Incorrect images in docs widget examples

[gselzer]

Looks like the wrong image is generated for at least the StageWidget and the ImagePreview docs pages...

[tlambert03]

thanks... yeah, there can be a race condition that sometimes prevents the right top level widget being grabbed (i.e. it may grab one from a previous run).

there is code in this branch that always picks the right one by using a subprocess for every widget. Slower, but always right:

pymmcore-widgets/docs/_hooks.py

Lines 140 to 176 in 7c53430

	# sub=True is slower... but sub=False is still prone to picking the wrong
	# top widget to show...
	def snapshot(filename: str, sub: bool = True) -> str:
	"""Run filename in a subprocess and snapshot top level widget.
	replace calls to `app.exec()` with a function that calls processEvents() and then
	grabs the top level widget, saving it to filename.
	"""
	fpath = Path(filename)
	# create a temporary file to save the screenshot
	dest = mkstemp(prefix=fpath.stem, suffix=".png")[1]
	atexit.register(os.remove, dest)
	# replace the app.exec() call with a function that saves the screenshot
	new_exec = SNAP.format(repr(dest))
	src = fpath.read_text().strip()
	src = src.replace("app.exec_()", new_exec).replace("app.exec()", new_exec)
	src = src.replace("QApplication([])", "QApplication.instance() or QApplication([])")
	if sub:
	subprocess.run(["python", "-c", src], check=True)
	else:
	exec(src, {"__name__": "__main__", "__file__": str(fpath)})
	from pymmcore_plus.core import _mmcore_plus
	del _mmcore_plus._instance
	_mmcore_plus._instance = None
	if app := QApplication.instance():
	app.processEvents()
	for w in QApplication.topLevelWidgets():
	w.close()
	w.deleteLater()
	app.processEvents()
	app.processEvents()
	return dest

we could use that in main

[gselzer]

Slower, but always right

Gotcha...like how much slower? It'd be great if we could guarantee correctness, at least for pushes to main?

[tlambert03]

not so slow we shouldn't use it on main as I implied above :)