Determining size of a propertised string

Determining size of a propertised string

[Elias Mårtenson]

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I have a string with a buch of properties applied (the main one: It uses a
different font). I now need to split the window, making the size of the
window just large enough to contain this text. If the string is not
propertised, I can simply count the number of lines in the text I'll be
inserting into the buffer and pass that as the HEIGHT parameter to
‘split-window’. But since the font used in this text is larger than the
default font, the window becomes slightly too small.

As far as I can tell, there seems to be no standard way of determining what
height to use in order to fit a given string. Is there a correct way to
handle this?

The context of this is the C-c C-k feature in gnu-apl-mode. It is used to
open a window that displays the APL keymap. It's common to use a slightly
larger font for APL since each character is important, and that makes this
problem immediately visible.

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Re: Determining size of a propertised string

[martin rudalics]

 > I have a string with a buch of properties applied (the main one: It uses a
 > different font). I now need to split the window, making the size of the
 > window just large enough to contain this text. If the string is not
 > propertised, I can simply count the number of lines in the text I'll be
 > inserting into the buffer and pass that as the HEIGHT parameter to
 > ‘split-window’. But since the font used in this text is larger than the
 > default font, the window becomes slightly too small.

Why can't you use ‘fit-window-to-buffer’?

martin

Re: Determining size of a propertised string

[Elias Mårtenson]

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On 29 November 2016 at 19:00, martin rudalics <rudalics@gmx.at> wrote:

> I have a string with a buch of properties applied (the main one: It uses a
> > different font). I now need to split the window, making the size of the
> > window just large enough to contain this text. If the string is not
> > propertised, I can simply count the number of lines in the text I'll be
> > inserting into the buffer and pass that as the HEIGHT parameter to
> > ‘split-window’. But since the font used in this text is larger than the
> > default font, the window becomes slightly too small.
>
> Why can't you use ‘fit-window-to-buffer’?


The short answer is that I didn't know about its existence. Thank you so
much for directing my attention to it.

The longer answer is that while this does indeed solve the problem at hand
(and I've already pushed it to gnu-apl-mode), there may be more complicated
cases where an answer to the original question may be needed.

So in the interest of satisfying my own curiosity, is there a way to
determine the height of a given string?

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Re: Determining size of a propertised string

[martin rudalics]

 > So in the interest of satisfying my own curiosity, is there a way to
 > determine the height of a given string?

"A given string" doesn't have a height per se.  It's assigned a height
only when you put it into a buffer and put that buffer in a window on a
display.  This may wrap the string and assigns the corresponding font,
text, overlay and other properties to that string's constituents.  You
can use the function ‘window-text-pixel-size’ in order to determine the
size of the string it would occupy, in pixels, at a given buffer
position on your display.  That's what ‘fit-window-to-buffer’ does.

martin