NAME

XUnionRectWithRegion − add a rectangle to a region. 

Synopsis

XUnionRectWithRegion(rectangle, src_region, dest_region_returnfP)
     XRectangle *rectangle;
     Region src_region;
     Region dest_region_return;

Arguments

rectangleSpecifies the rectangle to add to the region. 

src_region
Specifies the source region to be used.

dest_region_return
Specifies the resulting region.  May be the same as src_region. 

Description

XUnionRectWithRegion() computes the destination region from a union of the specified rectangle and the specified source region.  The source and destination regions may be the same.  One common application of this function is to simplify the combining of the rectangles specified in contiguous Expose events into a clip_mask in the GC, thus restricting the redrawn areas to the exposed rectangles.  Use XUnionRectWithRegion() to combine the rectangle in each Expose event into a region, then call XSetRegion().  XSetRegion() sets the clip_mask in a GC to the region.  In this case, src_region and dest_region_return would be the same region.  If src_region and dest_region_return are not the same region, src_region is copied to dest_region_return before the rectangle is added to dest_region_return.  For more information on regions, see Volume One, Chapter 6, Drawing Graphics and Text. 

Structures

typedef struct {
    short x, y;
    unsigned short width, height;
} XRectangle;

Region is a pointer to an opaque data type. 

See Also

XClipBox(), XDestroyRegion(), XEmptyRegion(), XEqualRegion(), XIntersectRegion(), XOffsetRegion(), XPointInRegion(), XPolygonRegion(), XRectInRegion(), XSetRegion(), XShrinkRegion(), XSubtractRegion(), XUnionRegion(),

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