From: Yuan Fu <casouri@gmail.com>
To: Eli Zaretskii <eliz@gnu.org>
Cc: emacs-devel <emacs-devel@gnu.org>
Subject: Re: Add a function that returns pixel distance between points?
Date: Mon, 1 Feb 2021 18:00:18 -0500 [thread overview]
Message-ID: <CDCD9F43-5BF9-4D20-8765-64C714CC850D@gmail.com> (raw)
In-Reply-To: <83v9bb6429.fsf@gnu.org>
> On Feb 1, 2021, at 1:22 PM, Eli Zaretskii <eliz@gnu.org> wrote:
>
>> From: Yuan Fu <casouri@gmail.com>
>> Date: Mon, 1 Feb 2021 09:16:52 -0500
>> Cc: "emacs-devel\\@gnu.org" <emacs-devel@gnu.org>
>>
>>> IOW, can you show a test case where using window-text-pixel-size
>>> returns incorrect results for :align-to due to line-prefix?
>>
>> Here is an example:
>>
>> (let ((width))
>> (insert "woome")
>> (setq width (car (window-text-pixel-size
>> nil (line-beginning-position) (point))))
>> (put-text-property (line-beginning-position) (point)
>> 'line-prefix " ")
>> (message "true width: %d returned width: %d"
>> width (car (window-text-pixel-size
>> nil (line-beginning-position) (point)))))
>>
>> Run it in an empty buffer and it will print the expected width and returned width. In the snippet I’m trying to measure the width of the text.
>
> This says:
>
> true width: 40 returned width: 64
>
> However, if I use :align-to with the value of 64 pixels, the stretch
> of whitespace ends where I'd expect it to end: aligned to right after
> "woome".
>
> So I still don't understand the problem you are facing. Which is why
> I asked for an example code which uses :align-to in a way similar to
> what you intend to do in your table rendering code, because I wanted
> to see a situation where :align-to produces incorrect results when
> using the return value of window-text-pixel-size in the presence of
> line-prefix. But the example you show doesn't use :align-to.
Ah, I see. Here is a demo that should show that.
(let (width-1 width-2 (start (point)))
(insert (propertize "| loooooong |\n| world |"
'line-prefix " "))
(goto-char start)
(search-forward "|")
(let ((start (point)))
(search-forward "|")
(setq width-1 (car (window-text-pixel-size
nil (1+ start) (- (point) 2)))))
(search-forward "|")
(let ((start (point)))
(search-forward "|")
(setq width-2 (car (window-text-pixel-size
nil (1+ start) (- (point) 2)))))
(let ((col-width (+ 2 (max width-1 width-2)))
cell-start)
(goto-char start)
(search-forward "|")
(setq cell-start (car (window-text-pixel-size
nil (line-beginning-position) (point))))
(search-forward "|")
(put-text-property (- (point) 2) (1- (point))
'display
`(space :align-to (,(+ cell-start col-width))))
(search-forward "|")
(setq cell-start (car (window-text-pixel-size
nil (line-beginning-position) (point))))
(search-forward "|")
(put-text-property (- (point) 2) (1- (point))
'display
`(space :align-to (,(+ cell-start col-width))))))
This code inserts a mini table
| looooong |
| world |
And tries to aligns it to
| looooong |
| world |
You will notice there are extra white space on the right of the cells, and the table actually looks like this:
| loooooong |
| world |
That’s because window-text-pixel-size returned a width that’s larger than the true with of the cells. If you enlarge the line-prefix, the extra space grows.
Yuan
next prev parent reply other threads:[~2021-02-01 23:00 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-30 20:47 Add a function that returns pixel distance between points? Yuan Fu
2021-01-31 3:31 ` Eli Zaretskii
2021-01-31 5:17 ` Yuan Fu
2021-01-31 5:52 ` Ihor Radchenko
2021-01-31 19:42 ` Yuan Fu
2021-01-31 15:24 ` Eli Zaretskii
2021-01-31 19:41 ` Yuan Fu
2021-01-31 20:13 ` Eli Zaretskii
2021-02-01 14:16 ` Yuan Fu
2021-02-01 18:22 ` Eli Zaretskii
2021-02-01 23:00 ` Yuan Fu [this message]
2021-02-02 16:29 ` Eli Zaretskii
2021-02-03 15:04 ` Eli Zaretskii
2021-02-03 16:48 ` Yuan Fu
2021-02-04 16:02 ` Eli Zaretskii
2021-02-05 10:15 ` martin rudalics
2021-02-05 12:25 ` Eli Zaretskii
2021-02-05 15:48 ` martin rudalics
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