bug#23510: Strange redisplay in global highlighted mode moving the scroll bar

[Angelo Graziosi <angelo.graziosi@alice.it>]

Stephen,

I tried your patch without an init file and calling "M-x hl-line-mode" 
and then "M-x global-hl-line-mode" and I think I can reproduce all your 
arguments below.

Now my init file contains

(setq global-hl-line-sticky-flag t)
(global-hl-line-mode 1)

so that I can see the line in all windows of the frame.

Obviously, no flickering in all case you describe below..


  Angelo

Il 16/05/2016 23:33, Stephen Berman ha scritto:
> On Sat, 14 May 2016 09:42:13 +0200 Angelo Graziosi <angelo.graziosi@alice.it> wrote:
>
>>> If my fix is found acceptable
>>
>> I have tested the patch with this init.el file:
>>
>> ;;
>> (global-hl-line-mode 1)
>>
>>
>> and it seems to work..
>
> I take it you mean you see no flickering?  That would confirm the patch
> fixes problem you reported.  You should also see, when you make the
> frame have two (or more) windows, that the current line of only the
> selected window is highlighted; this is the default behavior without the
> patch and should obtain with the patch as well.
>
>> Any other configuration for testing?
>
> The default for global-hl-line-mode, which you tested with the above, is
> for the value of global-hl-line-sticky-flag to be nil; if you set it to
> non-nil, then when you make the frame display two (or more) windows, the
> current line is highlighted in all of them.  A difference between the
> behavior of the existing version of hl-line.el and the behavior with my
> patch is that, in the former, the current line of each window displaying
> a different buffer becomes highlighted only as soon as that window is
> selected (and remains highlighted when another window is selected),
> while with my patch, the current line in all live (visible) windows is
> highlighted at once.  So this is a new feature and the question is, do
> you prefer this behavior to the original behavior?  (If all the windows
> display the same buffer, then with non-nil global-hl-line-sticky-flag
> the highlighting appears in all of them simultaneously both with and
> without the patch.)
>
> It would be helpful if you'd also test the behavior of the patch with
> the buffer local hl-line-mode.  Here, the default is for the value of
> hl-line-sticky-flag to be non-nil, which means that if the same buffer
> is displayed in two (or more) windows of a frame, the current line is
> highlighted in each of these windows, and in addtion, when you select a
> window displaying a different buffer, the line in the previously
> selected window (displaying the buffer in which hl-line-mode was
> enabled) remains highlighted.  If you set hl-line-sticky-flag to nil,
> then only the current line of the selected window is highlighted.  These
> behaviors of hl-line-mode should still be the same with the patch.  But
> without the patch, setting hl-line-sticky-flag to nil results in
> flickering of the highlighted line when moving the scroll bar with the
> mouse; with the patch, there should be no flickering.
>
> Steve Berman
>