WIP - mask a view's layer by its view coordinates

ui/views/controls/button/md_text_button.cc

 // Copyright 2015 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/md_text_button.h"
 
 #include "base/i18n/case_conversion.h"
 #include "ui/base/material_design/material_design_controller.h"
+#include "ui/compositor/paint_context.h"
+#include "ui/compositor/paint_recorder.h"
 #include "ui/gfx/canvas.h"
 #include "ui/gfx/color_palette.h"
 #include "ui/gfx/color_utils.h"
 #include "ui/native_theme/native_theme.h"
 #include "ui/views/animation/flood_fill_ink_drop_ripple.h"
 #include "ui/views/animation/ink_drop_highlight.h"
 #include "ui/views/animation/ink_drop_impl.h"
 #include "ui/views/animation/ink_drop_painted_layer_delegates.h"
 #include "ui/views/background.h"
 #include "ui/views/border.h"
 #include "ui/views/controls/button/blue_button.h"
 #include "ui/views/controls/focus_ring.h"
 #include "ui/views/painter.h"
 #include "ui/views/style/platform_style.h"
 
 namespace views {
 
 namespace {
 
 // Minimum size to reserve for the button contents.
 const int kMinWidth = 48;
 
+class VisibleMaskLayerDelegate : public ui::LayerDelegate {
+ public:
+  explicit VisibleMaskLayerDelegate(views::View* view, const ui::Layer* layer)
+      : view_(view), layer_(layer) {}
+  ~VisibleMaskLayerDelegate() override {}
+
+  // ui::LayerDelegate:
+  void OnPaintLayer(const ui::PaintContext& context) override {
+    ui::PaintRecorder recorder(context, layer_->size());
+    gfx::Rect bounds = view_->GetVisibleBounds();
+    recorder.canvas()->FillRect(bounds, SK_ColorBLACK);
+  }
+
+  void OnDelegatedFrameDamage(
+      const gfx::Rect& damage_rect_in_dip) override {}
+  void OnDeviceScaleFactorChanged(float device_scale_factor) override {}
+
+ private:
+views::View* view_;
+  const ui::Layer* const layer_;
+  DISALLOW_COPY_AND_ASSIGN(VisibleMaskLayerDelegate);
+};
+
 LabelButton* CreateButton(ButtonListener* listener,
                           const base::string16& text,
                           bool md) {
   if (md)
     return MdTextButton::Create(listener, text);
 
   LabelButton* button = new LabelButton(listener, text);
   button->SetStyle(CustomButton::STYLE_BUTTON);
   return button;
 }
@@ skipping 55 matching lines @@
 
 void MdTextButton::OnPaintBackground(gfx::Canvas* canvas) {
   LabelButton::OnPaintBackground(canvas);
   if (hover_animation().is_animating() || state() == STATE_HOVERED) {
     const int kHoverAlpha = is_prominent_ ? 0x0c : 0x05;
     SkScalar alpha = hover_animation().CurrentValueBetween(0, kHoverAlpha);
     canvas->FillRect(GetLocalBounds(), SkColorSetA(SK_ColorBLACK, alpha));
   }
 }
 
+bool MdTextButton::GetNeedsNotificationWhenVisibleBoundsChange() const {
+  return true;
+}
+
+void MdTextButton::OnVisibleBoundsChanged() {
+  gfx::Rect visible_bounds = GetVisibleBounds();
+  if (last_visible_bounds_ != visible_bounds)
+    SchedulePaint();
+  last_visible_bounds_ = visible_bounds;
+}
+
+void MdTextButton::OnLayerBoundsChanged(const gfx::Rect& old_bounds) {
+  LabelButton::OnLayerBoundsChanged(old_bounds);
+ // mask_layer_.SetBounds(layer()->bounds());
+}
+
 void MdTextButton::OnFocus() {
   LabelButton::OnFocus();
   FocusRing::Install(this);
 }
 
 void MdTextButton::OnBlur() {
   LabelButton::OnBlur();
   FocusRing::Uninstall(this);
 }
 
@@ skipping 83 matching lines @@
   label()->SetAutoColorReadabilityEnabled(false);
   set_request_focus_on_press(false);
   LabelButton::SetFontList(GetMdFontList());
 
   set_animate_on_state_change(true);
 
   // Paint to a layer so that the canvas is snapped to pixel boundaries (useful
   // for fractional DSF).
   SetPaintToLayer(true);
   layer()->SetFillsBoundsOpaquely(false);
+/*
+  mask_layer_.SetFillsBoundsOpaquely(false);
+  mask_layer_delegate_.reset(new VisibleMaskLayerDelegate(this, &mask_layer_));
+  mask_layer_.set_delegate(mask_layer_delegate_.get());
+  layer()->SetMaskLayer(&mask_layer_);
+*/
 }
 
 void MdTextButton::UpdatePadding() {
   // Don't use font-based padding when there's no text visible.
   if (GetText().empty()) {
     SetBorder(NullBorder());
     return;
   }
 
   // Text buttons default to 28dp in height on all platforms when the base font
@@ skipping 74 matching lines @@
         stroke_color, gfx::kDisabledControlAlpha);
   }
 
   DCHECK_EQ(SK_AlphaOPAQUE, static_cast<int>(SkColorGetA(bg_color)));
   set_background(Background::CreateBackgroundPainter(
       true, Painter::CreateRoundRectWith1PxBorderPainter(
                 bg_color, stroke_color, kInkDropSmallCornerRadius)));
 }
 
 }  // namespace views