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<HTML><HEAD><TITLE>Xlib Programming Manual: Event Structures</TITLE></HEAD><BODY><H1 ALIGN=center>10.2 Event Structures</H1>For each event type,a corresponding structure is declared in<B><TT>X11/Xlib.h</TT></B>.All the event structures have the following common members:<P><!.IN "XAnyEvent" "" "@DEF@"><CODE><PRE>typedef struct { int type; unsigned long serial; /* # of last request processed by server */ Bool send_event; /* true if this came from a <B><A HREF="../appendix/a.html#SendEvent">SendEvent</A></B> request */ Display *display; /* Display the event was read from */ Window window;} XAnyEvent;</PRE></CODE><P>The <B>type</B> member is set to the event type constant name that uniquely identifiesit.For example, when the X server reports a<B><A HREF="exposure/graphics-expose-and-no-expose.html">GraphicsExpose</A></B>event to a client application, it sends an<A HREF="exposure/graphics-expose-and-no-expose.html#XGraphicsExposeEvent">XGraphicsExposeEvent</A>structure with the <B>type</B> member set to<B><A HREF="exposure/graphics-expose-and-no-expose.html">GraphicsExpose</A></B>.The <B>display</B> member is set to a pointer to the display the event was read on.The <B>send_event</B> member is set to<B>True</B>if the event came from a<B><A HREF="../appendix/a.html#SendEvent">SendEvent</A></B>protocol request.The <B>serial</B> member is set from the serial number reported in the protocolbut expanded from the 16-bit least-significant bits to a full 32-bit value.The <B>window</B> member is set to the window that is most useful to toolkitdispatchers.<P>The X server can send events at any time in the input stream. Xlib stores any events received while waiting for a reply in an event queue for later use.Xlib also provides functions that allow you to check events in the event queue (see section "<A HREF="../event-handling/event-queue-management.html">Event Queue Management</A>").<P>In addition to the individual structures declared for each event type, the<B>XEvent</B>structure is a union of the individual structures declared for each event type.Depending on the type,you should access members of each event by using the <B>XEvent</B>union.<A NAME="XEvent"></A><P><!.IN "XEvent" "" "@DEF@"><CODE><PRE>typedef union _XEvent { int type; /* must not be changed */ XAnyEvent xany; <A HREF="keyboard-pointer/keyboard-pointer.html#XKeyEvent">XKeyEvent</A> xkey; <A HREF="keyboard-pointer/keyboard-pointer.html#XButtonEvent">XButtonEvent</A> xbutton; <A HREF="keyboard-pointer/keyboard-pointer.html#XMotionEvent">XMotionEvent</A> xmotion; <A HREF="window-entry-exit/#XCrossingEvent">XCrossingEvent</A> xcrossing; <A HREF="input-focus/#XFocusChangeEvent">XFocusChangeEvent</A> xfocus; <A HREF="exposure/expose.html#XExposeEvent">XExposeEvent</A> xexpose; <A HREF="exposure/graphics-expose-and-no-expose.html#XGraphicsExposeEvent">XGraphicsExposeEvent</A> xgraphicsexpose; <A HREF="exposure/graphics-expose-and-no-expose.html#XNoExposeEvent">XNoExposeEvent</A> xnoexpose; <A HREF="window-state-change/visibility.html#XVisibilityEvent">XVisibilityEvent</A> xvisibility; <A HREF="window-state-change/create.html#XCreateWindowEvent">XCreateWindowEvent</A> xcreatewindow; <A HREF="window-state-change/destroy.html#XDestroyWindowEvent">XDestroyWindowEvent</A> xdestroywindow; <A HREF="window-state-change/unmap.html#XUnmapEvent">XUnmapEvent</A> xunmap; <A HREF="window-state-change/map.html#XMapEvent">XMapEvent</A> xmap; <A HREF="structure-control/map.html#XMapRequestEvent">XMapRequestEvent</A> xmaprequest; <A HREF="window-state-change/reparent.html#XReparentEvent">XReparentEvent</A> xreparent; <A HREF="window-state-change/configure.html#XConfigureEvent">XConfigureEvent</A> xconfigure; <A HREF="window-state-change/gravity.html#XGravityEvent">XGravityEvent</A> xgravity; <A HREF="structure-control/resize.html#XResizeRequestEvent">XResizeRequestEvent</A> xresizerequest; <A HREF="structure-control/configure.html#XConfigureRequestEvent">XConfigureRequestEvent</A> xconfigurerequest; <A HREF="window-state-change/circulate.html#XCirculateEvent">XCirculateEvent</A> xcirculate; <A HREF="structure-control/circulate.html#XCirculateRequestEvent">XCirculateRequestEvent</A> xcirculaterequest; <A HREF="client-communication/property.html#XPropertyEvent">XPropertyEvent</A> xproperty; <A HREF="client-communication/selection-clear.html#XSelectionClearEvent">XSelectionClearEvent</A> xselectionclear; <A HREF="client-communication/selection-request.html#XSelectionRequestEvent">XSelectionRequestEvent</A> xselectionrequest; <A HREF="client-communication/selection.html#XSelectionEvent">XSelectionEvent</A> xselection; <A HREF="colormap-state.html#XColormapEvent">XColormapEvent</A> xcolormap; <A HREF="client-communication/client-message.html#XClientMessageEvent">XClientMessageEvent</A> xclient; <A HREF="window-state-change/mapping.html#XMappingEvent">XMappingEvent</A> xmapping; XErrorEvent xerror; <A HREF="key-map.html#XKeymapEvent">XKeymapEvent</A> xkeymap; long pad[24];} XEvent;</PRE></CODE><P>An<B>XEvent</B>structure's first entry always is the type member,which is set to the event type.The second member always is the serial number of the protocol requestthat generated the event.The third member always is send_event,which is a<B>Bool</B>that indicates if the event was sent by a different client.The fourth member always is a display,which is the display that the event was read from.Except for keymap events,the fifth member always is a window,which has been carefully selected to be useful to toolkit dispatchers.To avoid breaking toolkits,the order of these first five entries is not to change.Most events also contain a time member,which is the time at which an event occurred.In addition, a pointer to the generic event must be cast before itis used to access any other information in the structure.<H5 ALIGN=right><I>Next: <A HREF="mask.html">Event Masks</A></I></H5><HR><ADDRESS><A HREF="http://tronche.com/">Christophe Tronche</A>, <A HREF="mailto:ch.tronche@computer.org">ch.tronche@computer.org</A></ADDRESS></BODY></HTML>⌨️ 快捷键说明
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