vertical scrollbar error on MS Windows

[Peter Tury]

Hi,

I found that the vertical scrollbar doesn't work correctly in latest
EmacsW32 unpatched (see further version info below) when dragged by
the mouse.

1. start with emacs -Q
2. make your frame small enough for your test file (= make scrolling
possible): if you use the attached test file, then e.g. a 12 lines
tall frame will be OK.
3. visit the test file and take point to its end
4. drag the vertical scrollbar (slide? -- I don't know its English
name: what is dragged and moved inside the scrollbar) and move it up
slowly: after a while you will see line 38... then it goes out from
viewable area...
5. keep moving the scrollbar upwards... after a while line 38 appears
again -- as the first line of the viewable area!?

Similar things happens if you scroll downwards.

This behaviour is extremly embarrassing when you want to use scrolling
for what it is invented: go up/down quickly while seeing the floating
content. In Emacs the content doesn't float, but flicking (I think the
reason is the above detailed bug), what is very confusing and makes
scrolling a nightmare (this might be a bit strong expression :-))

Another interesting thing is the following: if you release the
scrollbar after 4., but before 5., then it "skips up" a bit, so it
doesn't remain under the mouse cursor... now, if you click with the
mouse (so the slide(?) will go (back) to the mouse cursor), the line
38's place will be the ~middle of the window...

As far as I remember scrolling was always problematic (in the same
way?) in W32 Emacses, so this is not a new bug?

I hope you can regenerate the situation easily and fix this bug.

Thanks in advance,
P



In GNU Emacs 22.0.93.1 (i386-mingw-nt5.1.2600)
of 2007-02-11 on LENNART-69DE564
X server distributor `Microsoft Corp.', version 5.1.2600
configured using `configure --with-gcc (3.4) --cflags -Ic:/g/include'

Important settings:
 value of $LC_ALL: nil
 value of $LC_COLLATE: nil
 value of $LC_CTYPE: nil
 value of $LC_MESSAGES: nil
 value of $LC_MONETARY: nil
 value of $LC_NUMERIC: nil
 value of $LC_TIME: nil
 value of $LANG: HUN
 locale-coding-system: cp1250
 default-enable-multibyte-characters: t

scrollt.txt
Description: Text document