Slightly clean up font handling in wxGraphicsContext in wxGTK

Returning true/false from wxCairoFontData::Apply() to indicate whether
Pango should or not be used was not very clear, so prefer to test for
the font explicitly in the code calling Apply() and make Apply() itself
void, consistently with the method with the same name in the other
classes.

Also avoid calling it at all from GetTextExtent() when using Pango, this
is completely unnecessary as the text colour doesn't have any bearing on
its extents.

Also use static_cast and const_cast as appropriate instead of C-style
casts.

src/generic/graphicc.cpp

@@ -337,7 +337,7 @@ public:
                     const wxColour& col);
     ~wxCairoFontData();
 
-    virtual bool Apply( wxGraphicsContext* context );
+    virtual void Apply( wxGraphicsContext* context );
 #ifdef __WXGTK__
     const wxFont& GetFont() const { return m_wxfont; }
 #endif
@@ -1046,7 +1046,7 @@ wxCairoFontData::~wxCairoFontData()
 #endif
 }
 
-bool wxCairoFontData::Apply( wxGraphicsContext* context )
+void wxCairoFontData::Apply( wxGraphicsContext* context )
 {
     cairo_t * ctext = (cairo_t*) context->GetNativeContext();
     cairo_set_source_rgba(ctext,m_red,m_green, m_blue,m_alpha);
@@ -1055,14 +1055,14 @@ bool wxCairoFontData::Apply( wxGraphicsContext* context )
     {
         // Nothing to do, the caller uses Pango layout functions to do
         // everything.
-        return true;
+        return;
     }
 #elif defined(__WXMAC__)
     if ( m_font )
     {
         cairo_set_font_face(ctext, m_font);
         cairo_set_font_size(ctext, m_size );
-        return true;
+        return;
     }
 #endif
 
@@ -1070,10 +1070,6 @@ bool wxCairoFontData::Apply( wxGraphicsContext* context )
     // we're using toy Cairo API even under wxGTK/wxMac.
     cairo_select_font_face(ctext, m_fontName, m_slant, m_weight );
     cairo_set_font_size(ctext, m_size );
-
-    // Indicate that we don't use native fonts for the platforms which care
-    // about this (currently only wxGTK).
-    return false;
 }
 
 //-----------------------------------------------------------------------------
@@ -2603,11 +2599,16 @@ void wxCairoContext::DoDrawText(const wxString& str, wxDouble x, wxDouble y)
     if ( !data )
         return;
 
-    if ( ((wxCairoFontData*)m_font.GetRefData())->Apply(this) )
+    wxCairoFontData* const
-    {
+        fontData = static_cast<wxCairoFontData*>(m_font.GetRefData());
+
+    fontData->Apply(this);
+
 #ifdef __WXGTK__
+    const wxFont& font = fontData->GetFont();
+    if ( font.IsOk() )
+    {
         wxGtkObject<PangoLayout> layout(pango_cairo_create_layout (m_context));
-        const wxFont& font = static_cast<wxCairoFontData*>(m_font.GetRefData())->GetFont();
         pango_layout_set_font_description(layout, font.GetNativeFontInfo()->description);
         pango_layout_set_text(layout, data, data.length());
         font.GTKSetPangoAttrs(layout);
@@ -2617,8 +2618,8 @@ void wxCairoContext::DoDrawText(const wxString& str, wxDouble x, wxDouble y)
 
         // Don't use Cairo text API, we already did everything.
         return;
-#endif
     }
+#endif // __WXGTK__
 
     // Cairo's x,y for drawing text is at the baseline, so we need to adjust
     // the position we move to by the ascent.
@@ -2649,13 +2650,20 @@ void wxCairoContext::GetTextExtent( const wxString &str, wxDouble *width, wxDoub
     if ( str.empty() && !descent && !externalLeading )
         return;
 
-    if ( ((wxCairoFontData*)m_font.GetRefData())->Apply((wxCairoContext*)this) )
+    wxCairoFontData* const
-    {
+        fontData = static_cast<wxCairoFontData*>(m_font.GetRefData());
+
 #ifdef __WXGTK__
+    // Use Pango instead of Cairo toy font API if we have the font.
+    const wxFont& font = fontData->GetFont();
+    if ( font.IsOk() )
+    {
+        // Note that there is no need to call Apply() at all in this case, it
+        // just sets the text colour, but we don't care about this when
+        // measuring its extent.
         int w, h;
 
         wxGtkObject<PangoLayout> layout(pango_cairo_create_layout (m_context));
-        const wxFont& font = static_cast<wxCairoFontData*>(m_font.GetRefData())->GetFont();
         pango_layout_set_font_description(layout, font.GetNativeFontInfo()->description);
         const wxCharBuffer data = str.utf8_str();
         if ( !data )
@@ -2676,8 +2684,10 @@ void wxCairoContext::GetTextExtent( const wxString &str, wxDouble *width, wxDoub
             *descent = h - PANGO_PIXELS(baseline);
         }
         return;
-#endif
     }
+#endif // __WXGTK__
+
+    fontData->Apply(const_cast<wxCairoContext*>(this));
 
     if (width)
     {