Copyright (c) 2012-2016 Hyperion Entertainment and contributors.

Window Types

From AmigaOS Documentation Wiki
Jump to: navigation, search

Window Types

There are three special window types: Backdrop, Borderless and GimmeZeroZero. Backdrop windows stay anchored to the back of the display. Borderless windows have no borders rendered by Intuition. GimmeZeroZero windows provide clipping to protect the borders from graphics rendered into the window.

These window types can be combined, although the combinations are not always useful. For instance, a borderless, backdrop window can be created; however, a borderless, GimmeZeroZero window does not make sense. A window is not required to be any of these types.

Backdrop Window Type

Backdrop windows open behind all other non-backdrop windows, but in front of other backdrop windows that might already be open. Depth arrangement of a backdrop window affects the order of the window relative to other backdrop windows, but backdrop windows always stay behind all non-backdrop windows. No amount of depth arrangement will ever move a non-backdrop window behind a backdrop window.

The only system gadget that can be attached to a backdrop window is the closewindow gadget. Application gadgets are not restricted in backdrop windows.

Backdrop windows may often be used in place of drawing directly into the display memory of a custom screen. Such a technique is preferred, as backdrop windows are compatible with the Intuition windowing system. Using a backdrop window eliminates the danger of writing to the screen memory at a "bad" time or at the wrong position and overwriting data in a window.

To provide a full screen display area that is compatible with the windowing system, create a full sized, borderless, backdrop window with no system gadgets. Use the ShowTitle() call to hide or reveal the screen's title bar, as appropriate. See the SDK for a complete list of arguments for ShowTitle().

Backdrop windows are created by specifying the WFLG_BACKDROP flag or the WA_Backdrop tag in the OpenWindowTagList() call.

Borderless Window Type

The borderless window type has no borders rendered by Intuition. Such a window will have no visual delineation from the rest of the display. Be aware that a Borderless window which does not cover the entire display may cause visual confusion for the user. When using a borderless window that does not cover the entire display, the application should provide some form of graphics to replace the borders provided by Intuition.

In general, none of the system gadgets or the window title should be specified for a borderless window, as they may cause at least part of the border to be rendered.

A typical application of a borderless window is to simulate graphics drawn directly into the screen, while remaining compatible with windows and menus. In this case, the application will often create a full sized, borderless, backdrop window.

Use the WFLG_BORDERLESS flag or the WA_Borderless tag to get this window type.

GimmeZeroZero Window Type

GimmeZeroZero windows provide a window border layer separate from the main (inner) window layer. This allows the application to freely render into the window without worrying about the window border and its contents.

System gadgets and the window title are placed in the border layer. Application gadgets go into the inner window by default, but may be placed in the border. To position application gadgets in the border layer, the GTYP_GZZGADGET flag and the appropriate Gadget border flag must be set in the Activation field of the Gadget.

The top left coordinates of the inner window are always (0,0), regardless of the size or contents of the border, thus the name "GimmeZeroZero." The application need not take the border size into account when rendering. The inner window always begins at (0,0) and extends to (GZZWidth,GZZHeight). The GZZWidth and GZZHeight variables are available in the Window structure.

The GZZMouseX and GZZMouseY variables provide the position of the mouse relative to the inner window. Note that the mouse positions in IDCMP_MOUSEMOVE events are always relative to the total window, even for GimmeZeroZero windows.

Requesters in a GimmeZeroZero window are also positioned relative to the inner window. See Intuition Requesters, for more information about requester location.

To specify a GimmeZeroZero window, set the WFLG_GIMMEZEROZERO flag or the WA_GimmeZeroZero tag in the OpenWindowTagList() call.

Warning!
The GimmeZeroZero window uses more system resources than other window types because the window creates a separate layer for the border display. Using multiple GimmeZeroZero windows will quickly degrade performance in the positioning and sizing of windows.

Applications should consider using regions as an alternative to GimmeZeroZero windows. See Layers Library, especially the InstallClipRegion() function, for information on setting up regions to limit graphics display in the window.