Fix copy/paste of points

[andy-sweet]

Fixes/Closes

Closes #5786

Description

The issue here is actually caused by copying constant color values used for text, which causes issues because a single value has ndim > 0. This PR fixes the issue by specifying the dimensionality of a single color value when copying values.

It might be worth reconsidering the implementation here and/or whether constant encodings are worth handling as a specific optimized case like this. But I think it's worth getting this PR in before a longer consideration.

Type of change

• Bug-fix (non-breaking change which fixes an issue)

How has this been tested?

• modified an existing test to reproduce the bug, then fixed it
• all other tests pass with my change
• manually tested this by copying and pasting lots of points

[brisvag]

I'm a bit confused, can you explain the change to test?

[andy-sweet]

I'm a bit confused, can you explain the change to test?

Sorry, the implementation comment in the test is not clear. Does the following help?

    # Use an index of 4 to ensure that constant color values, which are
    # RGBA 4-vectors, are handled correctly when copied, unlike in bug:
    # https://github.com/napari/napari/issues/5786

By trying to copy at an index of 4, we reproduce the bug in #5786, which is caused by the combination of two things.

1. Style encodings share the same code to handle scalar style values (e.g. strings) and non-scalar ones (e.g. RGBA colors).
2. There is some special casing to handle constant encodings, so we avoid storing/manipulating an array of values.

In the long term, I wonder if (2) is really worth it, since that is the major cause here and I think vispy will end up storing an array of RGBA color values anyway.

[brisvag]

ok, makes sense; yeah vispy ends up with rgba, so it's definitely fine to not special-case, but no need to do it here :P

[andy-sweet]

@brisvag: since you've already taken a look and this is small, do you mind reviewing? I updated the explanatory comment in the test as above.

[codecov]

Codecov Report

Merging #5795 (be07737) into main (d91f4ee) will increase coverage by 0.08%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #5795      +/-   ##
==========================================
+ Coverage   89.79%   89.87%   +0.08%     
==========================================
  Files         614      614              
  Lines       52196    52196              
==========================================
+ Hits        46870    46913      +43     
+ Misses       5326     5283      -43     

Impacted Files	Coverage Δ
napari/layers/utils/text_manager.py	94.69% <ø> (ø)
napari/layers/utils/_tests/test_text_manager.py	100.00% <100.00%> (ø)

... and 13 files with indirect coverage changes