Vague bug report: windows are slow when moved

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Vague bug report: windows are slow when moved

Postby dwks » 2008-02-26 20:37

Recently, after an upgrade of my Lenny system, I encountered a very strange bug. When graphical programs, i.e. SDL ones, that are running in windowed mode are moved, they sometimes slow down. [edit] In case this wasn't clear: by "moved" I mean the window is dragged to another position on the screen, while staying in the bounds of the screen before and after the move. [/edit]

In other words, a program which was running at 30FPS and taking 75% of the cpu (or 40FPS while taking 100%), once moved, suddenly starts running at 22FPS, again taking 100%. Move the program again, and it might start running fast again -- or it might not.

I've tested some Allegro as well as some SDL programs, so it's not like it's restricted to the SDL.

The other strange thing is that the ratio of slow moves to fast moves depends on the program used. The program I originally discovered the problem on, an SDL project of mine, is slow probably 80% of the time. A simple SDL test program that I wrote is slow perhaps 20% of the time. (It rotates an image with SDL_gfx and blits it, not framerate limited.) liquidwar, an Allegro game, is slow maybe 1% of the time.

I'm not sure if this is worth reporting or not, because first of all, it seems to be caused by my recent upgrade. If I open a new virtual terminal and log in from there, everything's just fine. (I'm keeping my original occasionally-slow Gnome session open in case anyone wants me to try something.) The other reason I'm posting it here instead of making a bug report is that it's very vague, and very random. I don't know why it only happens occasionally, I don't know what's causing the problem.

Thus, this post. Any suggestions or comments? (Besides "just log out and in again and everything will be fine" . . . .)

For reference, the list of packages I upgraded is available here: http://dwks.theprogrammingsite.com/sdl-slow-after-move-upgrade.txt
dwk

Seek and ye shall find. quaere et invenies. (Latin by dwks.)

"Testing can only prove the presence of bugs, not their absence." -- Edsger Dijkstra
dwks
 
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