Emitted when the user right-clicks the toolbar or uses the keybinding to display a popup menu.
Application developers should handle this signal if they want to display a context menu on the toolbar. The context-menu should appear at
the coordinates given by x and y. The mouse button number is given by the button parameter. If the
menu was popped up using the keybaord, button is -1.
| x |
the x coordinate of the point where the menu should appear |
| y |
the y coordinate of the point where the menu should appear |
| button |
the mouse button the user pressed, or -1 |
|
return true if the signal was handled, false if not |