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Diffstat (limited to 'docs/tmpl/vertical.sgml')
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diff --git a/docs/tmpl/vertical.sgml b/docs/tmpl/vertical.sgml index ccbea1ea..de80afd3 100644 --- a/docs/tmpl/vertical.sgml +++ b/docs/tmpl/vertical.sgml @@ -9,6 +9,21 @@ Laying text out in vertical directions Since 1.16, Pango is able to correctly lay vertical text out. In fact, it can set layouts of mixed vertical and non-vertical text. This section describes the types used for setting vertical text parameters. + +The way this is implemented is through the concept of +<firstterm>gravity</firstterm>. Gravity of normal Latin text is south. A +gravity value of east means that glyphs will be rotated ninety degrees +counterclockwise. So, to render vertical text one needs to set the gravity +and rotate the layout using the matrix machinery already in place. This has +the huge advantage that most algorithms working on a #PangoLayout do not need +any change as the assumption that lines run in the X direction and stack in +the Y direction holds even for vertical text layouts. + +Applications should only need to set base gravity on #PangoContext in use, and +let Pango decide the gravity assigned to each run of text. This automatically +handles text with mixed scripts. A very common use is to set the context base +gravity to auto and rotate the layout normally. Pango will make sure that +Asian languages take the right form, while other scripts are rotated normally. </para> <!-- ##### SECTION See_Also ##### --> |