Basic test of python-mpv mpv render context mapping used with GTK

mpv_render_context_gtk_example.py

#!/usr/bin/env python3
import ctypes

import gi

gi.require_version('Gtk', '3.0')
from gi.repository import Gtk, GLib

gi.require_version('GL', '1.0')
from OpenGL import GL, GLX

from mpv import MPV, MpvRenderContext, OpenGlCbGetProcAddrFn


def get_process_address(_, name):
    address = GLX.glXGetProcAddress(name.decode("utf-8"))
    return ctypes.cast(address, ctypes.c_void_p).value


class MainClass(Gtk.Window):

    def __init__(self, media):
        super(MainClass, self).__init__()
        self.media = media
        self.set_default_size(600, 400)
        self.connect("destroy", self.on_destroy)

        frame = Gtk.Frame()
        self.area = OpenGlArea()
        self.area.connect("realize", self.play)
        frame.add(self.area)
        self.add(frame)
        self.show_all()

    def on_destroy(self, widget, data=None):
        Gtk.main_quit()

    def play(self, arg1):
        self.area.play(self.media)


class OpenGlArea(Gtk.GLArea):

    def __init__(self, **properties):
        super().__init__(**properties)

        self._proc_addr_wrapper = OpenGlCbGetProcAddrFn(get_process_address)

        self.ctx = None
        self.mpv = MPV()  # log_handler=print, loglevel='debug')

        self.connect("realize", self.on_realize)
        self.connect("render", self.on_render)
        self.connect("unrealize", self.on_unrealize)

    def on_realize(self, area):
        print('\033[91mon_realize called\033[0m')
        self.make_current()
        self.ctx = MpvRenderContext(self.mpv, 'opengl',
                                    opengl_init_params={'get_proc_address': self._proc_addr_wrapper})
        self.ctx.update_cb = self.wrapped_c_render_func

    def on_unrealize(self, arg):
        print('\033[91munrealize called\033[0m')
        self.ctx.free()
        self.mpv.terminate()

    def wrapped_c_render_func(self):
        print('\033[91mwrapped_c_render_func called\033[0m')
        GLib.idle_add(self.call_frame_ready, None, GLib.PRIORITY_HIGH)

    def call_frame_ready(self, *args):
        print('\033[91mcall_frame_ready called\033[0m')
        if self.ctx.update():
            self.queue_render()

    def on_render(self, arg1, arg2):
        print('\033[91mon_render called\033[0m')
        if self.ctx:
            factor = self.get_scale_factor()
            rect = self.get_allocated_size()[0]

            width = rect.width * factor
            height = rect.height * factor

            fbo = GL.glGetIntegerv(GL.GL_DRAW_FRAMEBUFFER_BINDING)
            self.ctx.render(flip_y=True, opengl_fbo={'w': width, 'h': height, 'fbo': fbo})
            return True
        return False

    def play(self, media):
        self.mpv.play(media)


if __name__ == '__main__':
    import locale

    locale.setlocale(locale.LC_NUMERIC, 'C')

    application = MainClass(media='test.webm')
    Gtk.main()

Works great!

After testing this, I have 2 improvement suggestions 😃

1. Closing the GTK application will result in a Process finished with exit code 139 (interrupted by signal 11: SIGSEGV) error.
   It can be fixed by either replacing line 66 (del self.ctx) with self.ctx.free() or by calling self.ctx.free() before del self.ctx.

2. The function on_render(..) can be simplified, too (notice the removed - in height calculation):

        if self.ctx:
            factor = self.get_scale_factor()
            rect = self.get_allocated_size()[0]
   
            width = rect.width * factor
            height = rect.height * factor
   
            fbo = GL.glGetIntegerv(GL.GL_DRAW_FRAMEBUFFER_BINDING)
            self.ctx.render(flip_y=True, opengl_fbo={'w': width, 'h': height, 'fbo': fbo})
            return True
        return False

Thank you! I added your changes.

One final suggestion 🙈

I came across this while seeking very often in quick succession which printed
mpv_render_context_render() not being called or stuck in the logs (msg-level=all=v).

I then had a look at Celluloid (former gnome-mpv):

The Callback asks GLib to call a function whenever there are no higher priority events pending.
The function will emit another event whose handler then queues the redraw.

There is absolutely no difference during normal playback.
But during excessive seeking not all frames will be drawn.

Changes to the sample code

Notice I have omitted the second event ("frame-ready") as I could not notice a performance difference here.

Import

gi.require_version('Gtk', '3.0')
from gi.repository import Gtk, Gdk

Code

    def wrapped_c_render_func(self):
        print('\033[91mrender wrapper called\033[0m')
        if self.ctx.update():
            self.queue_render()

⏭️ should be changed to ⏭️

Import

gi.require_version('Gtk', '3.0')
from gi.repository import Gtk, GLib

Code

    def wrapped_c_render_func(self):
        print('\033[91mwrapped_c_render_func called\033[0m')
        GLib.idle_add(self.call_frame_ready, None, GLib.PRIORITY_HIGH)

    def call_frame_ready(self, *args):
        print('\033[91mcall_frame_ready called\033[0m')
        if self.ctx.update():
            self.queue_render()

That makes sense. I've updated the gist. Thank you!

On Ubuntu 22.04.1:
I have the import error :
from mpv import MPV, MpvRenderContext,OpenGlCbGetProcAddrFn
ImportError: cannot import name 'OpenGlCbGetProcAddrFn' from 'mpv' (/home/jp/.local/lib/python3.10/site-packages/mpv.py)

On Ubuntu 20.04, it was OK !!!!

Thanks for your response

Please use the MpvGlGetProcAddressFn function instead. The usage is the same. 👍