Port selection in conhost and Terminal to use til::generational (#17676)

In #17638, I am moving selection to an earlier phase of rendering (so
that further phases can take it into account). Since I am drafting off
the design of search highlights, one of the required changes is moving
to passing `span`s of `point_span`s around to make selection effectively
zero-copy.

We can't easily have zero-copy selection propagation without caching,
and we can't have caching without mandatory cache invalidation.

This pull request moves both conhost and Terminal to use
`til::generational` for all selection members that impact the ranges
that would be produced from `GetSelectionRects`.

This required a move from `std::optional<>` to a boolean to determine
whether a selection was active in Terminal.

We will no longer regenerate the selection rects from the selection
anchors plus the text buffer *every single frame*.

Apart from being annoying to read, there is one downside.

If you begin a selection on a narrow character, _and that narrow
character later turns into a wide character_, we will show it as
half-selected.

This should be a rare-enough case that we can accept it as a regression.

Author: DHowett

src/cascadia/TerminalCore/Terminal.hpp

@@ -15,6 +15,7 @@
 #include "../../types/inc/GlyphWidth.hpp"
 #include "../../cascadia/terminalcore/ITerminalInput.hpp"
 
+#include <til/generational.h>
 #include <til/ticket_lock.h>
 #include <til/winrt.h>
 
@@ -382,14 +383,15 @@ class Microsoft::Terminal::Core::Terminal final :
     // the pivot is the til::point that remains selected when you extend a selection in any direction
     //   this is particularly useful when a word selection is extended over its starting point
     //   see TerminalSelection.cpp for more information
-    struct SelectionAnchors
+    struct SelectionInfo
     {
         til::point start;
         til::point end;
         til::point pivot;
+        bool blockSelection = false;
+        bool active = false;
     };
-    std::optional<SelectionAnchors> _selection;
-    bool _blockSelection = false;
+    til::generational<SelectionInfo> _selection{};
     std::wstring _wordDelimiters;
     SelectionExpansion _multiClickSelectionMode = SelectionExpansion::Char;
     SelectionInteractionMode _selectionMode = SelectionInteractionMode::None;
@@ -474,6 +476,7 @@ class Microsoft::Terminal::Core::Terminal final :
     void _MoveByWord(SelectionDirection direction, til::point& pos);
     void _MoveByViewport(SelectionDirection direction, til::point& pos) noexcept;
     void _MoveByBuffer(SelectionDirection direction, til::point& pos) noexcept;
+    void _SetSelectionEnd(SelectionInfo* selection, const til::point position, std::optional<SelectionExpansion> newExpansionMode = std::nullopt);
 #pragma endregion
 
 #ifdef UNIT_TESTING

src/cascadia/TerminalCore/TerminalApi.cpp

@@ -339,23 +339,25 @@ void Terminal::SearchMissingCommand(const std::wstring_view command)
 void Terminal::NotifyBufferRotation(const int delta)
 {
     // Update our selection, so it doesn't move as the buffer is cycled
-    if (_selection)
+    if (_selection->active)
     {
+        auto selection{ _selection.write() };
+        wil::hide_name _selection;
         // If the end of the selection will be out of range after the move, we just
         // clear the selection. Otherwise we move both the start and end points up
         // by the given delta and clamp to the first row.
-        if (_selection->end.y < delta)
+        if (selection->end.y < delta)
         {
-            _selection.reset();
+            selection->active = false;
         }
         else
         {
             // Stash this, so we can make sure to update the pivot to match later.
-            const auto pivotWasStart = _selection->start == _selection->pivot;
-            _selection->start.y = std::max(_selection->start.y - delta, 0);
-            _selection->end.y = std::max(_selection->end.y - delta, 0);
+            const auto pivotWasStart = selection->start == selection->pivot;
+            selection->start.y = std::max(selection->start.y - delta, 0);
+            selection->end.y = std::max(selection->end.y - delta, 0);
             // Make sure to sync the pivot with whichever value is the right one.
-            _selection->pivot = pivotWasStart ? _selection->start : _selection->end;
+            selection->pivot = pivotWasStart ? selection->start : selection->end;
         }
     }
 

src/cascadia/TerminalCore/TerminalSelection.cpp

@@ -57,7 +57,7 @@ std::vector<til::inclusive_rect> Terminal::_GetSelectionRects() const noexcept
 
     try
     {
-        return _activeBuffer().GetTextRects(_selection->start, _selection->end, _blockSelection, false);
+        return _activeBuffer().GetTextRects(_selection->start, _selection->end, _selection->blockSelection, false);
     }
     CATCH_LOG();
     return result;
@@ -78,7 +78,7 @@ std::vector<til::point_span> Terminal::_GetSelectionSpans() const noexcept
 
     try
     {
-        return _activeBuffer().GetTextSpans(_selection->start, _selection->end, _blockSelection, false);
+        return _activeBuffer().GetTextSpans(_selection->start, _selection->end, _selection->blockSelection, false);
     }
     CATCH_LOG();
     return result;
@@ -158,13 +158,13 @@ const Terminal::SelectionEndpoint Terminal::SelectionEndpointTarget() const noex
 const bool Terminal::IsSelectionActive() const noexcept
 {
     _assertLocked();
-    return _selection.has_value();
+    return _selection->active;
 }
 
 const bool Terminal::IsBlockSelection() const noexcept
 {
     _assertLocked();
-    return _blockSelection;
+    return _selection->blockSelection;
 }
 
 // Method Description:
@@ -175,15 +175,18 @@ const bool Terminal::IsBlockSelection() const noexcept
 void Terminal::MultiClickSelection(const til::point viewportPos, SelectionExpansion expansionMode)
 {
     // set the selection pivot to expand the selection using SetSelectionEnd()
-    _selection = SelectionAnchors{};
-    _selection->pivot = _ConvertToBufferCell(viewportPos);
+    auto selection{ _selection.write() };
+    wil::hide_name _selection;
+
+    selection->pivot = _ConvertToBufferCell(viewportPos);
+    selection->active = true;
 
     _multiClickSelectionMode = expansionMode;
     SetSelectionEnd(viewportPos);
 
     // we need to set the _selectionPivot again
     // for future shift+clicks
-    _selection->pivot = _selection->start;
+    selection->pivot = selection->start;
 }
 
 // Method Description:
@@ -194,13 +197,21 @@ void Terminal::SetSelectionAnchor(const til::point viewportPos)
 {
     _assertLocked();
 
-    _selection = SelectionAnchors{};
-    _selection->pivot = _ConvertToBufferCell(viewportPos);
+    auto selection{ _selection.write() };
+    wil::hide_name _selection;
+
+    selection->pivot = _ConvertToBufferCell(viewportPos);
+    selection->active = true;
 
     _multiClickSelectionMode = SelectionExpansion::Char;
     SetSelectionEnd(viewportPos);
 
-    _selection->start = _selection->pivot;
+    selection->start = selection->pivot;
+}
+
+void Terminal::SetSelectionEnd(const til::point viewportPos, std::optional<SelectionExpansion> newExpansionMode)
+{
+    _SetSelectionEnd(_selection.write(), viewportPos, newExpansionMode);
 }
 
 // Method Description:
@@ -209,9 +220,10 @@ void Terminal::SetSelectionAnchor(const til::point viewportPos)
 // Arguments:
 // - viewportPos: the (x,y) coordinate on the visible viewport
 // - newExpansionMode: overwrites the _multiClickSelectionMode for this function call. Used for ShiftClick
-void Terminal::SetSelectionEnd(const til::point viewportPos, std::optional<SelectionExpansion> newExpansionMode)
+void Terminal::_SetSelectionEnd(SelectionInfo* selection, const til::point viewportPos, std::optional<SelectionExpansion> newExpansionMode)
 {
-    if (!IsSelectionActive())
+    wil::hide_name _selection;
+    if (!selection->active)
     {
         // capture a log for spurious endpoint sets without an active selection
         LOG_HR(E_ILLEGAL_STATE_CHANGE);
@@ -231,17 +243,17 @@ void Terminal::SetSelectionEnd(const til::point viewportPos, std::optional<Selec
     if (newExpansionMode.has_value())
     {
         // shift-click operations only expand the target side
-        auto& anchorToExpand = targetStart ? _selection->start : _selection->end;
+        auto& anchorToExpand = targetStart ? selection->start : selection->end;
         anchorToExpand = targetStart ? expandedAnchors.first : expandedAnchors.second;
 
         // the other anchor should then become the pivot (we don't expand it)
-        auto& anchorToPivot = targetStart ? _selection->end : _selection->start;
-        anchorToPivot = _selection->pivot;
+        auto& anchorToPivot = targetStart ? selection->end : selection->start;
+        anchorToPivot = selection->pivot;
     }
     else
     {
         // expand both anchors
-        std::tie(_selection->start, _selection->end) = expandedAnchors;
+        std::tie(selection->start, selection->end) = expandedAnchors;
     }
     _selectionMode = SelectionInteractionMode::Mouse;
     _selectionIsTargetingUrl = false;
@@ -307,7 +319,7 @@ std::pair<til::point, til::point> Terminal::_ExpandSelectionAnchors(std::pair<ti
 // - isEnabled: new value for _blockSelection
 void Terminal::SetBlockSelection(const bool isEnabled) noexcept
 {
-    _blockSelection = isEnabled;
+    _selection.write()->blockSelection = isEnabled;
 }
 
 Terminal::SelectionInteractionMode Terminal::SelectionMode() const noexcept
@@ -331,11 +343,13 @@ void Terminal::ToggleMarkMode()
         {
             // No selection --> start one at the cursor
             const auto cursorPos{ _activeBuffer().GetCursor().GetPosition() };
-            _selection = SelectionAnchors{};
-            _selection->start = cursorPos;
-            _selection->end = cursorPos;
-            _selection->pivot = cursorPos;
-            _blockSelection = false;
+            *_selection.write() = SelectionInfo{
+                .start = cursorPos,
+                .end = cursorPos,
+                .pivot = cursorPos,
+                .blockSelection = false,
+                .active = true,
+            };
             WI_SetAllFlags(_selectionEndpoint, SelectionEndpoint::Start | SelectionEndpoint::End);
         }
         else if (WI_AreAllFlagsClear(_selectionEndpoint, SelectionEndpoint::Start | SelectionEndpoint::End))
@@ -365,13 +379,13 @@ void Terminal::SwitchSelectionEndpoint() noexcept
         {
             // moving end --> now we're moving start
             _selectionEndpoint = SelectionEndpoint::Start;
-            _selection->pivot = _selection->end;
+            _selection.write()->pivot = _selection->end;
         }
         else if (WI_IsFlagSet(_selectionEndpoint, SelectionEndpoint::Start))
         {
             // moving start --> now we're moving end
             _selectionEndpoint = SelectionEndpoint::End;
-            _selection->pivot = _selection->start;
+            _selection.write()->pivot = _selection->start;
         }
     }
 }
@@ -381,9 +395,11 @@ void Terminal::ExpandSelectionToWord()
     if (IsSelectionActive())
     {
         const auto& buffer = _activeBuffer();
-        _selection->start = buffer.GetWordStart(_selection->start, _wordDelimiters);
-        _selection->pivot = _selection->start;
-        _selection->end = buffer.GetWordEnd(_selection->end, _wordDelimiters);
+        auto selection{ _selection.write() };
+        wil::hide_name _selection;
+        selection->start = buffer.GetWordStart(selection->start, _wordDelimiters);
+        selection->pivot = selection->start;
+        selection->end = buffer.GetWordEnd(selection->end, _wordDelimiters);
 
         // if we're targeting both endpoints, instead just target "end"
         if (WI_IsFlagSet(_selectionEndpoint, SelectionEndpoint::Start) && WI_IsFlagSet(_selectionEndpoint, SelectionEndpoint::End))
@@ -528,12 +544,16 @@ void Terminal::SelectHyperlink(const SearchDirection dir)
     }
 
     // 2. Select the hyperlink
-    _selection->start = result->first;
-    _selection->pivot = result->first;
-    _selection->end = result->second;
-    bufferSize.DecrementInBounds(_selection->end);
-    _selectionIsTargetingUrl = true;
-    _selectionEndpoint = SelectionEndpoint::End;
+    {
+        auto selection{ _selection.write() };
+        wil::hide_name _selection;
+        selection->start = result->first;
+        selection->pivot = result->first;
+        selection->end = result->second;
+        bufferSize.DecrementInBounds(selection->end);
+        _selectionIsTargetingUrl = true;
+        _selectionEndpoint = SelectionEndpoint::End;
+    }
 
     // 3. Scroll to the selected area (if necessary)
     _ScrollToPoint(_selection->end);
@@ -646,19 +666,23 @@ void Terminal::UpdateSelection(SelectionDirection direction, SelectionExpansion
     // 3. Actually modify the selection state
     _selectionIsTargetingUrl = false;
     _selectionMode = std::max(_selectionMode, SelectionInteractionMode::Keyboard);
+
+    auto selection{ _selection.write() };
+    wil::hide_name _selection;
+
     if (shouldMoveBothEndpoints)
     {
         // [Mark Mode] + shift unpressed --> move all three (i.e. just use arrow keys)
-        _selection->start = targetPos;
-        _selection->end = targetPos;
-        _selection->pivot = targetPos;
+        selection->start = targetPos;
+        selection->end = targetPos;
+        selection->pivot = targetPos;
     }
     else
     {
         // [Mark Mode] + shift --> updating a standard selection
         // This is also standard quick-edit modification
         bool targetStart = false;
-        std::tie(_selection->start, _selection->end) = _PivotSelection(targetPos, targetStart);
+        std::tie(selection->start, selection->end) = _PivotSelection(targetPos, targetStart);
 
         // IMPORTANT! Pivoting the selection here might have changed which endpoint we're targeting.
         // So let's set the targeted endpoint again.
@@ -673,10 +697,15 @@ void Terminal::UpdateSelection(SelectionDirection direction, SelectionExpansion
 void Terminal::SelectAll()
 {
     const auto bufferSize{ _activeBuffer().GetSize() };
-    _selection = SelectionAnchors{};
-    _selection->start = bufferSize.Origin();
-    _selection->end = { bufferSize.RightInclusive(), _GetMutableViewport().BottomInclusive() };
-    _selection->pivot = _selection->end;
+    const til::point end{ bufferSize.RightInclusive(), _GetMutableViewport().BottomInclusive() };
+    *_selection.write() = SelectionInfo{
+        .start = bufferSize.Origin(),
+        .end = end,
+        .pivot = end,
+        .blockSelection = false,
+        .active = true,
+    };
+
     _selectionMode = SelectionInteractionMode::Keyboard;
     _selectionIsTargetingUrl = false;
     _ScrollToPoint(_selection->start);
@@ -824,7 +853,7 @@ void Terminal::_MoveByBuffer(SelectionDirection direction, til::point& pos) noex
 void Terminal::ClearSelection()
 {
     _assertLocked();
-    _selection = std::nullopt;
+    _selection.write()->active = false;
     _selectionMode = SelectionInteractionMode::None;
     _selectionIsTargetingUrl = false;
     _selectionEndpoint = static_cast<SelectionEndpoint>(0);
@@ -858,7 +887,7 @@ Terminal::TextCopyData Terminal::RetrieveSelectedTextFromBuffer(const bool singl
 
     const auto& textBuffer = _activeBuffer();
 
-    const auto req = TextBuffer::CopyRequest::FromConfig(textBuffer, _selection->start, _selection->end, singleLine, _blockSelection, _trimBlockSelection);
+    const auto req = TextBuffer::CopyRequest::FromConfig(textBuffer, _selection->start, _selection->end, singleLine, _selection->blockSelection, _trimBlockSelection);
     data.plainText = textBuffer.GetPlainText(req);
 
     if (html || rtf)