Scroll To Text Fragments fragments should alwasy be scrolled to the c…

…ente of the screen.

https://bugs.webkit.org/show_bug.cgi?id=245169
<rdar://99904303>

Reviewed by Tim Horton.

Our code that scrolls selections into visible does not scroll them if they are already visible
at the current page scroll. We are wanting this to always go to the center so that it is easier
to hold the position, rather than have the scrolled text jump around a bit as additional content
is loaded in.

* Source/WebCore/editing/Editor.cpp:
(WebCore::TemporarySelectionChange::setSelection):
* Source/WebCore/editing/Editor.h:
* Source/WebCore/editing/FrameSelection.cpp:
(WebCore::FrameSelection::setSelection):
(WebCore::FrameSelection::updateAndRevealSelection):
* Source/WebCore/editing/FrameSelection.h:
* Source/WebCore/page/FrameView.cpp:
(WebCore::FrameView::scrollToFragment):
(WebCore::FrameView::textFragmentIndicatorTimerFired):

Canonical link: https://commits.webkit.org/254477@main

Source/WebCore/editing/Editor.cpp

@@ -278,6 +278,8 @@ void TemporarySelectionChange::setSelection(const VisibleSelection& selection, I
             options.add(FrameSelection::SmoothScroll);
         if (m_options & TemporarySelectionOption::RevealSelectionBounds)
             options.add(FrameSelection::RevealSelectionBounds);
+        if (m_options & TemporarySelectionOption::ForceCenterScroll)
+            options.add(FrameSelection::ForceCenterScroll);
     }
 
     m_document->selection().setSelection(selection, options);

Source/WebCore/editing/Editor.h

@@ -111,7 +111,7 @@ enum class MailBlockquoteHandling {
 class HTMLAttachmentElement;
 #endif
 
-enum class TemporarySelectionOption : uint8_t {
+enum class TemporarySelectionOption : uint16_t {
     RevealSelection = 1 << 0,
     DoNotSetFocus = 1 << 1,
 
@@ -128,6 +128,8 @@ enum class TemporarySelectionOption : uint8_t {
     RevealSelectionBounds = 1 << 6,
 
     UserTriggered = 1 << 7,
+
+    ForceCenterScroll = 1 << 8,
 };
 
 class TemporarySelectionChange {

Source/WebCore/editing/FrameSelection.cpp

@@ -466,7 +466,7 @@ void FrameSelection::setSelection(const VisibleSelection& selection, OptionSet<S
         return;
     }
 
-    updateAndRevealSelection(intent, options.contains(SmoothScroll) ? ScrollBehavior::Smooth : ScrollBehavior::Instant, options.contains(RevealSelectionBounds) ? RevealExtentOption::DoNotRevealExtent : RevealExtentOption::RevealExtent);
+    updateAndRevealSelection(intent, options.contains(SmoothScroll) ? ScrollBehavior::Smooth : ScrollBehavior::Instant, options.contains(RevealSelectionBounds) ? RevealExtentOption::DoNotRevealExtent : RevealExtentOption::RevealExtent, options.contains(ForceCenterScroll) ? ForceCenterScrollOption::ForceCenterScroll : ForceCenterScrollOption::DoNotForceCenterScroll);
 
     if (options & IsUserTriggered) {
         if (auto* client = protectedDocument->editor().client())
@@ -499,7 +499,7 @@ void FrameSelection::setNeedsSelectionUpdate(RevealSelectionAfterUpdate revealMo
         view->selection().clear();
 }
 
-void FrameSelection::updateAndRevealSelection(const AXTextStateChangeIntent& intent, ScrollBehavior scrollBehavior, RevealExtentOption revealExtent)
+void FrameSelection::updateAndRevealSelection(const AXTextStateChangeIntent& intent, ScrollBehavior scrollBehavior, RevealExtentOption revealExtent, ForceCenterScrollOption forceCenterScroll)
 {
     if (!m_pendingSelectionUpdate)
         return;
@@ -515,6 +515,9 @@ void FrameSelection::updateAndRevealSelection(const AXTextStateChangeIntent& int
             alignment = m_alwaysAlignCursorOnScrollWhenRevealingSelection ? ScrollAlignment::alignCenterAlways : ScrollAlignment::alignCenterIfNeeded;
         else
             alignment = m_alwaysAlignCursorOnScrollWhenRevealingSelection ? ScrollAlignment::alignTopAlways : ScrollAlignment::alignToEdgeIfNeeded;
+
+        if (forceCenterScroll == ForceCenterScrollOption::ForceCenterScroll)
+            alignment = ScrollAlignment::alignCenterAlways;
 
         revealSelection(m_selectionRevealMode, alignment, revealExtent, scrollBehavior);
     }

Source/WebCore/editing/FrameSelection.h

@@ -52,6 +52,7 @@ class VisiblePosition;
 
 enum EUserTriggered : bool { NotUserTriggered, UserTriggered };
 enum RevealExtentOption : bool { RevealExtent, DoNotRevealExtent };
+enum ForceCenterScrollOption : bool { DoNotForceCenterScroll, ForceCenterScroll };
 
 class CaretBase {
     WTF_MAKE_NONCOPYABLE(CaretBase);
@@ -128,7 +129,8 @@ class FrameSelection : private CaretBase {
         RevealSelectionUpToMainFrame = 1 << 8,
         SmoothScroll = 1 << 9,
         DelegateMainFrameScroll = 1 << 10,
-        RevealSelectionBounds = 1 << 11
+        RevealSelectionBounds = 1 << 11,
+        ForceCenterScroll = 1 << 12,
     };
     static constexpr OptionSet<SetSelectionOption> defaultSetSelectionOptions(EUserTriggered = NotUserTriggered);
 
@@ -268,7 +270,7 @@ class FrameSelection : private CaretBase {
 
 private:
     void updateSelectionAppearanceNow();
-    void updateAndRevealSelection(const AXTextStateChangeIntent&, ScrollBehavior = ScrollBehavior::Instant, RevealExtentOption = RevealExtentOption::RevealExtent);
+    void updateAndRevealSelection(const AXTextStateChangeIntent&, ScrollBehavior = ScrollBehavior::Instant, RevealExtentOption = RevealExtentOption::RevealExtent, ForceCenterScrollOption = ForceCenterScrollOption::DoNotForceCenterScroll);
     void updateDataDetectorsForSelection();
 
     bool setSelectionWithoutUpdatingAppearance(const VisibleSelection&, OptionSet<SetSelectionOption>, CursorAlignOnScroll, TextGranularity);

Source/WebCore/page/FrameView.cpp

@@ -2228,7 +2228,7 @@ bool FrameView::scrollToFragment(const URL& url)
 
             if (highlightRanges.size()) {
                 auto range = highlightRanges.first();
-                TemporarySelectionChange selectionChange(document, { range }, { TemporarySelectionOption::DelegateMainFrameScroll, TemporarySelectionOption::RevealSelectionBounds, TemporarySelectionOption::UserTriggered });
+                TemporarySelectionChange selectionChange(document, { range }, { TemporarySelectionOption::DelegateMainFrameScroll, TemporarySelectionOption::RevealSelectionBounds, TemporarySelectionOption::UserTriggered, TemporarySelectionOption::ForceCenterScroll });
                 m_pendingTextFragmentIndicatorRange = range;
                 m_pendingTextFragmentIndicatorText = plainText(range);
                 if (frame().settings().scrollToTextFragmentIndicatorEnabled())
@@ -2464,7 +2464,7 @@ void FrameView::textFragmentIndicatorTimerFired()
         return;
 
     auto range = m_pendingTextFragmentIndicatorRange.value();
-    TemporarySelectionChange selectionChange(document, { range }, { TemporarySelectionOption::DelegateMainFrameScroll, TemporarySelectionOption::RevealSelectionBounds, TemporarySelectionOption::UserTriggered });
+    TemporarySelectionChange selectionChange(document, { range }, { TemporarySelectionOption::DelegateMainFrameScroll, TemporarySelectionOption::RevealSelectionBounds, TemporarySelectionOption::UserTriggered, TemporarySelectionOption::ForceCenterScroll });
 
     auto textIndicator = TextIndicator::createWithRange(range, { TextIndicatorOption::DoNotClipToVisibleRect }, WebCore::TextIndicatorPresentationTransition::Bounce);
     if (textIndicator)