MacViews: draw combobox arrow backgrounds

ui/views/style/mac/combobox_background_mac.cc

+// Copyright 2016 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/style/mac/combobox_background_mac.h"
+
+#include "third_party/skia/include/core/SkPath.h"
+#include "third_party/skia/include/core/SkRRect.h"
+#include "ui/gfx/canvas.h"
+#include "ui/native_theme/native_theme_mac.h"
+#include "ui/views/controls/combobox/combobox.h"
+#include "ui/views/view.h"
+
+namespace views {
+
+void ComboboxBackgroundMac::Paint(gfx::Canvas* canvas, View* view) const {
+  DCHECK_EQ(view->GetClassName(), Combobox::kViewClassName);
+  Combobox* combobox = static_cast<Combobox*>(view);
+
+  gfx::Rect bounds = combobox->GetLocalBounds();
+  bounds.Inset(bounds.width() - combobox->GetArrowButtonWidth(), 0, 0, 0);

[tapted, 2016/03/23 03:08:01]

There's a minor visual glitch here -- see the unfocused border at
http://crbug.com/543683#c6. These lines should be

gfx::RectF bounds(combobox->GetLocalBounds());
bounds.Inset(bounds.width() - combobox->GetArrowButtonWidth(), 0.5, 0.5, 0.5);

(plus a change below)

The 0.5 is to cater for the border stroke inset (which is done so that the
border stroke aligns to a single line of pixels). I think a 0.5 literal is fine
(perhaps with a comment) since "half a pixel" should always work regardless of
the stroke thickness (the border will just paint over it, except for that
half-pixel on the outside of the rounded bits, which is causing the glitch)

There may be more to do when we update the focus ring style (but for now it
looks a bit funny with the glitch).

[Elly Fong-Jones, 2016/03/23 18:07:44]

Done.

+
+  ui::NativeTheme::State state = ui::NativeTheme::kNormal;
+  if (!combobox->enabled())
+    state = ui::NativeTheme::kDisabled;
+
+  skia::RefPtr<SkShader> shader =
+      ui::NativeThemeMac::GetButtonBackgroundShader(
+          state,
+          bounds.height());
+  SkPaint paint;
+  paint.setShader(shader.get());
+  paint.setStyle(SkPaint::kFill_Style);
+  paint.setAntiAlias(true);
+
+  SkPoint no_curve = SkPoint::Make(0, 0);
+  SkPoint curve = SkPoint::Make(
+      ui::NativeThemeMac::kComboboxCornerRadius,
+      ui::NativeThemeMac::kComboboxCornerRadius);
+  SkVector curves[4] = { no_curve, curve, curve, no_curve };
+
+  SkRRect fill_rect;
+  fill_rect.setRectRadii(gfx::RectToSkRect(bounds), curves);

[tapted, 2016/03/23 03:08:01]

this will need to be 

fill_rect.setRectRadii(gfx::RectFToSkRect(bounds), curves);

[Elly Fong-Jones, 2016/03/23 18:07:44]

Done.

+
+  SkPath path;
+  path.addRRect(fill_rect);
+
+  canvas->DrawPath(path, paint);
+}
+
+}  // namespace views