Fix LabelButtonBorder image blending.

ui/views/controls/button/label_button_border.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 "ui/views/controls/button/label_button_border.h"
 
 #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"
 #include "ui/native_theme/native_theme.h"
 #include "ui/views/controls/button/label_button.h"
 #include "ui/views/native_theme_delegate.h"
 
 namespace views {
 
 namespace {
@@ skipping 18 matching lines @@
     case ui::NativeTheme::kNormal:   return Button::STATE_NORMAL;
     case ui::NativeTheme::kPressed:  return Button::STATE_PRESSED;
     case ui::NativeTheme::kMaxState: NOTREACHED() << "Unknown state: " << state;
   }
   return Button::STATE_NORMAL;
 }
 
 // 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,
                  const gfx::Rect& rect,
                  const ui::NativeTheme::ExtraParams& extra) {
   if (border->style() == Button::STYLE_NATIVE_TEXTBUTTON) {
     theme->Paint(canvas->sk_canvas(), part, state, rect, extra);
   } 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);
   }
 }
 
 }  // namespace
 
 LabelButtonBorder::LabelButtonBorder(Button::ButtonStyle style)
     : style_(style) {
   if (style == Button::STYLE_BUTTON) {
     set_insets(gfx::Insets(9, 13, 9, 13));
     SetPainter(false, Button::STATE_NORMAL,
@@ skipping 19 matching lines @@
     SetPainter(false, Button::STATE_PRESSED,
                Painter::CreateImageGridPainter(kTextPressedImages));
   } else if (style == Button::STYLE_NATIVE_TEXTBUTTON) {
     set_insets(gfx::Insets(5, 12, 5, 12));
   }
 }
 
 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);
+    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));

[reed1, 2013/06/12 20:05:10]

Does this guy *not* actually create a layer if the passed alpha is 0xFF? ... I
hope so (for efficiency sake)

[msw, 2013/06/12 22:10:55]

I think Canvas does create a layer for 0xFF, it seems equivalent to Save().
The underlying code just passes through to Skia's SkCanvas::saveLayerAlpha:
https://code.google.com/p/chromium/codesearch#chromium/src/third_party/skia/s...
This animation halts at full opacity and reverts to the simpler path below.

+      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);
+      paint.setXfermode(SkLerpXfermode::Create(animation->GetCurrentValue()));

[reed1, 2013/06/12 20:05:10]

Create returns a new xfermode
setXfermode refs that mode (and will call unref when it dies)
... but we still have a dangling owner (Create), so we'll get a leak.

SkAutoTUnref<SkXfermode> mode(SkLerpXfermode::Create(...));
paint.setXfermode(mode);

The above will do the trick.

[msw, 2013/06/12 22:10:55]

I'm using skia::RefPtr instead; since SkAutoTUnref gives
** Presubmit ERRORS ** Banned functions were used.
      The use of SkAutoTUnref is dangerous because it implicitly
      converts to a raw pointer. Please use skia::RefPtr instead.

I found 2 other places using an SkXfermode::Create raw ptr:
https://code.google.com/p/chromium/codesearch#chromium/src/chrome/browser/spe...
https://code.google.com/p/chromium/codesearch#chromium/src/ui/views/controls/...
Would you like me to file a bug? Should Create return a skia::RefPtr?

+      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.
   if (style() == Button::STYLE_NATIVE_TEXTBUTTON &&
       view.focus_border() && extra.button.is_focused)
     view.focus_border()->Paint(view, canvas);
 }
 
 gfx::Insets LabelButtonBorder::GetInsets() const {
   return insets_;
 }
 
 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();
 }
 
 void LabelButtonBorder::SetPainter(bool focused,
                                    Button::ButtonState state,
                                    Painter* painter) {
   painters_[focused ? 1 : 0][state].reset(painter);
 }
 
 }  // namespace views