Re: [BUG] ov property line height failed on lone length line when exceeded window width

[Eli Zaretskii <eliz@gnu.org>]

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> From: "numbchild@gmail.com" <numbchild@gmail.com>
> Date: Wed, 3 Jun 2020 19:48:57 +0800
> 
> > Can you please describe how you set the overlay, or better yet, show the code which does so? 
> 
> The main functionality code set overlay on org-agenda is here:
> 
> (defun org-agenda-log-mode-colorize-block ()
>   "Set different line spacing based on clock time duration."
>   (save-excursion
>     (let* ((colors (cl-case (alist-get 'background-mode (frame-parameters))
>                 ('light
>                  (list "#F6B1C3" "#FFFF9D" "#BEEB9F" "#ADD5F7"))
>                 ('dark
>                  (list "#aa557f" "DarkGreen" "DarkSlateGray" "DarkSlateBlue"))))
>            pos
>            duration)
>       (nconc colors colors)
>       (goto-char (point-min))
>       (while (setq pos (next-single-property-change (point) 'duration))
>         (goto-char pos)
>         (when (and (not (equal pos (point-at-eol)))
>                    (setq duration (org-get-at-bol 'duration)))
>           ;; larger duration bar height
>           ;; FIXME (< duration 15)
>           (let ((line-height (if (< duration 15) 1.0 (+ 0.5 (/ duration 30))))
>                 (ov (make-overlay (point-at-bol) (1+ (point-at-eol)))))
>             (overlay-put ov 'face `(:background ,(car colors) :foreground "black"))
>             (setq colors (cdr colors))
>             (overlay-put ov 'line-height line-height)
>             (overlay-put ov 'line-spacing (1- line-height))))))))
> 
> (add-hook 'org-agenda-finalize-hook #'org-agenda-log-mode-colorize-block)
> 
> And for a minimal example of setting overlay code is here:
> 
> (let ((line-height 20)
>       (ov (make-overlay (point-at-bol) (1+ (point-at-eol)))))
>   (overlay-put ov 'face '(:background "yellow"))
>   (overlay-put ov 'line-height line-height)
>   (overlay-put ov 'line-spacing (1- line-height)))
> 
> > Did you per chance put the overlay on the part of the line that is not shown when you split the window?
> 
> About this problem, I suggest you check out my video link, it shows how the overlay line-height property failed
> when I split window with `split-window-right`. The line height property is gone. (I mean the visual effect is
> gone.)

In that case, this is the expected behavior: if the newline with the
line-height property is not visible, the setting has no effect.  It is
conceptually the same as having a tall character or image displayed on
a line: if you then truncate the line so that the tall element is not
visible, the line's height will be decreased to reflect what is
actually on display.

This is not a bug.  You are trying to use this property in a way that
it wasn't designed to support.