Restore source DC state when wxCairoContext is destroyed (wxMSW).

Since raw DC (encapsulated in source wxDC) can be modified in wxCairoContext explicitly (e.g. when context is instantiated from wxPrinterDC or wxEnhMetaFileDC) or implicitly (by some Cairo functions) we have to store its state in ctor and restore it in dtor to assure consistent state of the source wxDC.

src/common/cairo.cpp

@@ -184,7 +184,9 @@
     m( cairo_surface_t*, cairo_win32_surface_create, \
         (HDC hdc), (hdc), NULL ) \
     m( cairo_surface_t*, cairo_win32_printing_surface_create, \
-        (HDC hdc), (hdc), NULL )
+        (HDC hdc), (hdc), NULL ) \
+    m( HDC, cairo_win32_surface_get_dc, \
+       (cairo_surface_t *surface), (surface), NULL )
 #else
 #define wxCAIRO_PLATFORM_METHODS(m) 
 #endif

src/generic/graphicc.cpp

@@ -509,6 +509,7 @@ protected:
 #ifdef __WXMSW__
     cairo_surface_t* m_mswSurface;
     WindowHDC m_mswWindowHDC;
+    int m_mswStateSavedDC;
 #endif
 
 private:
@@ -1741,6 +1742,7 @@ wxCairoContext::wxCairoContext( wxGraphicsRenderer* renderer, const wxPrinterDC&
     // text rendering when printing using Cairo. Switch it to MM_TEXT
     // map mode to avoid this problem.
     HDC hdc = (HDC)dc.GetHDC();
+    m_mswStateSavedDC = ::SaveDC(hdc);
     ::SetMapMode(hdc, MM_TEXT);
     m_mswSurface = cairo_win32_printing_surface_create(hdc);
     Init( cairo_create(m_mswSurface) );
@@ -1792,7 +1794,9 @@ wxCairoContext::wxCairoContext( wxGraphicsRenderer* renderer, const wxWindowDC&
     m_enableOffset = dc.GetContentScaleFactor() <= 1;
 
 #ifdef __WXMSW__
-    m_mswSurface = cairo_win32_surface_create((HDC)dc.GetHDC());
+    HDC hdc = (HDC)dc.GetHDC();
+    m_mswStateSavedDC = ::SaveDC(hdc);
+    m_mswSurface = cairo_win32_surface_create(hdc);
     Init( cairo_create(m_mswSurface) );
 #endif
 
@@ -1850,13 +1854,15 @@ wxCairoContext::wxCairoContext( wxGraphicsRenderer* renderer, const wxMemoryDC&
     wxASSERT_MSG(bmp.IsOk(),
                  wxS("Should select a bitmap before creating wxCairoContext"));
 
+    HDC hdc = (HDC)dc.GetHDC();
+    m_mswStateSavedDC = ::SaveDC(hdc);
     bool hasBitmap = false;
 
     // cairo_win32_surface_create creates a 24-bit bitmap,
     // so if we 32bpp bitmap, we need to create a 32-bit surface instead.
     if (bmp.GetDepth() < 32)
     {
-        m_mswSurface = cairo_win32_surface_create(dc.GetHDC());
+        m_mswSurface = cairo_win32_surface_create(hdc);
     }
     else
     {
@@ -1937,7 +1943,7 @@ wxCairoContext::wxCairoContext( wxGraphicsRenderer* renderer, const wxMemoryDC&
         // Fallback if we failed to create Cairo surface from 32bpp bitmap.
         if( !hasBitmap )
         {
-            m_mswSurface = cairo_win32_surface_create(dc.GetHDC());
+            m_mswSurface = cairo_win32_surface_create(hdc);
         }
     }
 
@@ -2027,6 +2033,7 @@ wxCairoContext::wxCairoContext(wxGraphicsRenderer* renderer, const wxEnhMetaFile
     // text rendering when printing using Cairo. Switch it to MM_TEXT
     // map mode to avoid this problem.
     HDC hdc = (HDC)dc.GetHDC();
+    m_mswStateSavedDC = ::SaveDC(hdc);
     ::SetMapMode(hdc, MM_TEXT);
     m_mswSurface = cairo_win32_printing_surface_create(hdc);
     Init( cairo_create(m_mswSurface) );
@@ -2044,6 +2051,7 @@ wxCairoContext::wxCairoContext(wxGraphicsRenderer* renderer, const wxEnhMetaFile
 wxCairoContext::wxCairoContext( wxGraphicsRenderer* renderer, HDC handle )
 : wxGraphicsContext(renderer)
 {
+    m_mswStateSavedDC = ::SaveDC(handle);
     m_mswSurface = cairo_win32_surface_create(handle);
     Init( cairo_create(m_mswSurface) );
     m_width = 0;
@@ -2082,6 +2090,7 @@ wxCairoContext::wxCairoContext(wxGraphicsRenderer* renderer, HWND hWnd)
     double scaleY = ::GetDeviceCaps((HDC)m_mswWindowHDC, LOGPIXELSY) / 96.0f;
     m_enableOffset = scaleY <= 1.0;
 
+    m_mswStateSavedDC = 0;
     m_mswSurface = cairo_win32_surface_create((HDC)m_mswWindowHDC);
     Init(cairo_create(m_mswSurface));
     m_width = 0;
@@ -2101,6 +2110,7 @@ wxCairoContext::wxCairoContext( wxGraphicsRenderer* renderer, cairo_t *context )
 {
 #ifdef __WXMSW__
     m_mswSurface = NULL;
+    m_mswStateSavedDC = 0;
 #endif // __WXMSW__
     Init( context );
     m_width =
@@ -2135,6 +2145,7 @@ wxCairoContext::wxCairoContext( wxGraphicsRenderer* renderer, wxWindow *window)
 #endif
 
 #ifdef __WXMSW__
+    m_mswStateSavedDC = 0;
     m_mswSurface = cairo_win32_surface_create((HDC)m_mswWindowHDC);
     Init(cairo_create(m_mswSurface));
 #endif
@@ -2149,6 +2160,7 @@ wxCairoContext::wxCairoContext(wxGraphicsRenderer* renderer) :
 {
 #ifdef __WXMSW__
     m_mswSurface = NULL;
+    m_mswStateSavedDC = 0;
 #endif // __WXMSW__
     m_context = NULL;
 }
@@ -2163,7 +2175,14 @@ wxCairoContext::~wxCairoContext()
     }
 #ifdef __WXMSW__
     if ( m_mswSurface )
+    {
+        HDC hdc = cairo_win32_surface_get_dc(m_mswSurface);
+
         cairo_surface_destroy(m_mswSurface);
+
+        if ( hdc && m_mswStateSavedDC != 0 )
+            ::RestoreDC(hdc, m_mswStateSavedDC);
+    }
 #endif
 #ifdef __WXQT__
     if ( m_qtPainter != NULL )