public delegate void DrawingAreaDrawFunc (DrawingArea drawing_area, Context cr, int width, int height)
drawing_area needs to redraw, this function will be called.
This function should exclusively redraw the contents of the drawing area and must not call any widget functions that cause changes.
the DrawingArea to redraw
the context to draw to
the actual width of the contents. This value will be at least as wide as GtkDrawingArea:width.
the actual height of the contents. This value will be at least as wide as GtkDrawingArea:height.