func setup_btn(label string, onClick func()) *gtk.Button {
btn, err := gtk.ButtonNewWithLabel(label)
if err != nil {
log.Fatal("Unable to create button:", err)
}
btn.Connect("clicked", onClick)
return btn
}
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
}
func main() {
gtk.Init(nil)
win, err := gtk.WindowNew(gtk.WINDOW_TOPLEVEL)
if err != nil {
log.Fatal("Unable to create window:", err)
}
win.SetTitle("Grid Example")
win.Connect("destroy", func() {
gtk.MainQuit()
})
// Create a new grid widget to arrange child widgets
grid, err := gtk.GridNew()
if err != nil {
log.Fatal("Unable to create grid:", err)
}
// gtk.Grid embeds an Orientable struct to simulate the GtkOrientable
// GInterface. Set the orientation from the default horizontal to
// vertical.
grid.SetOrientation(gtk.ORIENTATION_VERTICAL)
// Create some widgets to put in the grid.
lab, err := gtk.LabelNew("Just a label")
if err != nil {
log.Fatal("Unable to create label:", err)
}
btn, err := gtk.ButtonNewWithLabel("Button with label")
if err != nil {
log.Fatal("Unable to create button:", err)
}
entry, err := gtk.EntryNew()
if err != nil {
log.Fatal("Unable to create entry:", err)
}
spnBtn, err := gtk.SpinButtonNewWithRange(0.0, 1.0, 0.001)
if err != nil {
log.Fatal("Unable to create spin button:", err)
}
nb, err := gtk.NotebookNew()
if err != nil {
log.Fatal("Unable to create notebook:", err)
}
// Calling (*gtk.Container).Add() with a gtk.Grid will add widgets next
// to each other, in the order they were added, to the right side of the
// last added widget when the grid is in a horizontal orientation, and
// at the bottom of the last added widget if the grid is in a vertial
// orientation. Using a grid in this manner works similar to a gtk.Box,
// but unlike gtk.Box, a gtk.Grid will respect its child widget's expand
// and margin properties.
grid.Add(btn)
grid.Add(lab)
grid.Add(entry)
grid.Add(spnBtn)
// Widgets may also be added by calling (*gtk.Grid).Attach() to specify
// where to place the widget in the grid, and optionally how many rows
// and columns to span over.
//
// Additional rows and columns are automatically added to the grid as
// necessary when new widgets are added with (*gtk.Container).Add(), or,
// as shown in this case, using (*gtk.Grid).Attach().
//
// In this case, a notebook is added beside the widgets inserted above.
// The notebook widget is inserted with a left position of 1, a top
// position of 1 (starting at the same vertical position as the button),
// a width of 1 column, and a height of 2 rows (spanning down to the
// same vertical position as the entry).
//
// This example also demonstrates how not every area of the grid must
// contain a widget. In particular, the area to the right of the label
// and the right of spin button have contain no widgets.
grid.Attach(nb, 1, 1, 1, 2)
nb.SetHExpand(true)
nb.SetVExpand(true)
// Add a child widget and tab label to the notebook so it renders.
nbChild, err := gtk.LabelNew("Notebook content")
if err != nil {
log.Fatal("Unable to create button:", err)
}
nbTab, err := gtk.LabelNew("Tab label")
if err != nil {
log.Fatal("Unable to create label:", err)
}
nb.AppendPage(nbChild, nbTab)
// Add the grid to the window, and show all widgets.
win.Add(grid)
win.ShowAll()
gtk.Main()
}