(A completely feeble attempt to mimic Michael Kaplan's blog entry titles which carry a much stronger voice.)
Jonathan Hardwick made a short table of inconsistencies in how various programs handle clicks on their notification icons. How are these supposed to work?
The final decision is up to the application, since it is the one that receives the mouse clicks and decides what to do. But what were the intended semantics for clicks on the notification icon?
Left single click: Display a simple interface item targetting the casual user. In most cases, this would be a context menu, but if you are something like the volume control, then a custom interface item (in this case, a slider control for controlling the volume) may be more appropriate.
Right single click: Display a context menu, but one which can contain options for more advanced users. In many cases, the menu will be identical to the left single click menu. (Important: See tomorrow's entry for additional discussion.)
As for double-clicks, you don't need a special rule because there is already a general principle for what double-clicks mean: The double-click action, generally speaking, is equivalent to viewing the context menu and choosing the default action.
For the programs on Jonathan's list, then, the actions should go like this:
- Left single click: Display a context menu showing applicable quick-access actions, with Open being the boldfaced default menu item.
- Left double click: Open the application window.
Note that if you go for the left single click, you'll run into a half-second delay because the icon is waiting to determine whether that first click is a standalone single click or whether it is the first half of an upcoming double-click.
Oh, and here's that further discussion on right clicks: The right click and left click distinction was an attempt to provide advanced functionality to advanced users, on the principle that most users don't really use the right mouse button much and will click with the left button by default. This was especially true back when the Windows 95 user interface guidelines were being developed, since the right mouse button was barely used at all in Windows 3.1. It's a new button, may as well use it for something new. In the intervening years, however, things have changed. The right mouse button is much more heavily used by applications, and even novice users are accustomed to right-clicking on things. Consequently, knowledge of the right mouse button no longer carries the mark of the geek that it once did. In fact, there is a nontrivial class of users who are accustomed to right-clicking on icons as their primary means of interacting with them.
The fact that applications which create notification icons historically have done a poor job of distinguishing the left click ("basic function menu") from the right click ("advanced function menu") only makes the distinction even more meaningless. For notification icons, the consequences of this shift in usage patterns and the general confusion in the world of applications that create notification icons is that you are probably best off making your right click menu the same as your left click menu.
Update: Here's a link to the official guidance regarding how users interact with notification icons.