rqt can't export a perspective with an active rqt_image_overlay layer plugin

[Kettenhoax]

When trying to export an rqt perspective including a rqt_image_overlay instance with an active layer using the GUI, it fails with with a terminal-printed error.
The GUI doesn't show a warning or error.

Traceback (most recent call last):
  File "/opt/ros/humble/local/lib/python3.10/dist-packages/qt_gui/perspective_manager.py", line 188, in save_settings_completed
    callback(*callback_args)
  File "/opt/ros/humble/local/lib/python3.10/dist-packages/qt_gui/perspective_manager.py", line 399, in _on_export_perspective_continued
    self._convert_values(data, self._export_value)
  File "/opt/ros/humble/local/lib/python3.10/dist-packages/qt_gui/perspective_manager.py", line 423, in _convert_values
    self._convert_values(groups[group], convert_function)
  File "/opt/ros/humble/local/lib/python3.10/dist-packages/qt_gui/perspective_manager.py", line 423, in _convert_values
    self._convert_values(groups[group], convert_function)
  File "/opt/ros/humble/local/lib/python3.10/dist-packages/qt_gui/perspective_manager.py", line 423, in _convert_values
    self._convert_values(groups[group], convert_function)
  File "/opt/ros/humble/local/lib/python3.10/dist-packages/qt_gui/perspective_manager.py", line 420, in _convert_values
    keys[key] = convert_function(keys[key])
  File "/opt/ros/humble/local/lib/python3.10/dist-packages/qt_gui/perspective_manager.py", line 463, in _export_value
    reimported = self._import_value(data)
  File "/opt/ros/humble/local/lib/python3.10/dist-packages/qt_gui/perspective_manager.py", line 428, in _import_value
    return eval(value['repr'])
  File "<string>", line 1
    [{'Color': <PyQt5.QtGui.QColor object at 0x7f60b8b9e340>, 'Enabled': True, 'Plugin': 'overlay_test_plugins::EmptyLayer', 'Topic': '/data'}]
               ^
SyntaxError: invalid syntax

It seems the color associated with the layer can't be serialized.

[ijnek]

Thanks for the bug report @Kettenhoax ! I don't think I'll get around to looking into it this week, but I'm happy to review a PR with a unit test during the week if you do come up with a fix.

[Kettenhoax]

Looking into this, I found that rqt plugins in general can't store QColors in perspective files. Since QColors are valid QVariants in terms of qt_gui_cpp::Settings, rqt_image_overlay doesn't violate api constraints as far as I could find.

I've opened an issue at ros-visualization/qt_gui_core#271, but would like to keep this one open.
Based on the upstream response we can serialize QColors in a different format instead.

[ijnek]

Thanks for looking into it! And yes, please keep this issue open too.