Fixed wxGraphicsPath concatenation (with AddPath) for Direct2D renderer.

Because only ID2D1PathGeometry with closed sink (in the immutable state) can be transferred to another geometry object with ID2D1PathGeometry::Stream() so appending one wxGraphicsPath to another has to be done with source path geometry in the non-writable state and closing this geometry has to be done prior to any other operation.
But we want source wxGraphicsPath to stay in the writable state after appending it to another path so we have to prepare a writable copy of the source ID2D1PathGeometry and assign it to the source wxGraphicPath after the appending.

See #17532

src/msw/graphicsd2d.cpp

@@ -1310,11 +1310,61 @@ void wxD2DPathData::GetCurrentPoint(wxDouble* x, wxDouble* y) const
 // adds another path
 void wxD2DPathData::AddPath(const wxGraphicsPathData* path)
 {
-    const wxD2DPathData* d2dPath = static_cast<const wxD2DPathData*>(path);
+    wxD2DPathData* d2dPath =
+         const_cast<wxD2DPathData*>(static_cast<const wxD2DPathData*>(path));
 
-    EnsureFigureOpen();
+    // Nothing to do if geometry of appended path is not initialized.
+    if ( d2dPath->m_pathGeometry == NULL || d2dPath->m_geometrySink == NULL )
+        return;
 
-    d2dPath->m_pathGeometry->Stream(m_geometrySink);
+    // Close current sub-path (leaving the figure as is).
+    EndFigure(D2D1_FIGURE_END_OPEN);
+
+    // Because only geometry with closed sink (immutable)
+    // can be transferred to another geometry object with
+    // ID2D1PathGeometry::Stream() so we have to make
+    // a writable copy of the appended geometry
+    // and re-assign it to the source path after actual appending.
+
+    // Close appended geometry sink.
+    d2dPath->EndFigure(D2D1_FIGURE_END_OPEN);
+    HRESULT hr;
+    hr = d2dPath->m_geometrySink->Close();
+    wxFAILED_HRESULT_MSG(hr);
+
+    // Transfer appended geometry to the current geometry sink.
+    hr = d2dPath->m_pathGeometry->Stream(m_geometrySink);
+    wxFAILED_HRESULT_MSG(hr);
+    // Copy auxiliary data if appended path is non-empty.
+    UINT32 segCount = 0;
+    UINT32 figCount = 0;
+    hr = d2dPath->m_pathGeometry->GetSegmentCount(&segCount);
+    wxFAILED_HRESULT_MSG(hr);
+    hr = d2dPath->m_pathGeometry->GetFigureCount(&figCount);
+    wxFAILED_HRESULT_MSG(hr);
+    if( segCount > 0 || figCount > 0 || d2dPath->m_currentPointSet || d2dPath->m_figureOpened )
+    {
+        m_currentPointSet = d2dPath->m_currentPointSet;
+        m_currentPoint = d2dPath->m_currentPoint;
+        m_figureOpened = d2dPath->m_figureOpened;
+        m_figureStart = d2dPath->m_figureStart;
+    }
+
+    // Make a writable copy of the appended geometry.
+    wxCOMPtr<ID2D1PathGeometry> srcPathGeometry;
+    wxCOMPtr<ID2D1GeometrySink> srcGeometrySink;
+    hr = m_direct2dfactory->CreatePathGeometry(&srcPathGeometry);
+    wxFAILED_HRESULT_MSG(hr);
+    hr = srcPathGeometry->Open(&srcGeometrySink);
+    wxFAILED_HRESULT_MSG(hr);
+    // Transfer appended geometry.
+    hr = d2dPath->m_pathGeometry->Stream(srcGeometrySink);
+    wxFAILED_HRESULT_MSG(hr);
+
+    // Assign a writable copy of the appendeed
+    // geometry back to the source path.
+    d2dPath->m_pathGeometry = srcPathGeometry;
+    d2dPath->m_geometrySink = srcGeometrySink;
 }
 
 // closes the current sub-path