Thanks for the response, DeAnna. Getting the scrollbar drawn initially
isn't the problem - I do pretty much what you describe.
The problem is that "the proper values" for the scrollbar's "max value" and
"page size" variables are always approximate. I don't know in advance of
rendering the entire page how many lines there are in it. Due to the
effects of word-wrapping (and soon font and style changes), the number of
characters on each line is variable.
I just found a semi-acceptable solution, though. I set the approximate
values at form init time, then I never update the scrollbars unless the "cur
value" and "max value" are the same but there is more text to see offscreen,
at which time I update the scrollbar with a re-approximated value for "max
value".
This eliminates the "haywire" behavior I saw before, and allows scrolling
all the way to the end. The drawback is that the scrollbar's "car" is never
very accurate, particularly at the moment when I update the scrollbar. At
that moment, the car is at the end, and then jumps back a bit when I
re-approximate the "max value".
I think I'll try continuously re-approximating the "max value" next.
Mark Peters
in article 51946@palm-dev-forum, DeAnna Davidson at [EMAIL PROTECTED] wrote
on 6/6/01 11:02 AM:
>
> Hi Mark,
>
> I usually draw the first page, render an approximated scrollbar until
> after the page is drawn, and then update the scrollbars with the proper
> values after the document is drawn. A bit hackish, but you don't have a
> blank screen and your bar is visible.
>
> DeAnna
>
> -----Original Message-----
> From: Mark A. Peters [mailto:[EMAIL PROTECTED]]
> Sent: Wednesday, June 06, 2001 2:02 PM
> To: Palm Developer Forum
> Subject: Scrollbars when line count unknown?
>
>
> Can anybody give me some advice on how to handle scrollbar updating when
> the
> exact size (in whatever units) of the thing being scrolled is not known,
> or
> too expensive to compute, and hence only approximations can be made?
>
> [...]
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