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22.17.6 Tool bars

A tool bar is a row of clickable icons at the top of a frame, just below the menu bar. See 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 (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 image
image 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:
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 (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.

— 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)

See Function Keys, for more information about how to add modifiers to function keys.