// Setup the TextView, put it in a ScrolledWindow, and add both to box.
func setupTextView(box *gtk.Box) *gtk.TextView {
sw, _ := gtk.ScrolledWindowNew(nil, nil)
tv, _ := gtk.TextViewNew()
sw.Add(tv)
box.PackStart(sw, true, true, 0)
return tv
}
func windowWidget() *gtk.Widget {
grid, err := gtk.GridNew()
if err != nil {
log.Fatal("Unable to create grid:", err)
}
grid.SetOrientation(gtk.ORIENTATION_VERTICAL)
// Just as a demonstration, we create and destroy a Label without ever
// adding it to a container. In native GTK, this would result in a
// memory leak, since gtk_widget_destroy() will not deallocate any
// memory when passed a GtkWidget with a floating reference.
//
// gotk3 handles this situation by always sinking floating references
// of any struct type embedding a glib.InitiallyUnowned, and by setting
// a finalizer to unreference the object when Go has lost scope of the
// variable. Due to this design, widgets may be allocated freely
// without worrying about handling memory incorrectly.
//
// The following code is not entirely useful (except to demonstrate
// this point), but it is also not "incorrect" as the C equivalent
// would be.
unused, err := gtk.LabelNew("This label is never used")
if err != nil {
// Calling Destroy() is also unnecessary in this case. The
// memory will still be freed with or without calling it.
unused.Destroy()
}
sw, err := gtk.ScrolledWindowNew(nil, nil)
if err != nil {
log.Fatal("Unable to create scrolled window:", err)
}
grid.Attach(sw, 0, 0, 2, 1)
sw.SetHExpand(true)
sw.SetVExpand(true)
labelsGrid, err := gtk.GridNew()
if err != nil {
log.Fatal("Unable to create grid:", err)
}
labelsGrid.SetOrientation(gtk.ORIENTATION_VERTICAL)
sw.Add(labelsGrid)
labelsGrid.SetHExpand(true)
insertBtn, err := gtk.ButtonNewWithLabel("Add a label")
if err != nil {
log.Fatal("Unable to create button:", err)
}
removeBtn, err := gtk.ButtonNewWithLabel("Remove a label")
if err != nil {
log.Fatal("Unable to create button:", err)
}
nLabels := 1
insertBtn.Connect("clicked", func() {
var s string
if nLabels == 1 {
s = fmt.Sprintf("Inserted %d label.", nLabels)
} else {
s = fmt.Sprintf("Inserted %d labels.", nLabels)
}
label, err := gtk.LabelNew(s)
if err != nil {
log.Print("Unable to create label:", err)
return
}
labelList.PushBack(label)
labelsGrid.Add(label)
label.SetHExpand(true)
labelsGrid.ShowAll()
nLabels++
})
removeBtn.Connect("clicked", func() {
e := labelList.Front()
if e == nil {
log.Print("Nothing to remove")
return
}
lab, ok := labelList.Remove(e).(*gtk.Label)
if !ok {
log.Print("Element to remove is not a *gtk.Label")
return
}
// (*Widget).Destroy() breaks this label's reference with all
// other objects (in this case, the Grid container it was added
// to).
lab.Destroy()
// At this point, only Go retains a reference to the GtkLabel.
// When the lab variable goes out of scope when this function
// returns, at the next garbage collector run, a finalizer will
// be run to perform the final unreference and free the widget.
})
grid.Attach(insertBtn, 0, 1, 1, 1)
grid.Attach(removeBtn, 1, 1, 1, 1)
return &grid.Container.Widget
}