Snapshot does not grab window content (incorrect alpha)

[costabel@…]

This is a summary of what was discussed on the X11-user list on June 10-12, thread "empty screenshot"

Problem: Open an X11 window containing graphics content, created by, for example,

• gnuplot
  
• a Tek window opened from an xterm drop-down menu (does not work on 2.3.0-rc4, see another bug, to be filed)
  
• xv
  
• xpdf
  
• display from ImageMagick
  

Then hit cmd-shift-4 and the space bar. This shows a camera symbol. Place it over the X11 window and click.

A snapshot of the window is taken and placed on the Desktop as Picture\ 1.png (count goes up with new snapshots).

An example of what this should show is attached (Picture\ 1.png).
An example of what happens with xquartz-2.2.1 or newer is attached (Picture\ 2.png): The window content is empty.
(Pictures will be attached as soon as I find out how to attach files to this tracker ;-) )

I have not tried to find what version of xquartz is the earliest to show this problem. In any case, the bug is not present in the stock X11 from 10.5.3.

[costabel@…]

good snapshot

[costabel@…]

bad snapshot

[jeremyhu@…]

This is probably because of the alpha channel being set to 0 instead of 1 when the window contents are dumped from X11 to the Window Server... We will probably need to migrate over some of the rootless-specific changes that were dropped when fb was moved from xserver into pixman

[jeremyhu@…]

I want to actually try getting this in 2.3.1.

I think I have a fix for this which I'm compiling now.