Initialize rows lazily

.github/actions/spelling/expect/expect.txt

@@ -440,6 +440,7 @@ DECMSR
 DECNKM
 DECNRCM
 DECOM
+decommit
 DECPCTERM
 DECPS
 DECRARA

src/buffer/out/Row.cpp

@@ -82,10 +82,7 @@ ROW::ROW(wchar_t* charsBuffer, uint16_t* charOffsetsBuffer, uint16_t rowWidth, c
     _attr{ rowWidth, fillAttribute },
     _columnCount{ rowWidth }
 {
-    if (_chars.data())
-    {
-        _init();
-    }
+    _init();
 }
 
 void ROW::SetWrapForced(const bool wrap) noexcept
@@ -147,6 +144,15 @@ void ROW::TransferAttributes(const til::small_rle<TextAttribute, uint16_t, 1>& a
     _attr.resize_trailing_extent(gsl::narrow<uint16_t>(newWidth));
 }
 
+void ROW::CopyFrom(const ROW& source)
+{
+    til::CoordType begin = 0;
+    CopyTextFrom(0, til::CoordTypeMax, source, begin, til::CoordTypeMax);
+    TransferAttributes(source.Attributes(), _columnCount);
+    _lineRendition = source._lineRendition;
+    _wrapForced = source._wrapForced;
+}
+
 // Returns the previous possible cursor position, preceding the given column.
 // Returns 0 if column is less than or equal to 0.
 til::CoordType ROW::NavigateToPrevious(til::CoordType column) const noexcept
@@ -445,7 +451,7 @@ catch (...)
     charsConsumed = ch - chBeg;
 }
 
-til::CoordType ROW::CopyRangeFrom(til::CoordType columnBegin, til::CoordType columnLimit, const ROW& other, til::CoordType& otherBegin, til::CoordType otherLimit)
+til::CoordType ROW::CopyTextFrom(til::CoordType columnBegin, til::CoordType columnLimit, const ROW& other, til::CoordType& otherBegin, til::CoordType otherLimit)
 try
 {
     const auto otherColBeg = other._clampedColumnInclusive(otherBegin);
@@ -464,8 +470,11 @@ try
     }
 
     WriteHelper h{ *this, columnBegin, columnLimit, chars };
-    if (!h.IsValid())
+    // If we were to copy text from ourselves, we'd overwrite
+    // our _charOffsets and break Finish() which reads from it.
+    if (!h.IsValid() || this == &other)
     {
+        assert(false); // You probably shouldn't call this function in the first place.
         return h.colBeg;
     }
     // Any valid charOffsets array is at least 2 elements long (the 1st element is the start offset and the 2nd
@@ -477,7 +486,7 @@ try
         otherBegin = other.size();
         return h.colBeg;
     }
-    h.CopyRangeFrom(charOffsets);
+    h.CopyTextFrom(charOffsets);
     h.Finish();
 
     otherBegin += h.colEnd - h.colBeg;
@@ -489,7 +498,7 @@ catch (...)
     throw;
 }
 
-[[msvc::forceinline]] void ROW::WriteHelper::CopyRangeFrom(const std::span<const uint16_t>& charOffsets) noexcept
+[[msvc::forceinline]] void ROW::WriteHelper::CopyTextFrom(const std::span<const uint16_t>& charOffsets) noexcept
 {
     // Since our `charOffsets` input is already in columns (just like the `ROW::_charOffsets`),
     // we can directly look up the end char-offset, but...

src/buffer/out/Row.hpp

@@ -60,6 +60,26 @@ struct RowWriteState
 class ROW final
 {
 public:
+    // The implicit agreement between ROW and TextBuffer is that TextBuffer supplies ROW with a charsBuffer of at
+    // least `columns * sizeof(wchar_t)` bytes and a charOffsetsBuffer of at least `(columns + 1) * sizeof(uint16_t)`
+    // bytes (see ROW::_charOffsets for why it needs space for 1 additional offset).
+    // These methods exists to make this agreement explicit and serve as a reminder.
+    //
+    // TextBuffer calculates the distance in bytes between two ROWs (_bufferRowStride) as the sum of these values.
+    // As such it's important that we return sizes with a minimum alignment of alignof(ROW).
+    static constexpr size_t CalculateRowSize() noexcept
+    {
+        return sizeof(ROW);
+    }
+    static constexpr size_t CalculateCharsBufferSize(size_t columns) noexcept
+    {
+        return (columns * sizeof(wchar_t) + 16) & ~15;
+    }
+    static constexpr size_t CalculateCharOffsetsBufferSize(size_t columns) noexcept
+    {
+        return (columns * sizeof(uint16_t) + 16) & ~15;
+    }
+
     ROW() = default;
     ROW(wchar_t* charsBuffer, uint16_t* charOffsetsBuffer, uint16_t rowWidth, const TextAttribute& fillAttribute);
 
@@ -78,6 +98,7 @@ class ROW final
 
     void Reset(const TextAttribute& attr);
     void TransferAttributes(const til::small_rle<TextAttribute, uint16_t, 1>& attr, til::CoordType newWidth);
+    void CopyFrom(const ROW& source);
 
     til::CoordType NavigateToPrevious(til::CoordType column) const noexcept;
     til::CoordType NavigateToNext(til::CoordType column) const noexcept;
@@ -88,7 +109,7 @@ class ROW final
     void ReplaceAttributes(til::CoordType beginIndex, til::CoordType endIndex, const TextAttribute& newAttr);
     void ReplaceCharacters(til::CoordType columnBegin, til::CoordType width, const std::wstring_view& chars);
     void ReplaceText(RowWriteState& state);
-    til::CoordType CopyRangeFrom(til::CoordType columnBegin, til::CoordType columnLimit, const ROW& other, til::CoordType& otherBegin, til::CoordType otherLimit);
+    til::CoordType CopyTextFrom(til::CoordType columnBegin, til::CoordType columnLimit, const ROW& other, til::CoordType& otherBegin, til::CoordType otherLimit);
 
     til::small_rle<TextAttribute, uint16_t, 1>& Attributes() noexcept;
     const til::small_rle<TextAttribute, uint16_t, 1>& Attributes() const noexcept;
@@ -121,7 +142,7 @@ class ROW final
         bool IsValid() const noexcept;
         void ReplaceCharacters(til::CoordType width) noexcept;
         void ReplaceText() noexcept;
-        void CopyRangeFrom(const std::span<const uint16_t>& charOffsets) noexcept;
+        void CopyTextFrom(const std::span<const uint16_t>& charOffsets) noexcept;
         void Finish();
 
         // Parent pointer.