NAME¶
Tk_CreateEventHandler, Tk_DeleteEventHandler - associate procedure callback with
an X event
SYNOPSIS¶
#include <tk.h>
Tk_CreateEventHandler(tkwin, mask, proc, clientData)
Tk_DeleteEventHandler(tkwin, mask, proc, clientData)
ARGUMENTS¶
- Tk_Window tkwin (in)
- Token for window in which events may occur.
- unsigned long mask (in)
- Bit-mask of events (such as ButtonPressMask) for
which proc should be called.
- Tk_EventProc *proc (in)
- Procedure to invoke whenever an event in mask occurs
in the window given by tkwin.
- ClientData clientData (in)
- Arbitrary one-word value to pass to proc.
DESCRIPTION¶
Tk_CreateEventHandler arranges for
proc to be invoked in the
future whenever one of the event types specified by
mask occurs in the
window specified by
tkwin. The callback to
proc will be made by
Tk_HandleEvent; this mechanism only works in programs that dispatch
events through
Tk_HandleEvent (or through other Tk procedures that call
Tk_HandleEvent, such as
Tk_DoOneEvent or
Tk_MainLoop).
Proc should have arguments and result that match the type
Tk_EventProc:
typedef void Tk_EventProc(
ClientData clientData,
XEvent * eventPtr);
The
clientData parameter to
proc is a copy of the
clientData argument given to
Tk_CreateEventHandler when the
callback was created. Typically,
clientData points to a data structure
containing application-specific information about the window in which the
event occurred.
EventPtr is a pointer to the X event, which will be one
of the ones specified in the
mask argument to
Tk_CreateEventHandler.
Tk_DeleteEventHandler may be called to delete a previously-created event
handler: it deletes the first handler it finds that is associated with
tkwin and matches the
mask,
proc, and
clientData
arguments. If no such handler exists, then
Tk_HandleEvent returns
without doing anything. Although Tk supports it, it's probably a bad idea to
have more than one callback with the same
mask,
proc, and
clientData arguments. When a window is deleted all of its handlers will
be deleted automatically; in this case there is no need to call
Tk_DeleteEventHandler.
If multiple handlers are declared for the same type of X event on the same
window, then the handlers will be invoked in the order they were created.
KEYWORDS¶
bind, callback, event, handler