The Select button should be used as the users primary method for ‘selecting’, choosing or dragging things.
The purpose of the Adjust button should be to perform the same as the select button with slight variations / speed-ups. The Adjust button should not simply duplicate the action of the Select button.
Another common use of using the mouse buttons is in conjunction with specific key presses, such as the Shift or Alt keys. Although this may be useful in some instances, the user should not be expected to try all variations for an application to become useful.
A dedicated mouse button is used for opening menus, often referred to as the Menu button. To ensure a consistent user experience all applications should adhere to this.
The notification of Double clicks to an application is provided by a single event code, rather than multiple event codes. This leads to a more responsive user experience as applications do not respond to single clicks prior to double clicks.