A CheckButton places a discrete ToggleButton next to a widget, (usually a Label).
See the section on ToggleButton widgets for more information about toggle/check buttons.
The important signal ( toggled ) is also inherited from ToggleButton.
checkbutton
├── check
╰── <child>
Button with indicator (see
set_mode) has a main CSS node with name checkbutton and a subnode with name
check.
button.check
├── check
╰── <child>
Button without indicator changes
the name of its main node to button and adds a .check style class to it. The subnode is invisible in this case.