Fix error when the window is minimized

[panxinmiao]

When the window is minimized, the application crashes.

Traceback (most recent call last):
  File "F:\rendercanvas\rendercanvas\_coreutils.py", line 50, in log_exception
    yield
  File "F:\rendercanvas\rendercanvas\_loop.py", line 241, in wrapper
    await async_func(*args)
  File "F:\rendercanvas\rendercanvas\_scheduler.py", line 164, in __scheduler_task
    canvas._process_events()
  File "F:\rendercanvas\rendercanvas\base.py", line 390, in _process_events
    self.__maybe_emit_resize_event()
  File "F:\rendercanvas\rendercanvas\base.py", line 361, in __maybe_emit_resize_event
    self._canvas_context._rc_set_size_dict(self._size_info)
  File "F:\rendercanvas\rendercanvas\contexts\basecontext.py", line 54, in _rc_set_size_dict
    self._wgpu_context.set_physical_size(*size_info["physical_size"])
  File "F:\wgpu-py\wgpu\_classes.py", line 277, in set_physical_size
    raise ValueError("Physical size values must be positive.")
ValueError: Physical size values must be positive.

I think physical_size can be (0, 0).

[Korijn]

I checked with git blame, this PR indeed restores the original behavior. Thank you!

[almarklein]

mmm, from what I can find, the original behavior was different from bitmap and screen presenting:

For bitmap, the case was basically ignored, making a texture of at least 1 pixel:

wgpu-py/wgpu/_classes.py

Lines 461 to 462 in 44a8943

	width, height = canvas.get_physical_size()
	width, height = max(width, 1), max(height, 1)

For screen it failed also for zero-size textures:

wgpu-py/wgpu/backends/wgpu_native/_api.py

Lines 881 to 884 in 44a8943

	new_size = tuple(self._get_canvas().get_physical_size())
	if new_size[0] <= 0 or new_size[1] <= 0:
	# It's the responsibility of the drawing /scheduling logic to prevent this case.
	raise RuntimeError("Cannot get texture for a canvas with zero pixels.")

I think the latter was done because zero-sized textures cause a crash later in the pipeline. Not sure if this behavior has changed in recent releases of wgpu-native.

---

Anyway ... thanks for the fix! I will probably dig a bit more into it though, because I feel I don't fully understand the consequences, and in what cases we can expect a zero-sized array.

I suspect that a zero-sized canvas can happen, but it will never be drawn to by rendercanvas, so the aforementioned pipeline error should not happen...

I just tried on MacOS, and for both glfw and Qt, a minimized window does not change its size. I can test on Windows and Linux next week when I am back in my office. Was the original issue on Windows @panxinmiao ?

[Vipitis]

This definitely happened to me on windows with glfw too

[panxinmiao]

Was the original issue on Windows @panxinmiao ?

Yes, I encountered this issue on Windows.

[almarklein]

I can easily reproduce on Windows too. So yeah, the window size can be (0, 0), but in that case there are no draws.