FillLayer::VisuallyEqual incorrect comparison when first layer is none.

Even if the first background layer has none for image, we may have subsequent layers with images. The previous implementation did an early exit if both images in the first layer were null. Implement VisuallyEqual without using operator== to fix this issue for all layers without missing the optimization that different background positions do not trigger a repaint if the background image for the layer is none. Bug: 793773 Change-Id: I846c75b2c4c273bcebecdf84685d834d946926b1 Reviewed-on: https://chromium-review.googlesource.com/822074 Commit-Queue: Rune Lillesveen <futhark@chromium.org> Reviewed-by: Fredrik Söderquist <fs@opera.com> Cr-Commit-Position: refs/heads/master@{#523412}

FillLayer::VisuallyEqual incorrect comparison when first layer is none.
Even if the first background layer has none for image, we may have subsequent layers with images. The previous implementation did an early exit if both images in the first layer were null. Implement VisuallyEqual without using operator== to fix this issue for all layers without missing the optimization that different background positions do not trigger a repaint if the background image for the layer is none. Bug: 793773 Change-Id: I846c75b2c4c273bcebecdf84685d834d946926b1 Reviewed-on: https://chromium-review.googlesource.com/822074 Commit-Queue: Rune Lillesveen <futhark@chromium.org> Reviewed-by: Fredrik Söderquist <fs@opera.com> Cr-Commit-Position: refs/heads/master@{#523412}
c34e49db · Rune Lillesveen · Commit Bot · 6dd82658 · c34e49db · c34e49db
Commit c34e49db authored Dec 12, 2017 by Rune Lillesveen Committed by Commit Bot Dec 12, 2017
3 changed files
--- a/third_party/WebKit/LayoutTests/external/wpt/css/css-backgrounds/background-image-none-gradient-repaint.html
+++ b/third_party/WebKit/LayoutTests/external/wpt/css/css-backgrounds/background-image-none-gradient-repaint.html
+<!DOCTYPE html>
+<html class="reftest-wait">
+<meta charset="utf-8">
+<title>CSS Backgrounds and Borders: Repaint gradient change in second layer</title>
+<link rel="author" title="Rune Lillesveen" href="mailto:futhark@chromium.org">
+<link rel="match" href="background-clip-color-repaint-ref.html">
+<link rel="help" href="https://drafts.csswg.org/css-backgrounds/#layering">
+<style>
+  #box {
+    width: 150px;
+    height: 150px;
+  }
+  .red {
+    background: none, linear-gradient(to right, red, red);
+  }
+  .green {
+    background: none, linear-gradient(to right, green, green);
+  }
+</style>
+<p>There should be a green square below.</p>
+<div id="box" class="red"></div>
+<script>
+  requestAnimationFrame(function(){
+    requestAnimationFrame(function(){
+      box.className = "green";
+      document.documentElement.classList.remove("reftest-wait");
+    });
+  });
+</script>
--- a/third_party/WebKit/Source/core/style/FillLayer.cpp
+++ b/third_party/WebKit/Source/core/style/FillLayer.cpp
@@ -164,10 +164,7 @@ FillLayer& FillLayer::operator=(const FillLayer& o) {
  return *this;
 }

-bool FillLayer::operator==(const FillLayer& o) const {
-  // We do not check the "isSet" booleans for each property, since those are
-  // only used during initial construction to propagate patterns into layers.
-  // All layer comparisons happen after values have all been filled in anyway.
+bool FillLayer::LayerPropertiesEqual(const FillLayer& o) const {
  return DataEquivalent(image_, o.image_) && x_position_ == o.x_position_ &&
         y_position_ == o.y_position_ &&
         background_x_origin_ == o.background_x_origin_ &&
@@ -177,14 +174,22 @@ bool FillLayer::operator==(const FillLayer& o) const {
         origin_ == o.origin_ && repeat_x_ == o.repeat_x_ &&
         repeat_y_ == o.repeat_y_ && size_type_ == o.size_type_ &&
         mask_source_type_ == o.mask_source_type_ &&
-         size_length_ == o.size_length_ && type_ == o.type_ &&
+         size_length_ == o.size_length_ && type_ == o.type_;
+}
+
+bool FillLayer::operator==(const FillLayer& o) const {
+  return LayerPropertiesEqual(o) &&
         ((next_ && o.next_) ? *next_ == *o.next_ : next_ == o.next_);
 }

 bool FillLayer::VisuallyEqual(const FillLayer& o) const {
-  if (!image_ && !o.image_ && clip_ == o.clip_)
-    return true;
-  return *this == o;
+  if (image_ || o.image_) {
+    if (!LayerPropertiesEqual(o))
+      return false;
+  }
+  if (next_ && o.next_)
+    return next_->VisuallyEqual(*o.next_);
+  return next_ == o.next_;
 }

 void FillLayer::FillUnsetProperties() {

--- a/third_party/WebKit/Source/core/style/FillLayer.h
+++ b/third_party/WebKit/Source/core/style/FillLayer.h
@@ -300,6 +300,7 @@ class CORE_EXPORT FillLayer {

  bool ImageIsOpaque(const Document&, const ComputedStyle&) const;
  bool ImageTilesLayer() const;
+  bool LayerPropertiesEqual(const FillLayer&) const;

  FillLayer* next_;