adding baseline options for super/sub scripting

This change list adds four options for a smaller font to be used as a style within the render text.

  Option           Example
  ------           -------
  SUPERSCRIPT      a mathematical exponent would be superscript
  SUPERIOR         8th, the "th" would be superior script
  INFERIOR         1/2, the "2" would be inferior ("1" is superior)
  SUBSCRIPT        H2O, the "2" would be subscript

Some imagination is needed to interpret the examples above.  To see a clearer references to what is meant, this wikipedia article may be helpful: http://en.wikipedia.org/wiki/Subscript_and_superscript

These options may be set in the same way options like BOLD and ITALIC can currently be set, e.g. with a call to my_render_text->ApplyStyle(gfx::SUPERSCRIPT, true, gfx::Range(1, 3));

BUG=459812

Review URL: https://codereview.chromium.org/924543004

Cr-Commit-Position: refs/heads/master@{#319492}

1 files changed, 36 insertions, 5 deletions

diff --git a/ui/gfx/render_text_harfbuzz.cc b/ui/gfx/render_text_harfbuzz.cc
index 0580abe..e33c208 100644
--- a/ui/gfx/render_text_harfbuzz.cc
+++ b/ui/gfx/render_text_harfbuzz.cc
@@ -19,6 +19,7 @@
 #include "ui/gfx/canvas.h"
 #include "ui/gfx/font_fallback.h"
 #include "ui/gfx/font_render_params.h"
+#include "ui/gfx/geometry/safe_integer_conversions.h"
 #include "ui/gfx/harfbuzz_font_skia.h"
 #include "ui/gfx/range/range_f.h"
 #include "ui/gfx/utf16_indexing.h"
@@ -421,6 +422,7 @@ class HarfBuzzLineBreaker {
     paint.getFontMetrics(&metrics);
 
     line->size.set_width(line->size.width() + width);
+    // TODO(dschuyler): Account for stylized baselines in string sizing.
     max_descent_ = std::max(max_descent_, metrics.fDescent);
     // fAscent is always negative.
     max_ascent_ = std::max(max_ascent_, -metrics.fAscent);
@@ -481,10 +483,13 @@ TextRunHarfBuzz::TextRunHarfBuzz()
       script(USCRIPT_INVALID_CODE),
       glyph_count(static_cast<size_t>(-1)),
       font_size(0),
+      baseline_offset(0),
+      baseline_type(0),
       font_style(0),
       strike(false),
       diagonal_strike(false),
-      underline(false) {}
+      underline(false) {
+}
 
 TextRunHarfBuzz::~TextRunHarfBuzz() {}
 
@@ -1030,7 +1035,7 @@ void RenderTextHarfBuzz::DrawVisualTextInternal(
                                      (glyphs_range.start() - j) :
                                      (glyphs_range.start() + j)];
         positions[j].offset(SkIntToScalar(origin.x()) + offset_x,
-                            SkIntToScalar(origin.y()));
+                            SkIntToScalar(origin.y() + run.baseline_offset));
       }
       for (BreakList<SkColor>::const_iterator it =
                colors().GetBreak(segment.char_range.start());
@@ -1139,17 +1144,18 @@ void RenderTextHarfBuzz::ItemizeTextToRuns(
   // Temporarily apply composition underlines and selection colors.
   ApplyCompositionAndSelectionStyles();
 
-  // Build the list of runs from the script items and ranged styles. Use an
-  // empty color BreakList to avoid breaking runs at color boundaries.
+  // Build the run list from the script items and ranged styles and baselines.
+  // Use an empty color BreakList to avoid breaking runs at color boundaries.
   BreakList<SkColor> empty_colors;
   empty_colors.SetMax(text.length());
-  internal::StyleIterator style(empty_colors, styles());
+  internal::StyleIterator style(empty_colors, baselines(), styles());
 
   for (size_t run_break = 0; run_break < text.length();) {
     internal::TextRunHarfBuzz* run = new internal::TextRunHarfBuzz;
     run->range.set_start(run_break);
     run->font_style = (style.style(BOLD) ? Font::BOLD : 0) |
                       (style.style(ITALIC) ? Font::ITALIC : 0);
+    run->baseline_type = style.baseline();
     run->strike = style.style(STRIKE);
     run->diagonal_strike = style.style(DIAGONAL_STRIKE);
     run->underline = style.style(UNDERLINE);
@@ -1218,6 +1224,31 @@ void RenderTextHarfBuzz::ShapeRun(const base::string16& text,
   const Font& primary_font = font_list().GetPrimaryFont();
   const std::string primary_family = primary_font.GetFontName();
   run->font_size = primary_font.GetFontSize();
+  run->baseline_offset = 0;
+  if (run->baseline_type != NORMAL_BASELINE) {
+    // Calculate a slightly smaller font. The ratio here is somewhat arbitrary.
+    // Proportions from 5/9 to 5/7 all look pretty good.
+    const float ratio = 5.0f / 9.0f;
+    run->font_size = gfx::ToRoundedInt(primary_font.GetFontSize() * ratio);
+    switch (run->baseline_type) {
+      case SUPERSCRIPT:
+        run->baseline_offset =
+            primary_font.GetCapHeight() - primary_font.GetHeight();
+        break;
+      case SUPERIOR:
+        run->baseline_offset =
+            gfx::ToRoundedInt(primary_font.GetCapHeight() * ratio) -
+            primary_font.GetCapHeight();
+        break;
+      case SUBSCRIPT:
+        run->baseline_offset =
+            primary_font.GetHeight() - primary_font.GetBaseline();
+        break;
+      case INFERIOR:  // Fall through.
+      default:
+        break;
+    }
+  }
 
   std::string best_family;
   FontRenderParams best_render_params;