Linux Manual Pages

Free Software * Books

Source Code

Free Media

Linux

XGetEventData

HOME

XGetEventData

NAME
SYNTAX
ARGUMENTS
STRUCTURES
DESCRIPTION
EXAMPLE CODE
NOTES
SEE ALSO

NAME

XGetEventData, XFreeEventData, XGenericEventCookie − retrieve and free additional event data through cookies.

SYNTAX

	Bool XGetEventData(Display *display, XGenericEventCookie *cookie);
	void XFreeEventData(Display *display, XGenericEventCookie *cookie);

ARGUMENTS


	display		Specifies the connection to the X server.
	cookie		Specifies the cookie to free or retrieve the data for.

STRUCTURES

typedef struct {

	int type;
	unsigned long serial;
	Bool send_event;
	Display *display;
	int extension;
	int evtype;
	unsigned int cookie;
	void *data;

} XGenericEventCookie;

DESCRIPTION

Some extension XGenericEvents require additional memory to store information. For these events, the library returns a XGenericEventCookie with a token (’cookie’) unique to this event. The XGenericEventCookie’s data pointer is undefined until XGetEventData is called.

The XGetEventData function retrieves this extra data for the given cookie. No round-trip to the server is required. If the cookie is invalid or the event is not an event handled by cookie handlers, False is returned. If XGetEventData returns True, the cookie’s data pointer points to the memory containing the event information. A client must call XFreeEventData to free this memory. XGetEventData returns False for multiple calls for the same event cookie.

The XFreeEventData function frees the data associated with a cookie. A client must call XFreeEventData for each cookie claimed with XGetEventData.

EXAMPLE CODE

XEvent event;
XGenericEventCookie *cookie = &ev;

XNextEvent(display, &event);
if (XGetEventData(display, cookie)) {
handle_cookie_event(cookie->data);
} else
handle_event(&event);
}
XFreeEventData(display, cookie);

NOTES

A cookie is defined as unclaimed if it has been returned to the client through XNextEvent but its data has not been retrieved via XGetEventData. Subsequent calls to XNextEvent may free memory associated with unclaimed cookies. Multi-threaded X clients must ensure that XGetEventData is called before the next call to XNextEvent.

Opportunity

Personal Opportunity - Free software gives you access to billions of dollars of software at no cost. Use this software for your business, personal use or to develop a profitable skill. Access to source code provides access to a level of capabilities/information that companies protect though copyrights. Open source is a core component of the Internet and it is available to you. Leverage the billions of dollars in resources and capabilities to build a career, establish a business or change the world. The potential is endless for those who understand the opportunity.

Business Opportunity - Goldman Sachs, IBM and countless large corporations are leveraging open source to reduce costs, develop products and increase their bottom lines. Learn what these companies know about open source and how open source can give you the advantage.

Free Software

Free Software provides computer programs and capabilities at no cost but more importantly, it provides the freedom to run, edit, contribute to, and share the software. The importance of free software is a matter of access, not price. Software at no cost is a benefit but ownership rights to the software and source code is far more significant.

Free Office Software - The Libre Office suite provides top desktop productivity tools for free. This includes, a word processor, spreadsheet, presentation engine, drawing and flowcharting, database and math applications. Libre Office is available for Linux or Windows.

Free Books

The Free Books Library is a collection of thousands of the most popular public domain books in an online readable format. The collection includes great classical literature and more recent works where the U.S. copyright has expired. These books are yours to read and use without restrictions.

Source Code - Want to change a program or know how it works? Open Source provides the source code for its programs so that anyone can use, modify or learn how to write those programs themselves. Visit the GNU source code repositories to download the source.

Education

Study at Harvard, Stanford or MIT - Open edX provides free online courses from Harvard, MIT, Columbia, UC Berkeley and other top Universities. Hundreds of courses for almost all major subjects and course levels. Open edx also offers some paid courses and selected certifications.

Linux Manual Pages - A man or manual page is a form of software documentation found on Linux/Unix operating systems. Topics covered include computer programs (including library and system calls), formal standards and conventions, and even abstract concepts.