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bug#19194: 24.4.50; `window-body-width' is not dynamic relative to font
From: |
Joe Corneli |
Subject: |
bug#19194: 24.4.50; `window-body-width' is not dynamic relative to font size changes |
Date: |
Thu, 27 Nov 2014 20:23:32 +0000 |
On Thu, Nov 27 2014, martin rudalics wrote:
> > I think you are totally right. To keep the buffer and window
> > distinction properly, my note should probably be read as a feature
> > request, not a bug report. The request is for a function such as
> > `buffer-body-width' that would return the width of the current displayed
> > buffer in em-length units.
>
> What is the width of a buffer? What are em-lenght units?
I mean, the distance (in useful units!) from the left side of the
buffer, as displayed within a given window, to the right side of that
window. If the buffer is displayed using *a fixed width font*, then one
useful unit is *columns*, i.e. the number of columns that can be
displayed before line wrap or continuation kicks in. However, if the
buffer is displayed using a variable-width font, then "columns" is *not*
necessarily a meaningful unit -- as has been pointed out in the earlier
discussion. In this case, see below for "ems."
To be clear, the width of the *window* calculated in non-buffer-specific
units is not generally "useful" for the purpose of measuring the number
of characters that can be fit, horizontally, into the buffer.
Nevertheless, if the window is displayed using *the default face* at the
default scale (and if the default font happens to be fixed width!) then
`window-body-width' does indeed return the number of columns.
>From Wikipedia:
«An em is a unit in the field of typography, equal to the currently
specified point size. For example, one em in a 16-point typeface is 16
points. Therefore, this unit is the same for all typefaces at a given
point size. [...] The name "em" was originally a reference to the
width of the the capital "M" in the typeface and size being used,
which was often the same as the point size.»
> (2) `text-scale-mode-amount' is buffer-local. So we have to choose the
> right buffer before evaluating it.
I agree, this is indeed an important.
> (3) `text-scale-mode-amount' constitutes a request to the display engine
> to scale a face height. What shall we do when our target machine
> can't display the character with the requested height and uses, for
> example, the nearest available height instead?
Presumably the function should fall back to the height (and
corresponding scale factor) that is actually used. This is an edge case
that I hadn't considered!
- bug#19194: 24.4.50; `window-body-width' is not dynamic relative to font size changes, (continued)
- bug#19194: 24.4.50; `window-body-width' is not dynamic relative to font size changes, martin rudalics, 2014/11/27
- bug#19194: 24.4.50; `window-body-width' is not dynamic relative to font size changes, Joe Corneli, 2014/11/27
- bug#19194: 24.4.50; `window-body-width' is not dynamic relative to font size changes, martin rudalics, 2014/11/27
- bug#19194: 24.4.50; `window-body-width' is not dynamic relative to font size changes, Eli Zaretskii, 2014/11/27
- bug#19194: 24.4.50; `window-body-width' is not dynamic relative to font size changes, martin rudalics, 2014/11/27
- bug#19194: 24.4.50; `window-body-width' is not dynamic relative to font size changes, Eli Zaretskii, 2014/11/27
- bug#19194: 24.4.50; `window-body-width' is not dynamic relative to font size changes, martin rudalics, 2014/11/28
- bug#19194: 24.4.50; `window-body-width' is not dynamic relative to font size changes, Eli Zaretskii, 2014/11/28
- bug#19194: 24.4.50; `window-body-width' is not dynamic relative to font size changes, martin rudalics, 2014/11/28
- bug#19194: 24.4.50; `window-body-width' is not dynamic relative to font size changes, Eli Zaretskii, 2014/11/28
- bug#19194: 24.4.50; `window-body-width' is not dynamic relative to font size changes,
Joe Corneli <=
- bug#19194: 24.4.50; `window-body-width' is not dynamic relative to font size changes, martin rudalics, 2014/11/28
bug#19194: 24.4.50; `window-body-width' is not dynamic relative to font size changes, Eli Zaretskii, 2014/11/27
- bug#19194: 24.4.50; `window-body-width' is not dynamic relative to font size changes, martin rudalics, 2014/11/27
- bug#19194: 24.4.50; `window-body-width' is not dynamic relative to font size changes, Eli Zaretskii, 2014/11/27
- bug#19194: 24.4.50; `window-body-width' is not dynamic relative to font size changes, martin rudalics, 2014/11/27
- bug#19194: 24.4.50; `window-body-width' is not dynamic relative to font size changes, Eli Zaretskii, 2014/11/27
- bug#19194: 24.4.50; `window-body-width' is not dynamic relative to font size changes, martin rudalics, 2014/11/28
- bug#19194: 24.4.50; `window-body-width' is not dynamic relative to font size changes, Eli Zaretskii, 2014/11/28