 Re: Animation with XPutImage?
In-Reply-To: 's message of Thu, 22 Apr 1993 09:28:30 GMT
Organization: Kubota Pacific Computer Inc.
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| 
| Shared memory PutImage  looks interesting, but I need someone to point me to some
| documentation. Is this method likely to give better results than server-
| resident pixmaps? I'd also be interested in looking at the XView code
| mentioned above...

There is no easy answer to this question: it depends on whether the display
device can hold pixmaps in off-screen memory, and if so, how efficiently
the server manages these resources .  

I have worked with graphics devices where the off-screen memory to 
main display copy rate eclipses that of the main memory to display copy
rate, and with those where the main memory to display is *faster* than
off-screen to display 

If your server uses the cfb code or something like it to render into
pixmaps in CPU main memory, the rates you can get through MIT-SHM are
likely to be equal  to CopyArea from pixmap to window, which is also then
just a copy from CPU main memory to graphics device.

One advanage of MIT-SHM is that if your images are large, you don't end up
growing the size of the server process to hold them.

One disadvantage of the MIT-SHM is that, in its sample implementation,
there is no provision for elegantly cleaning up the shared memory segments
if the client dies a sudden, violent death .  You have to 
be mindful of cluttering up the system with zombie shared memory segments.

	Ken
--
Kenneth Whaley			  748-6347
Kubota Pacific Computer, Inc.	 Email: 
2630 Walsh Avenue
Santa Clara, CA.  95051
