$widget->bind
$widget->bind(tag)
$widget->bind(sequence)
$widget->bind(tag,sequence)
Associate and destroy bindings:
$widget->bind(sequence,callback)
$widget->bind(tag,sequence,callback)
If sequence is specified without a callback, then the callback currently bound to sequence is returned, or undef is returned if there is no binding for sequence. If neither sequence nor callback is specified, then the return value is a list whose elements are all the sequences for which there exist bindings for tag.
If no tag is specified then the bind refers to $widget. If tag is specified then it is typically a class name and the bind refers to all instances of the class on the MainWindow associated with $widget. (It is possible for tag to be another ``widget object'' but this practice is deprecated.) Perl's ref($object) can be used to get the class name of any object. Each window has an associated list of tags, and a binding applies to a particular window if its tag is among those specified for the window. Although the bindtags method may be used to assign an arbitrary set of binding tags to a window, the default binding tags provide the following behavior:
If a tag is the name of an internal window the binding applies to that window.
If the tag is the name of a toplevel window the binding applies to the toplevel window and all its internal windows.
If the tag is the name of a class of widgets, such as Tk::Button, the binding applies to all widgets in that class;
If tag has the value all, the binding applies to all windows descended from the MainWindow of the application.
'<modifier-modifier-type-detail>'
The entire event pattern is surrounded by angle brackets, and normally needs to be quoted, as angle brackets are special to perl. Inside the angle brackets are zero or more modifiers, an event type, and an extra piece of information (detail) identifying a particular button or keysym. Any of the fields may be omitted, as long as at least one of type and detail is present. The fields must be separated by white space or dashes.
The third form of pattern is used to specify a user-defined, named virtual event; see Tk::event for details. It has the following syntax:
'<<name>>'
The entire virtual event pattern is surrounded by double angle brackets. Inside the angle brackets is the user-defined name of the virtual event. Modifiers, such as Shift or Control, may not be combined with a virtual event to modify it. Bindings on a virtual event may be created before the virtual event is defined, and if the definition of a virtual event changes dynamically, all windows bound to that virtual event will respond immediately to the new definition.
Control Mod2, M2 Shift Mod3, M3 Lock Mod4, M4 Button1, B1 Mod5, M5 Button2, B2 Meta, M Button3, B3 Alt Button4, B4 Double Button5, B5 Triple Mod1, M1 Quadruple
Where more than one value is listed, separated by commas, the values are equivalent. Most of the modifiers have the obvious X meanings. For example, Button1 requires that button 1 be depressed when the event occurs. For a binding to match a given event, the modifiers in the event must include all of those specified in the event pattern. An event may also contain additional modifiers not specified in the binding. For example, if button 1 is pressed while the shift and control keys are down, the pattern <Control-Button-1> will match the event, but <Mod1-Button-1> will not. If no modifiers are specified, then any combination of modifiers may be present in the event.
Meta and M refer to whichever of the M1 through M5 modifiers is associated with the meta key(s) on the keyboard (keysyms Meta_R and Meta_L). If there are no meta keys, or if they are not associated with any modifiers, then Meta and M will not match any events. Similarly, the Alt modifier refers to whichever modifier is associated with the alt key(s) on the keyboard (keysyms Alt_L and Alt_R).
The Double, Triple and Quadruple modifiers are a convenience for specifying double mouse clicks and other repeated events. They cause a particular event pattern to be repeated 2, 3 or 4 times, and also place a time and space requirement on the sequence: for a sequence of events to match a Double, Triple or Quadruple pattern, all of the events must occur close together in time and without substantial mouse motion in between. For example, <Double-Button-1> is equivalent to <Button-1><Button-1> with the extra time and space requirement.
Activate Destroy Map
ButtonPress, Button Enter MapRequest
ButtonRelease Expose Motion
Circulate FocusIn MouseWheel
CirculateRequest FocusOut Property
Colormap Gravity Reparent
Configure KeyPress, Key ResizeRequest
ConfigureRequest KeyRelease Unmap
Create Leave Visibility
Deactivate
Most of the above events have the same fields and behaviors as events in the X Windowing system. You can find more detailed descriptions of these events in any X window programming book. A couple of the events are extensions to the X event system to support features unique to the Macintosh and Windows platforms. We provide a little more detail on these events here. These include:
Activate
Deactivate
These two events are sent to every sub-window of a toplevel when they change state. In addition to the focus Window, the Macintosh platform and Windows platforms have a notion of an active window (which often has but is not required to have the focus). On the Macintosh, widgets in the active window have a different appearance than widgets in deactive windows. The Activate event is sent to all the sub-windows in a toplevel when it changes from being deactive to active. Likewise, the Deactive event is sent when the window's state changes from active to deactive. There are no use- ful percent substitutions you would make when binding to these events.
MouseWheel
Some mice on the Windows platform support a mouse wheel which is used for scrolling documents without using the scrollbars. By rolling the wheel, the system will generate MouseWheel events that the application can use to scroll. Like Key events the event is always routed to the window that currently has focus. When the event is received you can use the %D substitution to get the delta field for the event which is a integer value of motion that the mouse wheel has moved. The smallest value for which the system will report is defined by the OS. On Windows 95 & 98 machines this value is at least 120 before it is reported. However, higher resolution devices may be available in the future. The sign of the value determines which direction your widget should scroll. Positive values should scroll up and negative values should scroll down.
The last part of a long event specification is detail. In the case of a ButtonPress or ButtonRelease event, it is the number of a button (1-5). If a button number is given, then only an event on that particular button will match; if no button number is given, then an event on any button will match. Note: giving a specific button number is different than specifying a button modifier; in the first case, it refers to a button being pressed or released, while in the second it refers to some other button that is already depressed when the matching event occurs. If a button number is given then type may be omitted: if will default to ButtonPress. For example, the specifier <1> is equivalent to <ButtonPress-1>.
If the event type is KeyPress or KeyRelease, then detail may be specified in the form of an X keysym. Keysyms are textual specifications for particular keys on the keyboard; they include all the alphanumeric ASCII characters (e.g. ``a'' is the keysym for the ASCII character ``a''), plus descriptions for non-alphanumeric characters (``comma'' is the keysym for the comma character), plus descriptions for all the non-ASCII keys on the keyboard (``Shift_L'' is the keysm for the left shift key, and ``F1'' is the keysym for the F1 function key, if it exists). The complete list of keysyms is not presented here; it is available in other X documentation and may vary from system to system. If necessary, you can use the 'K' notation described below to print out the keysym name for a particular key. If a keysym detail is given, then the type field may be omitted; it will default to KeyPress. For example, <Control-comma> is equivalent to <Control-KeyPress-comma>.
NotifyAncestor NotifyNonlinearVirtual NotifyDetailNone NotifyPointer NotifyInferior NotifyPointerRoot NotifyNonlinear NotifyVirtual
For ConfigureRequest events, the string will be one of:
Above Opposite Below None BottomIf TopIf
For events other than these, the substituted string is undefined. (Note that this is not the same as Detail part of sequence use to specify the event.)
return and Tk->break may be used inside a callback to control the processing of matching callbacks. If return is invoked, then the current callback is terminated but Tk will continue processing callbacks associated with other tag's. If Tk->break is invoked within a callback, then that callback terminates and no other callbacks will be invoked for the event. (Tk->break is implemented via perl's die with a special value which is ``caught'' by the perl/Tk ``glue'' code.)
If more than one binding matches a particular event and they have the same tag, then the most specific binding is chosen and its callback is evaluated. The following tests are applied, in order, to determine which of several matching sequences is more specific: (a) an event pattern that specifies a specific button or key is more specific than one that doesn't; (b) a longer sequence (in terms of number of events matched) is more specific than a shorter sequence; (c) if the modifiers specified in one pattern are a subset of the modifiers in another pattern, then the pattern with more modifiers is more specific. (d) a virtual event whose physical pattern matches the sequence is less specific than the same physical pattern that is not associated with a virtual event. (e) given a sequence that matches two or more virtual events, one of the virtual events will be chosen, but the order is undefined.
If the matching sequences contain more than one event, then tests (c)-(e) are applied in order from the most recent event to the least recent event in the sequences. If these tests fail to determine a winner, then the most recently registered sequence is the winner.
If there are two (or more) virtual events that are both triggered by the same sequence, and both of those virtual events are bound to the same window tag, then only one of the virtual events will be triggered, and it will be picked at random:
$widget->eventAdd('<<Paste>>' => '<Control-y>');
$widget->eventAdd('<<Paste>>' => '<Button-2>');
$widget->eventAdd <<Scroll>>' => '<Button-2>');
$widget->bind('Tk::Entry','<<Paste>>',sub { print 'Paste'});
$widget->bind('Tk::Entry','<<Scroll>>', sub {print 'Scroll'});
If the user types Control-y, the <<Paste>> binding will be invoked, but if the user presses button 2 then one of either the <<Paste>> or the <<Scroll>> bindings will be invoked, but exactly which one gets invoked is undefined.
If an X event does not match any of the existing bindings, then the event is ignored. An unbound event is not considered to be an error.