0027: Menus II - Mnemonics (Shortcut Keys)

Today, we’ll cover two quick subjects, adding keyboard shortcuts to MenuItems and separating menus into two areas. Let’s get at it.

Mnemonic Shortcut Keys

There are two ways to set up a keyboard shortcut for a MenuItem. Both start with the call to MenuItem’s constructor, but one passes three arguments while the other passes only two. In the following example, both are illustrated.

Results of this example:
Current example output
Current example output
Current example terminal output
Current example terminal output (click for enlarged view)
The code file for this example is available here.

The Two-step Process

The code for creating the NewFileItem with its shortcut key uses the two-step process for hooking up the mnemonic and looks like this:

class NewFileItem : MenuItem
{
	string newFileLabel = "_New";
   
	this()
	{
		super(newFileLabel, true); // true turns on the mnemonic
		addOnActivate(&newFile);
		
	} // this()
	
	
	void newFile(MenuItem mi)
	{
		writeln("New file created.");
		
	} // newFile()
	
} // class NewFileItem

There are two things here that are different from our earlier examples:

  • our constructor passes along an extra Boolean argument, and
  • the newFileLabel text has an underscore in front of the ‘N.’

The extra argument (true) tells the super-class constructor to turn on the mnemonic for this MenuItem.

The underscore (_) decides which key, combined with Alt, will activate the MenuItem.

And from there, it’s business as usual. Except that…

The FileMenuHeader also has a mnemonic. Have a peek:

class FileMenuHeader : MenuItem
{
	string headerTitle = "_File";
	FileMenu fileMenu;
	
	this()
	{
		super(headerTitle);
		
		fileMenu = new FileMenu();
		setSubmenu(fileMenu);
		
		
	} // this()
	
} // class FileMenu

If you want a mnemonic on a MenuItem, you need a mnemonic on the Menu, too. It won’t show when your application is running (more’s the pity) and you don’t need to turn it on by passing a Boolean to the MenuItem that acts as a menu header, but the underscore does have to be there.

The One-step Process

With this method, a pointer to the callback is passed to the super-class along with the mnemonic label text and the Boolean switch:

class ExitItem : MenuItem
{
	string exitLabel = "E_xit";
   
	this()
	{
		super(&exit, exitLabel, true);
		
	} // this()
	
	
	void exit(MenuItem mi)
	{
		Main.quit();
		
	} // exit()
	
} // class ExitItem

Notice also that the underscore isn’t under the first letter in the Label text, indicating that any one of the letters in the text Label can be used as the shortcut key.

Separators

This is just about the easiest thing to do in GtkD. Pick the spot for the separator and:

SeparatorMenuItem separator = new SeparatorMenuItem();
append(separator);
Results of this example:
Current example output
Current example output
Current example terminal output
Current example terminal output (click for enlarged view)
The code file for this example is available here.

No muss, fuss, or foaming at the mouth.

Conclusion

Well, that’s that. Mnemonic shortcut keys and separators… Yup.

Bye, now.

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