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 :^)
...and don't let them leak out of their evaluation contexts.
Also keep the exceptions separate from the actual values.
This greatly reduces the number of assertions hit while entering random
data into a sheet.
Hide private members, and make the odd update() -> sheet->update(cell)
-> update(Badge<Sheet>) -> update_data() less odd by removing the
update(Badge<Sheet>) step.
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
This commit adds a generic interface for cell types and hooks it up.
There is no way to set these from the UI, and so they're not saved
anywhere yet.
Also implicitly converts numeric values (strictly integers) to numeric
javascript values, as numbery-looking + numbery-looking === string is
not very interesting. :^)
This commit just moves some code around:
- Give Cell its own file
- Pull all forward-declared classes/structs into Forward.h
- Clean up the order of member functions a bit
