Add a Canvas::SaveAndUnscale() method for pixel-accurate drawing.

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 244 matching lines @@
   gfx::Rect title_bounds = GetTitleBounds();
   title_bounds.set_x(view_->GetMirroredXForRect(title_bounds));
   canvas->DrawStringRectWithFlags(frame_->widget_delegate()->GetWindowTitle(),
                                   GetTitleFontList(),
                                   kTitleTextColor,
                                   title_bounds,
                                   gfx::Canvas::NO_SUBPIXEL_RENDERING);
 }
 
 void DefaultHeaderPainter::PaintHeaderContentSeparator(gfx::Canvas* canvas) {
-  SkColor color = (mode_ == MODE_ACTIVE) ?
-      kHeaderContentSeparatorColor :
-      kHeaderContentSeparatorInactiveColor;
-
+  const float scale = canvas->SaveAndUnscale();
+  gfx::RectF rect(0, painted_height_ * scale - 1, view_->width() * scale, 1);
   SkPaint paint;
-  paint.setColor(color);
-  // Draw the line as 1px thick regardless of scale factor.
-  paint.setStrokeWidth(0);
-
-  float thickness = 1 / canvas->image_scale();
-  SkScalar y = SkIntToScalar(painted_height_) - SkFloatToScalar(thickness);
-  canvas->sk_canvas()->drawLine(0, y, SkIntToScalar(view_->width()), y, paint);
+  paint.setColor((mode_ == MODE_ACTIVE) ?
+      kHeaderContentSeparatorColor : kHeaderContentSeparatorInactiveColor);
+  canvas->sk_canvas()->drawRect(gfx::RectFToSkRect(rect), paint);
+  canvas->Restore();
 }
 
 void DefaultHeaderPainter::LayoutLeftHeaderView() {
   if (left_header_view_) {
     // Vertically center the left header view with respect to the caption button
     // container.
     // Floor when computing the center of |caption_button_container_|.
     gfx::Size size = left_header_view_->GetPreferredSize();
     int icon_offset_y = caption_button_container_->height() / 2 -
                         size.height() / 2;
@@ skipping 65 matching lines @@
   return HeaderPainterUtil::GetTitleBounds(
       left_header_view_, caption_button_container_, GetTitleFontList());
 }
 
 bool DefaultHeaderPainter::UsesCustomFrameColors() const {
   return active_frame_color_ != kDefaultFrameColor ||
          inactive_frame_color_ != kDefaultFrameColor;
 }
 
 }  // namespace ash