Cache the size viewport structure inside TextBuffer (#6841)

Looking up the size of the viewport from the underlying dimensions of
the structures seemed like a good idea at the time (so it would only be
in one place), but it turns out to be more of a perf cost than we
expected. Not necessarily on any one hot path, but if we sort by
functions in WPR, it was the top consumer on the Terminal side. This
instead saves the size as a member of the `TextBuffer` and serves that
out. It only changes when it is constructed or resized traditionally, so
it's easy to update/keep track of. It impacted conhost/conpty to a
lesser degree but was still noticeable.

## Validation Steps Performed
- Run `time cat big.txt` under WPR. Checked before and after perf
  metrics.

## PR Checklist
* [x] Closes perf itch
* [x] I work here
* [x] Manual test
* [x] Documentation irrelevant.
* [x] Schema irrelevant.
* [x] Am core contributor.

src/buffer/out/search.cpp

@@ -261,7 +261,7 @@ wchar_t Search::_ApplySensitivity(const wchar_t wch) const noexcept
 // - Helper to increment a coordinate in respect to the associated screen buffer
 // Arguments
 // - coord - Updated by function to increment one position (will wrap X and Y direction)
-void Search::_IncrementCoord(COORD& coord) const
+void Search::_IncrementCoord(COORD& coord) const noexcept
 {
     _uiaData.GetTextBuffer().GetSize().IncrementInBoundsCircular(coord);
 }
@@ -270,7 +270,7 @@ void Search::_IncrementCoord(COORD& coord) const
 // - Helper to decrement a coordinate in respect to the associated screen buffer
 // Arguments
 // - coord - Updated by function to decrement one position (will wrap X and Y direction)
-void Search::_DecrementCoord(COORD& coord) const
+void Search::_DecrementCoord(COORD& coord) const noexcept
 {
     _uiaData.GetTextBuffer().GetSize().DecrementInBoundsCircular(coord);
 }

src/buffer/out/search.h

@@ -63,8 +63,8 @@ class Search final
     bool _CompareChars(const std::wstring_view one, const std::wstring_view two) const noexcept;
     void _UpdateNextPosition();
 
-    void _IncrementCoord(COORD& coord) const;
-    void _DecrementCoord(COORD& coord) const;
+    void _IncrementCoord(COORD& coord) const noexcept;
+    void _DecrementCoord(COORD& coord) const noexcept;
 
     static COORD s_GetInitialAnchor(Microsoft::Console::Types::IUiaData& uiaData, const Direction dir);
 

src/buffer/out/textBuffer.cpp

@@ -33,13 +33,16 @@ TextBuffer::TextBuffer(const COORD screenBufferSize,
     _cursor{ cursorSize, *this },
     _storage{},
     _unicodeStorage{},
-    _renderTarget{ renderTarget }
+    _renderTarget{ renderTarget },
+    _size{}
 {
     // initialize ROWs
     for (size_t i = 0; i < static_cast<size_t>(screenBufferSize.Y); ++i)
     {
         _storage.emplace_back(static_cast<SHORT>(i), screenBufferSize.X, _currentAttributes, this);
     }
+
+    _UpdateSize();
 }
 
 // Routine Description:
@@ -623,7 +626,7 @@ COORD TextBuffer::GetLastNonSpaceCharacter(std::optional<const Microsoft::Consol
 // Return Value:
 // - Coordinate position in screen coordinates of the character just before the cursor.
 // - NOTE: Will return 0,0 if already in the top left corner
-COORD TextBuffer::_GetPreviousFromCursor() const
+COORD TextBuffer::_GetPreviousFromCursor() const noexcept
 {
     COORD coordPosition = GetCursor().GetPosition();
 
@@ -652,9 +655,15 @@ const SHORT TextBuffer::GetFirstRowIndex() const noexcept
 {
     return _firstRow;
 }
-const Viewport TextBuffer::GetSize() const
+
+const Viewport TextBuffer::GetSize() const noexcept
+{
+    return _size;
+}
+
+void TextBuffer::_UpdateSize()
 {
-    return Viewport::FromDimensions({ 0, 0 }, { gsl::narrow<SHORT>(_storage.at(0).size()), gsl::narrow<SHORT>(_storage.size()) });
+    _size = Viewport::FromDimensions({ 0, 0 }, { gsl::narrow<SHORT>(_storage.at(0).size()), gsl::narrow<SHORT>(_storage.size()) });
 }
 
 void TextBuffer::_SetFirstRowIndex(const SHORT FirstRowIndex) noexcept
@@ -845,6 +854,9 @@ void TextBuffer::Reset()
         // Also take advantage of the row ID refresh loop to resize the rows in the X dimension
         // and cleanup the UnicodeStorage characters that might fall outside the resized buffer.
         _RefreshRowIDs(newSize.X);
+
+        // Update the cached size value
+        _UpdateSize();
     }
     CATCH_RETURN();
 

src/buffer/out/textBuffer.hpp

@@ -110,7 +110,7 @@ class TextBuffer final
 
     const SHORT GetFirstRowIndex() const noexcept;
 
-    const Microsoft::Console::Types::Viewport GetSize() const;
+    const Microsoft::Console::Types::Viewport GetSize() const noexcept;
 
     void ScrollRows(const SHORT firstRow, const SHORT size, const SHORT delta);
 
@@ -177,6 +177,8 @@ class TextBuffer final
                           std::optional<std::reference_wrapper<PositionInformation>> positionInfo);
 
 private:
+    void _UpdateSize();
+    Microsoft::Console::Types::Viewport _size;
     std::deque<ROW> _storage;
     Cursor _cursor;
 
@@ -193,7 +195,7 @@ class TextBuffer final
 
     void _SetFirstRowIndex(const SHORT FirstRowIndex) noexcept;
 
-    COORD _GetPreviousFromCursor() const;
+    COORD _GetPreviousFromCursor() const noexcept;
 
     void _SetWrapOnCurrentRow();
     void _AdjustWrapOnCurrentRow(const bool fSet);

src/types/ScreenInfoUiaProviderBase.cpp

@@ -368,7 +368,7 @@ IFACEMETHODIMP ScreenInfoUiaProviderBase::get_SupportedTextSelection(_Out_ Suppo
 
 #pragma endregion
 
-const COORD ScreenInfoUiaProviderBase::_getScreenBufferCoords() const
+const COORD ScreenInfoUiaProviderBase::_getScreenBufferCoords() const noexcept
 {
     return _getTextBuffer().GetSize().Dimensions();
 }

src/types/ScreenInfoUiaProviderBase.h

@@ -123,7 +123,7 @@ namespace Microsoft::Console::Types
         // mechanism for multi-threaded code.
         std::unordered_map<EVENTID, bool> _signalFiringMapping{};
 
-        const COORD _getScreenBufferCoords() const;
+        const COORD _getScreenBufferCoords() const noexcept;
         const TextBuffer& _getTextBuffer() const noexcept;
         const Viewport _getViewport() const noexcept;
         void _LockConsole() noexcept;