Error switching into fullscreen mode using Pyglet backend

[azhuchkov]

Running the following file with the command python test.py --window pyglet

#test.py

import moderngl_window as mglw

class Test(mglw.WindowConfig):
    gl_version = (3, 3)

    def on_render(self, time: float, frametime: float):
        self.ctx.clear(1.0, 0.0, 0.0, 0.0)

Test.run()

and then switching into fullscreen by pressing F11, I get only bottom left quarter of the screen red (the rest is black) and sometimes the following error (full output listed):

2025-08-02 01:38:30,046 - moderngl_window - INFO - Attempting to load window class: moderngl_window.context.pyglet.Window
2025-08-02 01:38:30.503 Python[73067:10459058] ApplePersistenceIgnoreState: Existing state will not be touched. New state will be written to /var/folders/dx/jsdfsdfsdfsdqd8qkymk79dzv940000gn/T/org.python.python.savedState
2025-08-02 01:38:30,595 - moderngl_window.context.base.window - INFO - Context Version:
2025-08-02 01:38:30,595 - moderngl_window.context.base.window - INFO - ModernGL: 5.12.0
2025-08-02 01:38:30,595 - moderngl_window.context.base.window - INFO - vendor: Intel Inc.
2025-08-02 01:38:30,595 - moderngl_window.context.base.window - INFO - renderer: Intel Iris Pro OpenGL Engine
2025-08-02 01:38:30,595 - moderngl_window.context.base.window - INFO - version: 4.1 INTEL-18.8.16
2025-08-02 01:38:30,595 - moderngl_window.context.base.window - INFO - python: 3.11.6 (main, Nov  2 2023, 04:51:19) [Clang 14.0.0 (clang-1400.0.29.202)]
2025-08-02 01:38:30,595 - moderngl_window.context.base.window - INFO - platform: darwin
2025-08-02 01:38:30,596 - moderngl_window.context.base.window - INFO - code: 410
2025-08-02 01:38:31.519 Python[73067:10459058] TSM AdjustCapsLockLEDForKeyTransitionHandling - _ISSetPhysicalKeyboardCapsLockLED Inhibit
Exception ignored on calling ctypes callback function: <function ObjCSubclass.method.<locals>.decorator.<locals>.objc_method at 0x10e3f5da0>
Traceback (most recent call last):
  File "/<...>/venv/lib/python3.11/site-packages/pyglet/libs/darwin/cocoapy/runtime.py", line 1503, in objc_method
    result = f(py_self, *args)
             ^^^^^^^^^^^^^^^^^
  File "/<...>/venv/lib/python3.11/site-packages/pyglet/window/cocoa/pyglet_view.py", line 349, in mouseExited_
    x, y = getMousePosition(self, nsevent)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/<...>/venv/lib/python3.11/site-packages/pyglet/window/cocoa/pyglet_view.py", line 74, in getMousePosition
    self._window._mouse_x = x
    ^^^^^^^^^^^^
  File "/<...>/venv/lib/python3.11/site-packages/pyglet/libs/darwin/cocoapy/runtime.py", line 1359, in __getattr__
    raise AttributeError(msg)
AttributeError: ObjCInstance b'PygletView' (140532901398960) has no attribute _window
2025-08-02 01:38:32,797 - moderngl_window - INFO - Duration: 2.08s @ 58.29 FPS

Installed Software

python 3.11.6

moderngl                5.12.0
moderngl-window         3.1.1
pyglet                  2.1.6

[azhuchkov]

The problem appears to be related to the dpi_scaling feature introduced in Pyglet 2.1. Its default value, "real," does not trigger on_resize events during transitions between fullscreen and windowed modes.

A quick fix is to:

import pyglet
pyglet.options.dpi_scaling = 'stretch'

Alternatively, you can pin Pyglet to version 2.0.

The error trace is still there and most likely a bug in the new version.