[ui] Viewer2D: Add the pixel (x,y) values in the toolbar (editable)

[nicolas-lambert-tc]

Description

Add the ability to display and edit x, y value of the current rgba color displayed in the viewer2D.

Features list

• Add x and y text fields to viewer2D to display the pixel's coordinates
• x and y can be edited by user to select a specific pixel

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 76.84%. Comparing base (4f1e003) to head (663aeb8).
Report is 49 commits behind head on develop.

✅ All tests successful. No failed tests found.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #2723      +/-   ##
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+ Coverage    76.74%   76.84%   +0.10%     
===========================================
  Files           40       41       +1     
  Lines         6084     6132      +48     
===========================================
+ Hits          4669     4712      +43     
- Misses        1415     1420       +5     

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[cbentejac]

Everything works well as long as the mouse is hovering over the image.

If it is hovering in the 2D Viewer but outside of the image, the (x, y) coordinates display the last "recorded" position of the mouse on the image, but these displayed values do not correspond to the actual values of mousePosition and so the displayed RGB values are off as well. What seems to happen is that x and y are reset to 0 as soon as the mouse goes out of the image, the RGB values are updated to match the colors of pixel (0, 0), but the text fields for x and y still display the previous values. Modifying the values works, but for example, if I only modify x, y will still display the last recorded position while its value will actually still be 0.

Prior to this PR, the behaviour for RGB values was to display "--" when the mouse position was outside of the image. This can be discussed but I think we might want the same for the (x, y) coordinates: when hovering outside of the image, the values become "unset", and should the user choose to set them, only then would we display the corresponding RGB values.

[cbentejac]

There's a remaining "issue" when the mouse is hovering outside of the picture: RGB values are still displayed while (x, y) are empty:

Also, I think it'd be visually better if the (x, y) coordinates displayed "--" instead of nothing when the mouse isn't hovering over any pixel.

[nicolas-lambert-tc]

There's a remaining "issue" when the mouse is hovering outside of the picture: RGB values are still displayed while (x, y) are empty:

Also, I think it'd be visually better if the (x, y) coordinates displayed "--" instead of nothing when the mouse isn't hovering over any pixel.

I've added a placeholder to represent the '--' and expose it as a property to let the possibility to change it from outside.

[cbentejac]

Everything's working functionally, just a few minor changes and we'll be good to go!