Improve RenderTextWin font fallback.

ui/gfx/render_text_unittest.cc

Index: ui/gfx/render_text_unittest.cc
===================================================================
--- ui/gfx/render_text_unittest.cc	(revision 112221)
+++ ui/gfx/render_text_unittest.cc	(working copy)
@@ -543,6 +543,105 @@
 }
 #endif
 
+TEST_F(RenderTextTest, GraphemePositions) {
+  scoped_ptr<RenderText> render_text(RenderText::CreateRenderText());
+
+  // LTR 2-character grapheme, LTR abc, LTR 2-character grapheme.
+  const string16 kText1 = WideToUTF16(L"\x0915\x093f"L"abc"L"\x0915\x093f");
+
+  // LTR ab, LTR 2-character grapheme, LTR cd.
+  const string16 kText2 = WideToUTF16(L"ab"L"\x0915\x093f"L"cd");
+
+  struct {
+    string16 text;
+    size_t index;
+    size_t expected_previous;
+    size_t expected_next;
+  } cases[] = {
+    { string16(), 0, 0, 0 },
+    { string16(), 1, 0, 0 },
+    { string16(), 50, 0, 0 },
+    { kText1, 0, 0, 2 },
+    { kText1, 1, 0, 2 },
+    { kText1, 2, 0, 3 },
+    { kText1, 3, 2, 4 },
+    { kText1, 4, 3, 5 },
+    { kText1, 5, 4, 7 },
+    { kText1, 6, 5, 7 },
+    { kText1, 7, 5, 7 },
+    { kText1, 8, 7, 7 },
+    { kText1, 50, 7, 7 },
+    { kText2, 0, 0, 1 },
+    { kText2, 1, 0, 2 },
+    { kText2, 2, 1, 4 },
+    { kText2, 3, 2, 4 },
+    { kText2, 4, 2, 5 },
+    { kText2, 5, 4, 6 },
+    { kText2, 6, 5, 6 },
+    { kText2, 7, 6, 6 },
+    { kText2, 50, 6, 6 },
+  };
+
+  for (size_t i = 0; i < ARRAYSIZE_UNSAFE(cases); i++) {
+    render_text->SetText(cases[i].text);
+
+    size_t next = render_text->GetIndexOfNextGrapheme(cases[i].index);
+    EXPECT_EQ(cases[i].expected_next, next);
+    EXPECT_TRUE(render_text->IsCursorablePosition(next));
+
+    size_t previous = render_text->GetIndexOfPreviousGrapheme(cases[i].index);
+    EXPECT_EQ(cases[i].expected_previous, previous);
+    EXPECT_TRUE(render_text->IsCursorablePosition(previous));
+  }
+}
+
+TEST_F(RenderTextTest, SelectionModels) {
+  // Simple Latin text.
+  const string16 kLatin = WideToUTF16(L"abc");
+  // LTR 2-character grapheme.
+  const string16 kLTRGrapheme = WideToUTF16(L"\x0915\x093f");
+  // LTR 2-character grapheme, LTR a, LTR 2-character grapheme.
+  const string16 kHindiLatin = WideToUTF16(L"\x0915\x093f"L"a"L"\x0915\x093f");
+  // RTL 2-character grapheme.
+  const string16 kRTLGrapheme = WideToUTF16(L"\x05e0\x05b8");
+  // RTL 2-character grapheme, LTR a, RTL 2-character grapheme.
+  const string16 kHebrewLatin = WideToUTF16(L"\x05e0\x05b8"L"a"L"\x05e0\x05b8");
+
+  struct {
+    string16 text;
+    size_t expected_left_end_caret;
+    SelectionModel::CaretPlacement expected_left_end_placement;
+    size_t expected_right_end_caret;
+    SelectionModel::CaretPlacement expected_right_end_placement;
+    size_t expected_next;
+  } cases[] = {
+    { string16(), 0, SelectionModel::LEADING, 0, SelectionModel::LEADING },
+    { kLatin, 0, SelectionModel::LEADING, 2, SelectionModel::TRAILING },
+    { kLTRGrapheme, 0, SelectionModel::LEADING, 0, SelectionModel::TRAILING },
+    { kHindiLatin, 0, SelectionModel::LEADING, 3, SelectionModel::TRAILING },
+    { kRTLGrapheme, 0, SelectionModel::TRAILING, 0, SelectionModel::LEADING },
+// TODO(asvitkine): This behaves differently on Linux. Why?

[xji, 2011/12/01 20:19:15]

Thanks for adding those tests!

In Windows, text is always displayed as left-to-right, (I wont use your case,
since for your case, the text is displayed exactly the same whether the
directionality is LTR or RTL, even though the rightmost character's logical
index is different for LTR and RTL).
Let's say the text is ABaCD where capital letter represents Hebrew,
it is displayed as  BAaDC

In Linux, pango use the directionality of first strong character's to determine
the direction of the text, so for above case, it is right-to-left, and it is
displayed as:  DCaBA
 
So for pango, the left-end is: (3, trailing), the right-end is (0, leading).
The expectation should be:
{ kHebrewLatin, 3, SelectionModel::TRAILING, 0, SelectionModel::LEADING },

[Alexei Svitkine (slow), 2011/12/01 20:58:58]

I see. I've added the Linux expectation.

+#if !defined(OS_LINUX)
+    { kHebrewLatin, 0, SelectionModel::TRAILING, 3, SelectionModel::LEADING },
+#endif
+  };
+
+  scoped_ptr<RenderText> render_text(RenderText::CreateRenderText());
+  for (size_t i = 0; i < ARRAYSIZE_UNSAFE(cases); i++) {
+    render_text->SetText(cases[i].text);
+
+    SelectionModel model = render_text->LeftEndSelectionModel();
+    EXPECT_EQ(cases[i].expected_left_end_caret, model.caret_pos());
+    EXPECT_TRUE(render_text->IsCursorablePosition(model.caret_pos()));
+    EXPECT_EQ(cases[i].expected_left_end_placement, model.caret_placement());
+
+    model = render_text->RightEndSelectionModel();
+    EXPECT_EQ(cases[i].expected_right_end_caret, model.caret_pos());
+    EXPECT_TRUE(render_text->IsCursorablePosition(model.caret_pos()));
+    EXPECT_EQ(cases[i].expected_right_end_placement, model.caret_placement());
+  }
+}
+
 TEST_F(RenderTextTest, MoveCursorLeftRightWithSelection) {
   scoped_ptr<RenderText> render_text(RenderText::CreateRenderText());
   render_text->SetText(WideToUTF16(L"abc\x05d0\x05d1\x05d2"));