box_select for line glyphs

This issue is to open discussion of implementing box_select for line glyphs. My proposal is to follow the example of box_select for patches and multi_polygons (see also #2325), which does two things: 1) adds a _hit_rect to the glyph that selects glyphs that are completely contained by the box_select; and 2) adds a note about the box_select behavior to the glyph documentation.

I have found that copying _hit_rect from box.ts is a simple solution and adequate for this selection behavior:

  protected _hit_rect(geometry: RectGeometry): Selection {
    return this._hit_rect_against_index(geometry)
  }

While it could be desirable to allow for partial overlap selections, this is a good place to start since it follows the pattern already established by the box, patches, and multi_polygons glyphs.

If this proposal is received favorably I can prepare a PR with the changes.

[4l1fe]

As a temporary workaround while it’s not yet implemented i do as follow:

from bokeh.plotting import figure, show
from bokeh.models.tools import BoxSelectTool
from bokeh.models.widgets import DataTable, TableColumn
from bokeh.models.sources import ColumnDataSource
from bokeh.layouts import row


source = ColumnDataSource({'x': [1, 2, 3, 4, 5], 'y': [6, 7, 2, 4, 5]})

p = figure(width=400, height=400)

p.line(source=source, line_width=2, color='blue')
dot = p.dot(source=source, color='blue', name='points')

p.add_tools(BoxSelectTool(dimensions='width', renderers=[dot]))

columns = [
    TableColumn(field='x'),
    TableColumn(field='y'),
]
table = DataTable(source=source, columns=columns)

show(row(p,table))

Loos like a line only:

Selected by BoxSelectTool:

The idea as you see to add the dot glyphs with the same line color and select only their renderer.

I left it here as the issue is easily found in google search and it might be helpful for those who work with the line plot and similar plot type selection.

[rsprouse]

Perhaps you are right that partial overlap is a better general solution for lines. For my use case (selecting time ranges of audio waveforms) the distinction is not very important since the time scale of a typical plot does not allow the viewer to select between individual samples anyway, and either behavior could be acceptable.

In informal testing the box.ts _hit_rect did not select partial overlaps, but I will check again.