---
name: "XtAppAddBlockHook"
section: "3"
platform: "linux"
package: "libxt"
version: "1.3.1-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/XtAppAddBlockHook"
---

# XtAppAddBlockHook(3)

register a block hook procedure

## NAME

XtAppAddBlockHook, XtRemoveBlockHook - register a block hook procedure

## SYNTAX

\#include \<X11/Intrinsic.h\>

XtBlockHookId XtAppAddBlockHook(XtAppContext *app\_context*, XtBlockHookProc *proc*, XtPointer *client\_data*);

void XtRemoveBlockHook(XtBlockHookId *id*);

## ARGUMENTS

- *app\_context*

  Specifies the application context.

- *proc*

  Specifies the block hook procedure.

- *num\_args*

  Specifies the application-specific data to be passed to the block hook.

## DESCRIPTION

**XtAppAddBlockHook** registers the specified procedure and returns an identifier for it. The hook is called at any time in the future when the Intrinsics are about to block pending some input.

Block hook procedures are removed automatically and the **XtBlockHookId** is destroyed when the application context in which they were added is destroyed.

**XtRemoveBlockHook** removes the specified block hook procedure from the list in which it was registered.

## SEE ALSO

*X Toolkit Intrinsics - C Language Interface*\
 *Xlib - C Language X Interface*