Vsync support for Wayland

[jwinarske]

vsync is missing

[HidenoriMatsubayashi]

Thank you. Actually, I don't understand what to use FlutterEngineOnVsync for. Could you tell me the purpose of it?

[guangoon]

VSync can be understood as a timed interrupt. The system will send a VSync signal every time it can proceed, and the CPU/GPU will immediately process the rendering after receiving the signal. Therefore, in Flutter, when rendering is needed, we need to monitor the VSync signal, and when a VSync signal is generated, we can start GPU rendering. and if we don't set VsyncCallback in embedder, engine will set a default VsyncCallback which is 60 fps.

[HidenoriMatsubayashi]

Thank you. That's quite understandable. What should this embedder do is to prepare the API so that the user program or plugins can receive Vsync, right?

[guangoon]

FlutterProjectArgs args = {};
args.vsync_callback =
you should implement this callback,
When this callback is triggered, you need request vsync signal,
when receive vsync signal callback, you need call FlutterEngineOnVsync.

[HidenoriMatsubayashi]

Thanks. I'll implement vsync.

[HidenoriMatsubayashi]

By the way, is there any good way to detect Vsync on Linux platforms? I couldn't find it.

[jwinarske]

For Wayland refer to this: https://lists.freedesktop.org/archives/wayland-devel/2016-March/027465.html

…

On Tue, Apr 13, 2021, 11:04 PM Hidenori Matsubayashi < ***@***.***> wrote: By the way, is there any good way to detect Vsync on Linux platforms? I couldn't find it. — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#68 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AC5R3W423PLE6S573E2YEQ3TIUWALANCNFSM423WSSAQ> .

[HidenoriMatsubayashi]

Thanks!

[jwinarske]

For DRM this is a good reference:
https://github.com/dvdhrm/docs/blob/master/drm-howto/modeset-vsync.c

[HidenoriMatsubayashi]

In terms of Wayland backend, I think wp_presentation is better than wl_callback_listener. We can also get a refresh rate by using it. However, we don't call wl_surface_commit because of using eglSwapBuffers which is called from Flutter Engine. So, wp_presentation events don't happen continuously every frame.