SDL事件处理（一些数据类型）

typedef enum {
       SDL_NOEVENT = 0,			/**< Unused (do not remove) */
       SDL_ACTIVEEVENT,			/**< Application loses/gains visibility */
       SDL_KEYDOWN,			/**< Keys pressed */
       SDL_KEYUP,			/**< Keys released */
       SDL_MOUSEMOTION,			/**< Mouse moved */
       SDL_MOUSEBUTTONDOWN,		/**< Mouse button pressed */
       SDL_MOUSEBUTTONUP,		/**< Mouse button released */
       SDL_JOYAXISMOTION,		/**< Joystick axis motion */
       SDL_JOYBALLMOTION,		/**< Joystick trackball motion */
       SDL_JOYHATMOTION,		/**< Joystick hat position change */
       SDL_JOYBUTTONDOWN,		/**< Joystick button pressed */
       SDL_JOYBUTTONUP,			/**< Joystick button released */
       SDL_QUIT,			/**< User-requested quit */
       SDL_SYSWMEVENT,			/**< System specific event */
       SDL_EVENT_RESERVEDA,		/**< Reserved for future use.. */
       SDL_EVENT_RESERVEDB,		/**< Reserved for future use.. */
       SDL_VIDEORESIZE,			/**< User resized video mode */
       SDL_VIDEOEXPOSE,			/**< Screen needs to be redrawn */
       SDL_EVENT_RESERVED2,		/**< Reserved for future use.. */
       SDL_EVENT_RESERVED3,		/**< Reserved for future use.. */
       SDL_EVENT_RESERVED4,		/**< Reserved for future use.. */
       SDL_EVENT_RESERVED5,		/**< Reserved for future use.. */
       SDL_EVENT_RESERVED6,		/**< Reserved for future use.. */
       SDL_EVENT_RESERVED7,		/**< Reserved for future use.. */
       /** Events SDL_USEREVENT through SDL_MAXEVENTS-1 are for your use */
       SDL_USEREVENT = 24,
       /** This last event is only for bounding internal arrays
	*  It is the number of bits in the event mask datatype -- Uint32
        */
       SDL_NUMEVENTS = 32
} SDL_EventType;

SDL2.0中的定义：
typedef enum
{
    SDL_FIRSTEVENT     = 0,     /**< Unused (do not remove) */

    /* Application events */
    SDL_QUIT           = 0x100, /**< User-requested quit */

    /* These application events have special meaning on iOS, see README-ios.txt for details */
    SDL_APP_TERMINATING,        /**< The application is being terminated by the OS Called on iOS in applicationWillTerminate() Called on Android in onDestroy() */
    SDL_APP_LOWMEMORY,          /**< The application is low on memory, free memory if possible. Called on iOS in applicationDidReceiveMemoryWarning() Called on Android in onLowMemory() */
    SDL_APP_WILLENTERBACKGROUND, /**< The application is about to enter the background Called on iOS in applicationWillResignActive()Called on Android in onPause()*/
    SDL_APP_DIDENTERBACKGROUND, /**< The application did enter the background and may not get CPU for some time Called on iOS in applicationDidEnterBackground()Called on Android in onPause() */
    SDL_APP_WILLENTERFOREGROUND, /**< The application is about to enter the foreground  Called on iOS in applicationWillEnterForeground()  Called on Android in onResume() */
    SDL_APP_DIDENTERFOREGROUND, /**< The application is now interactive Called on iOS in applicationDidBecomeActive() Called on Android in onResume() */
    /* Window events */
    SDL_WINDOWEVENT    = 0x200, /**< Window state change */
    SDL_SYSWMEVENT,             /**< System specific event */
    /* Keyboard events */
    SDL_KEYDOWN        = 0x300, /**< Key pressed */
    SDL_KEYUP,                  /**< Key released */
    SDL_TEXTEDITING,            /**< Keyboard text editing (composition) */
    SDL_TEXTINPUT,              /**< Keyboard text input */

    /* Mouse events */
    SDL_MOUSEMOTION    = 0x400, /**< Mouse moved */
    SDL_MOUSEBUTTONDOWN,        /**< Mouse button pressed */
    SDL_MOUSEBUTTONUP,          /**< Mouse button released */
    SDL_MOUSEWHEEL,             /**< Mouse wheel motion */

    /* Joystick events */
    SDL_JOYAXISMOTION  = 0x600, /**< Joystick axis motion */
    SDL_JOYBALLMOTION,          /**< Joystick trackball motion */
    SDL_JOYHATMOTION,           /**< Joystick hat position change */
    SDL_JOYBUTTONDOWN,          /**< Joystick button pressed */
    SDL_JOYBUTTONUP,            /**< Joystick button released */
    SDL_JOYDEVICEADDED,         /**< A new joystick has been inserted into the system */
    SDL_JOYDEVICEREMOVED,       /**< An opened joystick has been removed */

    /* Game controller events */
    SDL_CONTROLLERAXISMOTION  = 0x650, /**< Game controller axis motion */
    SDL_CONTROLLERBUTTONDOWN,          /**< Game controller button pressed */
    SDL_CONTROLLERBUTTONUP,            /**< Game controller button released */
    SDL_CONTROLLERDEVICEADDED,         /**< A new Game controller has been inserted into the system */
    SDL_CONTROLLERDEVICEREMOVED,       /**< An opened Game controller has been removed */
    SDL_CONTROLLERDEVICEREMAPPED,      /**< The controller mapping was updated */

    /* Touch events */
    SDL_FINGERDOWN      = 0x700,
    SDL_FINGERUP,
    SDL_FINGERMOTION,

    /* Gesture events */
    SDL_DOLLARGESTURE   = 0x800,
    SDL_DOLLARRECORD,
    SDL_MULTIGESTURE,

    /* Clipboard events */
    SDL_CLIPBOARDUPDATE = 0x900, /**< The clipboard changed */

    /* Drag and drop events */
    SDL_DROPFILE        = 0x1000, /**< The system requests a file open */

    /* Render events */
    SDL_RENDER_TARGETS_RESET = 0x2000, /**< The render targets have been reset */

    /** Events ::SDL_USEREVENT through ::SDL_LASTEVENT are for your use,
     *  and should be allocated with SDL_RegisterEvents()
     */
    SDL_USEREVENT    = 0x8000,

    /**
     *  This last event is only for bounding internal arrays
     */
    SDL_LASTEVENT    = 0xFFFF
} SDL_EventType;

typedef struct SDL_JoyBallEvent {
	Uint8 type;	
	Uint8 which;	
	Uint8 ball;	
	Sint16 xrel;	
	Sint16 yrel;	
} SDL_JoyBallEvent;

/** Joystick hat position change event structure */
typedef struct SDL_JoyHatEvent {
	Uint8 type;	
	Uint8 which;	
	Uint8 hat;	
	Uint8 value;	
} SDL_JoyHatEvent;

SDL2.0中的：
typedef struct SDL_JoyBallEvent
{
    Uint32 type;       
    Uint32 timestamp;
    SDL_JoystickID which; 
    Uint8 ball;         
    Uint8 padding1;
    Uint8 padding2;
    Uint8 padding3;
    Sint16 xrel;        
    Sint16 yrel;     
} SDL_JoyBallEvent;

/**
 *  \brief Joystick hat position change event structure (event.jhat.*)
 */
typedef struct SDL_JoyHatEvent
{
    Uint32 type;      
    Uint32 timestamp;
    SDL_JoystickID which; 
    Uint8 hat;         
    Uint8 value;       
    Uint8 padding1;
    Uint8 padding2;
} SDL_JoyHatEvent;

从上面也可以看出SDL2.0相对于SDL1.2事件类型的改变

而SDL_Event是各种事件的联合：
SDL1.2：
typedef union SDL_Event {
	Uint8 type;
	SDL_ActiveEvent active;
	SDL_KeyboardEvent key;
	SDL_MouseMotionEvent motion;
	SDL_MouseButtonEvent button;
	SDL_JoyAxisEvent jaxis;
	SDL_JoyBallEvent jball;
	SDL_JoyHatEvent jhat;
	SDL_JoyButtonEvent jbutton;
	SDL_ResizeEvent resize;
	SDL_ExposeEvent expose;
	SDL_QuitEvent quit;
	SDL_UserEvent user;
	SDL_SysWMEvent syswm;
} SDL_Event;

SDL2.0：

typedef union SDL_Event
{
    Uint32 type;                    /**< Event type, shared with all events */SDL_EventType中定义的。具体的去看SDL源码
    SDL_CommonEvent common;         /**< Common event data */
    SDL_WindowEvent window;         /**< Window event data */
    SDL_KeyboardEvent key;          /**< Keyboard event data */
    SDL_TextEditingEvent edit;      /**< Text editing event data */
    SDL_TextInputEvent text;        /**< Text input event data */
    SDL_MouseMotionEvent motion;    /**< Mouse motion event data */
    SDL_MouseButtonEvent button;    /**< Mouse button event data */
    SDL_MouseWheelEvent wheel;      /**< Mouse wheel event data */
    SDL_JoyAxisEvent jaxis;         /**< Joystick axis event data */
    SDL_JoyBallEvent jball;         /**< Joystick ball event data */
    SDL_JoyHatEvent jhat;           /**< Joystick hat event data */
    SDL_JoyButtonEvent jbutton;     /**< Joystick button event data */
    SDL_JoyDeviceEvent jdevice;     /**< Joystick device change event data */
    SDL_ControllerAxisEvent caxis;      /**< Game Controller axis event data */
    SDL_ControllerButtonEvent cbutton;  /**< Game Controller button event data */
    SDL_ControllerDeviceEvent cdevice;  /**< Game Controller device event data */
    SDL_QuitEvent quit;             /**< Quit request event data */
    SDL_UserEvent user;             /**< Custom event data */
    SDL_SysWMEvent syswm;           /**< System dependent window event data */
    SDL_TouchFingerEvent tfinger;   /**< Touch finger event data */
    SDL_MultiGestureEvent mgesture; /**< Gesture event data */
    SDL_DollarGestureEvent dgesture; /**< Gesture event data */
    SDL_DropEvent drop;             /**< Drag and drop event data */
    Uint8 padding[56];
} SDL_Event;