# NSMenu

FredKiefer@gmx.de
khelekir@encomix.es
mhanni@sprintmail.com
far@ix.netcom.com
ovidiu@net-community.com
1999 Free Software Foundation, Inc.
Software documentation for the NSMenu class
AppKit/NSMenu.h
NSCoding
NSCopying

Menus provide the user with a list of actions and/or submenus. Submenus themselves are full fledged menus and so a heirarchical structure of appears.

Every application has one special menu, the so called Application menu. This menu is always visible on the screen when the application is active. This menu normally contains items like, info, services, print, hide and quit.

After the info item normally some submenus follow containing the application specific actions.

On GNUstep the content of the menu is stacked vertically as oppossed to the Windows and Mac world, where they are stacked horizontally. Also because the menus are not part of any normal window they can be dragged around opened and closed independend of the application windows.

This can lead to a few menus being open simultanuously. The collection of open menus is remembered, when the program is started again, all the torn off menus aka detached menus, are displayed at their last known position.

The menu behaviour is richer than in most other environments and bear some explanation. This explanation is aimed at users of Menus but more so at the developer of custom menus.

Application menu
There alwasy at least one menu present and visible while the application is active. This is the application menu. This window can never be closed.
Attached menu
Normally when you click in a menu on a submenu item, the submenu is shown directly next to the menu you click in. The submenu is now called an attached menu. It is attached to the menu that was clicked in.
Detached menu
A menu is detached when it is not attached to its parent menu. A menu can become detached when the user drags a submenu away from its parents. A detached window contains in its title a close button.
Transient menu
A transient menu is a menu that dissappears as soon as the user stops interacting with the menus. Typically a transient menu is created when a right mouse click appears in an application window. The right mouse click will bring up the Application menu at the place the user clicks. While keeping the mouse button down the user can select items by moving around. When releasing the button, all transient menus will be removed from the screen and the action will be executed.

It is important to note that it is impossible to click in transient menus.

Attached transient menu
This is a menu that is attached and transient at the same time.
A single NSMenu instance can be displayed zero or one times when the user is not interaction with the menus. When the user is interaction with the menus it can occur that the same NSMenu is displayed in two locations at the same time. This is only possible when one of the displayed instances is a transient menu. To understand how the diffent kind of menus are created lets look at some user actions: The user clicks on an item which is not a submenu.
The item is highlighted until the action corresponding with the item is completed. More precisely, the application highlights the menu item, performs the action, and unhighlights the item. The user clicks on a submenu item which is not highlighted already
If the submenu is not a detached menu, the submenu will become an attached menu to the menu that is clicked in. The item that is clicked in will become highlighted and stays highlighted.

If the submenu is a detached menu, the transient version of the submenu will be shown

The user clicks on a submenu item which is highlighted
This means that the submenu is an attached submenu for this menu. After clicking the submenu item will no be no longer highlighted and the submenu will be removed from the screen. The user drags over a menu item
The item will be highlighted, if the item is a submenu item, the submenu will be shown as an attached submenu. This can be transient, or non transient.
Customizing the look of Menus
There are basically three ways of customizing the look of NSMenu Using custom NSMenuItemCell's. This you should do when you want to influence the look of the items displayed in the menu. Using custom NSMenuView. This is the class to modify if you want to change the way the menu is layout on the screen. So if you want to stack the menu items horizontally, you should change this class. This should be rarely needed. Reimplement NSMenu. This you should not do. But, if you implement everything yourself you can achieve anything.
Information for implementing custom NSMenuView class
When implementing a custom NSMenuView class it is important to keep the following information in mind. The menus (or the menu items) form a tree. Navigating through this tree is done with the methods [NSMenu -supermenu] , which returns the parent menu of the receiver, and with [NSMenu -itemAtIndex:] which returns a NSMenuItem on which we can call [<NSMenuItem>-submenu] for a child menu. The menus as displayed on the screen do NOT form a tree. This because detached and transient menus lead to duplicate menus on the screen. The displayed menus on the screen have the following structure: The ordered graph of displayed menus (note, NOT the set of NSMenus) form a collection of line graphs. The attached menus are precisely the non root vertices in this graph. An attached menu of a transient menu is itself a transient menu. The collection of transient menus form connect subgraph of the menu graph.
menuZone
Description forthcoming.
popUpContextMenu:
menu
withEvent:
event
forView:
view
Description forthcoming.
setMenuZone:
zone
Description forthcoming.
addItem:
newItem
Description forthcoming.
addItemWithTitle:
aString
action:
aSelector
keyEquivalent:
keyEquiv
Description forthcoming.
attachedMenu
Returns the menu that is attached to this menu.

If two instances of this menu are visible, return the attached window of the transient version of this menu.

If no menu is attached return `nil`.

autoenablesItems
Description forthcoming.
helpRequested:
event
Description forthcoming.
indexOfItem:
anObject
Description forthcoming.
indexOfItemWithRepresentedObject:
anObject
Description forthcoming.
indexOfItemWithSubmenu:
anObject
Description forthcoming.
indexOfItemWithTag:
aTag
Description forthcoming.
indexOfItemWithTarget:
anObject
andAction:
actionSelector
Description forthcoming.
indexOfItemWithTitle:
aTitle
Description forthcoming.
initWithTitle:
aTitle
Description forthcoming.
insertItem:
newItem
atIndex:
index
Description forthcoming.
insertItemWithTitle:
aString
action:
aSelector
keyEquivalent:
charCode
atIndex:
index
Description forthcoming.
isAttached
Returns if this menu is attached to its supermenu, return `nil` if it does not have a parent menu.

If two instances of this menu are visible, return the outcome of the check for the transient version of the menu.

Look for the semantics in the header. Note that this implementation works because there are... cases: This menu is transient, its supermenu is also transient. In this case we just do the check between the transient windows and everything is fine The menu is transient, its supermenu is not transient. This can go WRONG
isTornOff
If there are two instances of this menu visible, return `NO`. Otherwise, return `YES` if we are a detached menu and visible.
itemArray
Returns an array containing all menu items in this menu.
itemAtIndex:
index
Description forthcoming.
itemChanged:
anObject
Description forthcoming.
itemWithTag:
aTag
Description forthcoming.
itemWithTitle:
aString
Description forthcoming.
locationForSubmenu:
aSubmenu
Returns the position where submenu will be displayed when it will be displayed as an attached menu of this menu. The result is undefined when aSubmenu is not actually a submenu of this menu.
menuChangedMessagesEnabled
Description forthcoming.
menuRepresentation
Return the NSView that is used for drawing the menu. It is the view set with [NSMenu -setMenuRepresentation:] and therefore it should be safe to assume it is an NSView implementing the NSMenuView protocol.
numberOfItems
Description forthcoming.
performActionForItemAtIndex:
index
Description forthcoming.
performKeyEquivalent:
theEvent
Description forthcoming.
removeItem:
anItem
Description forthcoming.
removeItemAtIndex:
index
Description forthcoming.
setAutoenablesItems:
flag
Description forthcoming.
setMenuChangedMessagesEnabled:
flag
Description forthcoming.
setMenuRepresentation:
menuRep
Set the View that should be used to display the menu.

The default is NSMenuView, but a user can supply its own NSView object as long as it

Inherits from NSView
Implements NSMenuView protocol
setSubmenu:
aMenu
forItem:
anItem
Description forthcoming.
setSupermenu:
supermenu
Set the supermenu of this menu. TODO: add explanation if this will change remove this menu from the old supermenu or if it does not.
setTitle:
aTitle
Change the title of the menu.
sizeToFit
Description forthcoming.
submenuAction:
sender
Description forthcoming.
supermenu
Returns the supermenu of this menu. Return `nil` if this is the application menu.
title
Returns the current title.
update
Description forthcoming.
Software documentation for the NSMenu(GNUstepExtra) category
AppKit/NSMenu.h
This interface exist contains methods that are meant for the NSMenuView. If you write your own implementation of the NSMenuView interface you can use these methods to popup other menus or close them.
_ownedByPopUp
Warning the underscore at the start of the name of this method indicates that it is private, for internal use only, and you should not use the method in your code.
_setOwnedByPopUp:
popUp
Warning the underscore at the start of the name of this method indicates that it is private, for internal use only, and you should not use the method in your code.
close
Remove the window from the screen. This method can/should be used by the menurepresentation to remove a submenu from the screen.
closeTransient
Remove the transient version of the window from the screen. This method is used by NSMenuView implementations that need to open/close transient menus.
display
Show menu on the screen. This method can/should be used by the menurepresentation to display a submenu on the screen.
displayTransient
Display the transient version of the menu.
isPartlyOffScreen
Description forthcoming.
isTransient
Returns `YES` if there is a transient version of this menu displayed on the screen.
nestedSetFrameOrigin:
aPoint
Set the frame origin of the receiver to aPoint. If a submenu of the receiver is attached. The frame origin of the submenu is set appropriately.
setGeometry
Positions the menu according to the standard user defaults. If the position is not found in the defaults revert to positioning the window in the upper left corner.
setTornOff:
flag
When the flag is `YES` this method will detach the receiver from its parent and update the menurepresentation so it will display a close button if appropriate. If the flag is `NO` this method will update the menurepresentation so it will be able to remove the close button if needed. Note that it will not reattach to its parent menu.
shiftOnScreen
Description forthcoming.
window
Returns the window in which this menu is displayed. If there is a transient version it will return the window in which the transient version is displayed. If the Menu is not displayed at all the result is meaningless.
Software documentation for the NSObject(NSMenuActionResponder) informal protocol
AppKit/NSMenu.h
Description forthcoming.
validateMenuItem:
aMenuItem
Description forthcoming.
Software documentation for the NSMenuValidation protocol
AppKit/NSMenu.h
Specifies the protocol to which an object must confirm if it is to be used to validate menu items (in order to implement automatic enabling and disabling of menu items).
validateMenuItem:
menuItem

The receiver should return `YES` if the menuItem is valid... and should be enabled in the menu, `NO` if it is invalid and the user should not be able to select it.

This method is invoked automatically to determine whether menu items should be enabled or disabled automatically whenever [NSMenu -update] is invoked (usually by the applications event loop).

Software documentation for the NSMenuView protocol
AppKit/NSMenu.h
Description forthcoming.
detachSubmenu
This should ensure that if there is an attached submenu this submenu will be detached. Detaching means that this particular menu representation should be removed from the screen. It should implement a deep detach, that is, all attached submenus of this menu should also be detached.
highlightedItemIndex
Returns the currently highlighted item. Returns -1 if no item is highlighted.
imageAndTitleOffset
Method used by NSMenuItemCell to draw itself correctly and nicely lined up with the other menu items
imageAndTitleWidth
Methos used by NSMenuItemCell to draw itself correctly and nicely lined up with the other menu items.
keyEquivalentOffset
Methos used by NSMenuItemCell to draw itself correctly and nicely lined up with the other menu items.
keyEquivalentWidth
Used by NSItemCell to...
locationForSubmenu:
aSubmenu
Used by the NSMenu to determine where to position a submenu.
performActionWithHighlightingForItemAtIndex:
index
Description forthcoming.
setHighlightedItemIndex:
index
Set the currently highlighted item. This is used by the NSMenu class to restore the selected item when it is temporary set to another item. This happens when both the regular version and the transient version are on the screen. A value of -1 means that no item will be highlighted.
setMenu:
menu
Set the menu that this view object will be drawing. This method will NOT retain the menu. In normal usage an instance of NSMenu will use this method to supply the NSMenuView with reference to itself. The NSMenu will retain the NSMenuView.
sizeToFit
Hm, why is this method needed? Shouldn't this be done by the update method?
stateImageWidth
Method used by NSMenuItemCell to draw itself correctly and nicely lined up with the other menu items.
trackWithEvent:
event

This is method is responsible for handling all events while the user is interacting with this menu. It should pass on this call to another menurepresentation when the user moves the mouse cursor over either a submenu or over the supermenu.

The method returns when the interaction from the user with the menu system is over.

The method returns `NO` when the user releases the mouse button above a submenu item and `YES` in all other cases.

This return value can be used to determine if submenus should be removed from the screen or that they are supposed to stay.

The implementation should roughly follow the following logic:

{ while (have not released mouse button) { if (mouse hovers over submenu, or supermenu) { if ([(menurepresentation under mouse) trackWithEvent: the event]) { [self detachSubmenu]; return YES; } return NO; } //highlight item under mouse

if (highlighting submenu item) { [self attachSubmenuAtIndex:..]; } else { [self detachSubmenu]; } get next event. }

execute the menu action if applicable;

return YES | NO depending on the situation; }
Note that actual implementations tend to be more complicated because because of all kind of useability issues. Useabilities issues to look out for are: Menus that are only partly on the screen. Those need to be moved while navigation the menu. Submenus that are hard to reach. If the natural route to the content of a submenu travels through other menu items you do not want to remove the submenu immediately. Transient menus require slightly different behaviour from the normal menus. For example, when selecting a action from a transient menu that brings up a modal panel you would expect the transient menu to dissappear. However in the normal menu system you want it to stay, so you still have feedback on which menu action triggered the modal panel.
update
This will relayout the NSMenuView. It should be called when the menu changes. Changes include becoming detached, adding or removing submenu items etcetera. However, normally it does not need to be called directly because Because the NSMenuView is supposed to listen to the NSMenu notifications for the item added, removed and change notifications. It should be called explicitly when other changes occur, such as becoming detached or changing the title.