7.12. MENUS

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7.12

Menus

Menus are constructed using three procedures menubar this contains a list of the

menus, menu this contains a string (the name of the menu) followed by menus

and menuitems, menuitem these contain strings labelling the menuitem. One

can also provide actions to be carried out when then menuitem is selected.

Below is a standard example of a File menu with a quit option that hides

the window. This also has GUI components for implementing a chat window

(although none of the needed actions are there!)

(define w

(window "Hello"

(menubar

(menu "File"

(menuitem "quit"

(action (lambda(e) (.hide w)))))

(menu "Help"

(menuitem "about")

(menuitem "documentation")))

(border

(north

(label "Chat Central" (HelveticaBold 40)))

(center

(textarea 10 50))

(south

(row

(label ">>")

(textfield "chat here" 30))))))

(.pack w)

(.show w)

Observe that each menu can have zero or more menuitems and can also contain

submenus.

7.13

Tags and Naming

As we will see it is often useful to be able to give names to components (for

example if we want to read from or write to a component, we must have a way

of refering to it).

The  Tag  mechanism provides a simple way to name and refer to objects.

A tagger is created using the following expression

(let ((t (maketagger)))

EXPR)

This creates a tagger  t  which can be used in the following expression. To

assign a name  abc  to an object  X  you use the syntax: