Remove indirect usage of IsGlyphFullWidth in ScrollRegion

src/host/VtIo.cpp

@@ -359,6 +359,39 @@ void VtIo::FormatAttributes(std::wstring& target, const TextAttribute& attribute
     target.append(bufW, len);
 }
 
+wchar_t VtIo::SanitizeUCS2(wchar_t ch) noexcept
+{
+    // If any of the values in the buffer are C0 or C1 controls, we need to
+    // convert them to printable codepoints, otherwise they'll end up being
+    // evaluated as control characters by the receiving terminal. We use the
+    // DOS 437 code page for the C0 controls and DEL, and just a `?` for the
+    // C1 controls, since that's what you would most likely have seen in the
+    // legacy v1 console with raster fonts.
+    if (ch < 0x20)
+    {
+        static constexpr wchar_t lut[] = {
+            // clang-format off
+            L' ', L'☺', L'☻', L'♥', L'♦', L'♣', L'♠', L'•', L'◘', L'○', L'◙', L'♂', L'♀', L'♪', L'♫', L'☼',
+            L'►', L'◄', L'↕', L'‼', L'¶', L'§', L'▬', L'↨', L'↑', L'↓', L'→', L'←', L'∟', L'↔', L'▲', L'▼',
+            // clang-format on
+        };
+        ch = lut[ch];
+    }
+    else if (ch == 0x7F)
+    {
+        ch = L'⌂';
+    }
+    else if (ch > 0x7F && ch < 0xA0)
+    {
+        ch = L'?';
+    }
+    else if (til::is_surrogate(ch))
+    {
+        ch = UNICODE_REPLACEMENT;
+    }
+    return ch;
+}
+
 VtIo::Writer::Writer(VtIo* io) noexcept :
     _io{ io }
 {
@@ -592,7 +625,7 @@ void VtIo::Writer::WriteUTF16StripControlChars(std::wstring_view str) const
 
         for (it = begControlChars; it != end && IsControlCharacter(*it); ++it)
         {
-            WriteUCS2StripControlChars(*it);
+            WriteUCS2(SanitizeUCS2(*it));
         }
     }
 }
@@ -626,36 +659,6 @@ void VtIo::Writer::WriteUCS2(wchar_t ch) const
     _io->_back.append(buf, len);
 }
 
-void VtIo::Writer::WriteUCS2StripControlChars(wchar_t ch) const
-{
-    // If any of the values in the buffer are C0 or C1 controls, we need to
-    // convert them to printable codepoints, otherwise they'll end up being
-    // evaluated as control characters by the receiving terminal. We use the
-    // DOS 437 code page for the C0 controls and DEL, and just a `?` for the
-    // C1 controls, since that's what you would most likely have seen in the
-    // legacy v1 console with raster fonts.
-    if (ch < 0x20)
-    {
-        static constexpr wchar_t lut[] = {
-            // clang-format off
-            L' ', L'☺', L'☻', L'♥', L'♦', L'♣', L'♠', L'•', L'◘', L'○', L'◙', L'♂', L'♀', L'♪', L'♫', L'☼',
-            L'►', L'◄', L'↕', L'‼', L'¶', L'§', L'▬', L'↨', L'↑', L'↓', L'→', L'←', L'∟', L'↔', L'▲', L'▼',
-            // clang-format on
-        };
-        ch = lut[ch];
-    }
-    else if (ch == 0x7F)
-    {
-        ch = L'⌂';
-    }
-    else if (ch > 0x7F && ch < 0xA0)
-    {
-        ch = L'?';
-    }
-
-    WriteUCS2(ch);
-}
-
 // CUP: Cursor Position
 void VtIo::Writer::WriteCUP(til::point position) const
 {

src/host/VtIo.hpp

@@ -35,7 +35,6 @@ namespace Microsoft::Console::VirtualTerminal
             void WriteUTF16TranslateCRLF(std::wstring_view str) const;
             void WriteUTF16StripControlChars(std::wstring_view str) const;
             void WriteUCS2(wchar_t ch) const;
-            void WriteUCS2StripControlChars(wchar_t ch) const;
             void WriteCUP(til::point position) const;
             void WriteDECTCEM(bool enabled) const;
             void WriteSGR1006(bool enabled) const;
@@ -54,6 +53,7 @@ namespace Microsoft::Console::VirtualTerminal
 
         static void FormatAttributes(std::string& target, const TextAttribute& attributes);
         static void FormatAttributes(std::wstring& target, const TextAttribute& attributes);
+        static wchar_t SanitizeUCS2(wchar_t ch) noexcept;
 
         [[nodiscard]] HRESULT Initialize(const ConsoleArguments* const pArgs);
         [[nodiscard]] HRESULT CreateAndStartSignalThread() noexcept;

src/host/output.cpp

@@ -316,8 +316,8 @@ void ScrollRegion(SCREEN_INFORMATION& screenInfo,
                   const til::inclusive_rect scrollRectGiven,
                   const std::optional<til::inclusive_rect> clipRectGiven,
                   const til::point destinationOriginGiven,
-                  const wchar_t fillCharGiven,
-                  const TextAttribute fillAttrsGiven)
+                  wchar_t fillCharGiven,
+                  TextAttribute fillAttrsGiven)
 {
     // ------ 1. PREP SOURCE ------
     // Set up the source viewport.
@@ -357,16 +357,14 @@ void ScrollRegion(SCREEN_INFORMATION& screenInfo,
         return;
     }
 
-    // Determine the cell we will use to fill in any revealed/uncovered space.
-    // We generally use exactly what was given to us.
-    OutputCellIterator fillData(fillCharGiven, fillAttrsGiven);
-
     // However, if the character is null and we were given a null attribute (represented as legacy 0),
     // then we'll just fill with spaces and whatever the buffer's default colors are.
     if (fillCharGiven == UNICODE_NULL && fillAttrsGiven == TextAttribute{ 0 })
     {
-        fillData = OutputCellIterator(UNICODE_SPACE, screenInfo.GetAttributes());
-    }
+            fillAttrsGiven = screenInfo.GetAttributes();
+        }
+
+    fillCharGiven = Microsoft::Console::VirtualTerminal::VtIo::SanitizeUCS2(UNICODE_SPACE);
 
     // ------ 4. PREP TARGET ------
     // Now it's time to think about the target. We're only given the origin of the target
@@ -422,12 +420,13 @@ void ScrollRegion(SCREEN_INFORMATION& screenInfo,
     // So use the special subtraction function to get the viewports that fall
     // within the fill area but outside of the target area.
     const auto remaining = Viewport::Subtract(fill, target);
+    auto& textBuffer = screenInfo.GetTextBuffer();
 
     // Apply the fill data to each of the viewports we're given here.
     for (size_t i = 0; i < remaining.size(); i++)
     {
         const auto& view = remaining.at(i);
-        screenInfo.WriteRect(fillData, view);
+        textBuffer.FillRect(view.ToExclusive(), {&fillCharGiven, 1}, fillAttrsGiven);
 
         // If the region has image content it needs to be erased.
         ImageSlice::EraseBlock(screenInfo.GetTextBuffer(), view.ToExclusive());