Make the header/content separator into a hairline for apps in hidpi

ash/frame/default_header_painter.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 "ash/frame/default_header_painter.h"
 
 #include "ash/frame/caption_buttons/frame_caption_button_container_view.h"
 #include "ash/frame/header_painter_util.h"
 #include "base/debug/leak_annotations.h"
 #include "base/logging.h"  // DCHECK
@@ skipping 12 matching lines @@
 #include "ui/views/widget/native_widget_aura.h"
 #include "ui/views/widget/widget.h"
 #include "ui/views/widget/widget_delegate.h"
 
 using views::Widget;
 
 namespace {
 
 // Color for the window title text.
 const SkColor kTitleTextColor = SkColorSetRGB(40, 40, 40);
-// Size of header/content separator line.
-const int kHeaderContentSeparatorSize = 1;
 // Color of the active window header/content separator line.
 const SkColor kHeaderContentSeparatorColor = SkColorSetRGB(180, 180, 182);
 // Color of the inactive window header/content separator line.
 const SkColor kHeaderContentSeparatorInactiveColor =
     SkColorSetRGB(150, 150, 152);
 // Duration of crossfade animation for activating and deactivating frame.
 const int kActivationCrossfadeDurationMs = 200;
 
 // Tiles an image into an area, rounding the top corners.
 void TileRoundRect(gfx::Canvas* canvas,
@@ skipping 166 matching lines @@
   caption_button_container_->SetBounds(
       view_->width() - caption_button_container_size.width(),
       0,
       caption_button_container_size.width(),
       caption_button_container_size.height());
 
   if (window_icon_) {
     // Vertically center the window icon with respect to the caption button
     // container.
     int icon_size = HeaderPainterUtil::GetIconSize();
-    int icon_offset_y = (caption_button_container_->height() - icon_size) / 2;
+    // Floor when computing the center of |caption_button_container|.
+    int icon_offset_y = caption_button_container_->height() / 2 - icon_size / 2;
     window_icon_->SetBounds(HeaderPainterUtil::GetIconXOffset(), icon_offset_y,
         icon_size, icon_size);
   }
 
-  SetHeaderHeightForPainting(caption_button_container_->height() +
-      kHeaderContentSeparatorSize);
+  // The header/content separator line overlays the caption buttons.
+  SetHeaderHeightForPainting(caption_button_container_->height());
 }
 
 int DefaultHeaderPainter::GetHeaderHeightForPainting() const {
   return height_;
 }
 
 void DefaultHeaderPainter::SetHeaderHeightForPainting(int height) {
   height_ = height;
 }
 
@@ skipping 55 matching lines @@
                                   kTitleTextColor,
                                   title_bounds,
                                   gfx::Canvas::NO_SUBPIXEL_RENDERING);
 }
 
 void DefaultHeaderPainter::PaintHeaderContentSeparator(gfx::Canvas* canvas) {
   SkColor color = (mode_ == MODE_ACTIVE) ?
       kHeaderContentSeparatorColor :
       kHeaderContentSeparatorInactiveColor;
 
-  canvas->FillRect(gfx::Rect(0,
-                             height_ - kHeaderContentSeparatorSize,
-                             view_->width(),
-                             kHeaderContentSeparatorSize),
-                   color);
+  SkPaint paint;
+  paint.setColor(color);
+  // Draw the line as 1px thick regardless of scale factor.

[James Cook, 2014/03/17 16:55:59]

Thanks for this comment. It saves the reader from having to look up the oddity
of stroke width == 0, which I had to do the last time someone sent me a code
review with this line. :-)

+  paint.setStrokeWidth(0);
+
+  float thickness = 1 / canvas->image_scale();
+  SkScalar y = SkIntToScalar(height_) - SkFloatToScalar(thickness);
+  canvas->sk_canvas()->drawLine(0, y, SkIntToScalar(view_->width()), y, paint);
 }
 
 gfx::Rect DefaultHeaderPainter::GetLocalBounds() const {
   return gfx::Rect(view_->width(), height_);
 }
 
 gfx::Rect DefaultHeaderPainter::GetTitleBounds() const {
   return HeaderPainterUtil::GetTitleBounds(
       window_icon_, caption_button_container_, GetTitleFontList());
 }
 
 }  // namespace ash