The NeXTSTEP user interface is visual, so all operations-all menu commands and scrolling operations, for example-have a graphical representation on-screen and can be performed using the mouse. Keyboard alternatives are just that: alternatives. They should never be used for operations that can't be performed using the mouse.
The main consideration in deciding which operations should have keyboard alternatives is frequency of use. It's better to assign a keyboard alternative to a frequently used command than to one that's used less often. Infrequently used commands-such as the Info Panel command-should never be assigned keyboard alternatives.
Keyboard alternatives are allowed only for the commands in a menu, the buttons in a panel, or the items in a pull-down list. The characters used as keyboard alternatives must be displayed to the user in the menu, panel, or list. Menus put them on the commands themselves, and pull-down lists follow this example. A panel can present the keyboard alternatives for its buttons in any way that's appropriate to the design of the panel.
It's usually a good idea to assign keyboard alternatives to command~ that are needed while working on the keyboard (for example, the commands in the Find menu). The keyboard alternative frees users from having to switch their attention from the keyboard to the mouse and back again.
You can also use keyboard alternatives to enable proficient users to work with one hand on the keyboard and the other on the mouse. For example, Command-x, Command-c, and Command-v allow users to select with the mouse while carrying out cut, copy, and paste operations from the keyboard. These keyboard alternatives free users from having to move the cursor out of the region where they're working just to click a command.
If keyboard alternatives are assigned to any in a set of parallel commands for formatting or viewing data (for example, commands that sort a list of items in various ways), the command that restores the default should also be assigned a keyboard alternative. The keyboard can then take the user to an alternative format and back to the default, rather than just half way.
Note: You don't need to assign a keyboard alternative to every command. Remember that users can create their own global keyboard alternatives by using the Preferences application.
Choosing the Character
Any character except period (.) and space can be used in a keyboard alternative. If the character is a letter, it can be either uppercase or lowercase, although lowercase characters are preferred because they don't require the user to press two modifier keys (Shift and Command) at once.
When choosing the character for a keyboard alternative, try to make it mnemonic. If possible, it should be the first letter of the command it performs. If it's closely related to a command that already has a keyboard alternative, then you might want to choose a character physically near the existing one.
For example, the Find command's keyboard alternative is Command-f, taken from the first letter of the command. The Find command has two related commands: Find Next and Find Previous. The Find Next command's keyboard alternative (Command-g) was chosen because it's just to the right of the Find command's keyboard alternative. Similarly, the Find Previous command's keyboard alternative (Command-d) is just to the left.
Using the Alternate Key·
If necessary, your application can use the Alternate key with the Command key for keyboard alternatives. Using the Alternate key is not desirable. You should first exhaust all reasonable possibilities using the Command key alone or in combination with the Shift key before resorting to the Alternate key.
Implementing Special Keys 37
But, when necessary, a keyboard alternative requiring the Alternate key can be used. It should be displayed in italic.
The character displayed in italic is the one that would be typed if the Command and Alternate keys were not held down, not the character that's produced when the Alternate key is held down.
Note: Recognizing keyboard alternatives produced with the Alternate key is difficult to implement, and the meaning of italic characters in menus isn't explained in the NeXTSTEP user documentation. If you nevertheless choose to implement keyboard alternatives with the Alternate key, make sure that the documentation for your application explains the meaning of the italicized character.
Determining the Action that Is Performed
A keyboard alternative should almost always accomplish exactly the same thing as the mouse action. Even slight variations between a mouse action and its keyboard alternative run counter to the principle that every keyboard operation must match a corresponding mouse operation. However, in some cases it's acceptable to have a keyboard alternative do just a bit more than the mouse operation. These cases are rare and often go unnoticed by
users because the difference is both subtle and intuitive. The keyboard alternative simply does what the user wants, while also doing one or both of the following:
• Reducing the number of clicks or keystrokes the user needs to perform
• Eliminating the need to switch from the keyboard to the mouse and back again
For example, the Edit application has a Find panel that's brought up by the Find Panel menu command or its Command-fkeyboard alternative. Usually, the panel stays up until the user explicitly closes it, since it can be used many times in a row. However, a user who is concentrating on entering text often wants to find a word in a document but then doesn't want to use the Find panel for a while.
Edit accounts for both kinds of use by automatically closing the panel if the user is not likely to use the Find panel immediately. It assumes that this is the case if the user doesn't use the .mouse to conduct the search (instead, using Command-f to bring up the panel, and starting the search by pressing Return). Edit's behavior lets users find a word using a minimum number of actions, and relieves them of having to switch to the mouse to bring the document window back in front of the Find panel.
In general, you should start with all keyboard alternatives the same as their associated mouse action. In the rare case when a keyboard alternative should be different from its associated mouse action, the need becomes clear through everyday use.