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1 Menus


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1.1 Format of Menus

A menu is described using a menu description, which is a list of menu items, keyword-value pairs, strings, and submenus. The menu description specifies which items are present in the menu, what function each item invokes, and whether the item is selectable or not. Pop-up menus are directly described with a menu description, while menubars are described slightly differently (see below).

The first element of a menu must be a string, which is the name of the menu. This is the string that will be displayed in the parent menu or menubar, if any. This string is not displayed in the menu itself, except in the case of the top level pop-up menu, where there is no parent. In this case, the string will be displayed at the top of the menu if popup-menu-titles is non-nil.

Immediately following the first element there may optionally be up to three keyword-value pairs, as follows:

:included form

This can be used to control the visibility of a menu. The form is evaluated and the menu will be omitted if the result is nil.

:config symbol

This is an efficient shorthand for :included (memq symbol menubar-configuration). See the variable menubar-configuration.

:filter function

A menu filter is used to sensitize or incrementally create a submenu only when it is selected by the user and not every time the menubar is activated. The filter function is passed the list of menu items in the submenu and must return a list of menu items to be used for the menu. It is called only when the menu is about to be displayed, so other menus may already be displayed. Vile and terrible things will happen if a menu filter function changes the current buffer, window, or frame. It also should not raise, lower, or iconify any frames. Basically, the filter function should have no side-effects.

The rest of the menu consists of elements as follows:

The possible keywords are as follows:

:active form

form will be evaluated when the menu that this item is a part of is about to be displayed, and the item will be selectable only if the result is non-nil. If the item is unselectable, it will usually be displayed grayed-out to indicate this.

:suffix string

The string is appended to the displayed name. This provides a convenient way of adding the name of a command’s “argument” to the menu, like like ‘Kill Buffer NAME’.

:keys string

Normally, the keyboard equivalents of commands in menus are displayed when the “callback” is a symbol. This can be used to specify keys for more complex menu items. It is passed through substitute-command-keys first.

:style style

Specifies what kind of object this menu item is. style be one of the symbols

nil

A normal menu item.

toggle

A toggle button.

radio

A radio button.

button

A menubar button.

The only difference between toggle and radio buttons is how they are displayed. But for consistency, a toggle button should be used when there is one option whose value can be turned on or off, and radio buttons should be used when there is a set of mutally exclusive options. When using a group of radio buttons, you should arrange for no more than one to be marked as selected at a time.

:selected form

Meaningful only when style is toggle, radio or button. This specifies whether the button will be in the selected or unselected state. form is evaluated, as for :active.

:included form

This can be used to control the visibility of a menu item. The form is evaluated and the menu item is only displayed if the result is non-nil. Note that this is different from :active: If :active evaluates to nil, the item will be displayed grayed out, while if :included evaluates to nil, the item will be omitted entirely.

:config symbol

This is an efficient shorthand for :included (memq symbol menubar-configuration). See the variable menubar-configuration.

Variable: menubar-configuration

This variable holds a list of symbols, against which the value of the :config tag for each menubar item will be compared. If a menubar item has a :config tag, then it is omitted from the menubar if that tag is not a member of the menubar-configuration list.

For example:

 ("File"
  :filter file-menu-filter	; file-menu-filter is a function that takes
				; one argument (a list of menu items) and
				; returns a list of menu items
  [ "Save As..."    write-file  t ]
  [ "Revert Buffer" revert-buffer (buffer-modified-p) ]
  [ "Read Only"     toggle-read-only :style toggle :selected buffer-read-only ]
  )

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1.2 Format of the Menubar

A menubar is a list of menus, menu items, and strings. The format is similar to that of a menu, except:


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1.3 Menubar

Variable: current-menubar

This variable holds the description of the current menubar. This may be buffer-local. When the menubar is changed, the function set-menubar-dirty-flag has to be called in order for the menubar to be updated on the screen.

Constant: default-menubar

This variable holds the menubar description of the menubar that is visible at startup. This is the value that current-menubar has at startup.

Function: set-menubar-dirty-flag

This function tells XEmacs that the menubar widget has to be updated. Changes to the menubar will generally not be visible until this function is called.

The following convenience functions are provided for setting the menubar. They are equivalent to doing the appropriate action to change current-menubar, and then calling set-menubar-dirty-flag. Note that these functions copy their argument using copy-sequence.

Function: set-menubar menubar

This function sets the default menubar to be menubar (see section Format of Menus). This is the menubar that will be visible in buffers that have not defined their own, buffer-local menubar.

Function: set-buffer-menubar menubar

This function sets the buffer-local menubar to be menubar. This does not change the menubar in any buffers other than the current one.

Miscellaneous:

Variable: menubar-show-keybindings

If true, the menubar will display keyboard equivalents. If false, only the command names will be displayed.

Variable: activate-menubar-hook

Function or functions called before a menubar menu is pulled down. These functions are called with no arguments, and should interrogate and modify the value of current-menubar as desired.

The functions on this hook are invoked after the mouse goes down, but before the menu is mapped, and may be used to activate, deactivate, add, or delete items from the menus. However, using a filter (with the :filter keyword in a menu description) is generally a more efficient way of accomplishing the same thing, because the filter is invoked only when the actual menu goes down. With a complex menu, there can be a quite noticeable and sometimes aggravating delay if all menu modification is implemented using the activate-menubar-hook. See above.

These functions may return the symbol t to assert that they have made no changes to the menubar. If any other value is returned, the menubar is recomputed. If t is returned but the menubar has been changed, then the changes may not show up right away. Returning nil when the menubar has not changed is not so bad; more computation will be done, but redisplay of the menubar will still be performed optimally.

Variable: menu-no-selection-hook

Function or functions to call when a menu or dialog box is dismissed without a selection having been made.


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1.4 Modifying Menus

The following functions are provided to modify the menubar of one of its submenus. Note that these functions modify the menu in-place, rather than copying it and making a new menu.

Some of these functions take a menu path, which is a list of strings identifying the menu to be modified. For example, ("File") names the top-level “File” menu. ("File" "Foo") names a hypothetical submenu of “File”.

Others take a menu item path, which is similar to a menu path but also specifies a particular item to be modified. For example, ("File" "Save") means the menu item called “Save” under the top-level “File” menu. ("Menu" "Foo" "Item") means the menu item called “Item” under the “Foo” submenu of “Menu”.

Function: add-submenu menu-path submenu &optional before

This function adds a menu to the menubar or one of its submenus. If the named menu exists already, it is changed.

menu-path identifies the menu under which the new menu should be inserted. If menu-path is nil, then the menu will be added to the menubar itself.

submenu is the new menu to add (see section Format of Menus).

before, if provided, is the name of a menu before which this menu should be added, if this menu is not on its parent already. If the menu is already present, it will not be moved.

Function: add-menu-button menu-path menu-leaf &optional before

This function adds a menu item to some menu, creating the menu first if necessary. If the named item exists already, it is changed.

menu-path identifies the menu under which the new menu item should be inserted.

menu-leaf is a menubar leaf node (see section Format of Menus).

before, if provided, is the name of a menu before which this item should be added, if this item is not on the menu already. If the item is already present, it will not be moved.

Function: delete-menu-item menu-item-path

This function removes the menu item specified by menu-item-path from the menu hierarchy.

Function: enable-menu-item menu-item-path

This function makes the menu item specified by menu-item-path be selectable.

Function: disable-menu-item menu-item-path

This function makes the menu item specified by menu-item-path be unselectable.

Function: relabel-menu-item menu-item-path new-name

This function changes the string of the menu item specified by menu-item-path. new-name is the string that the menu item will be printed as from now on.

The following function can be used to search for a particular item in a menubar specification, given a path to the item.

Function: find-menu-item menubar menu-item-path &optional parent

This function searches menubar for the item given by menu-item-path starting from parent (nil means start at the top of menubar). This function returns (item . parent), where parent is the immediate parent of the item found (a menu description), and item is either a vector, list, or string, depending on the nature of the menu item.

This function signals an error if the item is not found.

The following deprecated functions are also documented, so that existing code can be understood. You should not use these functions in new code.

Function: add-menu menu-path menu-name menu-items &optional before

This function adds a menu to the menubar or one of its submenus. If the named menu exists already, it is changed. This is obsolete; use add-submenu instead.

menu-path identifies the menu under which the new menu should be inserted. If menu-path is nil, then the menu will be added to the menubar itself.

menu-name is the string naming the menu to be added; menu-items is a list of menu items, strings, and submenus. These two arguments are the same as the first and following elements of a menu description (see section Format of Menus).

before, if provided, is the name of a menu before which this menu should be added, if this menu is not on its parent already. If the menu is already present, it will not be moved.

Function: add-menu-item menu-path item-name function enabled-p &optional before

This function adds a menu item to some menu, creating the menu first if necessary. If the named item exists already, it is changed. This is obsolete; use add-menu-button instead.

menu-path identifies the menu under which the new menu item should be inserted. item-name, function, and enabled-p are the first, second, and third elements of a menu item vector (see section Format of Menus).

before, if provided, is the name of a menu item before which this item should be added, if this item is not on the menu already. If the item is already present, it will not be moved.


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1.5 Menu Filters

The following filter functions are provided for use in default-menubar. You may want to use them in your own menubar description.

Function: file-menu-filter menu-items

This function changes the arguments and sensitivity of these File menu items:

Delete Buffer

Has the name of the current buffer appended to it.

Print Buffer

Has the name of the current buffer appended to it.

Pretty-Print Buffer

Has the name of the current buffer appended to it.

Save Buffer

Has the name of the current buffer appended to it, and is sensitive only when the current buffer is modified.

Revert Buffer

Has the name of the current buffer appended to it, and is sensitive only when the current buffer has a file.

Delete Frame

Sensitive only when there is more than one visible frame.

Function: edit-menu-filter menu-items

This function changes the arguments and sensitivity of these Edit menu items:

Cut

Sensitive only when XEmacs owns the primary X Selection (if zmacs-regions is t, this is equivalent to saying that there is a region selected).

Copy

Sensitive only when XEmacs owns the primary X Selection.

Clear

Sensitive only when XEmacs owns the primary X Selection.

Paste

Sensitive only when there is an owner for the X Clipboard Selection.

Undo

Sensitive only when there is undo information. While in the midst of an undo, this is changed to ‘Undo More’.

Function: buffers-menu-filter menu-items

This function sets up the Buffers menu. See section Buffers Menu for more information.


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1.6 Pop-Up Menus

Function: popup-menu menu-desc

This function pops up a menu specified by menu-desc, which is a menu description (see section Format of Menus). The menu is displayed at the current mouse position.

Function: popup-menu-up-p

This function returns t if a pop-up menu is up, nil otherwise.

Variable: popup-menu-titles

If true (the default), pop-up menus will have title bars at the top.

Some machinery is provided that attempts to provide a higher-level mechanism onto pop-up menus. This only works if you do not redefine the binding for button3.

Command: popup-mode-menu

This function pops up a menu of global and mode-specific commands. The menu is computed by combining global-popup-menu and mode-popup-menu. This is the default binding for button3. You should generally not change this binding.

Variable: global-popup-menu

This holds the global popup menu. This is present in all modes. (This is nil by default.)

Variable: mode-popup-menu

The mode-specific popup menu. Automatically buffer local. This is appended to the default items in global-popup-menu.

Constant: default-popup-menu

This holds the default value of mode-popup-menu.

Variable: activate-popup-menu-hook

Function or functions run before a mode-specific popup menu is made visible. These functions are called with no arguments, and should interrogate and modify the value of global-popup-menu or mode-popup-menu as desired. Note: this hook is only run if you use popup-mode-menu for activating the global and mode-specific commands; if you have your own binding for button3, this hook won’t be run.

The following convenience functions are provided for displaying pop-up menus.

Function: popup-buffer-menu event

This function pops up a copy of the ‘Buffers’ menu (from the menubar) where the mouse is clicked.

Function: popup-menubar-menu event

This function pops up a copy of menu that also appears in the menubar.


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1.7 Buffers Menu

The following options control how the ‘Buffers’ menu is displayed. This is a list of all (or a subset of) the buffers currently in existence, and is updated dynamically.

User Option: buffers-menu-max-size

This user option holds the maximum number of entries which may appear on the ‘Buffers’ menu. If this is 10, then only the ten most-recently-selected buffers will be shown. If this is nil, then all buffers will be shown. Setting this to a large number or nil will slow down menu responsiveness.

Function: format-buffers-menu-line buffer

This function returns a string to represent buffer in the ‘Buffers’ menu. nil means the buffer shouldn’t be listed. You can redefine this.

User Option: complex-buffers-menu-p

If true, the ‘Buffers’ menu will contain several commands, as submenus of each buffer line. If this is false, then there will be only one command: select that buffer.

User Option: buffers-menu-switch-to-buffer-function

This user option holds the function to call to select a buffer from the ‘Buffers’ menu. switch-to-buffer is a good choice, as is pop-to-buffer.


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