Found and fixed a 20 years old bug in Xserver :)

[Enrico Weigelt, metux IT consult]

Hi folks,


if one's digging deeply enough into old code, sometimes suprising things
happen, eg. finding an 20 years old bug, exotic enough that nobody ever
stumpled across it before:

https://gitlab.freedesktop.org/xorg/xserver/-/issues/1741

This is a really strange one: DIX is denying creation of windows with
different depth than the parent has - but *only* under the condition
that the window has no border pixel or pixmap - if you just add a border
pixmap (even with zero border width, or clear it later), you shall pass.

Seriously, I don't have any clue what that really supposed to mean.
Unfortunately, we don't have any explaination in the git history - it
came from a big X11R6.6 snapshot, 20 years ago.

The fix is trivial: just remove the few lines checking for that case.

I've came along this one while porting Xnest to xcb and fixing another
bugs (https://gitlab.freedesktop.org/xorg/xserver/-/issues/1742),
preventing Xnest from using user-specified depth properly - after fixing
this one, got errors from upstream Xserver.

Already pushed MR for the DIX issue, another one for the Xnest issue
following soon.



have fun,

PS: unfortunately, X is a few years younger than me, so I'll never have
the pleasure of finding a bug older than myself in here :o

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Enrico Weigelt, metux IT consult
Free software and Linux embedded engineering
info at metux.net -- +49-151-27565287