Silent crash in VSCode arising from _cmap_utils.draw_colormap

[gselzer]

Describe the bug
All of a sudden this morning QColormapComboBox is crashing on me. It's silent if I just run e.g. examples/colormap_combo_box.py, but it's much uglier downstream e.g. in ndv. I have no idea what caused this to begin.

Using the hard crash I pasted below, I found that adding painter.end() to the end of _cmap_utils.draw_colormap resolved my issue. I'm a bit confused on why this is necessary though, as the docs say that this method doesn't normally need to be called?

To Reproduce
Steps to reproduce the behavior:

1. debug examples/colormap_combo_box.py within VSCode.
2. observe crash

Expected behavior
You know...not crashing.

Screenshots
Soft crash coming out of examples/colormap_combo_box.py:

Hard crash coming out of ndv:

WARNING: QBackingStore::endPaint() called with active painter; did you forget to destroy it or call QPainter::end() on it?
WARNING:vispy:QBackingStore::endPaint() called with active painter; did you forget to destroy it or call QPainter::end() on it?
Windows fatal exception: access violation

Thread 0x00004b90 (most recent call first):
  File "c:\Users\gjselzer\micromamba\envs\ndv\Lib\threading.py", line 338 in wait
  File "c:\Users\gjselzer\micromamba\envs\ndv\Lib\threading.py", line 634 in wait
  File "c:\Users\gjselzer\.vscode\extensions\ms-python.debugpy-2024.14.0-win32-x64\bundled\libs\debugpy\_vendored\pydevd\pydevd.py", line 325 in _on_run
  File "c:\Users\gjselzer\.vscode\extensions\ms-python.debugpy-2024.14.0-win32-x64\bundled\libs\debugpy\_vendored\pydevd\_pydevd_bundle\pydevd_daemon_thread.py", line 53 in run
  File "c:\Users\gjselzer\micromamba\envs\ndv\Lib\threading.py", line 1052 in _bootstrap_inner
  File "c:\Users\gjselzer\micromamba\envs\ndv\Lib\threading.py", line 1009 in _bootstrap

Thread 0x00005b90 (most recent call first):
  File "c:\Users\gjselzer\micromamba\envs\ndv\Lib\threading.py", line 338 in wait
  File "c:\Users\gjselzer\micromamba\envs\ndv\Lib\threading.py", line 634 in wait
  File "c:\Users\gjselzer\.vscode\extensions\ms-python.debugpy-2024.14.0-win32-x64\bundled\libs\debugpy\_vendored\pydevd\pydevd.py", line 279 in _on_run
  File "c:\Users\gjselzer\.vscode\extensions\ms-python.debugpy-2024.14.0-win32-x64\bundled\libs\debugpy\_vendored\pydevd\_pydevd_bundle\pydevd_daemon_thread.py", line 53 in run
  File "c:\Users\gjselzer\micromamba\envs\ndv\Lib\threading.py", line 1052 in _bootstrap_inner
  File "c:\Users\gjselzer\micromamba\envs\ndv\Lib\threading.py", line 1009 in _bootstrap

Thread 0x00003038 (most recent call first):
  File "c:\Users\gjselzer\.vscode\extensions\ms-python.debugpy-2024.14.0-win32-x64\bundled\libs\debugpy\_vendored\pydevd\_pydevd_bundle\pydevd_comm.py", line 227 in _read_line
  File "c:\Users\gjselzer\.vscode\extensions\ms-python.debugpy-2024.14.0-win32-x64\bundled\libs\debugpy\_vendored\pydevd\_pydevd_bundle\pydevd_comm.py", line 245 in _on_run
  File "c:\Users\gjselzer\.vscode\extensions\ms-python.debugpy-2024.14.0-win32-x64\bundled\libs\debugpy\_vendored\pydevd\_pydevd_bundle\pydevd_daemon_thread.py", line 53 in run
  File "c:\Users\gjselzer\micromamba\envs\ndv\Lib\threading.py", line 1052 in _bootstrap_inner
  File "c:\Users\gjselzer\micromamba\envs\ndv\Lib\threading.py", line 1009 in _bootstrap

Thread 0x000070ac (most recent call first):
  File "c:\Users\gjselzer\micromamba\envs\ndv\Lib\threading.py", line 338 in wait
  File "c:\Users\gjselzer\micromamba\envs\ndv\Lib\queue.py", line 180 in get
  File "c:\Users\gjselzer\.vscode\extensions\ms-python.debugpy-2024.14.0-win32-x64\bundled\libs\debugpy\_vendored\pydevd\_pydevd_bundle\pydevd_comm.py", line 390 in _on_run
  File "c:\Users\gjselzer\.vscode\extensions\ms-python.debugpy-2024.14.0-win32-x64\bundled\libs\debugpy\_vendored\pydevd\_pydevd_bundle\pydevd_daemon_thread.py", line 53 in run
  File "c:\Users\gjselzer\micromamba\envs\ndv\Lib\threading.py", line 1052 in _bootstrap_inner
  File "c:\Users\gjselzer\micromamba\envs\ndv\Lib\threading.py", line 1009 in _bootstrap

Current thread 0x00004ed8 (most recent call first):
  File "c:\Users\gjselzer\micromamba\envs\ndv\Lib\site-packages\superqt\cmap\_cmap_utils.py", line 121 in draw_colormap
  File "c:\Users\gjselzer\micromamba\envs\ndv\Lib\site-packages\superqt\cmap\_cmap_line_edit.py", line 130 in paintEvent
  File "C:\Users\gjselzer\code\pyapp-kit\ndv\src\ndv\views\_app.py", line 189 in run_app
  File "C:\Users\gjselzer\code\pyapp-kit\ndv/mvc.py", line 27 in <module>
  File "c:\Users\gjselzer\.vscode\extensions\ms-python.debugpy-2024.14.0-win32-x64\bundled\libs\debugpy\_vendored\pydevd\_pydevd_bundle\pydevd_runpy.py", line 118 in _run_code
  File "c:\Users\gjselzer\.vscode\extensions\ms-python.debugpy-2024.14.0-win32-x64\bundled\libs\debugpy\_vendored\pydevd\_pydevd_bundle\pydevd_runpy.py", line 127 in _run_module_code
  File "c:\Users\gjselzer\.vscode\extensions\ms-python.debugpy-2024.14.0-win32-x64\bundled\libs\debugpy\_vendored\pydevd\_pydevd_bundle\pydevd_runpy.py", line 310 in run_path
  File "c:\Users\gjselzer\.vscode\extensions\ms-python.debugpy-2024.14.0-win32-x64\bundled\libs\debugpy\adapter/../..\debugpy\launcher/../..\debugpy/..\debugpy\server\cli.py", line 351 in run_file
  File "c:\Users\gjselzer\.vscode\extensions\ms-python.debugpy-2024.14.0-win32-x64\bundled\libs\debugpy\adapter/../..\debugpy\launcher/../..\debugpy/..\debugpy\server\cli.py", line 501 in main
  File "c:\Users\gjselzer\.vscode\extensions\ms-python.debugpy-2024.14.0-win32-x64\bundled\libs\debugpy\adapter/../..\debugpy\launcher/../..\debugpy\__main__.py", line 71 in <module>
  File "c:\Users\gjselzer\micromamba\envs\ndv\Lib\runpy.py", line 88 in _run_code
  File "c:\Users\gjselzer\micromamba\envs\ndv\Lib\runpy.py", line 198 in _run_module_as_main

Desktop (please complete the following information):

• OS with version [e.g macOS 10.15.7] Windows 11 Pro 10.0.22631
• Qt Backend [e.g PyQt5, PySide2] PyQt5
• Python version 3.12.0

[tlambert03]

btw: was just able to reproduce this on the current superqt release ... but wanted to note that it requires that debugpy be running. which is an interesting detail :)