Subject: Re: bug#36633: Scrolling by pixels: visible stretch glyphs overwrite header-line.

From: Alan Third <[email-masked]>
Date: Sun, 14 Jul 2019 11:39:35 +0100

On Fri, Jul 12, 2019 at 07:10:44PM -0700, Keith David Bershatsky wrote:
> Step 1:  Launch Emacs 26.
> 
> Step 2:  Evaluate the following code.
> 
> (progn
>   (find-library "simple")
>   (pixel-scroll-mode 1)
>   (re-search-forward "\t\t\t\t\t" nil t)
>   (set-window-start (selected-window) (match-beginning 0))
>   (setq header-line-format "hello-world")
>   (setq buffer-display-table (make-display-table))
>   (aset buffer-display-table
>         ?\t
>         (vector (make-glyph-code ?\u00BB 'font-lock-warning-face)
>                 (make-glyph-code ?\t 'highlight)))
>   (setq tab-width 8))
> 
> Step 3:  Move the mousewheel downward one time; i.e., one ratchet.
> 
> Step 4:  Observe the visible stretch glyphs overwriting the header-line.

Hi Keith, I can’t replicate this behaviour. The worst I see is some
flickering of the header line, which is unfortunately to be expected
from the current implementation.

When you do it is the header line being overwritten and not
immediately updated?
-- 
Alan Third