The Menu method creates a new top-level window (given by
the $widget argument) and makes it into a menu
widget. Additional options, described above, may be specified on the command
line or in the option database to configure aspects of the menu such as its
colors and font. The menu command returns its
$widget argument. At the time this command is
invoked, there must not exist a window named
$widget, but $widget's
parent must exist.
A menu is a widget that displays a collection of one-line entries
arranged in one or more columns. There exist several different types of
entries, each with different properties. Entries of different types may be
combined in a single menu. Menu entries are not the same as entry widgets.
In fact, menu entries are not even distinct widgets; the entire menu is one
widget.
Menu entries are displayed with up to three separate fields. The
main field is a label in the form of a text string, a bitmap, or an image,
controlled by the -label, -bitmap, and -image options
for the entry. If the -accelerator option is specified for an entry
then a second textual field is displayed to the right of the label. The
accelerator typically describes a keystroke sequence that may be typed in
the application to cause the same result as invoking the menu entry. The
third field is an indicator. The indicator is present only for
checkbutton or radiobutton entries. It indicates whether the entry is
selected or not, and is displayed to the left of the entry's string.
In normal use, an entry becomes active (displays itself
differently) whenever the mouse pointer is over the entry. If a mouse button
is released over the entry then the entry is invoked. The effect of
invocation is different for each type of entry; these effects are described
below in the sections on individual entries.
Entries may be disabled, which causes their labels and
accelerators to be displayed with dimmer colors. The default menu bindings
will not allow a disabled entry to be activated or invoked. Disabled entries
may be re-enabled, at which point it becomes possible to activate and invoke
them again.
Whenever a menu's active entry is changed, a
<<MenuSelect>> virtual event is sent to the menu. The active
item can then be queried from the menu, and an action can be taken, such as
setting context-sensitive help text for the entry.
COMMAND ENTRIES
The most common kind of menu entry is a command entry, which
behaves much like a button widget. When a command entry is invoked, a
callback is executed. The callback is specified with the -command
option.
SEPARATOR ENTRIES
A separator is an entry that is displayed as a horizontal dividing
line. A separator may not be activated or invoked, and it has no behavior
other than its display appearance.
CHECKBUTTON ENTRIES
A checkbutton menu entry behaves much like a checkbutton widget.
When it is invoked it toggles back and forth between the selected and
deselected states. When the entry is selected, a particular value is stored
in a particular global variable (as determined by the -onvalue and
-variable options for the entry); when the entry is deselected
another value (determined by the -offvalue option) is stored in the
global variable. An indicator box is displayed to the left of the label in a
checkbutton entry. If the entry is selected then the indicator's center is
displayed in the color given by the -selectcolor option for the
entry; otherwise the indicator's center is displayed in the background color
for the menu. If a -command option is specified for a checkbutton
entry, then its value is evaluated each time the entry is invoked; this
happens after toggling the entry's selected state.
RADIOBUTTON ENTRIES
A radiobutton menu entry behaves much like a radiobutton widget.
Radiobutton entries are organized in groups of which only one entry may be
selected at a time. Whenever a particular entry becomes selected it stores a
particular value into a particular global variable (as determined by the
-value and -variable options for the entry). This action
causes any previously-selected entry in the same group to deselect itself.
Once an entry has become selected, any change to the entry's associated
variable will cause the entry to deselect itself. Grouping of radiobutton
entries is determined by their associated variables: if two entries have the
same associated variable then they are in the same group. An indicator
diamond is displayed to the left of the label in each radiobutton entry. If
the entry is selected then the indicator's center is displayed in the color
given by the -selectcolor option for the entry; otherwise the
indicator's center is displayed in the background color for the menu. If a
-command option is specified for a radiobutton entry, then its value
is evaluated each time the entry is invoked; this happens after selecting
the entry.
CASCADE ENTRIES
A cascade entry is one with an associated menu (determined by the
-menu option). Cascade entries allow the construction of cascading
menus. The postcascade method can be used to post and unpost the
associated menu just next to of the cascade entry. The associated menu must
be a child of the menu containing the cascade entry (this is needed in order
for menu traversal to work correctly).
A cascade entry posts its associated menu by invoking
$menu->post(x,y)
where menu is the path name of the associated menu, and
x and y are the root-window coordinates of the upper-right
corner of the cascade entry. On Unix, the lower-level menu is unposted by
executing
$menu->unpost
where menu is the name of the associated menu. On other
platforms, the platform's native code takes care of unposting the menu.
If a -command option is specified for a cascade entry then
it is evaluated whenever the entry is invoked. This is not supported on
Windows.
A tear-off entry appears at the top of the menu if enabled with
the tearOff option. It is not like other menu entries in that it
cannot be created with the add method and cannot be deleted with the
delete method. When a tear-off entry is created it appears as a
dashed line at the top of the menu. Under the default bindings, invoking the
tear-off entry causes a torn-off copy to be made of the menu and all of its
submenus.
MENUBARS
Any menu can be set as a menubar for a toplevel window (see the
Toplevel constructor for syntax). On the Macintosh, whenever the toplevel is
in front, this menu's cascade items will appear in the menubar across the
top of the main monitor. On Windows and Unix, this menu's items will be
displayed in a menubar accross the top of the window. These menus will
behave according to the interface guidelines of their platforms. For every
menu set as a menubar, a clone menu is made. See "CLONES" for more
information.
As noted, menubars may behave differently on different platforms.
One example of this concerns the handling of checkbuttons and radiobuttons
within the menu. While it is permitted to put these menu elements on
menubars, they may not be drawn with indicators on some platforms, due to
system restrictions.
SPECIAL MENUS IN MENUBARS
Certain menus in a menubar will be treated specially. On the
Macintosh, access to the special Apple and Help menus is provided. On
Windows, access to the Windows System menu in each window is provided. On X
Windows, a special right-justified help menu is provided. In all cases,
these menus must be created with the command name of the menubar menu
concatenated with the special name. So for a menubar named .menubar, on the
Macintosh, the special menus would be .menubar.apple and .menubar.help; on
Windows, the special menu would be .menubar.system; on X Windows, the help
menu would be .menubar.help.
When Tk sees an Apple menu on the Macintosh, that menu's contents
make up the first items of the Apple menu on the screen whenever the window
containing the menubar is in front. The menu is the first one that the user
sees and has a title which is an Apple logo. After all of the Tk-defined
items, the menu will have a separator, followed by all of the items in the
user's Apple Menu Items folder. Since the System uses a different menu
definition procedure for the Apple menu than Tk uses for its menus, and the
system APIs do not fully support everything Tk tries to do, the menu item
will only have its text displayed. No font attributes, images, bitmaps, or
colors will be displayed. In addition, a menu with a tearoff item will have
the tearoff item displayed as "(TearOff)".
When Tk see a Help menu on the Macintosh, the menu's contents are
appended to the standard help menu on the right of the user's menubar
whenever the user's menubar is in front. The first items in the menu are
provided by Apple. Similar to the Apple Menu, cusomization in this menu is
limited to what the system provides.
When Tk sees a System menu on Windows, its items are appended to
the system menu that the menubar is attached to. This menu has an icon
representing a spacebar, and can be invoked with the mouse or by typing
Alt+Spacebar. Due to limitations in the Windows API, any font changes,
colors, images, bitmaps, or tearoff images will not appear in the system
menu.
When Tk see a Help menu on X Windows, the menu is moved to be last
in the menubar and is right justified.
CLONES
When a menu is set as a menubar for a toplevel window, or when a
menu is torn off, a clone of the menu is made. This clone is a menu widget
in its own right, but it is a child of the original. Changes in the
configuration of the original are reflected in the clone. Additionally, any
cascades that are pointed to are also cloned so that menu traversal will
work right. Clones are destroyed when either the tearoff or menubar goes
away, or when the original menu is destroyed.
WIDGET METHODS
The Menu method creates a widget object. This object
supports the configure and cget methods described in
Tk::options which can be used to enquire and modify the options described
above. The widget also inherits all the methods provided by the generic
Tk::Widget class, and the Tk::Wm class.
Many of the methods for a menu take as one argument an indicator
of which entry of the menu to operate on. These indicators are called
indexes and may be specified in any of the following forms:
- number
- Specifies the entry numerically, where 0 corresponds to the top-most entry
of the menu, 1 to the entry below it, and so on.
- active
- Indicates the entry that is currently active. If no entry is active then
this form is equivalent to none. This form may not be
abbreviated.
- end
- Indicates the bottommost entry in the menu. If there are no entries in the
menu then this form is equivalent to none. This form may not be
abbreviated.
- last
- Same as end.
- none
- Indicates ``no entry at all''; this is used most commonly with the
activate option to deactivate all the entries in the menu. In most
cases the specification of none causes nothing to happen in the
method. This form may not be abbreviated.
- @number
- In this form, number is treated as a y-coordinate in the menu's
window; the entry closest to that y-coordinate is used. For example,
``@0'' indicates the top-most
entry in the window.
- pattern
- If the index doesn't satisfy one of the above forms then this form is
used. Pattern is pattern-matched against the label of each entry in
the menu, in order from the top down, until a matching entry is found. (In
perl/Tk the matching is under review, but exact match should work.)
The following methods are possible for menu widgets:
- $menu->activate(index)
- Change the state of the entry indicated by index to active
and redisplay it using its active colors. Any previously-active entry is
deactivated. If index is specified as none, or if the
specified entry is disabled, then the menu ends up with no active entry.
Returns an empty string.
- $menu->add(type,
?option, value, option, value, ...?)
- Add a new entry to the bottom of the menu. The new entry's type is given
by type and must be one of cascade, checkbutton,
command, radiobutton, or separator, or a unique
abbreviation of one of the above. If additional arguments are present,
they specify any of the following options:
- -activebackground
=> value
- Specifies a background color to use for displaying this entry when it is
active. If this option is specified as an empty string (the default), then
the activeBackground option for the overall menu is used. If the
$Tk::strictMotif variable has
been set to request strict Motif compliance, then this option is ignored
and the -background option is used in its place. This option is not
available for separator or tear-off entries.
- -activeforeground
=> value
- Specifies a foreground color to use for displaying this entry when it is
active. If this option is specified as an empty string (the default), then
the activeForeground option for the overall menu is used. This
option is not available for separator or tear-off entries.
- -accelerator
=> value
- Specifies a string to display at the right side of the menu entry.
Normally describes an accelerator keystroke sequence that may be typed to
invoke the same function as the menu entry. This option is not available
for separator or tear-off entries.
- -background
=> value
- Specifies a background color to use for displaying this entry when it is
in the normal state (neither active nor disabled). If this option is
specified as an empty string (the default), then the background
option for the overall menu is used. This option is not available for
separator or tear-off entries.
- -bitmap =>
value
- Specifies a bitmap to display in the menu instead of a textual label, in
any of the forms accepted by Tk_GetBitmap. This option overrides
the -label option but may be reset to an empty string to enable a
textual label to be displayed. If a -image option has been
specified, it overrides -bitmap. This option is not available for
separator or tear-off entries.
- -columnbreak
=> value
- When this option is zero, the appears below the previous entry. When this
option is one, the menu appears at the top of a new column in the
menu.
- -compound =>
value
- Specifies whether the button should display both an image and text, and if
so, where the image should be placed relative to the text. Valid values
for this option are bottom, center, left,
none, right and top. The default value is
none, meaning that the button will display either an image or text,
depending on the values of the -image and -bitmap options.
- -command =>
value
- For command, checkbutton, and radiobutton entries, specifies a callback to
execute when the menu entry is invoked. For cascade entries, specifies a
callback to execute when the entry is activated (i.e. just before its
submenu is posted). Not available for separator or tear-off entries.
- -font =>
value
- Specifies the font to use when drawing the label or accelerator string in
this entry. If this option is specified as an empty string (the default)
then the font option for the overall menu is used. This option is
not available for separator or tear-off entries.
- -foreground
=> value
- Specifies a foreground color to use for displaying this entry when it is
in the normal state (neither active nor disabled). If this option is
specified as an empty string (the default), then the foreground
option for the overall menu is used. This option is not available for
separator or tear-off entries.
- -hidemargin
=> value
- Specifies whether the standard margins should be drawn for this menu
entry. This is useful when creating palette with images in them, i.e.,
color palettes, pattern palettes, etc. 1 indicates that the margin for the
entry is hidden; 0 means that the margin is used.
- -image =>
value
- Specifies an image to display in the menu instead of a text string or
bitmap The image must have been created by some previous invocation of
image create. This option overrides the -label and
-bitmap options but may be reset to an empty string to enable a
textual or bitmap label to be displayed. This option is not available for
separator or tear-off entries.
- -indicatoron
=> value
- Available only for checkbutton and radiobutton entries. Value is a
boolean that determines whether or not the indicator should be
displayed.
- -label =>
value
- Specifies a string to display as an identifying label in the menu entry.
Not available for separator or tear-off entries.
- Available only for cascade entries. Specifies the path name of the submenu
associated with this entry. The submenu must be a child of the menu.
- -offvalue =>
value
- Available only for checkbutton entries. Specifies the value to store in
the entry's associated variable when the entry is deselected.
- -onvalue =>
value
- Available only for checkbutton entries. Specifies the value to store in
the entry's associated variable when the entry is selected.
- -selectcolor
=> value
- Available only for checkbutton and radiobutton entries. Specifies the
color to display in the indicator when the entry is selected. If the value
is an empty string (the default) then the selectColor option for
the menu determines the indicator color.
- -selectimage
=> value
- Available only for checkbutton and radiobutton entries. Specifies an image
to display in the entry (in place of the -image option) when it is
selected. Value is the name of an image, which must have been
created by some previous invocation of image create. This option is
ignored unless the -image option has been specified.
- -state =>
value
- Specifies one of three states for the entry: normal, active,
or disabled. In normal state the entry is displayed using the
foreground option for the menu and the background option
from the entry or the menu. The active state is typically used when the
pointer is over the entry. In active state the entry is displayed using
the activeForeground option for the menu along with the
activebackground option from the entry. Disabled state means that
the entry should be insensitive: the default bindings will refuse to
activate or invoke the entry. In this state the entry is displayed
according to the disabledForeground option for the menu and the
background option from the entry. This option is not available for
separator entries.
- -underline
=> value
- Specifies the integer index of a character to underline in the entry. This
option is also queried by the default bindings and used to implement
keyboard traversal. 0 corresponds to the first character of the text
displayed in the entry, 1 to the next character, and so on. If a bitmap or
image is displayed in the entry then this option is ignored. This option
is not available for separator or tear-off entries.
- -value =>
value
- Available only for radiobutton entries. Specifies the value to store in
the entry's associated variable when the entry is selected. If an empty
string is specified, then the -label option for the entry as the
value to store in the variable.
- -variable =>
value
- Available only for checkbutton and radiobutton entries. Specifies the name
of a global value to set when the entry is selected. For checkbutton
entries the variable is also set when the entry is deselected. For
radiobutton entries, changing the variable causes the currently-selected
entry to deselect itself.
The add method returns an empty string.
- $menu->clone($parent
?, cloneType?)
- Makes a clone of the current menu as a child of
$parent. This clone is a menu
in its own right, but any changes to the clone are propogated to the
original menu and vice versa. cloneType can be normal,
menubar, or tearoff. Should not normally be called outside
of the Tk library. See "CLONES" for more information.
- $menu->delete(index1?,
index2?)
- Delete all of the menu entries between index1 and index2
inclusive. If index2 is omitted then it defaults to index1.
Attempts to delete a tear-off menu entry are ignored (instead, you should
change the tearOff option to remove the tear-off entry).
- $menu->entrycget(index,
option)
- Returns the current value of a configuration option for the entry given by
index. Option may have any of the values accepted by the
add method.
- $menu->entryconfigure(index
?,options?)
- This method is similar to the configure method, except that it
applies to the options for an individual entry, whereas configure
applies to the options for the menu as a whole. Options may have
any of the values accepted by the add method. If options are
specified, options are modified as indicated in the method call and the
method returns an empty string. If no options are specified,
returns a list describing the current options for entry index (see
Tk::options for information on the format of this list).
- $menu->index(index)
- Returns the numerical index corresponding to index, or none
if index was specified as none.
- $menu->insert(index,
type?, -option=>value, ...?)
- Same as the add method except that it inserts the new entry just
before the entry given by index, instead of appending to the end of
the menu. The type, -option, and value arguments have
the same interpretation as for the add widget method. It is not
possible to insert new menu entries before the tear-off entry, if the menu
has one.
- $menu->invoke(index)
- Invoke the action of the menu entry. See the sections on the individual
entries above for details on what happens. If the menu entry is disabled
then nothing happens. If the entry has a callback associated with it then
the result of that callback is returned as the result of the invoke
widget method. Otherwise the result is an empty string. Note: invoking a
menu entry does not automatically unpost the menu; the default bindings
normally take care of this before invoking the invoke method.
- $menu->post(x,
y)
- Arrange for the menu to be displayed on the screen at the root-window
coordinates given by x and y. These coordinates are adjusted
if necessary to guarantee that the entire menu is visible on the screen.
This method normally returns an empty string. If the postCommand
option has been specified, then its value is executed before posting the
menu and the result of that callback is returned as the result of the
post widget method. If an error returns while executing the method,
then the error is returned without posting the menu.
- $menu->postcascade(index)
- Posts the submenu associated with the cascade entry given by index,
and unposts any previously posted submenu. If index doesn't
correspond to a cascade entry, or if
$menu isn't posted, the
method has no effect except to unpost any currently posted submenu.
- $menu->type(index)
- Returns the type of the menu entry given by index. This is the
type argument passed to the add widget method when the entry
was created, such as command or separator, or tearoff
for a tear-off entry.
- $menu->unpost
- Unmap the window so that it is no longer displayed. If a lower-level
cascaded menu is posted, unpost that menu. Returns an empty string. This
method does not work on Windows and the Macintosh, as those platforms have
their own way of unposting menus.
- $menu->yposition(index)
- Returns a decimal string giving the y-coordinate within the menu window of
the topmost pixel in the entry specified by index.