adding baseline options for super/sub scripting

ui/gfx/text_constants.h

Index: ui/gfx/text_constants.h
diff --git a/ui/gfx/text_constants.h b/ui/gfx/text_constants.h
index 82f2a3b7061386b425c825480db256fe8c9ca446..9e07059a8828988541489b004eada17a55620a15 100644
--- a/ui/gfx/text_constants.h
+++ b/ui/gfx/text_constants.h
@@ -42,6 +42,26 @@ enum TextStyle {
   NUM_TEXT_STYLES,
 };
 
+// Text baseline offset types

[msw, 2015/02/18 17:07:23]

nit: add trailing periods here and to the eg. comments below.

[dschuyler, 2015/02/18 22:36:03]

Done.

+// Figure of font metrics:
+//   +--------+--------+------------------------+-------------+
+//   |        |        | internal leading       | SUPERSCRIPT |
+//   |        |        +------------+-----------|             |
+//   |        | ascent |            | SUPERIOR  |-------------+
+//   | height |        | cap height |-----------|
+//   |        |        |            | INFERIOR  |-------------+
+//   |        |--------+------------+-----------| SUBSCRIPT   |

[msw, 2015/02/18 17:07:23]

nit q: should "SUBSCRIPT" be on the line below?

[dschuyler, 2015/02/18 22:36:03]

Done.

+//   |        | descent                         |             |
+//   +--------+---------------------------------+-------------+
+enum BaselineStyle {
+  NORMAL_BASELINE = 0,
+  SUPERSCRIPT,     // e.g. a mathematical exponent would be superscript
+  SUPERIOR,        // e.g. 8th, the "th" would be superior script
+  INFERIOR,        // e.g. 1/2, the "2" would be inferior ("1" is superior)
+  SUBSCRIPT,       // e.g. H2O, the "2" would be subscript
+  NUM_BASELINE_STYLES,
+};
+
 // Elision behaviors of text that exceeds constrained dimensions.
 enum ElideBehavior {
   NO_ELIDE = 0, // Do not modify the text, it may overflow its available bounds.