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?
In my case, I need to scroll formatted text similar to that displayed by a
web browser, where the exact number of lines depends upon the fonts, styles,
word-wrapping, etc. that are used within the document. Computing the exact
size of the thing is too expensive, since it requires rendering the entire
document before displaying the first page.
I've tried using approximations, but the methods I've tried cause the
scrollbars to go haywire, generating a large number of scroll repeat events
all out of proportion to the scrolling actually done by the user. I suspect
this is because the system's calculation of the scroll values (from the
distance the scroll bar has been dragged, I think) never matches reality,
and changing it to match reality confuses it.
I always know the character position of the displayed lines within the raw,
unformatted text, but that's it. I've tried setting the max value of the
scrollbar to the length of the unformatted text minus about a page worth of
text, and then always setting the current value to the index of the first
character in the top displayed line. This causes the "haywire" behavior
described above.
By the way, I'm simply drawing the text to a form with no UI elements
(except the scrollbar) on it, i.e., I'm not using a field object. Also, the
bad behavior only happens when I try to drag the scrollbar's car - it
behaves fine if I tap the scroll arrows.
Ideas?
Thanks,
Mark Peters
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