Dmitry Pavlov wrote at 07/09/2014 04:50 AM:
I have to do a simple spreadsheet editor and I wonder
whether Racket suits my needs. The main challenge
is that the spreadsheet editor should be able to edit
tables as big as 1000x1000 or 10000x100 cells.
For a million cells like that, when using any language and toolkit that
I know of, I would probably implement it with a mix of manual drawing
and using the occasional toolkit widgets in only small numbers at a time
(only for actively editing of a single cell).
Fortunately, doing the drawing and mouse-click object picking for a grid
is very easy to do efficiently and scalably, and doing it with
scrollbars is only a little bit more arithmetic. (If it were 2D objects
of arbitrary shape, position, and layering, then that would be harder to
do scalably, and likely require fancy data structures to do fast, but
simple spreadsheet-like grids are easy.)
I would first try it with a full redraw of the visible part of the grid
at each repaint/expose event. If that flickered, I would add
double-buffering to the full redraw. If there was still something slow
(say, if your anti-aliased text drawing was unusually slow while
scrolling or when redrawing on-the-fly while typing the edited contents
of a cell), then I would look at delaying/coalescing updates, or
simplifying the intermediate updates before getting to an idle update
when the full detail is done. As an extreme last resort, I would look
at doing partial (damage region) redraws to a double-buffer and block
moves within the buffer for scrolling and window resizes, but this is
more complicated and a likely source of hard-to-QA bugs. I doubt that
you will need the extreme last resort, so it should be pretty
straightforward.
For editing the contents of cells in this manually-drawn grid, you can
put the GUI toolkit editing controls:
* permanently in the enclosing GUI toolkit window (beside the grid, not
over it),
* in a transient pop-up window of some kind, or
* transiently in-place over the grid (with pixel-exact position and
geometry).
I think that this simple approach of a manually-drawn grid and minimal
use of toolkit controls will be fast with even a million cells, without
much programming difficulty.
Neil V.
____________________
Racket Users list:
http://lists.racket-lang.org/users
