Path: utzoo!attcan!uunet!samsung!emory!nastar!joel
From: joel@nastar.UUCP (Joel Rives)
Newsgroups: comp.windows.x
Subject: Re: Transparent Pixel values
Keywords: Pixmap, Window, Pixels
Message-ID: <633@nastar.UUCP>
Date: 6 Nov 89 19:11:58 GMT
References: <809@thor.wright.EDU> <9692@zodiac.ADS.COM>
Reply-To: joel@nastar.UUCP (Joel Rives)
Organization: Digital Transmissions Systems, Inc.
Lines: 21

>medmunds@verity.com (Mike Edmunds x7645) (medmunds@verity.com, <9692@zodiac.ADS.COM>):
>I've had some success with setting the clip_mask in a GC to a bitmap
>with objects drawn on it, and then painting through this "stencil"
>using XFillRectangle over the entire area.  Only pixels that were set
>in the bitmap are affected in the destination window.  If your
>original pixmap was more than one plane deep, you'll have to separate
>it into components (I keep a separate bitmap for each color) and paint
>multiple times.

According to the "Xlib -- C Language Interface", the XCopyArea() function
uses the clip-mask component of the GC specified in the call. I have used 
this feature to restrict displaying of a pixmap to a rectangular sub-region.
There is no reason that i can see why one could not use the stencil method
that Mike mentions. However, instead of using multiple calls to 
XFillRectangle(), simply make one call to XCopyArea(). The bitmap clip-mask
does not restrict the copy function to a single plane. It merely 
determines which pixels will be copied and which will be filtered out.



											Joel Rives