There's no need to leave the cell dirty when not updating it, and
there's definitely no need to update the cells as we're selecting them.
This makes navigating a sheet and selecting cells significantly faster
as we no longer update unrelated cells just because they appear to have
a cyclic update dependency :^)
Let's make SelectionBehavior a view concept where views can either
select individual items (row, index) or whole rows. Maybe some day
we'll do whole columns, but I don't think we need that now.
Make drag-selection the default behaviour, allowing (almost) any part of
the cell to initiate a select.
a small 5x5 rect at the corners of a cell can be used to initiate a
drag-copy instead.
Fixes#4268.
To initiate drag-to-select, the user can move the mouse to near the edge
of a cell, and click-and-drag when the cursor changes to a crosshair.
Fixes#4167.
Every time the scrollbar reaches the end, we append 100 more rows
(seamlessly!).
As a result of defaulting to 100 rows, we can also save with the
smallest number of rows required.
This partially deals with #4170.
Currently only supports setting the foregound and the background colours.
This patch also unifies `foreground_color' and `background_color' used
throughout to a `Format' struct, in hopes of getting more formatting
options one day :P
Until we have better control over cell content alignment, let's make
them all right-aligned by default since that makes numbers look nice,
and numbers are the bread & butter of spreadsheets. :^)
Customize the cell editing delegate to stop editing when one of the
various cursor movement keys is hit. This allows you to type into a
cell and then move to an adjacent cell by simply pressing an arrow.
This may not be the best factoring for this feature, but it's pretty
dang cool and we'll see how it evolves over time. :^)
Now that the table view has a cursor, we can distinguish it from the
selected cells. Draw the cells with a nice variant of the selection
color as background.