This is the class hierarchy tree used to implement widgets, with links to each class's detailed documentation.
Gtk.Object (Monodoc) + Gtk.Widget (Monodoc) | + Gtk.Misc (Monodoc) | | + Gtk.Label (Monodoc) | | | - Gtk.AccelLabel (Monodoc) | | + Gtk.Arrow (Monodoc) | | + Gtk.Image (Monodoc) | + Gtk.Container (Monodoc) | | + Gtk.Bin (Monodoc) | | | + Gtk.Alignment (Monodoc) | | | + Gtk.Frame (Monodoc) | | | | Gtk.AspectFrame (Monodoc) | | | + Gtk.Button (Monodoc) | | | | + Gtk.ToggleButton (Monodoc) | | | | | - Gtk.CheckButton (Monodoc) | | | | | - Gtk.RadioButton (Monodoc) | | | | + Gtk.OptionMenu (Monodoc) | | | + Gtk.Item (Monodoc) | | | | + Gtk.MenuItem (Monodoc) | | | | + Gtk.CheckMenuItem (Monodoc) | | | | | - Gtk.RadioMenuItem (Monodoc) | | | | + Gtk.ImageMenuItem (Monodoc) | | | | + Gtk.SeparatorMenuItem (Monodoc) | | | | + Gtk.TearoffMenuItem (Monodoc) | | | + Gtk.Window (Monodoc) | | | | + Gtk.Dialog (Monodoc) | | | | | - Gtk.ColorSelectionDialog (Monodoc) | | | | | - Gtk.FileSelection (Monodoc) | | | | | - Gtk.FontSelectionDialog (Monodoc) | | | | | - Gtk.InputDialog (Monodoc) | | | | | - Gtk.MessageDialog (Monodoc) | | | | + Gtk.Plug (Monodoc) | | | + Gtk.EventBox (Monodoc) | | | + Gtk.HandleBox (Monodoc) | | | + Gtk.ScrolledWindow (Monodoc) | | | + Gtk.Viewport (Monodoc) | | + Gtk.Box (Monodoc) | | | + Gtk.ButtonBox (Monodoc) | | | | - Gtk.HButtonBox (Monodoc) | | | | - Gtk.VButtonBox (Monodoc) | | | + Gtk.VBox (Monodoc) | | | | - Gtk.ColorSelection (Monodoc) | | | | - Gtk.FontSelection (Monodoc) | | | | - Gtk.GammaCurve (Monodoc) | | | + Gtk.HBox (Monodoc) | | | - Gtk.Combo (Monodoc) | | | - Gtk.Statusbar (Monodoc) | | + Gtk.Fixed (Monodoc) | | + Gtk.Paned (Monodoc) | | | - Gtk.HPaned (Monodoc) | | | - Gtk.VPaned (Monodoc) | | + Gtk.Layout (Monodoc) | | + Gtk.MenuShell (Monodoc) | | | - Gtk.MenuBar (Monodoc) | | | - Gtk.Menu (Monodoc) | | + Gtk.Notebook (Monodoc) | | + Gtk.Socket (Monodoc) | | + Gtk.Table (Monodoc) | | + Gtk.TextView (Monodoc) | | + Gtk.Toolbar (Monodoc) | | + Gtk.TreeView (Monodoc) | + Gtk.Calendar (Monodoc) | + Gtk.DrawingArea (Monodoc) | | - Gtk.Curve (Monodoc) | + Gtk.Editable (Monodoc) | | - Gtk.Entry (Monodoc) | | - Gtk.SpinButton (Monodoc) | + Gtk.Ruler (Monodoc) | | - Gtk.HRuler (Monodoc) | | - Gtk.VRuler (Monodoc) | + Gtk.Range (Monodoc) | | + Gtk.Scale (Monodoc) | | | - Gtk.HScale (Monodoc) | | | - Gtk.VScale (Monodoc) | | + Gtk.Scrollbar (Monodoc) | | - Gtk.HScrollbar (Monodoc) | | - Gtk.VScrollbar (Monodoc) | + Gtk.Separator (Monodoc) | | - Gtk.HSeparator (Monodoc) | | - Gtk.VSeparator (Monodoc) | + Gtk.Invisible (Monodoc) | + Gtk.Preview (Monodoc) | + Gtk.ProgressBar (Monodoc) + Gtk.Adjustment (Monodoc) + Gtk.CellRenderer (Monodoc) | - Gtk.CellRendererPixbuf (Monodoc) | - Gtk.CellRendererText (Monodoc) | - Gtk.CellRendererToggle (Monodoc) + Gtk.ItemFactory (Monodoc) + Gtk.Tooltips (Monodoc) + Gtk.TreeViewColumn (Monodoc)