Added Combobox/Listbox.Len() and its GTK+ implementation.

combobox.go

@@ -102,6 +102,19 @@ func (c *Combobox) SelectedIndex() int {
 	return -1
 }
 
+// Len returns the number of items in the Combobox.
+//
+// On platforms for which this function may return an error, it panics if one is returned.
+func (c *Combobox) Len() int {
+	c.lock.Lock()
+	defer c.lock.Unlock()
+
+	if c.created {
+		return c.sysData.len()
+	}
+	return len(c.initItems)
+}
+
 func (c *Combobox) make(window *sysData) (err error) {
 	c.lock.Lock()
 	defer c.lock.Unlock()

gtkcalls_unix.go

@@ -155,6 +155,13 @@ func gtk_combo_box_text_remove(widget *gtkWidget, index int) {
 	C.gtk_combo_box_text_remove(togtkcombobox(widget), C.gint(index))
 }
 
+func gtkComboBoxLen(widget *gtkWidget) int {
+	cb := (*C.GtkComboBox)(unsafe.Pointer(widget))
+	model := C.gtk_combo_box_get_model(cb)
+	// this is the same as with a Listbox so
+	return gtkTreeModelListLen(model)
+}
+
 func gtk_entry_new() *gtkWidget {
 	return fromgtkwidget(C.gtk_entry_new())
 }

listbox.go

@@ -96,6 +96,19 @@ func (l *Listbox) SelectedIndices() []int {
 	return nil
 }
 
+// Len returns the number of items in the Listbox.
+//
+// On platforms for which this function may return an error, it panics if one is returned.
+func (l *Listbox) Len() int {
+	l.lock.Lock()
+	defer l.lock.Unlock()
+
+	if l.created {
+		return l.sysData.len()
+	}
+	return len(l.initItems)
+}
+
 func (l *Listbox) make(window *sysData) (err error) {
 	l.lock.Lock()
 	defer l.lock.Unlock()

listbox_unix.go

@@ -211,3 +211,15 @@ func gListboxDelete(widget *gtkWidget, index int) {
 	}
 	C.gtk_list_store_remove(ls, &iter)
 }
+
+// this is a separate function because Combobox uses it too
+func gtkTreeModelListLen(model *C.GtkTreeModel) int {
+	// "As a special case, if iter is NULL, then the number of toplevel nodes is returned."
+	return int(C.gtk_tree_model_iter_n_children(model, (*C.GtkTreeIter)(nil)))
+}
+
+func gListboxLen(widget *gtkWidget) int {
+	tv := getTreeViewFrom(widget)
+	model := C.gtk_tree_view_get_model(tv)
+	return gtkTreeModelListLen(model)
+}

sysdata.go

@@ -67,6 +67,9 @@ func (c *cSysData) preferredSize() (int, int) {
 func (c *cSysData) setProgress(int) {
 	panic(runtime.GOOS + " sysData does not define setProgress()")
 }
+func (c *cSysData) len() int {
+	panic(runtime.GOOS + " sysData does not define len()")
+}
 
 // signal sends the event signal. This raise is done asynchronously to avoid deadlocking the UI task.
 // Thanks skelterjohn for this techinque: if we can't queue any more events, drop them

sysdata_unix.go

@@ -25,6 +25,7 @@ type classData struct {
 	selMulti	func(widget *gtkWidget) []int
 	smtexts	func(widget *gtkWidget) []string
 	delete	func(widget *gtkWidget, index int)
+	len		func(widget *gtkWidget) int
 	// ...
 	signals	map[string]func(*sysData) func() bool
 }
@@ -84,6 +85,7 @@ var classTypes = [nctypes]*classData{
 		insert:		gtk_combo_box_text_insert_text,
 		selected:		gtk_combo_box_get_active,
 		delete:		gtk_combo_box_text_remove,
+		len:			gtkComboBoxLen,
 	},
 	c_lineedit:		&classData{
 		make:		gtk_entry_new,
@@ -107,6 +109,7 @@ var classTypes = [nctypes]*classData{
 		selMulti:		gListboxSelectedMulti,
 		smtexts:		gListboxSelMultiTexts,
 		delete:		gListboxDelete,
+		len:			gListboxLen,
 	},
 	c_progressbar:		&classData{
 		make:		gtk_progress_bar_new,
@@ -294,3 +297,12 @@ func (s *sysData) setProgress(percent int) {
 	}
 	<-ret
 }
+
+func (s *sysData) len() int {
+	ret := make(chan int)
+	defer close(ret)
+	uitask <- func() {
+		ret <- classTypes[s.ctype].len(s.widget)
+	}
+	return <-ret
+}

test/main.go

@@ -117,11 +117,11 @@ mainloop:
 			lb2.Delete(4)
 		case <-b3.Clicked:
 			MsgBox("List Info",
-				"cb1: %d %q\ncb2: %d %q\nlb1: %d %q\nlb2: %d %q",
+				"cb1: %d %q (len %d)\ncb2: %d %q (len %d)\nlb1: %d %q (len %d)\nlb2: %d %q (len %d)",
-				cb1.SelectedIndex(), cb1.Selection(),
+				cb1.SelectedIndex(), cb1.Selection(), cb1.Len(),
-				cb2.SelectedIndex(), cb2.Selection(),
+				cb2.SelectedIndex(), cb2.Selection(), cb2.Len(),
-				lb1.SelectedIndices(), lb1.Selection(),
+				lb1.SelectedIndices(), lb1.Selection(), lb1.Len(),
-				lb2.SelectedIndices(), lb2.Selection())
+				lb2.SelectedIndices(), lb2.Selection(), lb2.Len())
 		case <-incButton.Clicked:
 			prog++
 			if prog > 100 {