---
name: "XQueryExtension"
section: "3"
platform: "linux"
package: "libx11"
version: "1.8.14-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/XQueryExtension"
---

# XQueryExtension(3)

list available extensions

## NAME

XQueryExtension, XListExtensions, XFreeExtensionList - list available extensions

## SYNTAX

Bool XQueryExtension(*display, name, major\_opcode\_return, first\_event\_return, first\_error\_return)*

*char \*\*XListExtensions(display, nextensions\_return)*

*XFreeExtensionList(list)*

## ARGUMENTS

- *display*

  *Specifies the connection to the X server.*

- *name*

  *Specifies the extension name.*

- *major\_opcode\_return*

  *Returns the major opcode.*

- *first\_event\_return*

  *Returns the first event code, if any.*

- *first\_error\_return*

  *Returns the first error code, if any.*

- *nextensions\_return*

  *Returns the number of extensions listed.*

- *list*

  *Specifies the list of extension names.*

## DESCRIPTION

*The XQueryExtension function determines if the named extension is* *present.* *If the extension is not present, XQueryExtension returns* *False; otherwise, it returns True.  If the extension is present,* *XQueryExtension returns the major opcode for the extension to* *major\_opcode\_return; otherwise, it returns zero.* *Any minor opcode and the* *request formats are specific to the extension.* *If the extension involves* *additional event types, XQueryExtension returns the base event type code* *to first\_event\_return; otherwise, it returns zero.* *The format of the events is* *specific to the extension.* *If the extension involves additional error codes,* *XQueryExtension returns the base error code to first\_error\_return;* *otherwise, it returns zero.* *The format of additional data in the errors is* *specific to the extension.* *If the extension name is not in the Host Portable* *Character Encoding the result is implementation-dependent.* *Uppercase and* *lowercase matter; the strings “thing”, “Thing”, and “thinG” are all* *considered different names.*

*The XListExtensions function returns a list of all extensions supported* *by the server.* *If the data returned by the server is in the Latin Portable* *Character Encoding, then the returned strings are in the Host Portable* *Character Encoding.* *Otherwise, the result is implementation-dependent.*

*The XFreeExtensionList function frees the memory allocated by* *XListExtensions.*