bug#12927: 24.2; global-hl-line-mode and "scroll-conservatively=1000" take jump up-down the text when hold DOWN key (in *info* buffer).

[Oleksandr Gavenko]

On 2012-11-20, Eli Zaretskii wrote:

>> Date: Mon, 19 Nov 2012 18:43:40 +0200
>> From: Eli Zaretskii <eliz@gnu.org>
>> Cc: 12927@debbugs.gnu.org
>> 
>> > From: Oleksandr Gavenko <gavenkoa@gmail.com>
>> > Date: Sun, 18 Nov 2012 23:13:22 +0200
>> > 
>> >   (setq scroll-conservatively 1000)
>> >   (global-hl-line-mode 1)
>> > 
>> > and "C-h i". I press and hold DOWN key. After some time cursor reach end of
>> > frame and then text scroll up but sometimes it seems as text jump down! 
>> > And I
>> > get fill that text moving have jerks.
>> 
>> This is some bad interaction between scroll-conservatively and
>> window-vscroll, it somehow succeeds to activate code paths that I
>> never before saw in action.
>> 
>> As a temporary work-around, set auto-window-vscroll to nil.  I will
>> try to find a better solution when I have time.
>
> Should be fixed in revision 110927 on the emacs-24 branch.  Please
> test.

I don't familiar with bzr:

  $ bzr up
  $ bzr info -v
  Repository checkout (format: 2a)
  Location:
    repository checkout root: .
          checkout of branch: bzr://bzr.savannah.gnu.org/emacs/trunk/
           shared repository: /home/user/devel/emacs/emacs-bzr

  Related branches:
    parent branch: bzr://bzr.savannah.gnu.org/emacs/trunk/
    submit branch: bzr://bzr.savannah.gnu.org/emacs/trunk/

  In the working tree:
        3541 unchanged
           0 modified
           0 added
           0 removed
           0 renamed
           2 unknown
        1514 ignored
         128 versioned subdirectories

  Branch history:
      110963 revisions
       10078 days old
     first revision: Thu 1985-04-18 00:48:29 +0000
    latest revision: Tue 2012-11-20 14:05:20 -0500

  Repository:
      123726 revisions

If that OK I perform clean build and test this build.

As previously:

  $ _dist/bin/emacs-24.3.50 -Q

  (setq scroll-conservatively 1000)
  (global-hl-line-mode 1)

"C-h i", then hold DOWN key - visually text scrolls up and some times jerks
down/up.

When I look to what happen with text I found some interesting thing which is
based on space between text boundary and window top/bottom (so info menu or
mode line hide of part text).

When (global-hl-line-mode -1) - text aligned to top of window. With "+1" text
some times make align to bottom of window so scroll down on less then half of
font weight pixels (and this happen when we move down and text must scroll
up!!).

So it needn't to hold DOWN, just  (setq scroll-conservatively 1000) and move
point to end of dir info buffer and press several times DOWN.

Sorry for my bad English. I expect you mostly understand that I try to say))

================================================================

Also I found that "(global-hl-line-mode 1)" slow down scrolling in CC-mode
enabled buffers in two or more times. Do I need report a bug?

-- 
Best regards!