MacViews: draw combobox arrow backgrounds

ui/native_theme/native_theme_mac.mm

Index: ui/native_theme/native_theme_mac.mm
diff --git a/ui/native_theme/native_theme_mac.mm b/ui/native_theme/native_theme_mac.mm
index f9627ff3cb75d417b719cf57873b6a7a6b481501..df2cd58549e4245817a3788ca1f0ca52774c9c8a 100644
--- a/ui/native_theme/native_theme_mac.mm
+++ b/ui/native_theme/native_theme_mac.mm
@@ -12,6 +12,7 @@
 #include "base/mac/sdk_forward_declarations.h"
 #include "base/macros.h"
 #import "skia/ext/skia_utils_mac.h"
+#include "third_party/skia/include/core/SkRRect.h"
 #include "third_party/skia/include/effects/SkGradientShader.h"
 #include "ui/gfx/geometry/rect.h"
 #include "ui/gfx/skia_util.h"
@@ -266,6 +267,60 @@ void NativeThemeMac::PaintMenuItemBackground(
   }
 }
 
+skia::RefPtr<SkShader>
+GetComboboxArrowBackgroundShader(NativeTheme::State state, int height) {
+  SkPoint gradient_points[2];
+  gradient_points[0].iset(0, 0);
+  gradient_points[1].iset(0, height);
+
+  // TODO(ellyjones): These colors are not exactly right, and the gradient
+  // probably needs more stops.
+  SkScalar gradient_positions[] = { 0.0, 0.38, 1.0 };
+
+  SkColor light_blue = SkColorSetRGB(0x4e, 0x97, 0xfd);

[tapted, 2016/03/21 07:09:04]

Are there things we can pick from ui/gfx/color_palette.h? The mocks we got are
meant to be inspired by MD colors, so it might be something from this list
(otherwise we should maybe add it, since it might be an "official" color

[Elly Fong-Jones, 2016/03/21 18:53:56]

Done. kGoogleBlue300 and kGoogleBlue700 turn out to produce a pleasing gradient.

+  SkColor dark_blue = SkColorSetRGB(0x3f, 0x68, 0xe5);
+
+  // TODO(ellyjones): Does this need to handle states other than kHovered and
+  // kNormal?

[tapted, 2016/03/21 07:09:04]

kDisabled. There's also "invalid"

[Elly Fong-Jones, 2016/03/21 18:53:56]

Done.

+  SkColor hovered_colors[] = { light_blue, light_blue, dark_blue };
+  SkColor normal_colors[] = { SK_ColorWHITE, SK_ColorWHITE, SK_ColorWHITE };
+  SkColor* gradient_colors = state == NativeTheme::kHovered ?
+                             hovered_colors :
+                             normal_colors;
+
+  skia::RefPtr<SkShader> gradient_shader = skia::AdoptRef(
+      SkGradientShader::CreateLinear(
+          gradient_points, gradient_colors, gradient_positions, 3,
+          SkShader::kClamp_TileMode));
+  return gradient_shader;
+}
+
+void NativeThemeMac::PaintComboboxArrowBackground(SkCanvas* canvas,
+                                                  State state,
+                                                  const gfx::Rect& rect) const {
+  // TODO(ellyjones): This constant is duplicated in FocusableRoundedBorder at
+  // the moment. Maybe this function should take this as a parameter instead.
+  const int kComboboxBorderRadius = 5;
+
+  skia::RefPtr<SkShader> shader =
+      GetComboboxArrowBackgroundShader(state, rect.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(kComboboxBorderRadius, kComboboxBorderRadius);
+  // Curve upper-right and lower-right corners of the background only.
+  SkVector curves[4] = { no_curve, curve, curve, no_curve };
+
+  SkRRect fill_rect;
+  fill_rect.setRectRadii(gfx::RectToSkRect(rect), curves);
+
+  canvas->drawRRect(fill_rect, paint);
+}
+
 NativeThemeMac::NativeThemeMac() {
 }