Provided a way to connect child widget signals in the GTK+ sysData and connected Area to draw. I think I'm getting the wrong child widget, though...

area_unix.go

@@ -16,7 +16,7 @@ import (
 // #define GDK_VERSION_MIN_REQUIRED GDK_VERSION_3_4
 // #define GDK_VERSION_MAX_ALLOWED GDK_VERSION_3_4
 // #include <gtk/gtk.h>
-// extern gboolean our_draw_callback(GtkWidget *, cairo_t *, gpointer);
+// extern gboolean our_area_draw_callback(GtkWidget *, cairo_t *, gpointer);
 // /* HACK - see https://code.google.com/p/go/issues/detail?id=7548 */
 // struct _cairo {};
 import "C"
@@ -30,8 +30,14 @@ func gtkAreaNew() *gtkWidget {
 	return fromgtkwidget(scrollarea)
 }
 
-//export our_draw_callback
-func our_draw_callback(widget *C.GtkWidget, cr *C.cairo_t, data C.gpointer) C.gboolean {
+func gtkAreaGetControl(scrollarea *gtkWidget) *gtkWidget {
+	viewport := C.gtk_bin_get_child((*C.GtkBin)(unsafe.Pointer(scrollarea)))
+	control := C.gtk_bin_get_child((*C.GtkBin)(unsafe.Pointer(viewport)))
+	return fromgtkwidget(control)
+}
+
+//export our_area_draw_callback
+func our_area_draw_callback(widget *C.GtkWidget, cr *C.cairo_t, data C.gpointer) C.gboolean {
 	var x, y, w, h C.double
 
 	s := (*sysData)(unsafe.Pointer(data))
@@ -64,4 +70,4 @@ func our_draw_callback(widget *C.GtkWidget, cr *C.cairo_t, data C.gpointer) C.gb
 	return C.FALSE		// signals handled without stopping the event chain (thanks to desrt again)
 }
 
-var draw_callback = C.GCallback(C.our_draw_callback)
+var area_draw_callback = C.GCallback(C.our_area_draw_callback)

implementation.md

@@ -49,7 +49,7 @@ As the GTK+ main loop system does not quite run in a sane way (it allows recursi
 
 GTK+ layout managers are not used since the UI library's layout managers are coded in a portable way. (`GtkFixed` is used instead.) This isn't ideal, but it works for now.
 
-All event handlers take the `sysData` as their user data parameter; this means all the event-handling code is stored in static functions in callbacks_unix.go. (Early versions of the package generated signal handlers for each control on the fly, but this needed to be changed to accommodoate Area, which not only needs the `sysData` but also needs to connect to a subwidget of a subwidget (specifically the subwidget of the `GtkViewport` of a `GtkScrolledWindow`); the current setup also avoids creating closures for each and every Window and Button created, and also means we can stop having to shove those callbacks in an ever-growing slice to prevent them from being garbage collected.)
+All event handlers take the `sysData` as their user data parameter; this means all the event-handling code is stored in static functions in callbacks_unix.go. (Early versions of the package generated signal handlers for each control on the fly, but this needed to be changed to accommodoate Area, which not only needs the `sysData` but also needs to connect to a subwidget of a subwidget (specifically the subwidget of the `GtkViewport` of a `GtkScrolledWindow`); the current setup also avoids creating closures for each and every Window and Button created, and also means we can stop having to shove those callbacks in an ever-growing slice to prevent them from being garbage collected.) Should the widget actually be a child widget of a `GtkScrolledWindow`, the `child` function and `childsigs` signal list are used to assign signals as well.
 
 The only major snag with the GTK+ implementation is the implementation of `Listbox`; see `listbox_unix.go` for details.
 

sysdata_unix.go

@@ -30,6 +30,8 @@ type classData struct {
 	len		func(widget *gtkWidget) int
 	// ...
 	signals	callbackMap
+	child		func(widget *gtkWidget) *gtkWidget
+	childsigs	callbackMap
 }
 
 var classTypes = [nctypes]*classData{
@@ -94,6 +96,10 @@ var classTypes = [nctypes]*classData{
 	},
 	c_area:			&classData{
 		make:		gtkAreaNew,
+		child:		gtkAreaGetControl,
+		childsigs:		callbackMap{
+			"draw":		area_draw_callback,
+		},
 	},
 }
 
@@ -127,6 +133,12 @@ func (s *sysData) make(initText string, window *sysData) error {
 			for signame, sigfunc := range ct.signals {
 				g_signal_connect(s.widget, signame, sigfunc, s)
 			}
+			if ct.child != nil {
+				child := ct.child(s.widget)
+				for signame, sigfunc := range ct.childsigs {
+					g_signal_connect(child, signame, sigfunc, s)
+				}
+			}
 			ret <- nil
 		}
 		<-ret