XErrorEvent - Man Page

The XErrorEvent structure contains:

typedef struct {
        int type;
        Display *display;       /* Display the event was read from */
        XID resourceid;         /* resource id */
        unsigned long serial;           /* serial number of failed request */
        unsigned char error_code;       /* error code of failed request */
        unsigned char request_code;     /* Major op-code of failed request */
        unsigned char minor_code;       /* Minor op-code of failed request */
} XErrorEvent;

When you receive this event, the structure members are set as follows.

The serial member is the number of requests, starting from one, sent over the network connection since it was opened. It is the number that was the value of NextRequest immediately before the failing call was made. The request_code member is a protocol request of the procedure that failed, as defined in X11/Xproto.h.

AllPlanes(3), XAnyEvent(3), XButtonEvent(3), XCreateWindowEvent(3), XCirculateEvent(3), XCirculateRequestEvent(3), XColormapEvent(3), XConfigureEvent(3), XConfigureRequestEvent(3), XCrossingEvent(3), XDestroyWindowEvent(3), XExposeEvent(3), XFocusChangeEvent(3), XGraphicsExposeEvent(3), XGravityEvent(3), XKeymapEvent(3), XMapEvent(3), XMapRequestEvent(3), XPropertyEvent(3), XReparentEvent(3), XResizeRequestEvent(3), XSelectionClearEvent(3), XSelectionEvent(3), XSelectionRequestEvent(3), XUnmapEvent(3), XVisibilityEvent(3)
Xlib - C Language X Interface

XAnyEvent(3), XButtonEvent(3), XCirculateEvent(3), XCirculateRequestEvent(3), XClientMessageEvent(3), XColormapEvent(3), XConfigureEvent(3), XConfigureRequestEvent(3), XCreateWindowEvent(3), XCrossingEvent(3), XDestroyWindowEvent(3), XExposeEvent(3), XFocusChangeEvent(3), XGraphicsExposeEvent(3), XGravityEvent(3), XKeymapEvent(3), XMapEvent(3), XMapRequestEvent(3), XPropertyEvent(3), XReparentEvent(3), XResizeRequestEvent(3), XSelectionClearEvent(3), XSelectionEvent(3), XSelectionRequestEvent(3), XUnmapEvent(3), XVisibilityEvent(3).