Enable subpixel positioning for UI

ui/views/controls/textfield/textfield_unittest.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/views/controls/textfield/textfield.h"
 
 #include <set>
 #include <string>
 #include <vector>
 
@@ skipping 1433 matching lines @@
 
   SendKeyEvent('b');
   EXPECT_STR_EQ("ab", textfield_->text());
   x = GetCursorBounds().x();
   EXPECT_LT(prev_x, x);
   prev_x = x;
 
   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);
   SendKeyEvent('\n');
 
   // RTL-LTR string in LTR context.
   SendKeyEvent(0x05E1);
   EXPECT_EQ(WideToUTF16(L"\x05E1"), textfield_->text());
   x = GetCursorBounds().x();
   EXPECT_EQ(GetDisplayRect().x(), x);
   prev_x = x;
 
   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());
   x = GetCursorBounds().x();
   EXPECT_LT(prev_x, x);
   prev_x = x;
 
   SendKeyEvent('b');
   EXPECT_EQ(WideToUTF16(L"\x05E1\x5E2" L"ab"), textfield_->text());
   x = GetCursorBounds().x();
   EXPECT_LT(prev_x, x);
 }
 
 TEST_F(TextfieldTest, TextCursorDisplayInRTLTest) {
   std::string locale = l10n_util::GetApplicationLocale("");
   base::i18n::SetICUDefaultLocale("he");
 
   InitTextfield();
   // LTR-RTL string in RTL context.
   SendKeyEvent('a');
   EXPECT_STR_EQ("a", textfield_->text());
   int x = GetCursorBounds().x();
   EXPECT_EQ(GetDisplayRect().right() - 1, x);
   int prev_x = x;
 
   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());
   x = GetCursorBounds().x();
   EXPECT_GT(prev_x, x);
   prev_x = x;
 
   SendKeyEvent(0x05E2);
   EXPECT_EQ(WideToUTF16(L"ab\x05E1\x5E2"), textfield_->text());
   x = GetCursorBounds().x();
@@ skipping 10 matching lines @@
 
   SendKeyEvent(0x05E2);
   EXPECT_EQ(WideToUTF16(L"\x05E1\x05E2"), textfield_->text());
   x = GetCursorBounds().x();
   EXPECT_GT(prev_x, x);
   prev_x = x;
 
   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');
   EXPECT_EQ(WideToUTF16(L"\x05E1\x5E2" L"ab"), textfield_->text());
   x = GetCursorBounds().x();
   EXPECT_EQ(prev_x, x);
 
   // Reset locale.
   base::i18n::SetICUDefaultLocale(locale);
 }
@@ skipping 524 matching lines @@
   TextfieldDestroyerController controller(textfield_);
   EXPECT_TRUE(controller.target());
 
   // Send a key to trigger OnKeyEvent().
   SendKeyEvent('X');
 
   EXPECT_FALSE(controller.target());
 }
 
 }  // namespace views