Expose Text Attributes to UI Automation

Jul 9, 2021 · Jun 3, 2021 · Jun 22, 2021 · Jun 29, 2021 · Jun 29, 2021 · Jun 29, 2021
commit 84bca57d2dbd28d1a3b9b98182c50616f11e3136
diff --git a/src/buffer/out/textBuffer.cpp b/src/buffer/out/textBuffer.cpp
@@ -184,6 +184,20 @@ TextBufferCellIterator TextBuffer::GetCellDataAt(const COORD at, const Viewport
     return TextBufferCellIterator(*this, at, limit);
 }
 
+// Routine Description:
+// - Retrieves read-only cell iterator at the given buffer location
+//   but restricted to operate only inside the given viewport.
+// Arguments:
+// - at - X,Y position in buffer for iterator start position
+// - limit - boundaries for the iterator to operate within
+// - until - X,Y position in buffer for last position for the iterator to read (inclusive)
+// Return Value:
+// - Read-only iterator of cell data.
+TextBufferCellIterator TextBuffer::GetCellDataAt(const COORD at, const Viewport limit, const COORD until) const
+{
+    return TextBufferCellIterator(*this, at, limit, until);
+}
+
 //Routine Description:
 // - Corrects and enforces consistent double byte character state (KAttrs line) within a row of the text buffer.
 // - This will take the given double byte information and check that it will be consistent when inserted into the buffer

diff --git a/src/buffer/out/textBuffer.hpp b/src/buffer/out/textBuffer.hpp
@@ -81,6 +81,7 @@ class TextBuffer final
     TextBufferCellIterator GetCellDataAt(const COORD at) const;
     TextBufferCellIterator GetCellLineDataAt(const COORD at) const;
     TextBufferCellIterator GetCellDataAt(const COORD at, const Microsoft::Console::Types::Viewport limit) const;
+    TextBufferCellIterator GetCellDataAt(const COORD at, const Microsoft::Console::Types::Viewport limit, const COORD until) const;
     TextBufferTextIterator GetTextDataAt(const COORD at) const;
     TextBufferTextIterator GetTextLineDataAt(const COORD at) const;
     TextBufferTextIterator GetTextDataAt(const COORD at, const Microsoft::Console::Types::Viewport limit) const;

diff --git a/src/buffer/out/textBufferCellIterator.cpp b/src/buffer/out/textBufferCellIterator.cpp
@@ -50,6 +50,25 @@ TextBufferCellIterator::TextBufferCellIterator(const TextBuffer& buffer, COORD p
     _GenerateView();
 }
 
+// Routine Description:
+// - Creates a new read-only iterator to seek through cell data stored within a screen buffer
+// Arguments:
+// - buffer - Text buffer to seek through
+// - pos - Starting position to retrieve text data from (within screen buffer bounds)
+// - limits - Viewport limits to restrict the iterator within the buffer bounds (smaller than the buffer itself)
+// - endPosInclusive - last position to iterate through (inclusive)
+TextBufferCellIterator::TextBufferCellIterator(const TextBuffer& buffer, COORD pos, const Viewport limits, const COORD endPosInclusive) :
+    TextBufferCellIterator(buffer, pos, limits)
+{
+    // Throw if the coordinate is not limited to the inside of the given buffer.
+    THROW_HR_IF(E_INVALIDARG, !_bounds.IsInBounds(endPosInclusive));
+
+    // Throw if pos is past endPos
+    THROW_HR_IF(E_INVALIDARG, _bounds.CompareInBounds(pos, endPosInclusive) > 0);
+
+    _endPosInclusive = endPosInclusive;
+}
+
 // Routine Description:
 // - Tells if the iterator is still valid (hasn't exceeded boundaries of underlying text buffer)
 // Return Value:
@@ -72,7 +91,8 @@ bool TextBufferCellIterator::operator==(const TextBufferCellIterator& it) const
            _exceeded == it._exceeded &&
            _bounds == it._bounds &&
            _pRow == it._pRow &&
-           _attrIter == it._attrIter;
+           _attrIter == it._attrIter &&
+           _endPosInclusive == _endPosInclusive;
 }
 
 // Routine Description:
@@ -98,12 +118,26 @@ TextBufferCellIterator& TextBufferCellIterator::operator+=(const ptrdiff_t& move
     auto newPos = _pos;
     while (move > 0 && !_exceeded)
     {
-        _exceeded = !_bounds.IncrementInBounds(newPos);
+        // If we have an endPos, check if we've exceeded it
+        if (_endPosInclusive.has_value())
+        {
+            _exceeded = _bounds.CompareInBounds(newPos, *_endPosInclusive) > 0;
+        }
+
+        // If we already exceeded from endPos, we'll short-circuit and _not_ increment
+        _exceeded |= !_bounds.IncrementInBounds(newPos);
         move--;
     }
     while (move < 0 && !_exceeded)
     {
-        _exceeded = !_bounds.DecrementInBounds(newPos);
+        // If we have an endPos, check if we've exceeded it
+        if (_endPosInclusive.has_value())
+        {
+            _exceeded = _bounds.CompareInBounds(newPos, *_endPosInclusive) < 0;
+        }
+
+        // If we already exceeded from endPos, we'll short-circuit and _not_ decrement
+        _exceeded |= !_bounds.DecrementInBounds(newPos);
         move++;
     }
     _SetPos(newPos);
@@ -265,3 +299,8 @@ const OutputCellView* TextBufferCellIterator::operator->() const noexcept
 {
     return &_view;
 }
+
+COORD TextBufferCellIterator::Pos() const noexcept
+{
+    return _pos;
+}
diff --git a/src/buffer/out/textBufferCellIterator.hpp b/src/buffer/out/textBufferCellIterator.hpp
@@ -27,6 +27,7 @@ class TextBufferCellIterator
 public:
     TextBufferCellIterator(const TextBuffer& buffer, COORD pos);
     TextBufferCellIterator(const TextBuffer& buffer, COORD pos, const Microsoft::Console::Types::Viewport limits);
+    TextBufferCellIterator(const TextBuffer& buffer, COORD pos, const Microsoft::Console::Types::Viewport limits, const COORD endPosInclusive);
 
     operator bool() const noexcept;
 
@@ -47,6 +48,8 @@ class TextBufferCellIterator
     const OutputCellView& operator*() const noexcept;
     const OutputCellView* operator->() const noexcept;
 
+    COORD Pos() const noexcept;
+
 protected:
     void _SetPos(const COORD newPos);
     void _GenerateView();
@@ -60,6 +63,7 @@ class TextBufferCellIterator
     const Microsoft::Console::Types::Viewport _bounds;
     bool _exceeded;
     COORD _pos;
+    std::optional<COORD> _endPosInclusive;
 
 #if UNIT_TESTING
     friend class TextBufferIteratorTests;

diff --git a/src/cascadia/TerminalControl/XamlUiaTextRange.cpp b/src/cascadia/TerminalControl/XamlUiaTextRange.cpp
@@ -5,6 +5,7 @@
 #include "XamlUiaTextRange.h"
 #include "../types/TermControlUiaTextRange.hpp"
 #include <UIAutomationClient.h>
+#include <UIAutomationCoreApi.h>
 
 // the same as COR_E_NOTSUPPORTED
 // we don't want to import the CLR headers to get it
@@ -89,12 +90,56 @@ namespace winrt::Microsoft::Terminal::Control::implementation
 
     winrt::Windows::Foundation::IInspectable XamlUiaTextRange::GetAttributeValue(int32_t textAttributeId) const
     {
-        // Copied functionality from Types::UiaTextRange.cpp
-        if (textAttributeId == UIA_IsReadOnlyAttributeId)
+        // Call the function off of the underlying UiaTextRange.
+        VARIANT result;
+        THROW_IF_FAILED(_uiaProvider->GetAttributeValue(textAttributeId, &result));
+
+        // Convert the resulting VARIANT into a format that is consumable by XAML.
+        switch (result.vt)
+        {
+        case VT_BSTR:
+        {
+            return box_value(result.bstrVal);
+        }
+        case VT_I4:
+        {
+            return box_value(result.iVal);
+        }
+        case VT_R8:
+        {
+            return box_value(result.dblVal);
+        }
+        case VT_BOOL:
+        {
+            return box_value(result.boolVal);
+        }
+        case VT_UNKNOWN:
         {
-            return winrt::box_value(false);
+            // This one is particularly special.
+            // We might return a special value like UiaGetReservedMixedAttributeValue
+            //  or UiaGetReservedNotSupportedValue.
+            // Some text attributes may return a real value, however, none of those
+            //  are supported at this time.
+            // So we need to figure out what was actually intended to be returned.
+
+            IUnknown* notSupportedVal;
+            UiaGetReservedNotSupportedValue(&notSupportedVal);
+            if (result.punkVal == notSupportedVal)
+            {
+                // See below for why we need to throw this special value.
+                winrt::throw_hresult(XAML_E_NOT_SUPPORTED);
+            }
+
+            IUnknown* mixedAttributeVal;
+            UiaGetReservedMixedAttributeValue(&mixedAttributeVal);
+            if (result.punkVal == mixedAttributeVal)
+            {
+                return Windows::UI::Xaml::DependencyProperty::UnsetValue();
+            }
+
+            __fallthrough;
         }
-        else
+        default:
         {
             // We _need_ to return XAML_E_NOT_SUPPORTED here.
             // Returning nullptr is an improper implementation of it being unsupported.
@@ -103,6 +148,7 @@ namespace winrt::Microsoft::Terminal::Control::implementation
             // Magically, this doesn't affect other forms of navigation...
             winrt::throw_hresult(XAML_E_NOT_SUPPORTED);
         }
+        }
     }
 
     void XamlUiaTextRange::GetBoundingRectangles(com_array<double>& returnValue) const