Implement baseline shifts

Add a new baseline-shift attribute, which is similar to
rise, but accumulates. In addition, it supports font-
relative values such as superscript and subscript.

We implement support for this by computing baseline
shifts for run during line post-processing, and storing
them in the runs. The renderer now takes these shifts
into account when rendering layout lines.

1 files changed, 4 insertions, 1 deletions

diff --git a/pango/pango-glyph-item.h b/pango/pango-glyph-item.h
index 6c2f9249..baea69fc 100644
--- a/pango/pango-glyph-item.h
+++ b/pango/pango-glyph-item.h
@@ -33,6 +33,8 @@ G_BEGIN_DECLS
  * PangoGlyphItem:
  * @item: corresponding `PangoItem`
  * @glyphs: corresponding `PangoGlyphString`
+ * @baseline: shift of the baseline, relative to the
+ *   containing lines baseline. Positive values shift upwards
  *
  * A `PangoGlyphItem` is a pair of a `PangoItem` and the glyphs
  * resulting from shaping the items text.
@@ -45,8 +47,9 @@ typedef struct _PangoGlyphItem PangoGlyphItem;
 
 struct _PangoGlyphItem
 {
-  PangoItem        *item;
+  PangoItem *item;
   PangoGlyphString *glyphs;
+  int y_offset;
 };
 
 #define PANGO_TYPE_GLYPH_ITEM (pango_glyph_item_get_type ())