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)),
       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 {
-  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_ };
-  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));
+  if (ui::MaterialDesignController::IsModeMaterial()) {

[Peter Kasting, 2016/03/25 05:07:46]

For simplicity, can we just draw a 1 px border for non-MD as well?  It seems
like the non-MD codepath is complex and different enough that that would be a
nice win, and I don't think the change would feel particularly bad or "out of
place" with the old UI.  IIRC I made some similar toolbar/tabstrip changes where
we now use 1 px borders for some of that stuff even pre-MD...

[Evan Stade, 2016/03/28 21:44:36]

There are several differences:
- stroke width, as you have noted.
- use of gradient
- color of stroke (blending in an alpha from the gradient colors)

So any sharing would have to either
- change things in non-MD, or
- still use some conditional codepaths, or
- simultaneously handle both UIs
The non-MD codepath already exists and is tested (in that it's been in use on
stable for many releases) and should go away soon anyway. I'd rather not touch
it.

[Peter Kasting, 2016/03/29 01:04:00]

Right, this would be an appearance change for non-MD.  That was intentional on
my part (the differences don't seem like they would look bad outside the MD
context).
Fair enough.  I'm OK with leaving it if that turns out to be simpler.

+    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);
 
-  InfoBarView* infobar = static_cast<InfoBarView*>(view);
-  SkCanvas* canvas_skia = canvas->sk_canvas();
-  canvas_skia->drawPath(infobar->fill_path(), paint);
+    SkPaint fill;
+    fill.setStyle(SkPaint::kFill_Style);
+    fill.setColor(top_color_);
 
-  paint.setShader(NULL);
-  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);
+    InfoBarView* infobar = static_cast<InfoBarView*>(view);
+    SkCanvas* canvas_skia = canvas->sk_canvas();
+    // The paths provided by |infobar| are in dp. Manually scale for px.
+    SkMatrix dsf_transform;
+    dsf_transform.setScale(SkFloatToScalar(scale), SkFloatToScalar(scale));
+    SkPath fill_path = infobar->fill_path();
+    fill_path.transform(dsf_transform);
+    canvas_skia->drawPath(fill_path, fill);
 
-  // Now draw the separator at the bottom.
-  canvas->FillRect(
-      gfx::Rect(0,
-                view->height() - InfoBarContainerDelegate::kSeparatorLineHeight,
-                view->width(), InfoBarContainerDelegate::kSeparatorLineHeight),
-      separator_color_);
+    SkPaint stroke;
+    stroke.setStyle(SkPaint::kStroke_Style);
+    stroke.setStrokeWidth(
+        SkIntToScalar(InfoBarContainerDelegate::kSeparatorLineHeight));
+    stroke.setColor(separator_color_);
+    SkPath stroke_path = infobar->stroke_path();
+    stroke_path.transform(dsf_transform);
+
+    // Top separator (with arrow shape).
+    stroke.setAntiAlias(true);
+    canvas_skia->drawPath(stroke_path, stroke);
+    // Bottom separator.
+    stroke.setAntiAlias(false);
+    SkScalar y = SkIntToScalar(view_size_px.height() -
+                               InfoBarContainerDelegate::kSeparatorLineHeight) +
+                 SK_ScalarHalf;
+    SkScalar w = SkIntToScalar(view_size_px.width());
+    canvas_skia->drawLine(0, y, w, y, stroke);
+  } else {
+    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_};
+    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));
+
+    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.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_);
+  }
 }