Forwarded from: https://launchpad.net/distros/ubuntu/+source/gnome-screensaver/+bug/22045

My laptop (Thinkpad T30) has a 16M Radeon 7500 Mobility chip in it handles opengl acceleration fairly well (good enough to use the opengl xscreensaver hacks at 16bpp without much issue). I personally like the GLSlideshow and Carousel hacks, and they look fine when I drive them xscreensaver. With gnome-screensaver, however, I am getting a lot of flicker between frames.

I've switched to gnome-screensaver's 'Pictures folder' for the time being, but it is hideously slow (though it doesn't flicker) -- apparently it doesn't even attempt to use opengl?

Anyway, I'd really prefer to use Carousel or GLSlideshow on my laptop as I do on
my desktops (which run it just fine with gnome-screensaver and modern nvidia cards)



Yeah, it's a Radeon 7500M, which has been well supported by opensource drivers for some time.

RE: comment #1, here's why I think it's a gnome-screensaver problem. If I apt-get install xscreensaver, killall gnome-screensaver, xscreensaver-demo, and select the same hack, when I lock the screen, it displays perfectly. When I apt-get install gnome-screensaver, killall xscreensaver, gnome-screensaver, and lock the screen, it flicker really badly.

I believe xscreensaver does some work to make sure the images are loaded the right way, so that may be that's where the difference is. If I'm not mistaken, my display has a fairly small texture size limit, so perhaps xscreensaver ensures that the images are scaled before turning them in to textures. Maybe gnome-screensaver just turns the jpegs into textures without any extra processing?




I have an ATI card (Radeon 9200se) and I am happily using the open source xserver-xorg-driver-ati driver on Dapper.

I am experiencing similar issues: the GL hacks are fine when run from xscreensaver or by themselves, while they flicker terribly when run by gnome-screensaver. Non-GL hacks show no issues.



Even though it looks like a driver problem, there still is the question why this only happens with gnome-screensaver? Plain hacks don't have this problem. Is gnome-screensaver doing something differently when displaying the hacks?




I just confirmed this with the Dapper Flight 4 Live CD. Here are the steps I went through to reproduce:

1) download dapper flight 4 live cd and burn it
2) boot
3) change DefaultDepth in /etc/X11/xorg.conf to 16 ( my T30 only has 16M of ram and a 1400x1050 screen, so direct rendering is only available for 1400x1050@16 bits)
4) restart gdm
5) load up the gnome-screensaver-preferences and select the GLText screensaver and note how it flickers
6) run gnome-screensaver-command --activate and see the flickery badness 7) sudo apt-get update && sudo apt-get install xscreensaver
8) run xscreensaver-demo and select GLText
9) hit Preview and note the lack of flicker.

Again, this is on my Thinkpad T30 with this card (as told by lspci): 0000:01:00.0 VGA compatible controller: ATI Technologies Inc Radeon Mobility M7 LW [Radeon Mobility 7500]