XtInstallAccelerators() XtInstallAccelerators()
Name
XtInstallAccelerators - install a widget's accelerators on another widget.
Synopsis
void XtInstallAccelerators(destination, source)
Widget destination;
Widget source;
Inputs
destination
Specifies the widget in which events specified in the accelerator table will be detected. Must be of class Core or any subclass
thereof.
source Specifies the widget whose actions will be invoked when events occur in destination. Must be of class Core or any subclass
thereof.
Description
XtInstallAccelerators() merges the accelerator table of source into the translation table of destination. After this call, events in the
destination widget will trigger actions in the source widget.
If the display_accelerator() method of source is non-NULL, XtInstallAccelerators() calls it with source and a canonical representation of
the accelerator table that was installed. This method is a hook that is intended to allow a widget to dynamically modify its appearance (a
menu button might display the key sequence that will invoke it, for example) when an accelerator is installed.
Usage
It is often convenient to be able to bind events in one widget to actions in another. In particular, it is often useful to be able to
invoke menu actions from the keyboard. The Intrinsics provide a facility, called accelerators, that let you accomplish this. An accelera-
tor table is a translation table that binds events in the destination widget to actions in the source widget. The accelerator table can be
installed on one or more destination widgets. When an event sequence in destination would cause an accelerator action to be invoked, and
if the source widget is sensitive, the actions are executed as though triggered by the same event sequence in source. The event is passed
to the action procedure without modification. The action procedures used within accelerators must assume neither that the source widget is
realized, nor that any fields of the event are in reference to the source widget's window if the widget is realized.
Every widget includes an XtNaccelerators resource, which is defined by the Core widget class. The actual value of this resource can be
hardcoded by the application or set in a resource file, just like any other resource.
In order for the XtNaccelerators resource to actually be used, however, the application must call XtInstallAccelerators() (or XtInstallAl-
lAccelerators()). This call takes two arguments. The destination widget is the widget whose translation table will be augmented with the
accelerator table from the source widget.
It is difficult to remember which of the two widgets in this call is which. If you want to install a keyboard accelerator so that a key-
stroke in a text widget invokes an action in a menu button, then the menu button is the source, and the text widget is the destination.
You must set the accelerator table in the XtNaccelerators resource of the menu button, and then install those accelerators on the text wid-
get.
If you are programming with the Motif widget set, you will generally not be able to use accelerators as described here. Motif provides a
different (and incompatible) style of accelerators for use with menus; see Volume 6, Motif Programming Manual for more information.
Example
Assume an application whose top-level shell widget is named topLevel, and which contains a Command widget instance named quit. Further
assume that the quit widget has the following XtNaccelerators resource defined for it:
*quit.accelerators: <KeyPress>q: notify()
The call:
XtInstallAccelerators (topLevel, quit);
would allow a "q" typed in the application's top-level window to invoke the quit widget's notify action. The notify action invokes the
callback list of the button, and assuming that a quit callback was registered, causes the application to terminate.
See Also
XtInstallAllAccelerators(1),
display_accelerator(4).
Xt - Translations and Actions XtInstallAccelerators()