Path: utzoo!attcan!uunet!munnari.oz.au!sirius.ucs.adelaide.edu.au!augean!flinders!lennon!rwhitby
From: rwhitby@lennon.austek.oz (Rod Whitby)
Newsgroups: comp.windows.x
Subject: Questions about ORing Clip Rectangles into a GC and setting DashList
Keywords: Xlib GC XSetClipRectangles XSetDashes
Message-ID: <328@lennon.austek.oz>
Date: 2 May 90 03:28:57 GMT
Organization: Austek Microsystems, Adelaide, S.A.
Lines: 44

be drawn with.

I have an exposure handler that accumulates the Expose rectangles and
marks the objects which are in the Exposed region.  When the Exposure
count reaches zero, the handler then redraws the marked objects,
setting the clip mask of each using XSetClipRectangles to be the
Exposed region.


I only allow objects to set their GC values using XCreateGC and an
XGCValues structure, and I keep a copy of the XGCValues used, so I
have knowledge of what values are in the object's GC (including the
Clip Mask).

My first question is:
> 	 Is there any way to set the GCDashList without using the
> XSetDashes convenience function ?  XSetDashes takes a dash list (char
> dash_list[]) and the length of the list, but the XGCValues structure
> only defines a single dash character (char dashes).


A problem with my exposure handler's strategy arises when one of the
objects already has a clip mask in it's GC.  If I just use
XSetClipRectangles to set the Clip Mask, then the object's existing
Clip Mask will be overwritten.  If the object sets its clip mask
using the XGCValues structure, then I have knowledge of the Pixmap it
used.

My second question is:
> 	Is there a way to OR a set of XRectangles (i.e the
> arguments to XSetClipRectangles) into a Pixmap (the value already
> stored in the object's GC)?  I want the clipped region to be the
> intersection of the existing Clip Mask and the Exposed region.

My thanks in advance for any answers to these questions.  Any comments
on my exposure handler's strategy are also welcome.

Rod Whitby
Austek Microsystems Pty. Ltd.
Technology Park 
Adelaide, SA 5095 Australia

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