Re: Emacs GTK scroll-bar flickering

[Miles Bader <miles@lsi.nec.co.jp>]

storm@cua.dk (Kim F. Storm) writes:
> Maybe the size of the thumb changes more often with emacs.  IIRC,
> emacs calculates the thumb size based on the #(characters in the
> window) / #(characters in the file) ratio, so just dragging the
> cursor may change the size of the thumb.
> 
> If GTK repaints the entire scroll bar when the thumb size changes,
> maybe that could explain the flicker.

I don't think that's it, or at least not entirely it, for several
reasons:

 (1) If I create a file containing a large number of identical lines,
     then scrolling in emacs shouldn't change the thumb size, as long as
     I don't get near the end of the file.  Nevertheless, dragging the
     scrollbar in emacs flickers noticeably.  My test file, BTW is 68
     lines of the following:

        alskdfjlaskdjfalskdjfalskfjlaskdfjalskfjdaskldfj

 (2) Gedit's scrollbar doesn't flicker _at all_ when the thumb-size
     changes.  I tested this by taking the above file, copying a bunch
     of lines from it, and then pasting into the end of the gedit
     buffer, while carefully watching the scrollbar end-buttons (which
     are one of the most obvious `flicker points' in emacs); the result
     was that the thumb shrank quite bit with a few pastes, but the
     scrollbar update was rock-stable, no flicker at all.

     It could be, of course, that gedit has some sort of additional
     graphic optimization to prevent flicker since it uses GTK for all
     its display.

-Miles
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