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EngControlSprites function

The EngControlSprites function tears down or redraws sprites on the specified WNDOBJ area.

Syntax


BOOL EngControlSprites(
   WNDOBJ *pwo,
   FLONG  fl
);

Parameters

pwo

Pointer to the WNDOBJ structure on which the sprites are being built or torn down.

fl

This parameter can be one of the following values:

ECS_TEARDOWN

Requests that GDI tear down and remove the sprite effect of any sprite that overlaps the WNDOBJ area. In other words, GDI redraws the sprite with a neutralized effect so the sprite is not visible on the screen. GDI restores the area beneath the sprite by making immediate calls to DrvCopyBits.

ECS_REDRAW

Requests that GDI redraw, restoring any sprites that overlap the WNDOBJ area. GDI redraws directly to the screen by making calls to DrvCopyBits.

Return value

EngControlSprites returns TRUE upon successfully completing the requested operation; otherwise, it returns FALSE.

Remarks

The invocation of ECS_TEARDOWN may be persistent. For example, the driver can call EngControlSprites once with ECS_TEARDOWN as soon as it has created the WNDOBJ, and no sprites will ever be drawn on top of the window.

The driver can call EngControlSprites with ECS_REDRAW numerous times without making intervening calls with ECS_TEARDOWN in order to force the repainting of a sprite at any time.

ECS_TEARDOWN always forces an immediate redraw of any sprites on top of the WNDOBJ area. GDI saves the bits beneath the sprites by calling DrvCopyBits to copy them from the screen, and then composites the sprites onto the screen by calling DrvCopyBits. This can be used to allow sprites to be composited onto a back-buffer just before a swap-buffer command is sent to the hardware (through DrvSwapBuffers or any other driver swap buffer mechanism). This permits seamless compositing of sprites, without flashing, when the window is double buffering.

ECS_TEARDOWN will never cause a WOC_SPRITE_NO_OVERLAP message to be sent, and likewise ECS_REDRAW will never cause a WOC_SPRITE_OVERLAP message to be sent.

EngControlSprites can be called even if no sprites currently overlap the WNDOBJ area.

Requirements

Target platform

Universal

Version

Available in Windows 2000 and later versions of the Windows operating systems.

Header

Winddi.h (include Winddi.h)

Library

Win32k.lib

DLL

Win32k.sys

See also

EngCreateWnd
WNDOBJ

 

 

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