Linked by Thom Holwerda on Sat 28th Jun 2008 22:09 UTC, submitted by diegocg
X11, Window Managers "Maybe I'm just naive, but designing a graphics API such that all image data had to be sent over a socket to another process every time the image needed to be drawn seems like complete idiocy. Unfortunately, that is precisely what the X Window System forces a program to do, and exactly what Cairo does when drawing images in Linux - a full copy of the image data, send to another process, no less, every time it is drawn. One would think there would be some room for improvement. Unsurprisingly, others felt the same way about X, and decided to write an extension, Xlib Shm or XShm for short, that allows images to placed in a shared memory segment from which the X server reads which allows the program to avoid the memory copy. GTK already makes use of the XShm extension, and it seems like a good idea to see if Gecko couldn't do the same."
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Exaggerating
by anda_skoa on Sun 29th Jun 2008 00:38 UTC
anda_skoa
Member since:
2005-07-07

I think the article is exaggerating the problem.

True, transferring an image from the application to the X server takes quite some time and can be sped up using the shared memory extension.

However, an image does not have to be transferred every time it needs to be drawn.
As long as the application does not explicitly free the resources associated with the X server side image, it can be drawn or bitblitted with basically no delay.

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