add new canvas Image item, with somewhat optimized API for asynchronous, threaded rendering directly into an image buffer suitable for use by cairo as a source surface (currently untested)

libs/canvas/canvas/image.h

@@ -0,0 +1,57 @@
+#ifndef __CANVAS_IMAGE__
+#define __CANVAS_IMAGE__
+
+#include <stdint.h>
+#include <boost/shared_ptr.hpp>
+#include <boost/shared_array.hpp>
+
+#include "canvas/item.h"
+
+namespace ArdourCanvas {
+
+class Image : public Item
+{
+public:
+    Image (Group *, Cairo::Format, int width, int height);
+    
+    struct Data {
+	Data (boost::shared_array<uint8_t> d, int w, int h, int s, Cairo::Format fmt)
+		: data (d)
+		, width (w)
+		, height (h)
+		, stride (s)
+		, format (fmt)
+	{}
+
+	boost::shared_array<uint8_t> data;
+	int width;
+	int height;
+	int stride;
+	Cairo::Format format;
+    };
+
+    boost::shared_ptr<Data> get_image ();
+    void put_image (boost::shared_ptr<Data>);
+
+    void render (Rect const &, Cairo::RefPtr<Cairo::Context>) const;
+    void compute_bounding_box () const;
+    XMLNode* get_state () const;
+    void set_state (XMLNode const *);
+    
+private:
+    Cairo::Format            _format;
+    int                      _width;
+    int                      _height;
+    int                      _data;
+    mutable boost::shared_ptr<Data>  _current;
+    boost::shared_ptr<Data>  _pending;
+    mutable bool             _need_render;
+    mutable Cairo::RefPtr<Cairo::Surface> _surface;
+
+    void accept_data ();
+    PBD::Signal0<void> DataReady;
+    PBD::ScopedConnectionList data_connections;
+};
+
+}
+#endif