Bug 1907808, part 1 - Text Fragments: Use ScrollSelectionIntoView() to scroll text directive into view. r=emilio

Differential Revision: https://phabricator.services.mozilla.com/D226813

dom/base/Selection.h

@@ -1231,7 +1231,7 @@ class MOZ_RAII AutoHideSelectionChanges final {
 
 constexpr bool IsValidRawSelectionType(RawSelectionType aRawSelectionType) {
   return aRawSelectionType >= nsISelectionController::SELECTION_NONE &&
-         aRawSelectionType <= nsISelectionController::SELECTION_URLSTRIKEOUT;
+         aRawSelectionType <= nsISelectionController::SELECTION_TARGET_TEXT;
 }
 
 constexpr SelectionType ToSelectionType(RawSelectionType aRawSelectionType) {

layout/base/PresShell.cpp

@@ -772,7 +772,6 @@ PresShell::PresShell(Document* aDocument)
     : mDocument(aDocument),
       mViewManager(nullptr),
       mAutoWeakFrames(nullptr),
-      mLastAnchorVerticalScrollViewPosition(WhereToScroll::Start),
 #ifdef ACCESSIBILITY
       mDocAccessible(nullptr),
 #endif  // ACCESSIBILITY
@@ -3187,24 +3186,35 @@ nsresult PresShell::GoToAnchor(const nsAString& aAnchorName,
       // From "Monkeypatching HTML § 7.4.6.3 Scrolling to a fragment:"
       // 3.9 Let blockPosition be "center" if scrollTarget is a range, "start"
       //     otherwise.
-      const auto verticalScrollPosition =
-          thereIsATextFragment ? WhereToScroll(WhereToScroll::Center)
-                               : WhereToScroll(WhereToScroll::Start);
+      // Implementation note: Use `ScrollSelectionIntoView` for text fragment,
+      // since the text fragment is stored as a `eTargetText` selection.
+      //
       // 3.3. TODO: Run the ancestor details revealing algorithm on target.
       // 3.4. Scroll target into view, with behavior set to "auto", block set to
       //      "start", and inline set to "nearest".
       // FIXME(emilio): Not all callers pass ScrollSmoothAuto (but we use auto
       // smooth scroll for `top` regardless below, so maybe they should!).
       ScrollingInteractionContext scrollToAnchorContext(true);
-      MOZ_TRY(ScrollContentIntoView(
-          target, ScrollAxis(verticalScrollPosition, WhenToScroll::Always),
-          ScrollAxis(),
-          ScrollFlags::AnchorScrollFlags | aAdditionalScrollFlags));
-
+      if (thereIsATextFragment) {
+        MOZ_TRY(ScrollSelectionIntoView(
+            SelectionType::eTargetText,
+            nsISelectionController::SELECTION_ANCHOR_REGION,
+            ScrollAxis(WhereToScroll::Center, WhenToScroll::Always),
+            ScrollAxis(),
+            ScrollFlags::AnchorScrollFlags | aAdditionalScrollFlags,
+            SelectionScrollMode::SyncFlush));
+      } else {
+        MOZ_TRY(ScrollContentIntoView(
+            target, ScrollAxis(WhereToScroll::Start, WhenToScroll::Always),
+            ScrollAxis(),
+            ScrollFlags::AnchorScrollFlags | aAdditionalScrollFlags));
+      }
       if (ScrollContainerFrame* rootScroll = GetRootScrollContainerFrame()) {
         mLastAnchorScrolledTo = target;
         mLastAnchorScrollPositionY = rootScroll->GetScrollPosition().y;
-        mLastAnchorVerticalScrollViewPosition = verticalScrollPosition;
+        mLastAnchorScrollType = thereIsATextFragment
+                                    ? AnchorScrollType::TextDirective
+                                    : AnchorScrollType::Anchor;
       }
     }
 
@@ -3300,21 +3310,28 @@ nsresult PresShell::GoToAnchor(const nsAString& aAnchorName,
 }
 
 nsresult PresShell::ScrollToAnchor() {
-  nsCOMPtr<nsIContent> lastAnchor = std::move(mLastAnchorScrolledTo);
-  if (!lastAnchor) {
-    return NS_OK;
+  NS_ASSERTION(mDidInitialize, "should have done initial reflow by now");
+  if (mLastAnchorScrollType == AnchorScrollType::Anchor) {
+    nsCOMPtr<nsIContent> lastAnchor = std::move(mLastAnchorScrolledTo);
+    if (!lastAnchor) {
+      return NS_OK;
+    }
+
+    ScrollContainerFrame* rootScroll = GetRootScrollContainerFrame();
+    if (!rootScroll ||
+        mLastAnchorScrollPositionY != rootScroll->GetScrollPosition().y) {
+      return NS_OK;
+    }
+    return ScrollContentIntoView(
+        lastAnchor, ScrollAxis(WhereToScroll::Start, WhenToScroll::Always),
+        ScrollAxis(), ScrollFlags::AnchorScrollFlags);
   }
 
-  NS_ASSERTION(mDidInitialize, "should have done initial reflow by now");
-  ScrollContainerFrame* rootScroll = GetRootScrollContainerFrame();
-  if (!rootScroll ||
-      mLastAnchorScrollPositionY != rootScroll->GetScrollPosition().y) {
-    return NS_OK;
-  }
-  return ScrollContentIntoView(
-      lastAnchor,
-      ScrollAxis(mLastAnchorVerticalScrollViewPosition, WhenToScroll::Always),
-      ScrollAxis(), ScrollFlags::AnchorScrollFlags);
+  return ScrollSelectionIntoView(
+      SelectionType::eTargetText,
+      nsISelectionController::SELECTION_ANCHOR_REGION,
+      ScrollAxis(WhereToScroll::Center, WhenToScroll::Always), ScrollAxis(),
+      ScrollFlags::AnchorScrollFlags, SelectionScrollMode::SyncFlush);
 }
 
 /*

layout/base/PresShell.h

@@ -3049,7 +3049,8 @@ class PresShell final : public nsStubDocumentObserver,
   // Text directives are supposed to be scrolled to the center of the viewport.
   // Since `ScrollToAnchor()` might get called after `GoToAnchor()` during a
   // load, the vertical view position should be preserved.
-  WhereToScroll mLastAnchorVerticalScrollViewPosition;
+  enum class AnchorScrollType : bool { Anchor, TextDirective };
+  AnchorScrollType mLastAnchorScrollType = AnchorScrollType::Anchor;
 
   // Information needed to properly handle scrolling content into view if the
   // pre-scroll reflow flush can be interrupted.  mContentToScrollTo is non-null