Improve conhost's scrolling performance (#16333)

`EnableScrollbar()` and especially `SetScrollInfo()` are prohibitively
expensive functions nowadays. This improves throughput of good old
`type` in cmd.exe by ~10x, by briefly releasing the console lock.

## Validation Steps Performed
* `type`ing a file in `cmd` is as fast while the window is scrolling
  as it is while it isn't scrolling ✅
* Scrollbar pops in and out when scroll-forward is disabled ✅

(cherry picked from commit 71a6f26)
Service-Card-Id: 91152166
Service-Version: 1.19

src/host/consoleInformation.cpp

@@ -35,6 +35,11 @@ void CONSOLE_INFORMATION::UnlockConsole() noexcept
     _lock.unlock();
 }
 
+til::recursive_ticket_lock_suspension CONSOLE_INFORMATION::SuspendLock() noexcept
+{
+    return _lock.suspend();
+}
+
 ULONG CONSOLE_INFORMATION::GetCSRecursionCount() const noexcept
 {
     return _lock.recursion_depth();

src/host/renderData.cpp

@@ -87,14 +87,16 @@ std::vector<Viewport> RenderData::GetSelectionRects() noexcept
 //      they're done with any querying they need to do.
 void RenderData::LockConsole() noexcept
 {
-    ::LockConsole();
+    auto& gci = ServiceLocator::LocateGlobals().getConsoleInformation();
+    gci.LockConsole();
 }
 
 // Method Description:
 // - Unlocks the console after a call to RenderData::LockConsole.
 void RenderData::UnlockConsole() noexcept
 {
-    ::UnlockConsole();
+    auto& gci = ServiceLocator::LocateGlobals().getConsoleInformation();
+    gci.UnlockConsole();
 }
 
 // Method Description:

src/host/screenInfo.cpp

@@ -34,7 +34,6 @@ SCREEN_INFORMATION::SCREEN_INFORMATION(
     const TextAttribute popupAttributes,
     const FontInfo fontInfo) :
     OutputMode{ ENABLE_PROCESSED_OUTPUT | ENABLE_WRAP_AT_EOL_OUTPUT },
-    ResizingWindow{ 0 },
     WheelDelta{ 0 },
     HWheelDelta{ 0 },
     _textBuffer{ nullptr },
@@ -641,64 +640,35 @@ VOID SCREEN_INFORMATION::UpdateScrollBars()
         return;
     }
 
-    if (gci.Flags & CONSOLE_UPDATING_SCROLL_BARS)
+    if (gci.Flags & CONSOLE_UPDATING_SCROLL_BARS || ServiceLocator::LocateConsoleWindow() == nullptr)
     {
         return;
     }
 
     gci.Flags |= CONSOLE_UPDATING_SCROLL_BARS;
-
-    if (ServiceLocator::LocateConsoleWindow() != nullptr)
-    {
-        ServiceLocator::LocateConsoleWindow()->PostUpdateScrollBars();
-    }
+    LOG_IF_WIN32_BOOL_FALSE(ServiceLocator::LocateConsoleWindow()->PostUpdateScrollBars());
 }
 
-VOID SCREEN_INFORMATION::InternalUpdateScrollBars()
+SCREEN_INFORMATION::ScrollBarState SCREEN_INFORMATION::FetchScrollBarState()
 {
     auto& gci = ServiceLocator::LocateGlobals().getConsoleInformation();
-    const auto pWindow = ServiceLocator::LocateConsoleWindow();
-
     WI_ClearFlag(gci.Flags, CONSOLE_UPDATING_SCROLL_BARS);
 
-    if (!IsActiveScreenBuffer())
-    {
-        return;
-    }
-
-    ResizingWindow++;
-
-    if (pWindow != nullptr)
-    {
-        const auto buffer = GetBufferSize();
-
-        // If this is the main buffer, make sure we enable both of the scroll bars.
-        //      The alt buffer likely disabled the scroll bars, this is the only
-        //      way to re-enable it.
-        if (!_IsAltBuffer())
-        {
-            pWindow->EnableBothScrollBars();
-        }
-
-        pWindow->UpdateScrollBar(true,
-                                 _IsAltBuffer(),
-                                 _viewport.Height(),
-                                 gci.IsTerminalScrolling() ? _virtualBottom : buffer.BottomInclusive(),
-                                 _viewport.Top());
-        pWindow->UpdateScrollBar(false,
-                                 _IsAltBuffer(),
-                                 _viewport.Width(),
-                                 buffer.RightInclusive(),
-                                 _viewport.Left());
-    }
-
     // Fire off an event to let accessibility apps know the layout has changed.
     if (_pAccessibilityNotifier)
     {
         _pAccessibilityNotifier->NotifyConsoleLayoutEvent();
     }
 
-    ResizingWindow--;
+    const auto buffer = GetBufferSize();
+    const auto isAltBuffer = _IsAltBuffer();
+    const auto maxSizeVer = gci.IsTerminalScrolling() ? _virtualBottom : buffer.BottomInclusive();
+    const auto maxSizeHor = buffer.RightInclusive();
+    return ScrollBarState{
+        .maxSize = { maxSizeHor, maxSizeVer },
+        .viewport = _viewport.ToExclusive(),
+        .isAltBuffer = isAltBuffer,
+    };
 }
 
 // Routine Description:

src/host/screenInfo.hpp

@@ -99,8 +99,14 @@ class SCREEN_INFORMATION : public ConsoleObjectHeader, public Microsoft::Console
     bool HasAccessibilityEventing() const noexcept;
     void NotifyAccessibilityEventing(const til::CoordType sStartX, const til::CoordType sStartY, const til::CoordType sEndX, const til::CoordType sEndY);
 
+    struct ScrollBarState
+    {
+        til::size maxSize;
+        til::rect viewport;
+        bool isAltBuffer = false;
+    };
     void UpdateScrollBars();
-    void InternalUpdateScrollBars();
+    ScrollBarState FetchScrollBarState();
 
     bool IsMaximizedBoth() const;
     bool IsMaximizedX() const;
@@ -158,7 +164,6 @@ class SCREEN_INFORMATION : public ConsoleObjectHeader, public Microsoft::Console
     bool CursorIsDoubleWidth() const;
 
     DWORD OutputMode;
-    WORD ResizingWindow; // > 0 if we should ignore WM_SIZE messages
 
     short WheelDelta;
     short HWheelDelta;

src/host/server.h

@@ -102,6 +102,7 @@ class CONSOLE_INFORMATION :
 
     void LockConsole() noexcept;
     void UnlockConsole() noexcept;
+    til::recursive_ticket_lock_suspension SuspendLock() noexcept;
     bool IsConsoleLocked() const noexcept;
     ULONG GetCSRecursionCount() const noexcept;
 

src/interactivity/inc/IConsoleWindow.hpp

@@ -25,13 +25,6 @@ namespace Microsoft::Console::Types
     public:
         virtual ~IConsoleWindow() = default;
 
-        virtual BOOL EnableBothScrollBars() = 0;
-        virtual int UpdateScrollBar(_In_ bool isVertical,
-                                    _In_ bool isAltBuffer,
-                                    _In_ UINT pageSize,
-                                    _In_ int maxSize,
-                                    _In_ int viewportPosition) = 0;
-
         virtual bool IsInFullscreen() const = 0;
 
         virtual void SetIsFullscreen(const bool fFullscreenEnabled) = 0;

src/interactivity/onecore/ConsoleWindow.cpp

@@ -11,20 +11,6 @@
 using namespace Microsoft::Console::Interactivity::OneCore;
 using namespace Microsoft::Console::Types;
 
-BOOL ConsoleWindow::EnableBothScrollBars() noexcept
-{
-    return FALSE;
-}
-
-int ConsoleWindow::UpdateScrollBar(bool /*isVertical*/,
-                                   bool /*isAltBuffer*/,
-                                   UINT /*pageSize*/,
-                                   int /*maxSize*/,
-                                   int /*viewportPosition*/) noexcept
-{
-    return 0;
-}
-
 bool ConsoleWindow::IsInFullscreen() const noexcept
 {
     return true;

src/interactivity/onecore/ConsoleWindow.hpp

@@ -24,9 +24,6 @@ namespace Microsoft::Console::Interactivity::OneCore
     {
     public:
         // Inherited via IConsoleWindow
-        BOOL EnableBothScrollBars() noexcept override;
-        int UpdateScrollBar(bool isVertical, bool isAltBuffer, UINT pageSize, int maxSize, int viewportPosition) noexcept override;
-
         bool IsInFullscreen() const noexcept override;
         void SetIsFullscreen(const bool fFullscreenEnabled) noexcept override;
         void ChangeViewport(const til::inclusive_rect& NewWindow) override;

src/interactivity/win32/window.cpp

@@ -438,7 +438,7 @@ void Window::_CloseWindow() const
         ShowWindow(hWnd, wShowWindow);
 
         auto& siAttached = GetScreenInfo();
-        siAttached.InternalUpdateScrollBars();
+        siAttached.UpdateScrollBars();
     }
 
     return status;
@@ -591,7 +591,7 @@ void Window::_UpdateWindowSize(const til::size sizeNew)
 
     if (WI_IsFlagClear(gci.Flags, CONSOLE_IS_ICONIC))
     {
-        ScreenInfo.InternalUpdateScrollBars();
+        ScreenInfo.UpdateScrollBars();
 
         SetWindowPos(GetWindowHandle(),
                      nullptr,
@@ -621,7 +621,7 @@ void Window::_UpdateWindowSize(const til::size sizeNew)
     if (!IsInFullscreen() && !IsInMaximized())
     {
         // Figure out how big to make the window, given the desired client area size.
-        siAttached.ResizingWindow++;
+        _resizingWindow++;
 
         // First get the buffer viewport size
         const auto WindowDimensions = siAttached.GetViewport().Dimensions();
@@ -691,7 +691,7 @@ void Window::_UpdateWindowSize(const til::size sizeNew)
             // If the change wasn't substantial, we may still need to update scrollbar positions. Note that PSReadLine
             // scrolls the window via Console.SetWindowPosition, which ultimately calls down to SetConsoleWindowInfo,
             // which ends up in this function.
-            siAttached.InternalUpdateScrollBars();
+            siAttached.UpdateScrollBars();
         }
 
         // MSFT: 12092729
@@ -716,7 +716,7 @@ void Window::_UpdateWindowSize(const til::size sizeNew)
         //   an additional Buffer message with the same size again and do nothing special.
         ScreenBufferSizeChange(siAttached.GetActiveBuffer().GetBufferSize().Dimensions());
 
-        siAttached.ResizingWindow--;
+        _resizingWindow--;
     }
 
     LOG_IF_FAILED(ConsoleImeResizeCompStrView());
@@ -879,26 +879,29 @@ void Window::HorizontalScroll(const WORD wScrollCommand, const WORD wAbsoluteCha
     LOG_IF_FAILED(ScreenInfo.SetViewportOrigin(true, NewOrigin, false));
 }
 
-BOOL Window::EnableBothScrollBars()
+void Window::UpdateScrollBars(const SCREEN_INFORMATION::ScrollBarState& state)
 {
-    return EnableScrollBar(_hWnd, SB_BOTH, ESB_ENABLE_BOTH);
-}
+    // If this is the main buffer, make sure we enable both of the scroll bars.
+    // The alt buffer likely disabled the scroll bars, this is the only way to re-enable it.
+    if (!state.isAltBuffer)
+    {
+        EnableScrollBar(_hWnd, SB_BOTH, ESB_ENABLE_BOTH);
+    }
 
-int Window::UpdateScrollBar(bool isVertical,
-                            bool isAltBuffer,
-                            UINT pageSize,
-                            int maxSize,
-                            int viewportPosition)
-{
-    SCROLLINFO si;
-    si.cbSize = sizeof(si);
-    si.fMask = isAltBuffer ? SIF_ALL | SIF_DISABLENOSCROLL : SIF_ALL;
-    si.nPage = pageSize;
-    si.nMin = 0;
-    si.nMax = maxSize;
-    si.nPos = viewportPosition;
-
-    return SetScrollInfo(_hWnd, isVertical ? SB_VERT : SB_HORZ, &si, TRUE);
+    SCROLLINFO si{
+        .cbSize = sizeof(SCROLLINFO),
+        .fMask = static_cast<UINT>(state.isAltBuffer ? SIF_ALL | SIF_DISABLENOSCROLL : SIF_ALL),
+    };
+
+    si.nMax = state.maxSize.width;
+    si.nPage = state.viewport.width();
+    si.nPos = state.viewport.left;
+    SetScrollInfo(_hWnd, SB_HORZ, &si, TRUE);
+
+    si.nMax = state.maxSize.height;
+    si.nPage = state.viewport.height();
+    si.nPos = state.viewport.top;
+    SetScrollInfo(_hWnd, SB_VERT, &si, TRUE);
 }
 
 // Routine Description:

src/interactivity/win32/window.hpp

@@ -65,12 +65,7 @@ namespace Microsoft::Console::Interactivity::Win32
         void HorizontalScroll(const WORD wScrollCommand,
                               const WORD wAbsoluteChange);
 
-        BOOL EnableBothScrollBars();
-        int UpdateScrollBar(bool isVertical,
-                            bool isAltBuffer,
-                            UINT pageSize,
-                            int maxSize,
-                            int viewportPosition);
+        void UpdateScrollBars(const SCREEN_INFORMATION::ScrollBarState& state);
 
         void UpdateWindowSize(const til::size coordSizeInChars);
         void UpdateWindowPosition(_In_ const til::point ptNewPos) const;
@@ -185,6 +180,7 @@ namespace Microsoft::Console::Interactivity::Win32
 
         static void s_ReinitializeFontsForDPIChange();
 
+        WORD _resizingWindow = 0; // > 0 if we should ignore WM_SIZE messages
         bool _fInDPIChange = false;
 
         static void s_ConvertWindowPosToWindowRect(const LPWINDOWPOS lpWindowPos,

src/interactivity/win32/windowproc.cpp

@@ -681,7 +681,16 @@ using namespace Microsoft::Console::Types;
 
     case CM_UPDATE_SCROLL_BARS:
     {
-        ScreenInfo.InternalUpdateScrollBars();
+        const auto state = ScreenInfo.FetchScrollBarState();
+
+        // EnableScrollbar() and especially SetScrollInfo() are prohibitively expensive functions nowadays.
+        // Unlocking early here improves throughput of good old `type` in cmd.exe by ~10x.
+        UnlockConsole();
+        Unlock = FALSE;
+
+        _resizingWindow++;
+        UpdateScrollBars(state);
+        _resizingWindow--;
         break;
     }
 
@@ -792,7 +801,7 @@ void Window::_HandleWindowPosChanged(const LPARAM lParam)
     // CONSOLE_IS_ICONIC bit appropriately. doing so in the WM_SIZE handler is incorrect because the WM_SIZE
     // comes after the WM_ERASEBKGND during SetWindowPos() processing, and the WM_ERASEBKGND needs to know if
     // the console window is iconic or not.
-    if (!ScreenInfo.ResizingWindow && (lpWindowPos->cx || lpWindowPos->cy) && !IsIconic(hWnd))
+    if (!_resizingWindow && (lpWindowPos->cx || lpWindowPos->cy) && !IsIconic(hWnd))
     {
         // calculate the dimensions for the newly proposed window rectangle
         til::rect rcNew;