Re: Scrollbar thumbs

[Stefan Monnier <monnier@iro.umontreal.ca>]

> Since 23.1, Emacs on w32 allows the scroll thumb to shrink while being
> dragged at the bottom of the buffer.  Previous versions fixed the size of
> the thumb while dragging, which I think is the brain damage which GTK forces
> on you that Miles is refering to, as you are unable to reach the bottom of
> the buffer by dragging the scrollbar in some circumstances because of
> assumptions Emacs makes to relate characters to pages of scrolling without
> wasting time doing a full calculation over the buffer.

Not sure how it works on w32, but yes on Gtk IIRC the thumb can't be
resized during dragging.  In Xaw3d the problem was halfway: the code
was/is able to resize the thumb during a drag, but the thumb may hit the
bottom too soon, in case we haven't resized it quickly enough.

My favorite solution to those problem nowadays is to set the thumb-size
to its minimum (typically 0, which results in a small but no invisible
thumb) during dragging: makes for smooth scrolling (without the need to
resize the thumb during scrolling) while still allowing the thumb size
to correctly reflect the begin&end of the viewed area when
not scrolling.


        Stefan