XUL:Attribute:toolbarbutton.type

type: Type: string; The type of button. If this attribute is not present, a normal button is created. You can set this attribute to the value menu to create a button with a menu popup. This will typically cause the button to be displayed differently.

menu: Set the type attribute to the value menu to create a button with a menu popup. Place a menupopup element inside the button in this case. The user may click anywhere on the button to open and close the menu.
menu-button: You can also use the value menu-button to create a button with a menu. Unlike the menu type, this type requires the user to press the arrow to open the menu, but a different command may be invoked when the main part of the button is pressed. This type of button would be used for browser's back and forward buttons.
checkbox: Use this type to create a toggle button which will switch the checked state each time the button is pressed.
radio: Use this type to create a radio button. You can also create a group of toolbarbutton using this type and the attribute group.

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