CDP: add contrast algorithm param to HighlightConfig

This CL adds a new parameter to HighlightConfig to indicate
what kind of contrast ratio the overlay needs to compute.
Previously, it was computing the contrast ratio according to
the AA threshold. With this change, it is possible to show
the contrast according to AAA and APCA thresholds.

Frontend CL: https://crrev.com/c/2546705

Bug: 1121900
Change-Id: I319eb472e513d3ccc2ba0c2d90a6bdd60ba6d94e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2545509
Commit-Queue: Alex Rudenko <alexrudenko@chromium.org>
Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
Reviewed-by: Andrey Kosyakov <caseq@chromium.org>
Reviewed-by: Mathias Bynens <mathias@chromium.org>
Cr-Commit-Position: refs/heads/master@{#829611}

third_party/blink/public/devtools_protocol/browser_protocol.pdl

@@ -5679,6 +5679,12 @@ experimental domain Overlay
       # The hatching color for the box (default: transparent)
       optional DOM.RGBA hatchColor
 
+  type ContrastAlgorithm extends string
+    enum
+      aa
+      aaa
+      apca
+
   # Configuration data for the highlighting of page elements.
   type HighlightConfig extends object
     properties
@@ -5714,6 +5720,8 @@ experimental domain Overlay
       optional GridHighlightConfig gridHighlightConfig
       # The flex container highlight configuration (default: all transparent).
       optional FlexContainerHighlightConfig flexContainerHighlightConfig
+      # The contrast algorithm to use for the contrast ratio (default: aa).
+      optional ContrastAlgorithm contrastAlgorithm
 
   type ColorFormat extends string
     enum

third_party/blink/renderer/core/inspector/inspector_highlight.cc

@@ -19,6 +19,7 @@
 #include "third_party/blink/renderer/core/geometry/dom_rect.h"
 #include "third_party/blink/renderer/core/inspector/dom_traversal_utils.h"
 #include "third_party/blink/renderer/core/inspector/inspector_dom_agent.h"
+#include "third_party/blink/renderer/core/inspector/protocol/Overlay.h"
 #include "third_party/blink/renderer/core/layout/adjust_for_absolute_zoom.h"
 #include "third_party/blink/renderer/core/layout/geometry/physical_offset.h"
 #include "third_party/blink/renderer/core/layout/layout_box.h"
@@ -229,9 +230,26 @@ String ToHEXA(const Color& color) {
                         color.Blue(), color.Alpha());
 }
 
+namespace ContrastAlgorithmEnum = protocol::Overlay::ContrastAlgorithmEnum;
+
+String ContrastAlgorithmToString(const ContrastAlgorithm& contrast_algorithm) {
+  // It reuses the protocol string constants to avoid duplicating the string
+  // values. These string values are sent to the overlay code that is expected
+  // to handle them properly.
+  switch (contrast_algorithm) {
+    case ContrastAlgorithm::AA:
+      return ContrastAlgorithmEnum::Aa;
+    case ContrastAlgorithm::AAA:
+      return ContrastAlgorithmEnum::Aaa;
+    case ContrastAlgorithm::APCA:
+      return ContrastAlgorithmEnum::Apca;
+  }
+}
+
 void AppendStyleInfo(Node* node,
                      protocol::DictionaryValue* element_info,
-                     const InspectorHighlightContrastInfo& node_contrast) {
+                     const InspectorHighlightContrastInfo& node_contrast,
+                     const ContrastAlgorithm& contrast_algorithm) {
   std::unique_ptr<protocol::DictionaryValue> computed_style =
       protocol::DictionaryValue::create();
   CSSComputedStyleDeclaration* style =
@@ -276,6 +294,8 @@ void AppendStyleInfo(Node* node,
     contrast->setString("fontWeight", node_contrast.font_weight);
     contrast->setString("backgroundColor",
                         ToHEXA(node_contrast.background_color));
+    contrast->setString("contrastAlgorithm",
+                        ContrastAlgorithmToString(contrast_algorithm));
     element_info->setValue("contrast", std::move(contrast));
   }
 }
@@ -1407,8 +1427,10 @@ InspectorHighlight::InspectorHighlight(
     element_info_ = BuildElementInfo(element);
   else if (append_element_info && text_node)
     element_info_ = BuildTextNodeInfo(text_node);
-  if (element_info_ && highlight_config.show_styles)
-    AppendStyleInfo(node, element_info_.get(), node_contrast);
+  if (element_info_ && highlight_config.show_styles) {
+    AppendStyleInfo(node, element_info_.get(), node_contrast,
+                    highlight_config.contrast_algorithm);
+  }
 
   if (element_info_ && is_locked_ancestor)
     element_info_->setString("isLockedAncestor", "true");

third_party/blink/renderer/core/inspector/inspector_highlight.h

@@ -18,6 +18,7 @@ namespace blink {
 class Color;
 
 enum class ColorFormat { RGB, HEX, HSL };
+enum class ContrastAlgorithm { AA, AAA, APCA };
 
 struct CORE_EXPORT LineStyle {
   USING_FAST_MALLOC(LineStyle);
@@ -122,7 +123,8 @@ struct CORE_EXPORT InspectorHighlightConfig {
   bool show_accessibility_info;
 
   String selector_list;
-  ColorFormat color_format;
+  ColorFormat color_format = ColorFormat::HEX;
+  ContrastAlgorithm contrast_algorithm = ContrastAlgorithm::AA;
 
   std::unique_ptr<InspectorGridHighlightConfig> grid_highlight_config;
   std::unique_ptr<InspectorFlexContainerHighlightConfig>

third_party/blink/renderer/core/inspector/inspector_overlay_agent.cc

@@ -1573,6 +1573,17 @@ base::Optional<BoxStyle> InspectorOverlayAgent::ToBoxStyle(
   return box_style;
 }
 
+ContrastAlgorithm GetContrastAlgorithm(const String& contrast_algorithm) {
+  namespace ContrastAlgorithmEnum = protocol::Overlay::ContrastAlgorithmEnum;
+  if (contrast_algorithm == ContrastAlgorithmEnum::Aaa) {
+    return ContrastAlgorithm::AAA;
+  } else if (contrast_algorithm == ContrastAlgorithmEnum::Apca) {
+    return ContrastAlgorithm::APCA;
+  } else {
+    return ContrastAlgorithm::AA;
+  }
+}
+
 // static
 std::unique_ptr<InspectorHighlightConfig>
 InspectorOverlayAgent::ToHighlightConfig(
@@ -1614,6 +1625,10 @@ InspectorOverlayAgent::ToHighlightConfig(
     highlight_config->color_format = ColorFormat::HEX;
   }
 
+  namespace ContrastAlgorithmEnum = protocol::Overlay::ContrastAlgorithmEnum;
+  highlight_config->contrast_algorithm = GetContrastAlgorithm(
+      config->getContrastAlgorithm(ContrastAlgorithmEnum::Aa));
+
   highlight_config->grid_highlight_config =
       InspectorOverlayAgent::ToGridHighlightConfig(
           config->getGridHighlightConfig(nullptr));