selection_tools VispyMouseMode incompatible with custom BaseCartesianData classes

[mmorys]

Describe the bug
The currently documented means for creating a custom Glue data class involves inheriting from BaseCartesianData. A custom data class inheriting from BaseCartesianData will not be of type Data.

In order to utilize selection tools with a 3D scatter plot, the data must pass two type-checks to verify it is of type Data, making selection incompatible with custom data types.

glue-vispy-viewers/glue_vispy_viewers/common/selection_tools.py

Line 40 in 53ff179

if isinstance(layer_artist.layer, Data):

glue-vispy-viewers/glue_vispy_viewers/common/selection_tools.py

Line 47 in 53ff179

if isinstance(layer_artist.layer, Data):

Expected behavior
I would expect full compatibility of 3D Scatter plots with custom data classes.

Simple Fix
I am able to make the selection tool work properly in my local installation of glue-vispy-viewers with a simple change of these lines (and of course importing BaseCartesianData from glue.core) to:

if isinstance(layer_artist.layer, BaseCartesianData): 

I don't know what side effects this may have, but I could submit a pull request with this fix.

Details:

• Operating System: Windows 10 64bit
• Python version: 3.8.6
• Glue version: 1.0.1
• How you installed glue: conda
• Glue-vispy-viewers version: 1.0.2