Fixed reporting transformation settings for wxGraphicsContext with Cairo renderer.

When wxGraphicsContext is created from "native" Cairo context (cairo_t*) then transformation settings applied initially to the underlying source Cairo context need to be stored (in a dedicated variable) to make possible determining what transformations were applied to wxGC instance since its creation. Only these explicitly applied transformations are reported by GetTransform().

src/generic/graphicc.cpp

@@ -2099,8 +2099,11 @@ wxCairoContext::wxCairoContext( wxGraphicsRenderer* renderer, cairo_t *context )
     m_mswStateSavedDC = 0;
 #endif // __WXMSW__
     Init( context );
-    m_width =
+    m_width = 0;
     m_height = 0;
+    // Store transformation settings of the underlying source context.
+    if ( m_context )
+        cairo_get_matrix(m_context, &m_internalTransform);
 }
 
 wxCairoContext::wxCairoContext( wxGraphicsRenderer* renderer, wxWindow *window)