xwininfo -id $(xdotool getactivewindow)
should give a lot of information about the active window, including the relative number of pixels between the X window and the out edge of a decoration. It works fine in Xfce under Arch Linux, but people using my scripts have complained that it doesn't work under Ubuntu 14.04 Unity, and just reports:
Relative upper-left X: 0
Relative upper-left Y: 0
For any window even though they do have a 28 pixel title bar and 1 px borders on sides and bottom. I got that information from https://wiki.ubuntu.com/Unity/Theming, which probably also has enough information for whoever works on this to get xwininfo properly determine the Relative upper-left X and Y numbers. They will almost always be 28 and 1, but could have been changed by following the instructions on that link.
The information I needed from xwininfo Relative information is available from:
xprop _NET_FRAME_EXTENTS --xid=$(xdotool getactivewindow)
So, however that is working, seems like it should work the same in xwininfo.
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This bug has been migrated to freedesktop.org's GitLab instance and has been closed from further activity.
You can subscribe and participate further through the new bug through this link to our GitLab instance: https://gitlab.freedesktop.org/xorg/app/xwininfo/issues/1.