A tool bar is a row of clickable icons at the top of a frame, just below the menu bar. See Tool Bars in The GNU Emacs Manual. 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 (see 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 (see Help display).
In addition, you should use the :image property;
this is how you specify the image to display in the tool bar:
:image imageimage is either a single image specification (see Images) or a vector of four image specifications. If you use a vector of four, one of them is used, depending on circumstances:
Used when the item is enabled and selected.
Used when the item is enabled and deselected.
Used when the item is disabled and selected.
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.
Some toolkits display both an image and a text in the toolbar. If you
want to force using only the image, use a :vert-only
non-nil property.
Like the menu bar, the tool bar can display separators (see 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 (see 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.
By default, the global map binds [tool-bar] as follows:
(keymap-global-set "<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.
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))
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.
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.
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.
If this variable is non-nil, tool bar items display
in raised form when the mouse moves over them.
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.
This variable specifies the shadow width for tool bar items. The value is an integer, a number of pixels. The default is 1.
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)
See Function Keys, for more information about how to add modifiers to function keys.
If you have functions that change whether a tool bar item is enabled
or not, this status is not necessarily updated visually immediately.
To force recalculation of the tool bar, call
force-mode-line-update (see Mode Line Format).