Scatterplotgraph: Implement manual repositioning of points

[janezd]

Description of changes

• Implement moving of points (a single point or selection) by dragging them.

  The functionality is enabled if the widget (not graph!) implements a method set_coordinates.

• Implement this in MDS.

• Also, implement saving of coordinate hints in MDS.

I don't know how to write reasonable tests for this. Test on biolab/orange3-network#293.

Includes

• Code changes
• Tests
• Documentation

[Copilot]

Pull request overview

Adds support for manually repositioning points in scatterplot-based visualizations by dragging (single point or current selection), gated by the widget providing a set_coordinates hook.

Changes:

• Extend InteractiveViewBox.mouseDragEvent to detect draggable points and apply a drag delta during mouse drags.
• Add get_dragged_points / move_dragged_points to OWScatterPlotBase to support dragging a point or the full current selection.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
Orange/widgets/visualize/utils/plotutils.py	Adds drag-handling branch to InteractiveViewBox.mouseDragEvent to initiate/track point dragging.
Orange/widgets/visualize/owscatterplotgraph.py	Implements scatterplot-specific point hit-testing and coordinate updates via set_coordinates.

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[codecov]

Codecov Report

❌ Patch coverage is 44.56522% with 51 lines in your changes missing coverage. Please review.
✅ Project coverage is 88.98%. Comparing base (99bb865) to head (a0ee8b2).

❌ Your patch check has failed because the patch coverage (44.56%) is below the target coverage (95.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #7286      +/-   ##
==========================================
- Coverage   89.02%   88.98%   -0.05%     
==========================================
  Files         336      336              
  Lines       74427    74513      +86     
==========================================
+ Hits        66257    66302      +45     
- Misses       8170     8211      +41     

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[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 5 comments.

[VesnaT]

On point(s) move the output should be updated.

[janezd]

On point(s) move the output should be updated.

I admire your ability to catch such things.

My first fix was to call commit on all drag events, which looked nice in a trivial workflow -- I dragged a point in the MDS and it instantly updated in the scatter plot. In reality, it could cause too many updates and redraws; now the new coordinates are committed when dragging is finished.