Give extending classes access to some of the data grid's paint utilities.

[ghost]

Hi, my name is Logan McNichols. I am an intern for Jupyter Cal Poly. I am working on a tabular data editor powered by the DataGrid along with @kgoo124 and @ryuntalan.

We are working on a design that involves painting LabIcons onto the DataGrid's canvas to correspond the the type of field in a given column. To achieve this, we would like to provide getters for some of the DataGrid's properties and change some private methods to protected.

This PR would change the access modifier from private to protected on the following methods.

• paintContent
repaintContent
  & repaintOverlay

It would also add getters for the following properties.

• _canvasGC
• _rowSections
• _columnSections
• _columnHeaderSections
• _rowHeaderSections.

Fixes #110

[blink1073]

Thanks for pushing the boundaries on the grid! Just a couple of comments

[nmichaud]

I'm not sure this is necessary - it's possible to leverage a combination of metadata and renderers to draw images/icons onto the grid. What are you trying to do in a subclass?

[kgoo124]

@nmichaud We are creating a ghost row/column for the data grid to add new rows/columns. Here is a prototype of what we created.

[nmichaud]

@kgoo124 ah ok, that looks interesting! Definitely not possible with the current grid code. It looks like you want to draw on the canvas outside of the grid region.

[kgoo124]

@nmichaud yes that's right. Since the ghost rows/columns serve as UI to add a new row/column, we want to be able to paint an extra row/column on the grid without having the manage the data model underneath it

[blink1073]

Thanks!