A toolbar is a bar of icons displayed along one edge of a frame. You can view a toolbar as a series of menu shortcuts—the most common menu options can be accessed with a single click rather than a series of clicks and/or drags to select the option from a menu. Consistent with this, a help string (called the help-echo) describing what an icon in the toolbar (called a toolbar button) does, is displayed in the minibuffer when the mouse is over the button.
In SXEmacs, a toolbar can be displayed along any of the four edges of the frame, and two or more different edges can be displaying toolbars simultaneously. The contents, thickness, and visibility of the toolbars can be controlled separately, and the values can be per-buffer, per-frame, etc., using specifiers (see Specifiers).
Normally, there is one toolbar displayed in a frame. Usually, this is
the standard toolbar, but certain modes will override this and
substitute their own toolbar. In some cases (e.g. the VM package), a
package will supply its own toolbar along a different edge from the
standard toolbar, so that both can be visible at once. This standard
toolbar is usually positioned along the top of the frame, but this can
be changed using
Note that, for each of the toolbar properties (contents, thickness,
and visibility), there is a separate specifier for each of the four
toolbar positions (top, bottom, left, and right), and an additional
specifier for the “default” toolbar, i.e. the toolbar whose
position is controlled by
way this works is that
things so that the appropriate position-specific specifiers for the
default position inherit from the corresponding default specifiers.
That way, if the position-specific specifier does not give a value
(which it usually doesn’t), then the value from the default
specifier applies. If you want to control the default toolbar, you
just change the default specifiers, and everything works. A package
such as VM that wants to put its own toolbar in a different location
from the default just sets the position-specific specifiers, and if
the user sets the default toolbar to the same position, it will just
not be visible.