Make UTextFromTextBuffer newline aware (#17120)

This PR achieves two things:
* When encountering rows with newlines (`WasForceWrapped` = `false`)
  we'll now copy the contents out of the row and append a `\n`.
  To make `utext_clone` cheap, it adds a reference counted buffer.
* Text extraction in `Terminal::GetHyperlinkAtBufferPosition`
  was fixed by using a higher level `TextBuffer::GetPlainText`
  instead of iterating through each cell.

Closes #16676
Closes #17065

## Validation Steps Performed
* In pwsh execute the following:
  ``"`e[999C`e[22Dhttps://example.com/foo`nbar"``
* Hovering over the URL only underlines `.../foo` and not `bar` ✅
* The tooltip ends in `.../foo` and not `.../fo` ✅

src/buffer/out/UTextAdapter.cpp

@@ -6,19 +6,87 @@
 
 #include "textBuffer.hpp"
 
+// All of these are somewhat annoying when trying to implement RefcountBuffer.
+// You can't stuff a unique_ptr into ut->q (= void*) after all.
+#pragma warning(disable : 26402) // Return a scoped object instead of a heap-allocated if it has a move constructor (r.3).
+#pragma warning(disable : 26403) // Reset or explicitly delete an owner<T> pointer '...' (r.3).
+#pragma warning(disable : 26409) // Avoid calling new and delete explicitly, use std::make_unique<T> instead (r.11).
+
 struct RowRange
 {
     til::CoordType begin;
     til::CoordType end;
 };
 
+struct RefcountBuffer
+{
+    size_t references;
+    size_t capacity;
+    wchar_t data[1];
+
+    static RefcountBuffer* EnsureCapacityForOverwrite(RefcountBuffer* buffer, size_t capacity)
+    {
+        // We must not just ensure that `buffer` has at least `capacity`, but also that its reference count is <= 1, because otherwise we would resize a shared buffer.
+        if (buffer != nullptr && buffer->references <= 1 && buffer->capacity >= capacity)
+        {
+            return buffer;
+        }
+
+        const auto oldCapacity = buffer ? buffer->capacity << 1 : 0;
+        const auto newCapacity = std::max(capacity + 128, oldCapacity);
+        const auto newBuffer = static_cast<RefcountBuffer*>(::operator new(sizeof(RefcountBuffer) - sizeof(data) + newCapacity * sizeof(wchar_t)));
+
+        if (!newBuffer)
+        {
+            return nullptr;
+        }
+
+        if (buffer)
+        {
+            buffer->Release();
+        }
+
+        // Copying the old buffer's data is not necessary because utextAccess() will scribble right over it.
+        newBuffer->references = 1;
+        newBuffer->capacity = newCapacity;
+        return newBuffer;
+    }
+
+    void AddRef() noexcept
+    {
+        // With our usage patterns, either of these two would indicate
+        // an unbalanced AddRef/Release or a memory corruption.
+        assert(references > 0 && references < 1000);
+        references++;
+    }
+
+    void Release() noexcept
+    {
+        // With our usage patterns, either of these two would indicate
+        // an unbalanced AddRef/Release or a memory corruption.
+        assert(references > 0 && references < 1000);
+        if (--references == 0)
+        {
+            ::operator delete(this);
+        }
+    }
+};
+
 constexpr size_t& accessLength(UText* ut) noexcept
 {
+    static_assert(sizeof(ut->p) == sizeof(size_t));
     return *std::bit_cast<size_t*>(&ut->p);
 }
 
+constexpr RefcountBuffer*& accessBuffer(UText* ut) noexcept
+{
+    static_assert(sizeof(ut->q) == sizeof(RefcountBuffer*));
+    return *std::bit_cast<RefcountBuffer**>(&ut->q);
+}
+
 constexpr RowRange& accessRowRange(UText* ut) noexcept
 {
+    static_assert(sizeof(ut->a) == sizeof(RowRange));
     return *std::bit_cast<RowRange*>(&ut->a);
 }
 
@@ -56,11 +124,16 @@ static UText* U_CALLCONV utextClone(UText* dest, const UText* src, UBool deep, U
     }
 
     dest = utext_setup(dest, 0, status);
-    if (*status <= U_ZERO_ERROR)
+    if (*status > U_ZERO_ERROR)
     {
-        memcpy(dest, src, sizeof(UText));
+        return dest;
     }
 
+    memcpy(dest, src, sizeof(UText));
+    if (const auto buf = accessBuffer(dest))
+    {
+        buf->AddRef();
+    }
     return dest;
 }
 
@@ -82,7 +155,9 @@ try
 
         for (til::CoordType y = range.begin; y < range.end; ++y)
         {
-            length += textBuffer.GetRowByOffset(y).GetText().size();
+            const auto& row = textBuffer.GetRowByOffset(y);
+            // Later down below we'll add a newline to the text if !wasWrapForced, so we need to account for that here.
+            length += row.GetText().size() + !row.WasWrapForced();
         }
 
         accessLength(ut) = length;
@@ -126,11 +201,13 @@ try
     const auto range = accessRowRange(ut);
     auto start = ut->chunkNativeStart;
     auto limit = ut->chunkNativeLimit;
-    auto y = accessCurrentRow(ut);
-    std::wstring_view text;
 
     if (neededIndex < start || neededIndex >= limit)
     {
+        auto y = accessCurrentRow(ut);
+        std::wstring_view text;
+        bool wasWrapForced = false;
+
         if (neededIndex < start)
         {
             do
@@ -138,12 +215,17 @@ try
                 --y;
                 if (y < range.begin)
                 {
+                    assert(false);
                     return false;
                 }
 
-                text = textBuffer.GetRowByOffset(y).GetText();
+                const auto& row = textBuffer.GetRowByOffset(y);
+                text = row.GetText();
+                wasWrapForced = row.WasWrapForced();
+
                 limit = start;
-                start -= text.size();
+                // Later down below we'll add a newline to the text if !wasWrapForced, so we need to account for that here.
+                start -= text.size() + !wasWrapForced;
             } while (neededIndex < start);
         }
         else
@@ -153,15 +235,32 @@ try
                 ++y;
                 if (y >= range.end)
                 {
+                    assert(false);
                     return false;
                 }
 
-                text = textBuffer.GetRowByOffset(y).GetText();
+                const auto& row = textBuffer.GetRowByOffset(y);
+                text = row.GetText();
+                wasWrapForced = row.WasWrapForced();
+
                 start = limit;
-                limit += text.size();
+                // Later down below we'll add a newline to the text if !wasWrapForced, so we need to account for that here.
+                limit += text.size() + !wasWrapForced;
             } while (neededIndex >= limit);
         }
 
+        if (!wasWrapForced)
+        {
+            const auto newSize = text.size() + 1;
+            const auto buffer = RefcountBuffer::EnsureCapacityForOverwrite(accessBuffer(ut), newSize);
+
+            memcpy(&buffer->data[0], text.data(), text.size() * sizeof(wchar_t));
+            til::at(buffer->data, text.size()) = L'\n';
+
+            text = { &buffer->data[0], newSize };
+            accessBuffer(ut) = buffer;
+        }
+
         accessCurrentRow(ut) = y;
         ut->chunkNativeStart = start;
         ut->chunkNativeLimit = limit;
@@ -256,18 +355,32 @@ catch (...)
     return 0;
 }
 
+static void U_CALLCONV utextClose(UText* ut) noexcept
+{
+    if (const auto buffer = accessBuffer(ut))
+    {
+        buffer->Release();
+    }
+}
+
 static constexpr UTextFuncs utextFuncs{
     .tableSize = sizeof(UTextFuncs),
     .clone = utextClone,
     .nativeLength = utextNativeLength,
     .access = utextAccess,
+    .close = utextClose,
 };
 
 // Creates a UText from the given TextBuffer that spans rows [rowBeg,RowEnd).
-UText Microsoft::Console::ICU::UTextFromTextBuffer(const TextBuffer& textBuffer, til::CoordType rowBeg, til::CoordType rowEnd) noexcept
+Microsoft::Console::ICU::unique_utext Microsoft::Console::ICU::UTextFromTextBuffer(const TextBuffer& textBuffer, til::CoordType rowBeg, til::CoordType rowEnd) noexcept
 {
 #pragma warning(suppress : 26477) // Use 'nullptr' rather than 0 or NULL (es.47).
-    UText ut = UTEXT_INITIALIZER;
+    unique_utext ut{ UTEXT_INITIALIZER };
+
+    UErrorCode status = U_ZERO_ERROR;
+    utext_setup(&ut, 0, &status);
+    FAIL_FAST_IF(status > U_ZERO_ERROR);
+
     ut.providerProperties = (1 << UTEXT_PROVIDER_LENGTH_IS_EXPENSIVE) | (1 << UTEXT_PROVIDER_STABLE_CHUNKS);
     ut.pFuncs = &utextFuncs;
     ut.context = &textBuffer;

src/buffer/out/UTextAdapter.h

@@ -10,8 +10,9 @@ class TextBuffer;
 namespace Microsoft::Console::ICU
 {
     using unique_uregex = wistd::unique_ptr<URegularExpression, wil::function_deleter<decltype(&uregex_close), &uregex_close>>;
+    using unique_utext = wil::unique_struct<UText, decltype(&utext_close), &utext_close>;
 
-    UText UTextFromTextBuffer(const TextBuffer& textBuffer, til::CoordType rowBeg, til::CoordType rowEnd) noexcept;
+    unique_utext UTextFromTextBuffer(const TextBuffer& textBuffer, til::CoordType rowBeg, til::CoordType rowEnd) noexcept;
     unique_uregex CreateRegex(const std::wstring_view& pattern, uint32_t flags, UErrorCode* status) noexcept;
     til::point_span BufferRangeFromMatch(UText* ut, URegularExpression* re);
 }

src/buffer/out/textBuffer.cpp

@@ -1995,25 +1995,10 @@ size_t TextBuffer::SpanLength(const til::point coordStart, const til::point coor
 // - end - where to end getting text
 // Return Value:
 // - Just the text.
-std::wstring TextBuffer::GetPlainText(const til::point& start, const til::point& end) const
+std::wstring TextBuffer::GetPlainText(const til::point start, const til::point end) const
 {
-    std::wstring text;
-    auto spanLength = SpanLength(start, end);
-    text.reserve(spanLength);
-
-    auto it = GetCellDataAt(start);
-
-    for (; it && spanLength > 0; ++it, --spanLength)
-    {
-        const auto& cell = *it;
-        if (cell.DbcsAttr() != DbcsAttribute::Trailing)
-        {
-            const auto chars = cell.Chars();
-            text.append(chars);
-        }
-    }
-
-    return text;
+    const auto req = CopyRequest::FromConfig(*this, start, end, true, false, false, false);
+    return GetPlainText(req);
 }
 
 // Routine Description:

src/buffer/out/textBuffer.hpp

@@ -196,7 +196,7 @@ public:
 
     size_t SpanLength(const til::point coordStart, const til::point coordEnd) const;
 
-    std::wstring GetPlainText(const til::point& start, const til::point& end) const;
+    std::wstring GetPlainText(til::point start, til::point end) const;
 
     struct CopyRequest
     {

src/cascadia/TerminalCore/Terminal.cpp

@@ -522,14 +522,7 @@ std::wstring Terminal::GetHyperlinkAtBufferPosition(const til::point bufferPos)
     // Case 2 - Step 2: get the auto-detected hyperlink
     if (result.has_value() && result->value == _hyperlinkPatternId)
     {
-        std::wstring uri;
-        const auto startIter = _activeBuffer().GetCellDataAt(result->start);
-        const auto endIter = _activeBuffer().GetCellDataAt(result->stop);
-        for (auto iter = startIter; iter != endIter; ++iter)
-        {
-            uri += iter->Chars();
-        }
-        return uri;
+        return _activeBuffer().GetPlainText(result->start, result->stop);
     }
     return {};
 }