bug#41972: Customization via display-buffer-alist, savehist-mode, and hl-line-mode together are not compatible with mouse-wheel scrolling.

[Konrad Podczeck]

To see this, make an init-file just containing:

(savehist-mode)
(setq mouse-wheel-progressive-speed nil)
(add-hook 'text-mode-hook 'hl-line-mode)
(add-hook 'prog-mode-hook 'hl-line-mode)


(setq display-buffer-base-action
  '((display-buffer-reuse-window display-buffer-pop-up-frame)
  (reusable-frames . t)))

(setq display-buffer-alist
   '(
   ("[.]"
    (display-buffer-reuse-window display-buffer-pop-up-frame)
    (dedicated . t)
       (pop-up-frame-parameters
       (tool-bar-lines . 1)
       (left . 1)
       (top . 0)
       (height . 46)
       (width . 82)
       (font . "SF MONO-15")
       (line-spacing . 3)
      ))))

With this, the speed of scrolling via the mouse-wheel becomes much too large. 
The problem goes away if either the line with savehist-mode is commented out, 
or the two lines with hl-line-mode.

I used the pretest 27.0.91, and in case the problem is platform-specific, I use 
the NS-port.