XLIB Programming Manual, Rel. 5, Third Edition

Name

Expose — xexpose

When Generated

An Expose event is generated when a window becomes visible or a previously invisible part of a window becomes visible. Only InputOutput windows generate or need to respond to Expose events; InputOnly windows never generate or need to respond to them. The Expose event provides the position and size of the exposed area within the window and a rough count of the number of remaining exposure events for the current window.

Select With

This event is selected with ExposureMask.

XEvent Structure Name

typedef union _XEvent {
    ...
    XExposeEvent xexpose;
    ...
} XEvent;

Event Structure

typedef struct {
    int type;
    unsigned long serial;    /* # of last request processed by server */
    Bool send_event;         /* True if this came from SendEvent request */
    Display *display;        /* Display the event was read from */
    Window window;
    int x, y;
    int width, height;
    int count;               /* If nonzero, at least this many more */
} XExposeEvent;

Event Structure Members

x, y

The coordinates of the upper-left corner of the exposed region relative to the origin of the window.

width, height

The width and height in pixels of the exposed region.

count

The approximate number of remaining contiguous Expose events that were generated as a result of a single function call.

Notes

A single action such as a window movement or a function call can generate several exposure events on one window or on several windows. The server guarantees that all exposure events generated from a single action will be sent contiguously, so that they ...