Lazy scatterplot for Vector & Table

[JaroslavTulach]

Pull Request Description

First of all this PR demonstrates how to implement lazy visualization:

• one needs to write/enhance Enso visualization libraries - this PR adds two optional parameters (bounds and limit) to process_to_json_text function.
• the process_to_json_text can be tested by standard Enso test harness which this PR also does
• then one has to modify JavaScript on the IDE side to construct setPreprocessor expression using the optional parameters

The idea of scatter plot lazy visualization is to limit the amount of points the IDE requests. Initially the limit is set to limit=1024. The Scatter_Plot.enso then processes the data and selects/generates the limit subset. Right now it includes min, max in both x, y axis plus randomly chosen points up to the limit.

The D3 visualization widget is capable of zooming in. When that happens the JavaScript widget composes new expression with bounds set to the newly visible area. By calling setPreprocessor the engine recomputes the visualization data, filters out any data outside of the bounds and selects another limit points from the new data. The IDE visualization then updates itself to display these more detailed data. Users can zoom-in to see the smallest detail where the number of points gets bellow limit or they can select Fit all to see all the data without any bounds.

Important Notes

Randomly selecting limit samples from the dataset may be misleading. Probably implementing k-means clustering (where k=limit) would generate more representative approximation.

Checklist

Please include the following checklist in your PR:

• Implement the same algorithm for Table and Column
• The documentation has been updated if necessary.
• All code conforms to the
  Scala,
  Java,
  and
  Rust
  style guides.
• All code has been tested:
  • Unit tests have been written where possible.
  • If GUI codebase was changed: Enso GUI was tested when built using BOTH
    ./run ide build and ./run ide watch.

[farmaazon]

Reviewed the JS part only!

[jdunkerley]

Looks a reasonable approach - one concern is how to allow loading of more points after the first 32.

[JaroslavTulach]

CCing @4e6: Calling this.setPreprocessor repeatedly with different code snippet seems to work, but ideally we shall have a single snippet and just invoke it with different limit and bounds argument. I hope it will be possible to do something like that with hidden modules.

#3661 introduces this.setPreprocessor(module, method) - it shall also allow providing arguments somehow.

[jdunkerley]

One slight change - just want to think if an easier way to do the extremes.

[JaroslavTulach]

Thanks James for the 6473ad1 simplification of the computation of the sample.