to ask the user for their screen display preferences. You..."