This section shows the hierarchy of widgets in C version. I’m not sure this is correct or not in ocaml version. And the names of widgets used in this section are C version, not ocaml version.
For your reference, here is the class hierarchy tree used to implement widgets. (Deprecated widgets and auxiliary classes have been omitted.)
GObject
|
GtkObject
+GtkWidget
| +GtkMisc
| | +GtkLabel
| | | `GtkAccelLabel
| | +GtkArrow
| | `GtkImage
| +GtkContainer
| | +GtkBin
| | | +GtkAlignment
| | | +GtkFrame
| | | | `GtkAspectFrame
| | | +GtkButton
| | | | +GtkToggleButton
| | | | | `GtkCheckButton
| | | | | `GtkRadioButton
| | | | `GtkOptionMenu
| | | +GtkItem
| | | | +GtkMenuItem
| | | | +GtkCheckMenuItem
| | | | | `GtkRadioMenuItem
| | | | +GtkImageMenuItem
| | | | +GtkSeparatorMenuItem
| | | | `GtkTearoffMenuItem
| | | +GtkWindow
| | | | +GtkDialog
| | | | | +GtkColorSelectionDialog
| | | | | +GtkFileSelection
| | | | | +GtkFontSelectionDialog
| | | | | +GtkInputDialog
| | | | | `GtkMessageDialog
| | | | `GtkPlug
| | | +GtkEventBox
| | | +GtkHandleBox
| | | +GtkScrolledWindow
| | | `GtkViewport
| | +GtkBox
| | | +GtkButtonBox
| | | | +GtkHButtonBox
| | | | `GtkVButtonBox
| | | +GtkVBox
| | | | +GtkColorSelection
| | | | +GtkFontSelection
| | | | `GtkGammaCurve
| | | `GtkHBox
| | | +GtkCombo
| | | `GtkStatusbar
| | +GtkFixed
| | +GtkPaned
| | | +GtkHPaned
| | | `GtkVPaned
| | +GtkLayout
| | +GtkMenuShell
| | | +GtkMenuBar
| | | `GtkMenu
| | +GtkNotebook
| | +GtkSocket
| | +GtkTable
| | +GtkTextView
| | +GtkToolbar
| | `GtkTreeView
| +GtkCalendar
| +GtkDrawingArea
| | `GtkCurve
| +GtkEditable
| | +GtkEntry
| | `GtkSpinButton
| +GtkRuler
| | +GtkHRuler
| | `GtkVRuler
| +GtkRange
| | +GtkScale
| | | +GtkHScale
| | | `GtkVScale
| | `GtkScrollbar
| | +GtkHScrollbar
| | `GtkVScrollbar
| +GtkSeparator
| | +GtkHSeparator
| | `GtkVSeparator
| +GtkInvisible
| +GtkPreview
| `GtkProgressBar
+GtkAdjustment
+GtkCellRenderer
| +GtkCellRendererPixbuf
| +GtkCellRendererText
| +GtkCellRendererToggle
+GtkItemFactory
+GtkTooltips
`GtkTreeViewColumn