PySDL2 example. Partially done.

[cztomczak]

PySDL2 is a wrapper around the SDL2 library, a cross-platform development library designed to provide low level access to audio, keyboard, mouse, joystick, and graphics hardware via OpenGL and Direct3D.

https://github.com/marcusva/py-sdl2

Known issues (pull requests are welcome):

• There are issues when running on slow machine - key events are being
  lost (noticed on Mac only so far), see comments in this issue for more details
• Performance is still not perfect, see comments in this issue for further details
• Keyboard modifiers that are not yet handled in this example:
  ctrl, marking text inputs with the shift key.
• Backspace key doesn't work on Mac
• Dragging with mouse not implemented
• Window size is fixed, cannot be resized

[cztomczak]

pysdl2.py example added in the examples/ directory via PR #379. Currently tested only on Linux.

[cztomczak]

I have tested pysdl2.py example on Windows and it runs very slow. Page loading is slow, typing is slow, scrolling is slow. I have installed sdl2+pysdl2 using these steps:

1. Download SDL2.dll from http://www.libsdl.org/download-2.0.php (2.0.7 version as of now)
2. Put SDL2.dll in C:\Python27\ (or wherever you installed Python)
3. Install pysdl2: pip install pysdl2 (version 0.9.6)

I don't know why the issue with app working so slow. Either PySDL2 support for Windows is broken or there is something that needs to be fixed in pysdl2.py example.

[cztomczak]

@neilmunday Adding a call to SDL_DELAY at the end of rendering loop didn't help (tried 1ms, 5ms, 10ms). I've added a print that counts how many times messageloopwork is called in the rendering loop and its about 100 times in a second, so that should be fine, as other examples execute it in a 10ms timer. I see that you haven't set necessary flags for off-screen rendering optimizations, as described in Issue #240 ("Tweaking OSR performance"). Here are the switches that should be set:

switches = {
            # Tweaking OSR performance by setting the same Chromium flags
            # as in upstream cefclient (# Issue #240).
            "disable-surfaces": "",
            "disable-gpu": "",
            "disable-gpu-compositing": "",
            "enable-begin-frame-scheduling": "",
        }
        browserSettings = {
            # Tweaking OSR performance (Issue #240)
            "windowless_frame_rate": 100
        }

I've applied these and it now renders much better, however it still doesn't render as smoothly as when running hello_world.py example. Typing is fine now. I don't feel any lag while typing, although it sometimes lags during initial loading when typing. Scrolling is still not as smooth as in hello_world. I've increased scroll delta to 40, however it's not about it, I test scrolling by dragging scrollbar. I guess it needs synchronizing FPS/frame rate between CEF and SDL. I've found this article:

http://lazyfoo.net/SDL_tutorials/lesson14/index.php

With such code:

        // If we want to cap the frame rate
        if( ( cap == true ) && ( fps.get_ticks() < 1000 / FRAMES_PER_SECOND ) )
        {
            //Sleep the remaining frame time
            SDL_Delay( ( 1000 / FRAMES_PER_SECOND ) - fps.get_ticks() );
        }

I've updated pysdl2.py example in commit 5dbd9d6 - added performance switches and frame rate browser setting described earlier.

@neilmunday Please test this updated example on Linux and see how these switches affect it now, as I've tested this only on Windows. It would be great if you could improve performance further by adding code that synchronizes frame rate between CEF <> SDL (the code above or similar). I think that having frame rate at 60 FPS would be sufficient for web browser. PR is welcome.

[neilmunday]

@cztomczak I've just tested the updated example under Fedora 26 with SDL2 2.0.7 and PySDL 0.9.6 and it works fine.

[neilmunday]

I have tried using SDL2_gfx's frame rater manager and it works really well under Linux. However, there do not appear to be any Windows binaries that I can see for this SDL2 add-on which is shame.

Ref: http://www.ferzkopp.net/Software/SDL2_gfx/Docs/html/_s_d_l2__framerate_8c.html

[cztomczak]

Adding such code within if platform == linux block code is fine, if you want to go this way.