[WIP] TabularEditor triggering column size recompute

[aaronayres35]

closes #1434

This PR adds a new update_column_widths Event trait to the qt4 TabularEditor, along with a listener that will call self.control.resizeColumnsToContents whenever this event is fired. EDIT: I've changed the approach.

Code I am using to manually test this:

from numpy import sqrt
from numpy.random import random

from traits.api import HasTraits, Property, Array, Any, Instance, Str
from traitsui.api import View, Item, TabularAdapter, TabularEditor, ModelView, TextEditor
from traitsui.testing.api import UITester


# -- Tabular Adapter Definition -------------------------------------------
class ArrayAdapter(TabularAdapter):

    columns = [('i', 'index'), ('x', 0), ('y', 1), ('z', 2)]

    font = 'Courier 10'
    alignment = 'right'
    format = '%.4f'  # Str('%.4f', update=True)

    index_text = Property()
    index_image = Property()

    def _get_index_text(self):
        return str(self.row)

    def _get_index_image(self):
        x, y, z = self.item
        if sqrt((x - 0.5) ** 2 + (y - 0.5) ** 2 + (z - 0.5) ** 2) <= 0.25:
            return '@icons:red_ball'

        return None



class ShowArray(ModelView):

    data = Array

    form = Str('%.4f')

    def object_form_changed(self, info):
        info.data.adapter.format = self.form
        info.data.update = True
        # with the first approach I was using the following line instead.
        # info.data.update_column_widths = True 

    traits_view = View(
        Item(
            'form',
            editor=TextEditor(auto_set=False)
        ),
        Item(
            'data',
            show_label=False,
            editor=TabularEditor(
                adapter=ArrayAdapter(),
                auto_resize=True,
                # Do not allow any kind of editing of the array:
                editable=False,
                operations=[],
                drag_move=False
            )
        ),
        title='Array Viewer',
        width=0.3,
        height=0.8,
        resizable=True
    )


# Create the demo:
demo = ShowArray(model=HasTraits(), data=random((2, 3)))

# Run the demo (if invoked from the command line):
if __name__ == '__main__':
    demo.configure_traits()

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[aaronayres35]

Actually thinking about this more I do not like this approach... In my example code, one could replace the line info.data.update_column_widths = True with info.data.control.resizeColumnsToContents() and then the new Event trait is useless.

Any time a user is trying to fire the update Event Trait, they must have access to the editor. I am unsure why they couldn't just manually call editor.control.resizeColumnsToContents() then at their own leisure.

Additionally, there exists an auto_resize trait that seems like it should be dictating this sort of behavior.

EDIT: I've updated the PR to now check auto_resize whenever update is fired and use that to determine whether or not to call resizeColumnsToContents()

[aaronayres35]

@rahulporuri This PR isn't really ready for review if it is ready to merge, but I've opened it to get your ideas on some different approaches / so we can further discuss what makes sense