Enable subpixel positioning for UI

ui/views/controls/textfield/textfield_unittest.cc

Index: ui/views/controls/textfield/textfield_unittest.cc
diff --git a/ui/views/controls/textfield/textfield_unittest.cc b/ui/views/controls/textfield/textfield_unittest.cc
index 84da7d4e37f0473ee520dd9fd47c223d63990270..2ec05f49130bec552b0a3184e03ad2483a384e70 100644
--- a/ui/views/controls/textfield/textfield_unittest.cc
+++ b/ui/views/controls/textfield/textfield_unittest.cc
@@ -1451,12 +1451,12 @@ TEST_F(TextfieldTest, TextCursorDisplayTest) {
   SendKeyEvent(0x05E1);
   EXPECT_EQ(WideToUTF16(L"ab\x05E1"), textfield_->text());
   x = GetCursorBounds().x();
-  EXPECT_EQ(prev_x, x);
+  EXPECT_GE(1, std::abs(x - prev_x));

[msw, 2014/11/24 21:51:00]

If I read this right, entering an RTL character in an LTR string could cause the
cursor position to shift by a pixel or less? Why is this expectation changing?
Can you avoid this?

[ckocagil, 2014/11/25 01:39:47]

When the cursor is placed between two glyphs, we place it at
std::round(boundary) which is visually better. But when it's placed at the
rightmost position we use std::ceil to ensure it doesn't overlap the last glyph.
So these values are off by one if the boundary gets rounded down.
I tried, but there are many assumptions in tests. I'd prefer fixing this in a
followup CL.

[msw, 2014/11/25 04:52:06]

Add an explanatory comment and/or TODO.

 
   SendKeyEvent(0x05E2);
   EXPECT_EQ(WideToUTF16(L"ab\x05E1\x5E2"), textfield_->text());
   x = GetCursorBounds().x();
-  EXPECT_EQ(prev_x, x);
+  EXPECT_GE(1, std::abs(x - prev_x));
 
   // Clear text.
   SendKeyEvent(ui::VKEY_A, false, true);
@@ -1472,7 +1472,7 @@ TEST_F(TextfieldTest, TextCursorDisplayTest) {
   SendKeyEvent(0x05E2);
   EXPECT_EQ(WideToUTF16(L"\x05E1\x05E2"), textfield_->text());
   x = GetCursorBounds().x();
-  EXPECT_EQ(prev_x, x);
+  EXPECT_GE(1, std::abs(x - prev_x));
 
   SendKeyEvent('a');
   EXPECT_EQ(WideToUTF16(L"\x05E1\x5E2" L"a"), textfield_->text());
@@ -1501,7 +1501,7 @@ TEST_F(TextfieldTest, TextCursorDisplayInRTLTest) {
   SendKeyEvent('b');
   EXPECT_STR_EQ("ab", textfield_->text());
   x = GetCursorBounds().x();
-  EXPECT_EQ(prev_x, x);
+  EXPECT_GE(1, std::abs(x - prev_x));
 
   SendKeyEvent(0x05E1);
   EXPECT_EQ(WideToUTF16(L"ab\x05E1"), textfield_->text());
@@ -1532,7 +1532,7 @@ TEST_F(TextfieldTest, TextCursorDisplayInRTLTest) {
   SendKeyEvent('a');
   EXPECT_EQ(WideToUTF16(L"\x05E1\x5E2" L"a"), textfield_->text());
   x = GetCursorBounds().x();
-  EXPECT_EQ(prev_x, x);
+  EXPECT_GE(1, std::abs(x - prev_x));
   prev_x = x;
 
   SendKeyEvent('b');