Xlib and the Intrinsics provide a level of mapping between
physical keys and keysyms. Motif adds one more level of mapping on top of
keysyms; Motif can map keysyms to virtual keysyms. Table 7-1 describes the
purpose of some common Motif virtual keysyms.
Table 9. Purpose of Common Motif Virtual Keysyms
|osfActivate||Activates a default action|
|osfAddMode||Toggles the selection mode between Normal and Add mode|
|osfBackSpace||Deletes the previous character|
|osfBeginLine||Moves the cursor to the beginning of the line|
|osfCancel||Cancels the current operation|
|osfClear||Clears the current selection|
|osfCopy||Copies to the clipboard|
|osfCut||Cuts to the clipboard|
|osfDeselectAll||Deselects the current selection|
|osfDown||Moves the cursor down|
|osfEndLine||Moves the cursor to the end of the line|
|osfHelp||Calls the function specified by the XmNhelpCallback resource|
|osfInsert||Toggles between Replace and Insert mode (if specified without modifiers)|
|osfLeft||Moves the cursor left|
|osfMenu||Activates the Popup Menu|
|osfMenuBar||Traverses to the MenuBar|
|osfPageDown||Moves down one page|
|osfPageLeft||Moves left one page|
|osfPageRight||Moves right one page|
|osfPageUp||Moves up one page|
|osfPaste||Pastes from the clipboard|
|osfPrimaryPaste||Pastes the primary selection|
|osfRestore||Restores a previous setting|
|osfRight||Moves the cursor right|
|osfSelect||Establishes the current selection|
|osfSelectAll||Selects an entire block of data|
|osfSwitchDirection||Toggles the string layout direction|
|osfUndo||Undoes the most recent action|
|osfUp||Moves the cursor up|
We recommend that the translations string of Motif widgets use Motif virtual keysyms instead of traditional keysyms whenever possible. For example, the following well-defined translations string uses five different Motif virtual keysyms:
static char defaultTranslations = "\ :<Key>osfActivate: PrimitiveParentActivate()\n\ :<Key>osfCancel: PrimitiveParentCancel()\n\ :<Key>osfHelp: PrimitiveHelp()\n\ :<Key>osfDelete: MyDeletionMethod()\n\ :<Key>osfInsert: MyInsertionMethod()\n\
Virtual keysyms let your widget provide consistent behavior across a wide variety of keyboards. (For more information on virtual keysyms, refer to the Motif Style Guide and to the VirtualBindings reference page of the Motif Programmer's Reference.)
The following subsections take a closer look at some commonly used bindings for certain virtual keysyms.
The PrimitiveParentActivate action is ordinarily bound to the osfActivate virtual keysym. The PrimitiveParentCancel action is ordinarily bound to the osfCancel virtual keysym.
When activated, the PrimitiveParentActivate action routine typically does the following:
In other words, the ultimate responsibility for handling the PrimitiveParentActivate action belongs to the widget named by XmNdefaultButton.
The PrimitiveParentCancel action routine works like PrimitiveParentActivate. The only difference is that PrimitiveParentCancel depends on the XmNcancelButton resource rather than XmNdefaultButton.
(See Chapter 4 for more details on the parent_process method.)
You may associate any action routine with the osfHelp virtual keysym. One interesting choice of an action routine is PrimitiveHelp.
Specifying PrimitiveHelp causes Motif to invoke the callback associated with the widget's XmNhelpCallback resource. It is quite possible, however, that your widget does not define such a callback. In that case, PrimitiveHelp looks for a help callback inside the widget that is managing your widget.
For example, the ExmString widget binds the PrimitiveHelp action to the osfHelp virtual keysym. Suppose that an XmForm widget is managing several ExmString widgets. Furthermore, suppose that none of the ExmString widgets define a help callback. In this case, PrimitiveHelp automatically tries to find a help callback inside the XmForm widget. Therefore, the help callback of XmForm can serve as the help callback for all the widgets that it manages. If the XmForm widget does not define a help callback, then Motif looks for a help callback in the widget that manages the XmForm widget. Motif keeps going up the parent chain until it finds a help callback.
You may associate any action with the virtual keysyms osfMenuBar and osfMenu; however, there is a good possibility that Motif will never execute the action you specify.
If your application defines a menu bar, the menu bar will grab any osfMenuBar events before your widget can process it. Similarly, if your application defines any popup menus, the popup menu widget will grab any osfMenu events before your widget can process it.
You should be very careful about defining any of the following virtual keysyms inside the tm_table string of the CoreClassPart:
As we mentioned earlier in this chapter, the translations field of the PrimitiveClassPart takes precedence over the tm_table field of the CoreClassPart. The PrimitiveClassPart of XmPrimitive defines actions for all six of the preceding virtual keysyms. Therefore, if your widget inherits these translations (by specifying XtInheritTranslations), then Motif will ignore any translations defined for these virtual keysyms in the tm_table field. Therefore, if you really do want to provide a non-default binding for any of these virtual keysyms, you should set the translations field of the PrimitiveClassPart to either NULL or to the name of a new translations string. Another possibility is to update the translations string as part of your widget's initialize method.