Created attachment 154065 [details] [review]
13_nvidia_gamma_fade_fallback.patch

Since http://git.gnome.org/browse/gnome-screensaver/commit/?id=f423a56d536b4ce19383ed74c1550ebd12f88541, the fade-out no longer works with the proprietary NVIDIA driver. It seems that the RANDR gamma fade is not supported on these drivers.

Running in xtrace, I see this:

000:<:002c: 12: RANDR-Request(152,0): QueryVersion major-version=1 minor-version=3
000:>:002c:32: Reply to QueryVersion: major-version=1 minor-version=3

This comes from calling gnome_rr_screen_new in check_randr_extension. Apparently version 1.3 of the RANDR extension exists. However, I also see this a few lines afterwards:

000:<:007c:  8: RANDR-Request(152,22): GetCrtcGammaSize crtc=0x00000147
000:>:007c:32: Reply to GetCrtcGammaSize: size=0x0000

This is called from crtc_initialize in gnome-desktop when populating ScreenInfo. Because it appears that RANDR 1.3 exists, fade_type is set to FADE_TYPE_XRANDR, but note that crtc->gamma_size is 0 for this CRTC.

When attempting to fade, I see the following lines in xtrace:

000:<:00c9:  8: RANDR-Request(152,23): GetCrtcGamma crtc=0x00000147
000:>:00c9:32: Reply to GetCrtcGamma: red=; green=; blue=;

This comes from calling gnome_rr_crtc_get_gamma in xrandr_fade_setup. xrandr_fade_setup returns TRUE, and then xrandr_fade_set_alpha_gamma is called repeatedly for the duration of the fade. However, xrandr_crtc_whack_gamma bails out early because gamma_info->size is 0, and we get no fade at all (instead, the screen just turns black at the end of the fade).

I've attached a patch which I uploaded to Ubuntu, which makes sure it correctly falls back to XF86VM gamma fade on a particular screen when crtc->gamma_size is 0 for any CRTC.