What Is "line-height" Attribute?

XSL-FO Tutorials - Herong's Tutorial Examples

∟What Is "line-height" Attribute?

This section describes 'line-height' attribute for 'inline' formatting object. It is used to control the line height of the output inline area.

What Is "line-height" Attribute? "line-height" is an attribute for inline-level formatting objects to specify the height of the output inline area, which will impact the height of the parent line area.

There are several rules you need to remember about "line-height" attribute:

The height of the entire line area is the maximum "line-height" value of each individual inline areas stacked in the line.
If not specified, "line-height" of an inline area is determined by font size of the text in the area.
The margin, border and padding attributes of an inline-level formatting object do not apply the calculation of "line-height". In other words, if you want increase the line height, you have to specify "line-height" explicitly.
The best way to specify "line-height" is to use a percentage value, which will be used to calculate the actual height as this percentage multiplied by the computed font size. For example, line-height="200%" means the height will be 2 times of the font size.

Here is my tutorial example, inline-line-height-Attribute.fo, that shows an "inline" formatting object with "line-height" specified:

<?xml version="1.0" encoding="utf-8"?>
<!-- inline-line-height-Attribute.fo
 - Copyright (c) 2006 HerongYang.com. All Rights Reserved.
-->
<fo:root xmlns:fo="http://www.w3.org/1999/XSL/Format">
 <fo:layout-master-set>
  <fo:simple-page-master master-name="page" 
   margin="0.1in" page-height="4in" page-width="3in">
   <fo:region-body region-name="body" background-color="#eeeeee"/>
  </fo:simple-page-master>
 </fo:layout-master-set>
 <fo:page-sequence master-reference="page">
  <fo:flow flow-name="body">
   <fo:block margin="0.1in" padding="0.2in" 
    border-width="1px" border-style="solid"
    background-color="#eeffff" color="#000000" 
    text-align="justify" font-family="sans-serif">
    Once upon a time there were three little pigs 
    <fo:inline font-weight="bold" background-color="#ffeeee"
    padding="3pt" border-width="5px" line-height="200%"
    border-style="solid">who lived with their Mother</fo:inline>.
    Early one morning they woke up and their mother said, 
    "you're too big for this house and its time you left home."
   </fo:block>
  </fo:flow>
 </fo:page-sequence>
</fo:root>

If you process this example XSL-FO document with RenderX XEP tool to a PDF file, you should see the height of lines where the "inline" formatting object is presented is higher than other lines: