Split into snap-on-input and -output

src/host/_stream.cpp

@@ -206,6 +206,7 @@ void WriteCharsLegacy(SCREEN_INFORMATION& screenInfo, const std::wstring_view& t
             writer.Submit();
         }
 
+        screenInfo.SnapOnOutput();
         return;
     }
 
@@ -328,6 +329,8 @@ void WriteCharsLegacy(SCREEN_INFORMATION& screenInfo, const std::wstring_view& t
     {
         writer.Submit();
     }
+
+    screenInfo.SnapOnOutput();
 }
 
 // This is the main entrypoint for conhost to write VT to the buffer.
@@ -375,6 +378,8 @@ void WriteCharsVT(SCREEN_INFORMATION& screenInfo, const std::wstring_view& str)
         write(offset, std::wstring_view::npos);
         writer.Submit();
     }
+
+    screenInfo.SnapOnOutput();
 }
 
 // Erases all contents of the given screenInfo, including the current screen and scrollback.

src/host/screenInfo.cpp

@@ -1521,31 +1521,7 @@ void SCREEN_INFORMATION::ClipToScreenBuffer(_Inout_ til::inclusive_rect* const p
 
 void SCREEN_INFORMATION::MakeCurrentCursorVisible()
 {
-    MakeLocationVisibleWithSnap(_textBuffer->GetCursor().GetPosition());
-}
-
-static constexpr bool IsInputKey(WORD vkey)
-{
-    return vkey != VK_CONTROL &&
-           vkey != VK_LCONTROL &&
-           vkey != VK_RCONTROL &&
-           vkey != VK_MENU &&
-           vkey != VK_LMENU &&
-           vkey != VK_RMENU &&
-           vkey != VK_SHIFT &&
-           vkey != VK_LSHIFT &&
-           vkey != VK_RSHIFT &&
-           vkey != VK_LWIN &&
-           vkey != VK_RWIN &&
-           vkey != VK_SNAPSHOT;
-}
-
-void SCREEN_INFORMATION::SnapOnInput(const WORD vkey)
-{
-    if (IsInputKey(vkey))
-    {
-        MakeCurrentCursorVisible();
-    }
+    MakeCursorVisible(_textBuffer->GetCursor().GetPosition());
 }
 
 // Routine Description:
@@ -1693,30 +1669,41 @@ void SCREEN_INFORMATION::SetCursorDBMode(const bool DoubleCursor)
     return STATUS_SUCCESS;
 }
 
-void SCREEN_INFORMATION::MakeLocationVisible(til::point position)
+static constexpr bool IsInputKey(WORD vkey)
 {
-    const auto viewportOrigin = _viewport.Origin();
-    const auto viewportSize = _viewport.Dimensions();
-    const auto bufferSize = _textBuffer->GetSize().Dimensions();
-    auto origin = viewportOrigin;
-
-    // Ensure the given position is in bounds.
-    position.x = std::clamp(position.x, 0, bufferSize.width - 1);
-    position.y = std::clamp(position.y, 0, bufferSize.height - 1);
-
-    origin.x = std::min(origin.x, position.x); // shift left if left
-    origin.x = std::max(origin.x, position.x - (viewportSize.width - 1)); // shift right if right
+    return vkey != VK_CONTROL &&
+           vkey != VK_LCONTROL &&
+           vkey != VK_RCONTROL &&
+           vkey != VK_MENU &&
+           vkey != VK_LMENU &&
+           vkey != VK_RMENU &&
+           vkey != VK_SHIFT &&
+           vkey != VK_LSHIFT &&
+           vkey != VK_RSHIFT &&
+           vkey != VK_LWIN &&
+           vkey != VK_RWIN &&
+           vkey != VK_SNAPSHOT;
+}
 
-    origin.y = std::min(origin.y, position.y); // shift up if above
-    origin.y = std::max(origin.y, position.y - (viewportSize.height - 1)); // shift down if below
+void SCREEN_INFORMATION::MakeCursorVisible(til::point position)
+{
+    _makeLocationVisible(position, ViewportMovementMask::Vertical | ViewportMovementMask::Horizontal);
+}
 
-    if (origin != viewportOrigin)
+void SCREEN_INFORMATION::SnapOnInput(const WORD vkey)
+{
+    if (IsInputKey(vkey))
     {
-        std::ignore = SetViewportOrigin(true, origin, false);
+        _makeLocationVisible(_textBuffer->GetCursor().GetPosition(), ViewportMovementMask::Vertical);
     }
 }
 
-void SCREEN_INFORMATION::MakeLocationVisibleWithSnap(til::point position)
+void SCREEN_INFORMATION::SnapOnOutput()
+{
+    _makeLocationVisible(_textBuffer->GetCursor().GetPosition(), ViewportMovementMask::HorizontalCenter);
+}
+
+void SCREEN_INFORMATION::_makeLocationVisible(til::point position, ViewportMovementMask movements)
 {
     const auto viewportOrigin = _viewport.Origin();
     const auto viewportSize = _viewport.Dimensions();
@@ -1727,23 +1714,35 @@ void SCREEN_INFORMATION::MakeLocationVisibleWithSnap(til::point position)
     position.x = std::clamp(position.x, 0, bufferSize.width - 1);
     position.y = std::clamp(position.y, 0, bufferSize.height - 1);
 
-    // If the position is horizontally outside the viewport, snap the
-    // viewport to the nearest multiple of half the viewport width.
-    if (position.x < origin.x || position.x >= (origin.x + viewportSize.width))
+    if (WI_IsAnyFlagSet(movements, ViewportMovementMask::Vertical))
+    {
+        origin.y = std::min(origin.y, position.y); // shift up if above
+        origin.y = std::max(origin.y, position.y - (viewportSize.height - 1)); // shift down if below
+    }
+
+    if (WI_IsAnyFlagSet(movements, ViewportMovementMask::Horizontal))
     {
-        const auto div = viewportSize.width / 2;
-        // We want our viewport to be centered around the position (= "half-width" offset).
-        // Since the origin is the left edge, we must subtract a half-width from the position.
-        origin.x = position.x - div;
-        // Round down to the nearest multiple of the viewport width.
-        // This also works if origin.x is negative, because the "modulo operator"
-        // is not a modulo operator, it's a remainder operator. The remainder of a
-        // negative number is negative and so origin.x cannot end up being less than 0.
-        origin.x -= origin.x % div;
+        origin.x = std::min(origin.x, position.x); // shift left if left
+        origin.x = std::max(origin.x, position.x - (viewportSize.width - 1)); // shift right if right
     }
 
-    origin.y = std::min(origin.y, position.y); // shift up if above
-    origin.y = std::max(origin.y, position.y - (viewportSize.height - 1)); // shift down if below
+    if (WI_IsAnyFlagSet(movements, ViewportMovementMask::HorizontalCenter))
+    {
+        // If the position is horizontally outside the viewport, snap the
+        // viewport to the nearest multiple of half the viewport width.
+        if (position.x < origin.x || position.x >= (origin.x + viewportSize.width))
+        {
+            const auto div = viewportSize.width / 2;
+            // We want our viewport to be centered around the position (= "half-width" offset).
+            // Since the origin is the left edge, we must subtract a half-width from the position.
+            origin.x = position.x - div;
+            // Round down to the nearest multiple of the viewport width.
+            // This also works if origin.x is negative, because the "modulo operator"
+            // is not a modulo operator, it's a remainder operator. The remainder of a
+            // negative number is negative and so origin.x cannot end up being less than 0.
+            origin.x -= origin.x % div;
+        }
+    }
 
     if (origin != viewportOrigin)
     {

src/host/screenInfo.hpp

@@ -47,6 +47,14 @@ Revision History:
 #include "../types/inc/Viewport.hpp"
 class ConversionAreaInfo; // forward decl window. circular reference
 
+enum class ViewportMovementMask
+{
+    Vertical = 0x1,
+    Horizontal = 0x2,
+    HorizontalCenter = 0x4,
+};
+DEFINE_ENUM_FLAG_OPERATORS(ViewportMovementMask);
+
 class SCREEN_INFORMATION : public ConsoleObjectHeader, public Microsoft::Console::IIoProvider
 {
 public:
@@ -71,7 +79,9 @@ class SCREEN_INFORMATION : public ConsoleObjectHeader, public Microsoft::Console
     void GetRequiredConsoleSizeInPixels(_Out_ til::size* const pRequiredSize) const;
 
     void MakeCurrentCursorVisible();
+    void MakeCursorVisible(til::point position);
     void SnapOnInput(WORD vkey);
+    void SnapOnOutput();
 
     void ClipToScreenBuffer(_Inout_ til::inclusive_rect* const psrClip) const;
 
@@ -185,9 +195,6 @@ class SCREEN_INFORMATION : public ConsoleObjectHeader, public Microsoft::Console
     void SetCursorDBMode(const bool DoubleCursor);
     [[nodiscard]] NTSTATUS SetCursorPosition(const til::point Position, const bool TurnOn);
 
-    void MakeLocationVisible(til::point position);
-    void MakeLocationVisibleWithSnap(til::point position);
-
     [[nodiscard]] NTSTATUS UseAlternateScreenBuffer(const TextAttribute& initAttributes);
     void UseMainScreenBuffer();
 
@@ -237,6 +244,7 @@ class SCREEN_INFORMATION : public ConsoleObjectHeader, public Microsoft::Console
     void _CalculateViewportSize(const til::rect* const prcClientArea, _Out_ til::size* const pcoordSize);
     void _AdjustViewportSize(const til::rect* const prcClientNew, const til::rect* const prcClientOld, const til::size* const pcoordSize);
     void _InternalSetViewportSize(const til::size* pcoordSize, const bool fResizeFromTop, const bool fResizeFromLeft);
+    void _makeLocationVisible(til::point position, ViewportMovementMask movements);
 
     static void s_CalculateScrollbarVisibility(const til::rect* const prcClientArea,
                                                const til::size* const pcoordBufferSize,

src/host/selection.cpp

@@ -216,7 +216,7 @@ void Selection::ExtendSelection(_In_ til::point coordBufferPos)
         }
 
         // scroll if necessary to make cursor visible.
-        screenInfo.MakeLocationVisible(coordBufferPos);
+        screenInfo.MakeCursorVisible(coordBufferPos);
 
         _dwSelectionFlags |= CONSOLE_SELECTION_NOT_EMPTY;
         _srSelectionRect.left = _srSelectionRect.right = _coordSelectionAnchor.x;
@@ -227,7 +227,7 @@ void Selection::ExtendSelection(_In_ til::point coordBufferPos)
     else
     {
         // scroll if necessary to make cursor visible.
-        screenInfo.MakeLocationVisible(coordBufferPos);
+        screenInfo.MakeCursorVisible(coordBufferPos);
     }
 
     // remember previous selection rect

src/host/selectionInput.cpp

@@ -920,7 +920,7 @@ bool Selection::_HandleMarkModeSelectionNav(const INPUT_KEY_INFO* const pInputKe
 
             cursor.SetHasMoved(true);
             _coordSelectionAnchor = textBuffer.GetCursor().GetPosition();
-            ScreenInfo.MakeLocationVisible(_coordSelectionAnchor);
+            ScreenInfo.MakeCursorVisible(_coordSelectionAnchor);
             _srSelectionRect.left = _srSelectionRect.right = _coordSelectionAnchor.x;
             _srSelectionRect.top = _srSelectionRect.bottom = _coordSelectionAnchor.y;
         }