dgl: add the Context structure

dgl/Base.hpp

@@ -184,6 +184,15 @@ enum Key {
     kKeySuper
 };
 
+/**
+   Type of graphics context.
+ */
+enum ContextType
+{
+    kContextGL,
+    kContextCairo
+};
+
 // -----------------------------------------------------------------------
 // Base DGL classes
 
@@ -197,6 +206,22 @@ public:
     virtual void idleCallback() = 0;
 };
 
+/**
+   Graphics context.
+ */
+struct Context
+{
+    ContextType type;
+    union {
+#ifdef HAVE_DGL
+        struct { /* nothing for now */ } gl;
+#endif
+#ifdef HAVE_DCAIRO
+        struct { cairo_t* graphics; } cairo;
+#endif
+    };
+};
+
 // -----------------------------------------------------------------------
 
 END_NAMESPACE_DGL

dgl/Widget.hpp

@@ -312,9 +312,7 @@ public:
     */
     Window& getParentWindow() const noexcept;
 
-#ifdef HAVE_DCAIRO
-    cairo_t* getContext() const noexcept;
-#endif
+    const Context& getContext() const noexcept;
 
    /**
       Check if this widget contains the point defined by @a x and @a y.

dgl/Window.hpp

@@ -119,9 +119,7 @@ public:
     Application& getApp() const noexcept;
     intptr_t getWindowId() const noexcept;
 
-#ifdef HAVE_DCAIRO
-    cairo_t* getContext() const noexcept;
-#endif
+    const Context& getContext() const noexcept;
 
     void addIdleCallback(IdleCallback* const callback);
     void removeIdleCallback(IdleCallback* const callback);

dgl/src/Widget.cpp

@@ -189,12 +189,10 @@ Window& Widget::getParentWindow() const noexcept
     return pData->parent;
 }
 
-#ifdef HAVE_DCAIRO
-cairo_t* Widget::getContext() const noexcept
+const Context& Widget::getContext() const noexcept
 {
     return pData->parent.getContext();
 }
-#endif
 
 bool Widget::contains(int x, int y) const noexcept
 {

dgl/src/Window.cpp

@@ -214,13 +214,14 @@ struct Window::PrivateData {
         }
 
 #ifdef HAVE_DGL
-        PuglContextType contextType = PUGL_GL;
+        const ContextType contextType = kContextGL;
 #endif
 #ifdef HAVE_DCAIRO
-        PuglContextType contextType = PUGL_CAIRO;
+        const ContextType contextType = kContextCairo;
 #endif
+        fContext.type = contextType;
 
-        puglInitContextType(fView, contextType);
+        puglInitContextType(fView, (PuglContextType)contextType);
         puglInitUserResizable(fView, fResizable);
         puglInitWindowSize(fView, static_cast<int>(fWidth), static_cast<int>(fHeight));
 
@@ -1059,6 +1060,7 @@ struct Window::PrivateData {
 
     Application& fApp;
     Window*      fSelf;
+    Context      fContext;
     PuglView*    fView;
 
     bool fFirstInit;
@@ -1384,12 +1386,15 @@ intptr_t Window::getWindowId() const noexcept
     return puglGetNativeWindow(pData->fView);
 }
 
-#ifdef HAVE_DCAIRO
-cairo_t* Window::getContext() const noexcept
+const Context& Window::getContext() const noexcept
 {
-    return (cairo_t*)puglGetContext(pData->fView);
-}
+    Context& context = pData->fContext;
+#ifdef HAVE_DCAIRO
+    if (context.type == kContextCairo)
+        context.cairo.graphics = (cairo_t*)puglGetContext(pData->fView);
 #endif
+    return context;
+}
 
 void Window::_addWidget(Widget* const widget)
 {