On 2018-09-12 2:48 p.m., Kazlauskas, Nicholas wrote: > On 09/12/2018 04:13 AM, Michel Dänzer wrote: >> On 2018-09-11 6:18 p.m., Nicholas Kazlauskas wrote: >>> These patches are part of a proposed new interface for supporting >>> variable refresh rate via DRM properties. >>> >>> https://patchwork.freedesktop.org/series/49486/ >>> >>> When notified of a window that is FreeSync capable via X these >>> patches help track when the window is fullscreen to manage the >>> variable_refresh property on the CRTC. >> >> I'm afraid the Xorg driver support will have to be more or less redone >> from scratch for upstreaming: >> >> Whether or not a client wants variable refresh rate enabled can be >> tracked via the window property mechanism supported by the core X11 >> protocol, no need for a protocol extension. >> >> That should also allow simpler tracking of when variable refresh rate >> can actually be enabled: It can be enabled while a window is flipping, >> and its corresponding property allows it. This should be straightforward >> with the Present extension, because that also explicitly marks the end >> of a window flipping (via an "unflip"). DRI2 is trickier; it's probably >> okay not to support variable refresh rate with that, at least initially. >> >> >> I can look into this after the upcoming Xorg driver 18.1 releases. Or I >> can give guidance if one of you wants to look into it. > > I can a look into this. I agree that the extension method is less than > ideal - in being vendor specific mostly. It does have the nice property > that it remains independent of the application's render backend, though. Not sure what you mean by that. Surely a window property is just as independent. :) > I imagine you're suggesting specifying a window property hint like > _NET_WM_BYPASS_COMPOSITOR - maybe a define new one like > _NET_WM_VARIABLE_REFRESH (even though the two are closely related in > terms of fullscreen behavior). Then in each backend the property could > probably be checked before the present as appropriate. Right. (Not sure the _NET_WM prefix is appropriate, as it's nothing to do with the window manager, but that's a detail) > This patch series already has the problem you're describing about DRI2 > where there's not a nice explicit end notification for flipping - it's > only disabled when the window no longer covers the CRTC or the window is > destroyed (which is the case for most applications but likely not all). Right. I think it's better to just not bother with DRI2, at least until there's a specific scenario where variable refresh is really needed with DRI2. -- Earthling Michel Dänzer | http://www.amd.com Libre software enthusiast | Mesa and X developer
