windowless frame rate never exceeds 30

[fabia...@web.de]

So, I'm having the issue that my 60 fps application only gets 30 cef OnPaint updates per second. I'm fully aware of the "windowless_frame_rate" : 60 option. I know that it works, because setting it to 1 really does give me 1 update a second. I also know that I can get 60 fps and that there are 60 fps because using the devconsole I can profile the browser while it is running and it is doing 16 ms / 60 fps internally. However, that is not how often the OnPaint gets called.

If I print the frames that happen and the times a frame got "painted" (OnPaint) I get this log :

[...]
INFO:STDOUT:Frame happened
INFO:STDOUT:Frame happened
INFO:STDOUT:Painting a frame
INFO:STDOUT:Frame happened
INFO:STDOUT:Frame happened
INFO:STDOUT:Painting a frame
INFO:STDOUT:Frame happened
INFO:STDOUT:Frame happened
INFO:STDOUT:Painting a frame
INFO:STDOUT:Frame happened
INFO:STDOUT:Frame happened
INFO:STDOUT:Painting a frame
INFO:STDOUT:Frame happened
INFO:STDOUT:Frame happened
INFO:STDOUT:Painting a frame
INFO:STDOUT:Frame happened
INFO:STDOUT:Frame happened
INFO:STDOUT:Painting a frame
INFO:STDOUT:Frame happened
INFO:STDOUT:Frame happened
INFO:STDOUT:Painting a frame
INFO:STDOUT:Frame happened
INFO:STDOUT:Frame happened
INFO:STDOUT:Painting a frame
INFO:STDOUT:Frame happened
INFO:STDOUT:Frame happened
INFO:STDOUT:Painting a frame
[...]

I've completely emptied the OnPaint except for a print to make sure it completes in time, but same deal.

So, half the frames get rendered offscreen but never get sent to OnPaint. This creates a noticable delay in the application. Especially since due to engine infrastructure, it is already one main frame behind, so cef is then up to 4 frames (64milliseconds!) behind input.

[fabia...@web.de]

here's the internal 60fps:
https://i.imgur.com/NKOQ7Ie.png
Which I'd like to get from it.
Also, why is 60 the limit? My main application does adaptive v-sync, I'd like to be able to set cef to that. But that could for example be 144hz. Why is it capped at 60? (or 30, actually)

[Czarek Tomczak]

OnPaint will get called only when something changes on a web page.

You didn't provide basic information. What OS and cefpython version? What example are you running, what framework?

[Czarek Tomczak]

Run with --debug flag and attach debug.log file.

[Czarek Tomczak]

See also what flags to set for best performance: https://github.com/cztomczak/cefpython/issues/240

[fabia...@web.de]

So, this problem was first discovered by trying to drag a jquery ui dialog box and it lagging far behind.

Here's the debug log: https://pastebin.com/eTCchkXW

It isn't one of the examples or established frameworks, as I'm writing a vulkan game engine and I hope to use cef for the UI. It is still loosely based on one of the examples, I forgot which by now.

There is always something to update, as for the sake of testing this bug I created a permament css animation.

Should it help, here's the python module handling it:
https://pastebin.com/3zwQa8Ez
and here's the main html:
https://pastebin.com/27GSEfZY
I won't run without the rest of the engine, but maybe it helps.

Looking at the run flags, it looks like the important ones should be already automatically set as I tell it to offscreen render.

[fabia...@web.de]

Oh yeah, Python 3.6.3 64 bit, latest modules of everything according to pypi and windows 7 and 10 64 bit.

[Czarek Tomczak]

The debug.log you provided doesn't contain any logs, only some errors (false-positive).

You are not setting any of the important offscreen flags for best performance, thus the slow frame rate you get is expected.

[fabia...@web.de]

In the image you can see that the framework is internally rendering at 60 fps. With 16 ms between frames. You can also see that a frame is rendered in about 1/10th of the time (about 2 ms) So in theory it could render at 500 fps with these settings. This is admittedly on a beast machine, but the point stands, there are 60 fps, half of which do not get an OnPaint.