This signal is emitted when a widget is supposed to render itself. The widget's top left corner must be painted at the origin of the passed in context and be sized to the values returned by Widget.getAllocatedWidth and Widget.getAllocatedHeight.
Signal handlers connected to this signal can modify the cairo context passed as cr in any way they like and don't need to restore it. The signal emission takes care of calling cairo_save() before and cairo_restore() after invoking the handler.
The signal handler will get a cr with a clip region already set to the widget's dirty region, i.e. to the area that needs repainting. Complicated widgets that want to avoid redrawing themselves completely can get the full extents of the clip region with Cairo.getClipRectangle, or they can get a finer-grained representation of the dirty region with cairo_copy_clip_rectangle_list().