elisp: Tool Bar
21.17.6 Tool bars
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A “tool bar” is a row of clickable icons at the top of a frame, just
below the menu bar. 
(emacs)Tool Bars. Emacs normally shows a
tool bar on graphical displays.
On each frame, the frame parameter ‘tool-bar-lines’ controls how many
lines’ worth of height to reserve for the tool bar. A zero value
suppresses the tool bar. If the value is nonzero, and
‘auto-resize-tool-bars’ is non-‘nil’, the tool bar expands and contracts
automatically as needed to hold the specified contents. If the value is
‘grow-only’, the tool bar expands automatically, but does not contract
automatically.
The tool bar contents are controlled by a menu keymap attached to a
fake function key called ‘tool-bar’ (much like the way the menu bar is
controlled). So you define a tool bar item using ‘define-key’, like
this:
(define-key global-map [tool-bar KEY] ITEM)
where KEY is a fake function key to distinguish this item from other
items, and ITEM is a menu item key binding (Extended Menu
Items), which says how to display this item and how it behaves.
The usual menu keymap item properties, ‘:visible’, ‘:enable’,
‘:button’, and ‘:filter’, are useful in tool bar bindings and have their
normal meanings. The REAL-BINDING in the item must be a command, not a
keymap; in other words, it does not work to define a tool bar icon as a
prefix key.
The ‘:help’ property specifies a help-echo string to display while
the mouse is on that item. This is displayed in the same way as
‘help-echo’ text properties (Help display).
In addition, you should use the ‘:image’ property; this is how you
specify the image to display in the tool bar:
‘:image IMAGE’
IMAGE is either a single image specification (Images) or a
vector of four image specifications. If you use a vector of four,
one of them is used, depending on circumstances:
item 0
Used when the item is enabled and selected.
item 1
Used when the item is enabled and deselected.
item 2
Used when the item is disabled and selected.
item 3
Used when the item is disabled and deselected.
The GTK+ and NS versions of Emacs ignores items 1 to 3, because
disabled and/or deselected images are autocomputed from item 0.
If IMAGE is a single image specification, Emacs draws the tool bar
button in disabled state by applying an edge-detection algorithm to the
image.
The ‘:rtl’ property specifies an alternative image to use for
right-to-left languages. Only the GTK+ version of Emacs supports this
at present.
Like the menu bar, the tool bar can display separators (Menu
Separators). Tool bar separators are vertical rather than horizontal,
though, and only a single style is supported. They are represented in
the tool bar keymap by ‘(menu-item "--")’ entries; properties like
‘:visible’ are not supported for tool bar separators. Separators are
rendered natively in GTK+ and Nextstep tool bars; in the other cases,
they are rendered using an image of a vertical line.
The default tool bar is defined so that items specific to editing do
not appear for major modes whose command symbol has a ‘mode-class’
property of ‘special’ (Major Mode Conventions). Major modes may
add items to the global bar by binding ‘[tool-bar FOO]’ in their local
map. It makes sense for some major modes to replace the default tool
bar items completely, since not many can be accommodated conveniently,
and the default bindings make this easy by using an indirection through
‘tool-bar-map’.
-- Variable: tool-bar-map
By default, the global map binds ‘[tool-bar]’ as follows:
(global-set-key [tool-bar]
`(menu-item ,(purecopy "tool bar") ignore
:filter tool-bar-make-keymap))
The function ‘tool-bar-make-keymap’, in turn, derives the actual
tool bar map dynamically from the value of the variable
‘tool-bar-map’. Hence, you should normally adjust the default
(global) tool bar by changing that map. Some major modes, such as
Info mode, completely replace the global tool bar by making
‘tool-bar-map’ buffer-local and setting it to a different keymap.
There are two convenience functions for defining tool bar items, as
follows.
-- Function: tool-bar-add-item icon def key &rest props
This function adds an item to the tool bar by modifying
‘tool-bar-map’. The image to use is defined by ICON, which is the
base name of an XPM, XBM or PBM image file to be located by
‘find-image’. Given a value ‘"exit"’, say, ‘exit.xpm’, ‘exit.pbm’
and ‘exit.xbm’ would be searched for in that order on a color
display. On a monochrome display, the search order is ‘.pbm’,
‘.xbm’ and ‘.xpm’. The binding to use is the command DEF, and KEY
is the fake function key symbol in the prefix keymap. The
remaining arguments PROPS are additional property list elements to
add to the menu item specification.
To define items in some local map, bind ‘tool-bar-map’ with ‘let’
around calls of this function:
(defvar foo-tool-bar-map
(let ((tool-bar-map (make-sparse-keymap)))
(tool-bar-add-item ...)
...
tool-bar-map))
-- Function: tool-bar-add-item-from-menu command icon &optional map
&rest props
This function is a convenience for defining tool bar items which
are consistent with existing menu bar bindings. The binding of
COMMAND is looked up in the menu bar in MAP (default ‘global-map’)
and modified to add an image specification for ICON, which is found
in the same way as by ‘tool-bar-add-item’. The resulting binding
is then placed in ‘tool-bar-map’, so use this function only for
global tool bar items.
MAP must contain an appropriate keymap bound to ‘[menu-bar]’. The
remaining arguments PROPS are additional property list elements to
add to the menu item specification.
-- Function: tool-bar-local-item-from-menu command icon in-map
&optional from-map &rest props
This function is used for making non-global tool bar items. Use it
like ‘tool-bar-add-item-from-menu’ except that IN-MAP specifies the
local map to make the definition in. The argument FROM-MAP is like
the MAP argument of ‘tool-bar-add-item-from-menu’.
-- Variable: auto-resize-tool-bars
If this variable is non-‘nil’, the tool bar automatically resizes
to show all defined tool bar items—but not larger than a quarter of
the frame’s height.
If the value is ‘grow-only’, the tool bar expands automatically,
but does not contract automatically. To contract the tool bar, the
user has to redraw the frame by entering ‘C-l’.
If Emacs is built with GTK or Nextstep, the tool bar can only show
one line, so this variable has no effect.
-- Variable: auto-raise-tool-bar-buttons
If this variable is non-‘nil’, tool bar items display in raised
form when the mouse moves over them.
-- Variable: tool-bar-button-margin
This variable specifies an extra margin to add around tool bar
items. The value is an integer, a number of pixels. The default
is 4.
-- Variable: tool-bar-button-relief
This variable specifies the shadow width for tool bar items. The
value is an integer, a number of pixels. The default is 1.
-- Variable: tool-bar-border
This variable specifies the height of the border drawn below the
tool bar area. An integer specifies height as a number of pixels.
If the value is one of ‘internal-border-width’ (the default) or
‘border-width’, the tool bar border height corresponds to the
corresponding frame parameter.
You can define a special meaning for clicking on a tool bar item with
the shift, control, meta, etc., modifiers. You do this by setting up
additional items that relate to the original item through the fake
function keys. Specifically, the additional items should use the
modified versions of the same fake function key used to name the
original item.
Thus, if the original item was defined this way,
(define-key global-map [tool-bar shell]
'(menu-item "Shell" shell
:image (image :type xpm :file "shell.xpm")))
then here is how you can define clicking on the same tool bar image with
the shift modifier:
(define-key global-map [tool-bar S-shell] 'some-command)
Function Keys, for more information about how to add
modifiers to function keys.
Info Catalog
elisp: Menu Bar
elisp: Menu Keymaps
elisp: Modifying Menus