Add RenderText DirectionalityMode enum and support; etc.

ui/gfx/render_text.h

Index: ui/gfx/render_text.h
diff --git a/ui/gfx/render_text.h b/ui/gfx/render_text.h
index a6265b06feae687d13eb1f361e8eb956216548ea..b36b0ce78b1f7145c9a87cb5b7aed4da1e1be6e1 100644
--- a/ui/gfx/render_text.h
+++ b/ui/gfx/render_text.h
@@ -95,18 +95,26 @@ typedef std::vector<StyleRange> StyleRanges;
 // WORD_BREAK cursor movements should stop at the nearest word boundaries.
 // LINE_BREAK cursor movements should stop at the text ends as shown on screen.
 enum BreakType {
-  CHARACTER_BREAK,
+  CHARACTER_BREAK = 0,

[Alexei Svitkine (slow), 2012/07/27 11:40:36]

Does our style guide require this?

[msw, 2012/07/28 01:17:11]

Not explicitly, but the Google C++ style guide shows both enum examples
specifying at least the first value. The Chromium style guide only shows one
enum example (wrt namespaces) and doesn't supply a value. I think it's optional,
but beneficial; I'll remove it if you disagree.

   WORD_BREAK,
   LINE_BREAK,
 };
 
 // Horizontal text alignment styles.
 enum HorizontalAlignment {
-  ALIGN_LEFT,
+  ALIGN_LEFT = 0,
   ALIGN_CENTER,
   ALIGN_RIGHT,
 };
 
+// The directionality modes used to determine the base text direction.
+enum DirectionalityMode {
+  DERIVE_FROM_TEXT = 0, // Use the first strong character's direction.

[Alexei Svitkine (slow), 2012/07/27 11:40:36]

This is not a good name for an enum entry in the gfx namespace.

gfx::DERIVE_FROM_TEXT doesn't tell me what it's talking about (what is it
deriving from the text?).

I suggest prefixing these names with DIRECTIONALITY_*.

I also dislike that these enums are in render_text.h. Code that uses e.g. Label
shouldn't know about RenderText and include its header.

How about making a gfx_constants.h header file and moving these three enums
there?

[msw, 2012/07/28 01:17:11]

Done (ui/gfx/text_constants.h and "DIRECTIONALITY_*" w/o "DERIVE_").

+  DERIVE_FROM_UI,       // Use the UI's language/locale direction.
+  FORCE_LTR,            // Use LTR regardless of the text content or UI locale.
+  FORCE_RTL,            // Use RTL regardless of the text content or UI locale.
+};
+
 // RenderText represents an abstract model of styled text and its corresponding
 // visual layout. Support is built in for a cursor, a selection, simple styling,
 // complex scripts, and bi-directional text. Implementations provide mechanisms
@@ -246,8 +254,9 @@ class UI_EXPORT RenderText {
   // Apply |default_style_| over the entire text range.
   void ApplyDefaultStyle();
 
-  // Returns the dominant direction of the current text.
-  virtual base::i18n::TextDirection GetTextDirection() = 0;
+  // Set the text directionality mode and get the text direction yielded.
+  void SetDirectionalityMode(DirectionalityMode mode);
+  base::i18n::TextDirection GetTextDirection();
 
   // Returns the visual movement direction corresponding to the logical end
   // of the text, considering only the dominant direction returned by
@@ -439,6 +448,12 @@ class UI_EXPORT RenderText {
   // Horizontal alignment of the text with respect to |display_rect_|.
   HorizontalAlignment horizontal_alignment_;
 
+  // The text directionality mode, defaults to DERIVE_FROM_TEXT.
+  DirectionalityMode directionality_mode_;
+
+  // The cached text direction, potentially computed from the text or UI locale.
+  base::i18n::TextDirection text_direction_;
+
   // A list of fonts used to render |text_|.
   FontList font_list_;