On 22 May 2004, Sven Neumann wrote:

> So this API would allow you to queue a redraw even after the buffer is
> only halfway written. Of course you would also have to run the main
> loop for the redraw to actually happen. Anyway, I consider this rather
> bad style. IMO, if the preview takes considerable time, then it
> shouldn't be shown halfway done but instead the progress API should be
> used to draw a progress indicator in place of the preview. What do
> others think?

There are a lot of image applications that perodically update the
preview.  In fact, this is essentially what the gimp color balance tools
do -- load a large image and adjust the sliders intermittantly and you can
watch the previews go by.  There are good arguments for incremental
update, and good arguments for a progressbar.  Superimposing a busy cursor
over the preview or replacing it with a progress indicator makes judging
between slight differences in the settings harder.

But I think the real issue here is that slow previews should be computed
in small chunks in an idle handler so as to not impede interactivity.


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