bug#23806: 24.5; can not set line height

[Eli Zaretskii <eliz@gnu.org>]

> From: ynyaaa@gmail.com
> Cc: 23806@debbugs.gnu.org
> Date: Tue, 21 Jun 2016 10:45:10 +0900
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > The node "Line Height" in the ELisp manual describes the line-spacing
> > variable and frame parameter, which are more general-purpose ways of
> > controlling vertical layout of text.
> 
> The manual also describes the line-spacing property at the newlines,
> which has same problems as the line-height property.

Yes, and its documentation also refers to a "display line".

> I want to use the line-height property because the line-spacing variable
> can not affect partial buffer contents

What do you mean by "partial buffer contents"?

> and can not add spacing both above and below lines.

Such an extension could be added.

> By the way it is written in the manual,
>        If the property value is a list of the form ‘(HEIGHT TOTAL)’,
>     (snip) In
>     this case, the other ways to specify the line spacing are ignored.
> 
> Setting the line-height property to '(1.0 1.0) ignores the line-spacing
> property, but the line-spacing variable or frame parameter takes effect.
> 
> Setting the line-height property to 't ignores the line-spacing
> property, this behavior is not documented.

It's documented, sort of, by saying that only the visible content
determines the line height in this case.  But I made that more
explicit.

> In the manual:
>        Finally, a newline can have a ‘line-spacing’ text or overlay property
>     that overrides the default frame line spacing and the buffer local
>     ‘line-spacing’ variable, for the display line ending in that newline.
> 
> The line-spacing property overrides the line-spacing variable or frame
> parameter only if the property value is bigger.

Actually, it doesn't override, but compared, and the largest value
used instead.

I fixed these inaccuracies, and I'm marking the bug done.

Thanks.