class TGSplitButton: public TGTextButton

TGButton, TGTextButton, TGPictureButton, TGCheckButton,
TGRadioButton and TGSplitButton

This header defines all GUI button widgets.

TGButton is a button abstract base class. It defines general button
behaviour.

TGTextButton and TGPictureButton yield an action as soon as they are
clicked. These buttons usually provide fast access to frequently
used or critical commands. They may appear alone or placed in a
group.

The action they perform can be inscribed with a meaningful tooltip
set by SetToolTipText(const char* text, Long_t delayms=400).

The text button has a label indicating the action to be taken when
the button is pressed. The text can be a hot string ("&Exit") that
defines the label "Exit" and keyboard mnemonics Alt+E for button
selection. A button label can be changed by SetText(new_label).

Selecting a text or picture button will generate the event:
kC_COMMAND, kCM_BUTTON, button id, user data.

The purpose of TGCheckButton and TGRadioButton is for selecting
different options. Like text buttons, they have text or hot string
as a label.

Radio buttons are grouped usually in logical sets of two or more
buttons to present mutually exclusive choices.

Selecting a check button will generate the event:
kC_COMMAND, kCM_CHECKBUTTON, button id, user data.

Selecting a radio button will generate the event:
kC_COMMAND, kCM_RADIOBUTTON, button id, user data.

If a command string has been specified (via SetCommand()) then this
command string will be executed via the interpreter whenever a
button is selected. A command string can contain the macros:
$MSG   -- kC_COMMAND, kCM[CHECK|RADIO]BUTTON packed message
(use GET_MSG() and GET_SUBMSG() to unpack)
$PARM1 -- button id
$PARM2 -- user data pointer
Before executing these macros are expanded into the respective
Long_t's

TGSplitButton implements a button with added menu functionality.
There are 2 modes of operation available.

If the button is split, a menu will popup when the menu area of the
button is clicked. Activating a menu item changes the functionality
of the button by having it emit a additional signal when it is
clicked. The signal emitted when the button is clicked, is the
ItemClicked(Int_t) signal with a different fixed value for the
Int_t that corresponds to the id of the activated menu entry.

If the button is not split, clicking it will popup the menu and the
ItemClicked(Int_t) signal will be emitted when a menu entry is
acitvated. The value of the Int_t is again equal to the value of
the id of the activated menu entry.

The mode of operation of a SplitButton can be changed on the fly
by calling the SetSplit(Bool_t) method.