Respect background color when calculating scale bar color

[Czaki]

Description

Currently color of the scale bar is calculated base on the canvas color assigned in the theme. But since #2270 is possible to overwrite background color. In this PR I add support to respect this option (used for example, in PartSeg).

Type of change

• Bug-fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

References

How has this been tested?

• example: the test suite for my feature covers cases x, y, and z
• example: all tests pass with my change
• example: I check if my changes works with both PySide and PyQt backends
  as there are small differences between the two Qt bindings.

Final checklist:

• My PR is the minimum possible work for the desired functionality
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• If I included new strings, I have used trans. to make them localizable.
  For more information see our translations guide.

[codecov]

Codecov Report

Merging #5270 (9514f5a) into main (d5ffbac) will increase coverage by 0.27%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #5270      +/-   ##
==========================================
+ Coverage   88.76%   89.03%   +0.27%     
==========================================
  Files         579      578       -1     
  Lines       49093    48946     -147     
==========================================
+ Hits        43576    43579       +3     
+ Misses       5517     5367     -150     

Impacted Files	Coverage Δ
...apari/_vispy/_tests/test_vispy_scale_bar_visual.py	100.00% <100.00%> (ø)
napari/_vispy/overlays/scale_bar.py	97.50% <100.00%> (+0.06%)	⬆️
napari/utils/_tests/test_key_bindings.py	96.96% <0.00%> (-0.21%)	⬇️
napari/utils/shortcuts.py	100.00% <0.00%> (ø)
napari/_qt/menus/__init__.py	100.00% <0.00%> (ø)
napari/utils/_tests/test_interactions.py	100.00% <0.00%> (ø)
napari/layers/points/_points_key_bindings.py	100.00% <0.00%> (ø)
...ri/_qt/_qapp_model/_tests/test_qapp_model_menus.py	100.00% <0.00%> (ø)
napari/utils/colormaps/vendored/colorconv.py
napari/_qt/menus/help_menu.py
... and 22 more

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[andy-sweet]

Thanks for the fix. Not ideal, but I think it's good enough to merge, so I'll do so after 24 hours unless anyone objects.

One optional suggestion is to add a test to cover the original bug. There were some existing issues with the design/implementation here, so I might consider changing some things in the future, but wouldn't want to break this again.

Here's my best attempt at writing a test, which unfortunately needs make_napari_viewer.

def test_box_color_with_background_color_override(make_napari_viewer):
    viewer = make_napari_viewer()
    qt_viewer = viewer.window._qt_viewer

    qt_viewer.canvas.background_color_override = [1, 0, 0]

    np.testing.assert_equal(qt_viewer.scale_bar.node.text.color.rgb, [[0, 1, 1]])

[andy-sweet]

Not great that we have to use private state here (or more generally that the scale bar has access to the whole of the viewer), but I can't think of anything better right now.

[Czaki]

I have fixed this by use the parent of node and allowing to use of this fix with ViewerModel not only Viewer.