3e56efcfb6
A window with either dimension > 32767 can be positioned such that coordinates > 32767 are visible on the screen. Attempts to draw to those pixels will generate coordinates wrapped around to negative values. The optimized clipping macro, 'isClipped', in fbbits.h, computes clipping in window space rather than screen space using int16 values, and so it too has coordinates wrapped around to negative values and hence ends up accepting the wrapped drawing coordinates. Two possible fixes for this problem 1) Detect wrapped region coordinates and clip those to 32767. 2) Detect negative incoming coordinates and reject those This patch takes the second approach as it is much shorter, simply detecting when either X or Y incoming coordinate is negative, which can never be 'within' any drawable. Signed-off-by: Keith Packard <keithp@keithp.com> Reviewed-by: Adam Jackson <ajax@redhat.com>
X Server
The X server accepts requests from client applications to create windows,
which are (normally rectangular) "virtual screens" that the client program
can draw into.
Windows are then composed on the actual screen by the X server
(or by a separate composite manager) as directed by the window manager,
which usually communicates with the user via graphical controls such as buttons
and draggable titlebars and borders.
For a comprehensive overview of X Server and X Window System, consult the
following article:
http://en.wikipedia.org/wiki/X_server
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