Draw infobar arrow border with width of 1px on any scale factor.

chrome/browser/ui/views/infobars/infobar_background.cc

 // Copyright (c) 2012 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 "chrome/browser/ui/views/infobars/infobar_background.h"
 
 #include "chrome/browser/ui/infobar_container_delegate.h"
 #include "chrome/browser/ui/views/infobars/infobar_view.h"
 #include "components/infobars/core/infobar.h"
 #include "third_party/skia/include/effects/SkGradientShader.h"
+#include "ui/base/material_design/material_design_controller.h"
 #include "ui/gfx/canvas.h"
 #include "ui/gfx/color_utils.h"
+#include "ui/gfx/scoped_canvas.h"
 #include "ui/views/view.h"
 
 InfoBarBackground::InfoBarBackground(
     infobars::InfoBarDelegate::Type infobar_type)
-    : separator_color_(SK_ColorBLACK),
-      top_color_(infobars::InfoBar::GetTopColor(infobar_type)),
+    : top_color_(infobars::InfoBar::GetTopColor(infobar_type)),
       bottom_color_(infobars::InfoBar::GetBottomColor(infobar_type)) {
   SetNativeControlColor(
       color_utils::AlphaBlend(top_color_, bottom_color_, 128));
 }
 
 InfoBarBackground::~InfoBarBackground() {
 }
 
 void InfoBarBackground::Paint(gfx::Canvas* canvas, views::View* view) const {
+  if (ui::MaterialDesignController::IsModeMaterial()) {
+    PaintMd(canvas, view);
+    return;
+  }
+
   SkPoint gradient_points[2];
   gradient_points[0].iset(0, 0);
   gradient_points[1].iset(0, view->height());
-  SkColor gradient_colors[2] = { top_color_, bottom_color_ };
+  SkColor gradient_colors[2] = {top_color_, bottom_color_};
   SkPaint paint;
   paint.setStrokeWidth(
       SkIntToScalar(InfoBarContainerDelegate::kSeparatorLineHeight));
   paint.setStyle(SkPaint::kFill_Style);
   paint.setStrokeCap(SkPaint::kRound_Cap);
   paint.setShader(SkGradientShader::MakeLinear(
-      gradient_points, gradient_colors, NULL, 2, SkShader::kClamp_TileMode));
+      gradient_points, gradient_colors, nullptr, 2, SkShader::kClamp_TileMode));
 
+  SkCanvas* canvas_skia = canvas->sk_canvas();
   InfoBarView* infobar = static_cast<InfoBarView*>(view);
-  SkCanvas* canvas_skia = canvas->sk_canvas();
   canvas_skia->drawPath(infobar->fill_path(), paint);
 
-  paint.setShader(NULL);
-  paint.setColor(SkColorSetA(separator_color_,
-                             SkColorGetA(gradient_colors[0])));
+  paint.setShader(nullptr);
+  SkColor separator_color =
+      infobar->container_delegate()->GetInfoBarSeparatorColor();
+  paint.setColor(
+      SkColorSetA(separator_color,
+                  SkColorGetA(gradient_colors[0])));
   paint.setStyle(SkPaint::kStroke_Style);
   // Anti-alias the path so it doesn't look goofy when the edges are not at 45
   // degree angles, but don't anti-alias anything else, especially not the fill,
   // lest we get weird color bleeding problems.
   paint.setAntiAlias(true);
   canvas_skia->drawPath(infobar->stroke_path(), paint);
   paint.setAntiAlias(false);
 
   // Now draw the separator at the bottom.
   canvas->FillRect(
       gfx::Rect(0,
                 view->height() - InfoBarContainerDelegate::kSeparatorLineHeight,
                 view->width(), InfoBarContainerDelegate::kSeparatorLineHeight),
-      separator_color_);
+      separator_color);
 }
+
+void InfoBarBackground::PaintMd(gfx::Canvas* canvas, views::View* view) const {
+  InfoBarView* infobar = static_cast<InfoBarView*>(view);
+  const infobars::InfoBarContainer::Delegate* delegate =
+      infobar->container_delegate();
+  SkPath stroke_path, fill_path;
+  SkColor separator_color = SK_ColorBLACK;
+  if (delegate) {
+    separator_color = delegate->GetInfoBarSeparatorColor();
+    int arrow_x;
+    if (delegate->DrawInfoBarArrows(&arrow_x) && infobar->arrow_height() > 0) {
+      SkScalar arrow_fill_height = SkIntToScalar(infobar->arrow_height());
+      SkScalar arrow_fill_half_width =
+          SkIntToScalar(infobar->arrow_half_width());
+      stroke_path.moveTo(SkIntToScalar(arrow_x) - arrow_fill_half_width,
+                         SkIntToScalar(infobar->arrow_height()));
+      stroke_path.rLineTo(arrow_fill_half_width, -arrow_fill_height);
+      stroke_path.rLineTo(arrow_fill_half_width, arrow_fill_height);
+
+      fill_path = stroke_path;
+      fill_path.close();
+    }
+  }
+  fill_path.addRect(0, SkIntToScalar(infobar->arrow_height()),
+                    SkIntToScalar(infobar->width()),
+                    SkIntToScalar(infobar->height()));
+
+  gfx::ScopedCanvas scoped(canvas);
+  // Undo the scale factor so we can stroke with a width of 1px (not 1dp).
+  const float scale = canvas->UndoDeviceScaleFactor();
+  // View bounds are in dp. Manually scale for px.
+  gfx::SizeF view_size_px = gfx::ScaleSize(gfx::SizeF(view->size()), scale);
+
+  SkPaint fill;
+  fill.setStyle(SkPaint::kFill_Style);
+  fill.setColor(top_color_);
+
+  SkCanvas* canvas_skia = canvas->sk_canvas();
+  // The paths provided by |infobar| are in dp. Manually scale for px.

[Peter Kasting, 2016/04/02 02:42:11]

Nit: I think this comment is slightly out of date, since we no longer get the
paths from the infobar.

[Evan Stade, 2016/04/04 17:24:29]

Done.

+  SkMatrix dsf_transform;
+  dsf_transform.setScale(SkFloatToScalar(scale), SkFloatToScalar(scale));
+  fill_path.transform(dsf_transform);
+  // Skia considers the middle of the pixel to be a fractional value (e.g. 0.5).

[Peter Kasting, 2016/04/02 02:42:11]

Nit: This comment is confusing to me since it sounds like the value might be
other than 0.5 sometimes, and also since it's not really clear why Skia's
perception of pixel centers matters.  How about this:

In order to affect exactly the pixels we want, the fill and stroke paths need to
go through the pixel centers instead of along the pixel edges/corners.  Skia
considers integral coordinates to be the edges between pixels, so offset by 0.5
to get to the centers.

[Evan Stade, 2016/04/04 17:24:29]

Done.

+  fill_path.offset(SK_ScalarHalf, SK_ScalarHalf);
+  canvas_skia->drawPath(fill_path, fill);
+
+  SkPaint stroke;
+  stroke.setStyle(SkPaint::kStroke_Style);
+  const int kSeparatorThicknessPx = 1;
+  stroke.setStrokeWidth(SkIntToScalar(kSeparatorThicknessPx));
+  stroke.setColor(separator_color);
+  stroke_path.transform(dsf_transform);
+  stroke_path.offset(SK_ScalarHalf, SK_ScalarHalf);
+
+  // Top separator (just the arrow shape).

[Peter Kasting, 2016/04/02 02:42:11]

Nit: Maybe fill this out more:

...(just the arrow shape; the rest of the separator line has already been drawn
by the toolbar or previous infobar).

[Evan Stade, 2016/04/04 17:24:29]

Done.

+  stroke.setAntiAlias(true);
+  canvas_skia->drawPath(stroke_path, stroke);
+  // Bottom separator.
+  stroke.setAntiAlias(false);
+  SkScalar y = SkIntToScalar(view_size_px.height() - kSeparatorThicknessPx) +
+               SK_ScalarHalf;
+  SkScalar w = SkIntToScalar(view_size_px.width());
+  canvas_skia->drawLine(0, y, w, y, stroke);
+}