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bug#64986: 30.0.50; window-text-pixel-size sometimes returns 0 width whe
From: |
Eli Zaretskii |
Subject: |
bug#64986: 30.0.50; window-text-pixel-size sometimes returns 0 width when called from temporary buffer |
Date: |
Tue, 01 Aug 2023 15:07:52 +0300 |
> From: Ihor Radchenko <yantar92@posteo.net>
> Date: Tue, 01 Aug 2023 07:47:32 +0000
>
> (with-current-buffer (get-buffer-create " *Org string width*")
> (setq-local display-line-numbers nil
> line-prefix nil
> wrap-prefix nil)
> (setq-local buffer-invisibility-spec
> (if (listp current-invisibility-spec)
> (mapcar (lambda (el)
> ;; Consider ellipsis to have 0 width.
> ;; It is what Emacs 28+ does, but we have
> ;; to force it in earlier Emacs versions.
> (if (and (consp el) (cdr el))
> (list (car el))
> el))
> current-invisibility-spec)
> current-invisibility-spec))
> (setq-local char-property-alias-alist
> current-char-property-alias-alist)
> (let (pixel-width symbol-width)
> (with-silent-modifications
> (erase-buffer)
> (insert string)
> (setq pixel-width
> (car (window-text-pixel-size
> nil (line-beginning-position) (point-max))))
> (unless pixels
> (erase-buffer)
> (insert "a")
> (setq symbol-width
> (car (window-text-pixel-size ;; <---- unexpected return
> nil (line-beginning-position) (point-max))))))
> (if pixels
> pixel-width
> (/ pixel-width symbol-width)))))))
You are using window-text-pixel-size incorrectly. Its doc string
says:
Return the size of the text of WINDOW's buffer in pixels.
Note the "WINDOW's buffer" part: it is there for a reason.
So what your code is doing is measure the size of the text of the
buffer shown in WINDOW (in your case, the selected window) between
buffer positions 1 and 2. And the buffer shown in the selected
window, the one created by org-test-with-temp-text-in-file, begins
with an empty line, so the function correctly returns zero as the
horizontal dimensions of the text.
Your code seems to assume that with-current-buffer makes the named
buffer be "temporarily shown" in the selected window, but that is not
what happens: it just makes that buffer the current buffer.
This tricky part is why we now have buffer-text-pixel-size: it takes
care of making the buffer "temporarily shown" in the window. So I
believe you should use that function instead.