3D Graphics Programming with QuickDraw 3D 1.5.4

Clipping Information

Draw regions contain information about the clipping state. A region may be in one of three states, encoded by the following enumeration:



 
typedef enum TQ3XClipMaskState {

    kQ3XClipMaskFullyExposed,

    kQ3XClipMaskPartiallyExposed,

    kQ3XClipMaskNotExposed

} TQ3XClipMaskState;

A fully exposed draw region has no overlapping windows; a partially exposed draw region has some overlapping windows; a not exposed draw region is entirely offscreen or completely covered by another window. You can determine the clipping state with the Q3XDrawRegion_GetClipFlags function.

If the clipping state is kQ3XClipMaskPartiallyExposed , you can use the Q3XDrawRegion_GetClipMask function to query the draw region for a bitmap that describes the clipping of the window. In the Mac OS environment, you can also use the Q3XDrawRegion_GetClipRegion routine to get information about clipping in the form of a handle to a QuickDraw region (a rgnHandle), or you can use the Q3XDrawRegion_GetGDHandle routine to return a GDHandle .

Q3XDrawRegion_GetClipFlags

The Q3XDrawRegion_GetClipFlags function lets you get the clipping state of a draw region.



 
TQ3Status Q3XDrawRegion_GetClipFlags(

                     TQ3XDrawRegion       drawRegion,

                     TQ3XClipMaskState    *clipMaskState);

drawRegion: A draw region.
clipMaskState: The draw region's clipping mask state.

DESCRIPTION

The Q3XDrawRegion_GetClipFlags function returns, in the clipMaskState parameter, one of three values that define the draw region's clipping mask state. The TQ3XClipMaskState values that can be returned are enumerated on [link] .

Q3XDrawRegion_GetClipMask

The Q3XDrawRegion_GetClipMask function lets you get a bitmap that describes the clipping state of a partially exposed draw region.



 
TQ3Status Q3XDrawRegion_GetClipMask(

                     TQ3XDrawRegion    drawRegion,

                     TQ3Bitmap         **clipMask);

drawRegion: A draw region.
clipMask: A bitmap that describes the clipping of the draw region's window.

DESCRIPTION

The Q3XDrawRegion_GetClipMask function returns, in the clipMask parameter, a bitmap that describes the clipping of the window for the partially exposed draw region drawRegion. In this bitmap, 1 bits indicate exposed pixels and 0 bits indicate occluded pixels.

On a Macintosh, additional window-system-specific information about clipping is available, in the form of a RgnHandle describing the clip region, or a GDHandle :

Q3XDrawRegion_GetClipRegion

The Q3XDrawRegion_GetClipRegion function lets you obtain a Mac OS RgnHandle value that describes the clip region of a partially exposed draw region.



 
TQ3Status Q3XDrawRegion_GetClipRegion(

                     TQ3XDrawRegion    drawRegion,

                     RgnHandle         *rgnHandle);

drawRegion: A draw region.
rgnHandle: A handle to a QuickDraw region.

DESCRIPTION

The Q3XDrawRegion_GetClipRegion function returns, in the rgnHandle parameter, a handle to a QuickDraw region that describes the clipping of the window for the partially exposed draw region drawRegion.

Q3XDrawRegion_GetGDHandle

The Q3XDrawRegion_GetGDHandle function lets you obtain a Mac OS GDHandle value that describes the clip region of a partially exposed draw region.



 
TQ3Status Q3XDrawRegion_GetGDHandle(

                     TQ3XDrawRegion    drawRegion,

                     GDHandle          *gdHandle);

drawRegion: A draw region.
gdHandle: A handle to a gDevice record.

DESCRIPTION

The Q3XDrawRegion_GetGDHandle function returns, in the gdHandle parameter, a handle to a gDevice record that describes the clipping of the window for the partially exposed draw region drawRegion. For further information about gDevice records, see Inside Macintosh: QuickDraw Objects.