continued doesn't include a final newline.) In the most common case,
the line height equals the height of the default frame font.
- There are several other ways to change the line height, either by
-specifying an absolute height for the display line, or by adding
-additional vertical space below each line.
+ There are several ways to explicitly control or change the line
+height, either by specifying an absolute height for the display line,
+or by adding additional vertical space below one or all lines.
@kindex line-height @r{(text property)}
- A newline can have a @code{line-height} text or overlay property that
-controls the total height of the display line ending in that newline.
-We will call the property value @var{line-height}.
+ A newline can have a @code{line-height} text or overlay property
+that controls the total height of the display line ending in that
+newline. If the property value is zero, the displayed height of the
+line is exactly what its contents need; no line-spacing is added.
+This case is useful for tiling small images or image slices without
+adding blank areas between the images.
- If @var{line-height} property is 0, the height of the line is
-determined solely from its contents; nothing is added. Any
-@code{line-spacing} property on this newline is ignored. This case is
-useful for tiling small images or image slices without adding blank
-areas between the images.
+ If the property value is not zero, it specifies a desired height,
+@var{line-height}. There are several ways it can do this:
- If @var{line-height} property is a positive integer, the value
-specifies the minimum line height in pixels. The line's ascent height
-is increased as necessary to achieve the specified height.
+@table @code
+@item @var{integer}
+If the property is a positive integer, @var{line-height} is that integer.
+@item @var{float}
+If the property is a float, @var{float}, @var{line-height} is @var{float}
+times the frame's default line height.
+@item (@var{ratio} . @var{face})
+If the property is a cons of the format shown, @var{line-height} is
+@var{ratio} times the height of face @var{face}. @var{ratio} can be
+any type of number. If @var{face} is @code{t}, it refers to the
+current face.
+@end table
- If @var{line-height} property is a floating point number, the
-minimum line height is the product of @var{line-height} and the
-default frame line height.
+ Thus, any valid nonzero property value specifies a height in pixels,
+@var{line-height}, one way or another. If the line contents' height
+is less than @var{line-height}, Emacs adds extra vertical space above
+the line to achieve the total height @var{line-height}. Otherwise,
+@var{line-height} has no effect.
- If @var{line-height} property is a cons @code{(@var{ratio} . @var{face})},
-the minimum line height is calculated as @var{ratio} times the height
-of face @var{face}. The @var{ratio} is an integer or a floating point
-number. If @var{face} is @code{t}, it refers to the current face.
+ If you don't specify the @code{line-height} propery, the line's
+height consists of the contents' height plus the line spacing.
@vindex default-line-spacing
- You can specify additional line spacing for all lines in a frame
-with the @code{line-spacing} frame parameter, @xref{Window Frame
-Parameters}. However, if the variable @code{default-line-spacing} is
+ You can specify the line spacing for all lines in a frame with the
+@code{line-spacing} frame parameter, @xref{Window Frame Parameters}.
+However, if the variable @code{default-line-spacing} is
non-@code{nil}, it overrides the frame's @code{line-spacing}
parameter. An integer value specifies the number of pixels put below
lines on window systems. A floating point number specifies the
-spacing relative to the default frame line height.
+spacing relative to the frame's default line height.
@vindex line-spacing
- You can specify additional line spacing for all lines in a buffer
-via the buffer-local @code{line-spacing} variable. An integer value
-specifies the number of pixels put below lines on window systems. A
-floating point number specifies the spacing relative to the default
-frame line height.
+ You can specify the line spacing for all lines in a buffer via the
+buffer-local @code{line-spacing} variable. An integer value specifies
+the number of pixels put below lines on window systems. A floating
+point number specifies the spacing relative to the default frame line
+height. This overrides line spacings specified for the frame.
@kindex line-spacing @r{(text property)}
Finally, a newline can have a @code{line-spacing} text or overlay
property that controls the height of the display line ending with that
newline. The property value overrides the default frame line spacing
-and the buffer local @code{line-spacing} variable. We will call the
-property value @var{line-spacing}.
+and the buffer local @code{line-spacing} variable.
- If the @var{line-spacing} value is a positive integer, the value
-specifies additional vertical space, below the display line, in
-pixels.
+ One way or another, these mechanisms specify a line spacing for each
+line. Let's call the value @var{line-spacing}.
+
+ If the @var{line-spacing} value is a positive integer, it specifies
+the number of pixels of additional vertical space. This space appears
+below the display line contents.
If the @var{line-spacing} value is a floating point number or cons,
-the additional vertical space is the product of @var{line-spacing} and
-the default frame line height.
+the additional vertical space is @var{line-spacing} times the frame
+default line height.
+@ignore @c I think we may want to delete this, so don't document it -- rms.
If the @var{line-spacing} value is a cons @code{(total . @var{spacing})}
where @var{spacing} is any of the forms described above, the value of
@var{spacing} specifies the total displayed height of the line,
regardless of the height of the characters in it. This is equivalent
to using the @code{line-height} property.
+@end ignore
@node Faces
@section Faces
projects / emacs.git / commitdiff