Fix LabelButtonBorder image blending.

ui/views/controls/button/label_button_border.cc

Index: ui/views/controls/button/label_button_border.cc
diff --git a/ui/views/controls/button/label_button_border.cc b/ui/views/controls/button/label_button_border.cc
index ef827667f9e119114afaac3ba7f2c2eae4ba1ef3..210b50accb7593612a91f719cad8e4c603825b65 100644
--- a/ui/views/controls/button/label_button_border.cc
+++ b/ui/views/controls/button/label_button_border.cc
@@ -6,6 +6,8 @@
 
 #include "base/logging.h"
 #include "grit/ui_resources.h"
+#include "third_party/skia/include/core/SkPaint.h"
+#include "third_party/skia/include/effects/SkLerpXfermode.h"
 #include "ui/base/animation/animation.h"
 #include "ui/gfx/canvas.h"
 #include "ui/gfx/rect.h"
@@ -44,6 +46,7 @@ Button::ButtonState GetButtonState(ui::NativeTheme::State state) {
 // A helper function to paint the native theme or images as appropriate.
 void PaintHelper(LabelButtonBorder* border,
                  gfx::Canvas* canvas,
+                 const SkPaint& paint,
                  const ui::NativeTheme* theme,
                  ui::NativeTheme::Part part,
                  ui::NativeTheme::State state,
@@ -54,11 +57,8 @@ void PaintHelper(LabelButtonBorder* border,
   } else {
     Painter* painter =
         border->GetPainter(extra.button.is_focused, GetButtonState(state));
-    // Paint any corresponding unfocused painter if there is no focused painter.
-    if (!painter && extra.button.is_focused)
-      painter = border->GetPainter(false, GetButtonState(state));
     if (painter)
-      painter->Paint(canvas, rect.size());
+      painter->PaintWithSkPaint(canvas, rect.size(), paint);
   }
 }
 
@@ -98,29 +98,38 @@ LabelButtonBorder::LabelButtonBorder(Button::ButtonStyle style)
 LabelButtonBorder::~LabelButtonBorder() {}
 
 void LabelButtonBorder::Paint(const View& view, gfx::Canvas* canvas) {
-  const NativeThemeDelegate* native_theme_delegate =
-      static_cast<const LabelButton*>(&view);
-  ui::NativeTheme::Part part = native_theme_delegate->GetThemePart();
-  gfx::Rect rect(native_theme_delegate->GetThemePaintRect());
+  const NativeThemeDelegate* delegate = static_cast<const LabelButton*>(&view);
+  const ui::NativeTheme::Part part = delegate->GetThemePart();
+  const gfx::Rect rect(delegate->GetThemePaintRect());
   ui::NativeTheme::ExtraParams extra;
   const ui::NativeTheme* theme = view.GetNativeTheme();
-  const ui::Animation* animation = native_theme_delegate->GetThemeAnimation();
-  ui::NativeTheme::State state = native_theme_delegate->GetThemeState(&extra);
+  const ui::Animation* animation = delegate->GetThemeAnimation();
+  SkPaint paint;
 
   if (animation && animation->is_animating()) {
     // Composite the background and foreground painters during state animations.
-    int alpha = animation->CurrentValueBetween(0, 0xff);
-    state = native_theme_delegate->GetBackgroundThemeState(&extra);
-    canvas->SaveLayerAlpha(static_cast<uint8>(0xff - alpha));
-    PaintHelper(this, canvas, theme, part, state, rect, extra);
-    canvas->Restore();
-
-    state = native_theme_delegate->GetForegroundThemeState(&extra);
-    canvas->SaveLayerAlpha(static_cast<uint8>(alpha));
-    PaintHelper(this, canvas, theme, part, state, rect, extra);
-    canvas->Restore();
+    ui::NativeTheme::State back = delegate->GetBackgroundThemeState(&extra);
+    ui::NativeTheme::State fore = delegate->GetForegroundThemeState(&extra);

[sky, 2013/06/13 16:22:04]

foreground, or fg.

+    if (style() == Button::STYLE_NATIVE_TEXTBUTTON) {
+      // NativeTheme does not support image interpolation, use alpha blending.
+      PaintHelper(this, canvas, paint, theme, part, back, rect, extra);
+      const int alpha = animation->CurrentValueBetween(0, 0xff);
+      canvas->SaveLayerAlpha(static_cast<uint8>(alpha));
+      PaintHelper(this, canvas, paint, theme, part, fore, rect, extra);
+      canvas->Restore();
+    } else {
+      canvas->Save();
+      // Use linear interpolation to blend background and foreground images.
+      PaintHelper(this, canvas, paint, theme, part, back, rect, extra);
+      skia::RefPtr<SkXfermode> mode(
+          skia::AdoptRef(SkLerpXfermode::Create(animation->GetCurrentValue())));
+      paint.setXfermode(mode.get());
+      PaintHelper(this, canvas, paint, theme, part, fore, rect, extra);
+      canvas->Restore();
+    }
   } else {
-    PaintHelper(this, canvas, theme, part, state, rect, extra);
+    ui::NativeTheme::State state = delegate->GetThemeState(&extra);
+    PaintHelper(this, canvas, paint, theme, part, state, rect, extra);
   }
 
   // Draw the Views focus border for the native theme style.
@@ -135,6 +144,9 @@ gfx::Insets LabelButtonBorder::GetInsets() const {
 
 Painter* LabelButtonBorder::GetPainter(bool focused,
                                        Button::ButtonState state) {
+  // Use any corresponding unfocused painter if there is no focused painter.
+  if (focused && !painters_[1][state])
+    return painters_[0][state].get();
   return painters_[focused ? 1 : 0][state].get();
 }