Bug 1867939, part 4: Implemented the `::target-text` CSS Pseudo Element. r=emilio,devtools-reviewers,nchevobbe

This patch implements the `::target-text` pseudo element.
Similarly to the Custom Highlight API, this is done implementing
a new Selection type.

Differential Revision: https://phabricator.services.mozilla.com/D195687

devtools/server/actors/page-style.js

@@ -704,6 +704,7 @@ class PageStyleActor extends Actor {
       case "::first-line":
       case "::selection":
       case "::highlight":
+      case "::target-text":
         return true;
       case "::marker":
         return this._nodeIsListItem(node);

dom/base/nsISelectionController.idl

@@ -41,11 +41,12 @@ interface nsISelectionController : nsISelectionDisplay
    const short SELECTION_FIND                      = 8;
    const short SELECTION_URLSECONDARY              = 9;
    const short SELECTION_URLSTRIKEOUT              = 10;
+   const short SELECTION_TARGET_TEXT               = 11;
    // Custom Highlight API
    // (see https://drafts.csswg.org/css-highlight-api-1/#enumdef-highlighttype)
-   const short SELECTION_HIGHLIGHT                 = 11;
+   const short SELECTION_HIGHLIGHT                 = 12;
    // End of RawSelectionType values.
-   const short NUM_SELECTIONTYPES                  = 12;
+   const short NUM_SELECTIONTYPES                  = 13;
 
    // SelectionRegion values:
    const short SELECTION_ANCHOR_REGION = 0;
@@ -311,6 +312,7 @@ enum class SelectionType : RawSelectionType
   eFind = nsISelectionController::SELECTION_FIND,
   eURLSecondary = nsISelectionController::SELECTION_URLSECONDARY,
   eURLStrikeout = nsISelectionController::SELECTION_URLSTRIKEOUT,
+  eTargetText = nsISelectionController::SELECTION_TARGET_TEXT,
   eHighlight = nsISelectionController::SELECTION_HIGHLIGHT,
 };
 
@@ -327,6 +329,7 @@ static const SelectionType kPresentSelectionTypes[] = {
   SelectionType::eFind,
   SelectionType::eURLSecondary,
   SelectionType::eURLStrikeout,
+  SelectionType::eTargetText,
   SelectionType::eHighlight,
 };
 

layout/generic/nsFrameSelection.cpp

@@ -156,9 +156,10 @@ PeekOffsetStruct::PeekOffsetStruct(nsSelectionAmount aAmount,
 
 }  // namespace mozilla
 
-// Array which contains index of each SelecionType in Selection::mDOMSelections.
-// For avoiding using if nor switch to retrieve the index, this needs to have
-// -1 for SelectionTypes which won't be created its Selection instance.
+// Array which contains index of each SelectionType in
+// Selection::mDOMSelections. For avoiding using if nor switch to retrieve the
+// index, this needs to have -1 for SelectionTypes which won't be created its
+// Selection instance.
 static const int8_t kIndexOfSelections[] = {
     -1,  // SelectionType::eInvalid
     -1,  // SelectionType::eNone
@@ -172,6 +173,7 @@ static const int8_t kIndexOfSelections[] = {
     7,   // SelectionType::eFind
     8,   // SelectionType::eURLSecondary
     9,   // SelectionType::eURLStrikeout
+    10,  // SelectionType::eTargetText
     -1,  // SelectionType::eHighlight
 };
 

layout/generic/nsIFrame.cpp

@@ -2402,6 +2402,15 @@ already_AddRefed<ComputedStyle> nsIFrame::ComputeHighlightSelectionStyle(
       *element, PseudoStyleType::highlight, aHighlightName, Style());
 }
 
+already_AddRefed<ComputedStyle> nsIFrame::ComputeTargetTextStyle() const {
+  const Element* element = FindElementAncestorForMozSelection(GetContent());
+  if (!element) {
+    return nullptr;
+  }
+  return PresContext()->StyleSet()->ProbePseudoElementStyle(
+      *element, PseudoStyleType::targetText, nullptr, Style());
+}
+
 template <typename SizeOrMaxSize>
 static inline bool IsIntrinsicKeyword(const SizeOrMaxSize& aSize) {
   // All keywords other than auto/none/-moz-available depend on intrinsic sizes.

layout/generic/nsIFrame.h

@@ -937,6 +937,8 @@ class nsIFrame : public nsQueryFrame {
   already_AddRefed<ComputedStyle> ComputeHighlightSelectionStyle(
       nsAtom* aHighlightName);
 
+  already_AddRefed<ComputedStyle> ComputeTargetTextStyle() const;
+
   /**
    * Accessor functions for geometric parent.
    */

layout/generic/nsTextFrame.cpp

@@ -5676,6 +5676,10 @@ bool nsTextFrame::GetSelectionTextColors(SelectionType aSelectionType,
           aHighlightName, aBackground);
       return hasForeground || hasBackground;
     }
+    case SelectionType::eTargetText: {
+      aTextPaintStyle.GetTargetTextColors(aForeground, aBackground);
+      return true;
+    }
     case SelectionType::eURLSecondary:
       aTextPaintStyle.GetURLSecondaryColor(aForeground);
       *aBackground = NS_RGBA(0, 0, 0, 0);

layout/generic/nsTextPaintStyle.cpp

@@ -213,6 +213,24 @@ void nsTextPaintStyle::GetHighlightColors(nscolor* aForeColor,
   *aBackColor = NS_TRANSPARENT;
 }
 
+void nsTextPaintStyle::GetTargetTextColors(nscolor* aForeColor,
+                                           nscolor* aBackColor) {
+  NS_ASSERTION(aForeColor, "aForeColor is null");
+  NS_ASSERTION(aBackColor, "aBackColor is null");
+  const RefPtr<const ComputedStyle> targetTextStyle =
+      mFrame->ComputeTargetTextStyle();
+  if (targetTextStyle) {
+    *aForeColor = targetTextStyle->GetVisitedDependentColor(
+        &nsStyleText::mWebkitTextFillColor);
+    *aBackColor = targetTextStyle->GetVisitedDependentColor(
+        &nsStyleBackground::mBackgroundColor);
+    return;
+  }
+  // XXX(:jjaschke): Before shipping this feature, a sensible set of colors must
+  // be set (Bug 1867940).
+  // in the meantime, use the colors of find selection.
+  GetHighlightColors(aForeColor, aBackColor);
+}
 bool nsTextPaintStyle::GetCustomHighlightTextColor(nsAtom* aHighlightName,
                                                    nscolor* aForeColor) {
   NS_ASSERTION(aForeColor, "aForeColor is null");

layout/generic/nsTextPaintStyle.h

@@ -65,6 +65,7 @@ class MOZ_STACK_CLASS nsTextPaintStyle {
    */
   bool GetSelectionColors(nscolor* aForeColor, nscolor* aBackColor);
   void GetHighlightColors(nscolor* aForeColor, nscolor* aBackColor);
+  void GetTargetTextColors(nscolor* aForeColor, nscolor* aBackColor);
   // Computes colors for custom highlights.
   // Returns false if there are no rules associated with `aHighlightName`.
   bool GetCustomHighlightTextColor(nsAtom* aHighlightName, nscolor* aForeColor);

layout/inspector/tests/test_getCSSPseudoElementNames.html

@@ -22,6 +22,7 @@
       "::highlight",
       "::placeholder",
       "::selection",
+      "::target-text",
       "::-moz-color-swatch",
       "::-moz-focus-inner",
       "::-moz-meter-bar",

layout/style/nsCSSPseudoElementList.h

@@ -51,6 +51,7 @@ CSS_PSEUDO_ELEMENT(highlight, ":highlight", 0)
 CSS_PSEUDO_ELEMENT(selection, ":selection",
                    CSS_PSEUDO_ELEMENT_CONTAINS_ELEMENTS)
 
+CSS_PSEUDO_ELEMENT(targetText, ":target-text", 0)
 // XXXbz should we really allow random content to style these?  Maybe
 // use our flags to prevent that?
 CSS_PSEUDO_ELEMENT(mozFocusInner, ":-moz-focus-inner", 0)

layout/style/nsCSSPseudoElements.h

@@ -130,6 +130,8 @@ class nsCSSPseudoElements {
     switch (aType) {
       case Type::highlight:
         return mozilla::StaticPrefs::dom_customHighlightAPI_enabled();
+      case Type::targetText:
+        return mozilla::StaticPrefs::dom_text_fragments_enabled();
       case Type::sliderTrack:
       case Type::sliderThumb:
       case Type::sliderFill:

servo/components/style/gecko/pseudo_element.rs

@@ -159,6 +159,11 @@ impl PseudoElement {
         matches!(*self, Self::Highlight(_))
     }
 
+    /// Whether this pseudo-element is the ::target-text pseudo.
+    #[inline]
+    pub fn is_target_text(&self) -> bool {
+        *self == PseudoElement::TargetText
+    }
     /// Whether this pseudo-element supports user action selectors.
     pub fn supports_user_action_state(&self) -> bool {
         (self.flags() & structs::CSS_PSEUDO_ELEMENT_SUPPORTS_USER_ACTION_STATE) != 0
@@ -168,6 +173,7 @@ impl PseudoElement {
     pub fn enabled_in_content(&self) -> bool {
         match *self {
             Self::Highlight(..) => pref!("dom.customHighlightAPI.enabled"),
+            Self::TargetText => pref!("dom.text_fragments.enabled"),
             Self::SliderFill | Self::SliderTrack | Self::SliderThumb => {
                 pref!("layout.css.modern-range-pseudos.enabled")
             },

xpcom/ds/StaticAtoms.py

@@ -2487,6 +2487,7 @@ STATIC_ATOMS = [
     PseudoElementAtom("PseudoElement_firstLine", ":first-line"),
     PseudoElementAtom("PseudoElement_highlight", ":highlight"),
     PseudoElementAtom("PseudoElement_selection", ":selection"),
+    PseudoElementAtom("PseudoElement_targetText", ":target-text"),
     PseudoElementAtom("PseudoElement_mozFocusInner", ":-moz-focus-inner"),
     PseudoElementAtom("PseudoElement_mozNumberSpinBox", ":-moz-number-spin-box"),
     PseudoElementAtom("PseudoElement_mozNumberSpinUp", ":-moz-number-spin-up"),