screen update problems with Intel HD 4600 + virtual screen

[Krzysztof Hałasa]

Hello,

I'm having screen update problems problems with an Intel HD 4600 with
panning + virtual screen. Fedora 20 + updates, CPU is Core i7 4770K,
I'm using xrandr --output HDMI1 --panning 4096x2404. The physical screen
size is 1920x1200.
Another setup also experiencing this problem is Core i5 4200M with
a 1600x900 physical screen (LVDS) and (a bit larger) virtual screen
(again with panning).

xorg-x11-drv-intel-2.21.15-5.fc20.x86_64
xorg-x11-server-Xorg-1.14.4-9.fc20.x86_64

I'm using pretty bare openbox (with no icons etc.).

The problem is that windows (e.g. start menu popup) aren't always drawn
when they are positioned outside the original physical screen area. For
example, I press the "popup menu" mouse button with the screen panned to
the right/down and the menu doesn't show up, or only a part shows up. It
looks like some kind of optimization to prevent displaying invisible
windows, except that the check for being visible uses the initial
physical screen coordinates (e.g. starting at 0x0) instead of the part
currently visible due to panning.

A mouse movement causing minimal panning seems to force update the
screen.

Any idea what's wrong?
-- 
Krzysztof Halasa

Research Institute for Automation and Measurements PIAP
Al. Jerozolimskie 202, 02-486 Warsaw, Poland