Tk\_CreateEventHandler(3) Tk Library Procedures Tk\_CreateEventHandler(3)

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# [NAME](#NAME)

Tk\_CreateEventHandler, Tk\_DeleteEventHandler, Tk\_GetButtonMask, Tk\_SendVirtualEvent - associate procedure callback with an X event

# [SYNOPSIS](#SYNOPSIS)

```
#include <tk.h>

Tk_CreateEventHandler(tkwin, mask, proc, clientData)

Tk_DeleteEventHandler(tkwin, mask, proc, clientData)

Tk_GetButtonMask(button)

Tk_SendVirtualEvent(tkwin, eventName, detail)
```

# [ARGUMENTS](#ARGUMENTS)

unsigned *button* (in)

Button number.

const char *\*eventName* (in)

The name of the virtual event.

Tcl\_Obj *\*detail* (in)

Detail information for the virtual event. May be NULL.

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*.

void *\*clientData* (in)

Arbitrary one-word value to pass to *proc*.

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# [DESCRIPTION](#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 **Tcl\_DoOneEvent** or **Tk\_MainLoop**).

*Proc* should have arguments and result that match the type **Tk\_EventProc**:

```
typedef void Tk_EventProc(


        void *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.

**Tk\_GetButtonMask** returns the button mask corresponding to the button. E.g it will return *Button1Mask* for button *Button1*.

**Tk\_SendVirtualEvent** sends a virtual event to Tk's event queue.

# [KEYWORDS](#KEYWORDS)

bind, callback, event, handler

Tk

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Document: Tk_CreateEventHandler(3) from tk 9.0.4-r2 (Chainguard OS)
Source: https://downloads.sourceforge.net/sourceforge/tcl/tk9.0.4-src.tar.gz