bug#23806: 24.5; can not set line height

bug#23806: 24.5; can not set line height

[ynyaaa]

`line-height' property is effective only at the newlines,
so there are no chances to set line height
  (1) when the line is wrapped
  (2) when the line is truncated
  (3) when the line is at the bottom of a buffer
        and not terminated by newline



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bug#23806: 24.5; can not set line height

[Eli Zaretskii]

tags 23806 + notabug
thanks

> From: ynyaaa@gmail.com
> Date: Mon, 20 Jun 2016 11:15:11 +0900
> 
> `line-height' property is effective only at the newlines,
> so there are no chances to set line height
>   (1) when the line is wrapped
>   (2) when the line is truncated
>   (3) when the line is at the bottom of a buffer
>         and not terminated by newline

Yes.  As clearly documented in the ELisp manual:

     A newline can have a ‘line-height’ text or overlay property that
  controls the total height of the display line ending in that newline.

It talks about "display lines", not physical lines.

The line-height property you put on a newline is designed and
implemented to cater to a specific use case: to allow control of the
effect the newline itself has on the line height.  Since the newline
only affects the height of the display line that ends in that newline,
this is what this feature supports.  It is not a general-purpose way
of controlling the vertical spacing of lines on display.

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.

bug#23806: 24.5; can not set line height

[ynyaaa]

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.

I want to use the line-height property because the line-spacing variable
can not affect partial buffer contents and can not add spacing both
above and below lines.


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.


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.

bug#23806: 24.5; can not set line height

[Eli Zaretskii]

> 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.