Skip paint chunks with effectively invisible opacity.

third_party/WebKit/Source/core/paint/PaintLayerPainter.cpp

 // Copyright 2014 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 "core/paint/PaintLayerPainter.h"
 
 #include "core/frame/LocalFrame.h"
 #include "core/layout/LayoutView.h"
 #include "core/paint/ClipPathClipper.h"
 #include "core/paint/FilterPainter.h"
@@ skipping 46 matching lines @@
 static ShouldRespectOverflowClipType ShouldRespectOverflowClip(
     PaintLayerFlags paint_flags,
     const LayoutObject& layout_object) {
   return (paint_flags & kPaintLayerPaintingOverflowContents ||
           (paint_flags & kPaintLayerPaintingChildClippingMaskPhase &&
            layout_object.HasClipPath()))
              ? kIgnoreOverflowClip
              : kRespectOverflowClip;
 }
 
-bool PaintLayerPainter::PaintedOutputInvisible(

[chrishtr, 2017/04/26 19:58:21]

I think we still need this for SPv1.

[wkorman, 2017/04/27 00:02:32]

Restored SPv1 behavior.

-    const PaintLayerPaintingInfo& painting_info) {
-  const LayoutObject& layout_object = paint_layer_.GetLayoutObject();
-  if (layout_object.HasBackdropFilter())
-    return false;
-
-  // Always paint when 'will-change: opacity' is present. Reduces jank for
-  // common animation implementation approaches, for example, an element that
-  // starts with opacity zero and later begins to animate.
-  if (layout_object.StyleRef().HasWillChangeOpacityHint())
-    return false;
-
-  if (RuntimeEnabledFeatures::slimmingPaintV2Enabled()) {
-    if (layout_object.StyleRef().Opacity())
-      return false;
-
-    const EffectPaintPropertyNode* effect =
-        layout_object.PaintProperties()->Effect();
-    if (effect && effect->RequiresCompositingForAnimation()) {
-      return false;
-    }
-  }
-
-  // 0.0004f < 1/2048. With 10-bit color channels (only available on the
-  // newest Macs; otherwise it's 8-bit), we see that an alpha of 1/2048 or
-  // less leads to a color output of less than 0.5 in all channels, hence
-  // not visible.
-  static const float kMinimumVisibleOpacity = 0.0004f;
-  if (paint_layer_.PaintsWithTransparency(
-          painting_info.GetGlobalPaintFlags())) {
-    if (layout_object.StyleRef().Opacity() < kMinimumVisibleOpacity) {
-      return true;
-    }
-  }
-  return false;
-}
-
 PaintResult PaintLayerPainter::Paint(
     GraphicsContext& context,
     const PaintLayerPaintingInfo& painting_info,
     PaintLayerFlags paint_flags) {
   // https://code.google.com/p/chromium/issues/detail?id=343772
   DisableCompositingQueryAsserts disabler;
 
   if (paint_layer_.GetCompositingState() != kNotComposited) {
     if (painting_info.GetGlobalPaintFlags() &
         kGlobalPaintFlattenCompositingLayers) {
@@ skipping 14 matching lines @@
   if (ShouldSuppressPaintingLayer(paint_layer_))
     return kFullyPainted;
 
   if (paint_layer_.GetLayoutObject().View()->GetFrame() &&
       paint_layer_.GetLayoutObject()
           .View()
           ->GetFrame()
           ->ShouldThrottleRendering())
     return kFullyPainted;
 
-  // If this layer is totally invisible then there is nothing to paint.
-  if (PaintedOutputInvisible(painting_info))
-    return kFullyPainted;
-
   if (paint_layer_.PaintsWithTransparency(painting_info.GetGlobalPaintFlags()))
     paint_flags |= kPaintLayerHaveTransparency;
 
   if (paint_layer_.PaintsWithTransform(painting_info.GetGlobalPaintFlags()) &&
       !(paint_flags & kPaintLayerAppliedTransform))
     return PaintLayerWithTransform(context, painting_info, paint_flags);
 
   return PaintLayerContentsCompositingAllPhases(context, painting_info,
                                                 paint_flags);
 }
@@ skipping 1089 matching lines @@
           context, layout_object, kPaintPhaseClippingMask))
     return;
 
   IntRect snapped_clip_rect = PixelSnappedIntRect(clip_rect.Rect());
   LayoutObjectDrawingRecorder drawing_recorder(
       context, layout_object, kPaintPhaseClippingMask, snapped_clip_rect);
   context.FillRect(snapped_clip_rect, Color::kBlack);
 }
 
 }  // namespace blink