WebEvent是iOS专有的类，负责封装和携带从UIKit得到的系统事件信息，并由WebKit层的WAKResponder子类传递到WebCore的EventHandler。
UIKit层的逻辑可参考《iOS私有API（三） UIWebView下的手势识别器gestureRecognizer》，WebKit层的相关类可参考《WebCore::Widget浅探》。
开源码中WebEvent的声明为：
typedef enum {
WebEventMouseDown,
WebEventMouseUp,
WebEventMouseMoved,
WebEventScrollWheel,
WebEventKeyDown,
WebEventKeyUp,
WebEventTouchBegin,
WebEventTouchChange,
WebEventTouchEnd,
WebEventTouchCancel
} WebEventType;
typedef enum {
WebEventTouchPhaseBegan,
WebEventTouchPhaseMoved,
WebEventTouchPhaseStationary,
WebEventTouchPhaseEnded,
WebEventTouchPhaseCancelled
} WebEventTouchPhaseType;
// These enum values are copied directly from GSEvent for compatibility.
typedef enum
{
WebEventFlagMaskAlphaShift = 0x00010000,
WebEventFlagMaskShift = 0x00020000,
WebEventFlagMaskControl = 0x00040000,
WebEventFlagMaskAlternate = 0x00080000,
WebEventFlagMaskCommand = 0x00100000,
} WebEventFlagValues;
typedef unsigned WebEventFlags;
// These enum values are copied directly from GSEvent for compatibility.
typedef enum
{
WebEventCharacterSetASCII = 0,
WebEventCharacterSetSymbol = 1,
WebEventCharacterSetDingbats = 2,
WebEventCharacterSetUnicode = 253,
WebEventCharacterSetFunctionKeys = 254,
} WebEventCharacterSet;
@interface WebEvent : NSObject {
@private
WebEventType _type;
CFTimeInterval _timestamp;
CGPoint _locationInWindow;
NSString *_characters;
NSString *_charactersIgnoringModifiers;
WebEventFlags _modifierFlags;
BOOL _keyRepeating;
BOOL _popupVariant;
uint16_t _keyCode;
BOOL _tabKey;
WebEventCharacterSet _characterSet;
float _deltaX;
float _deltaY;
unsigned _touchCount;
NSArray *_touchLocations;
NSArray *_touchIdentifiers;
NSArray *_touchPhases;
BOOL _isGesture;
float _gestureScale;
float _gestureRotation;
}
- (WebEvent *)initWithMouseEventType:(WebEventType)type
timeStamp:(CFTimeInterval)timeStamp
location:(CGPoint)point;
- (WebEvent *)initWithScrollWheelEventWithTimeStamp:(CFTimeInterval)timeStamp
location:(CGPoint)point
deltaX:(float)deltaX
deltaY:(float)deltaY;
- (WebEvent *)initWithTouchEventType:(WebEventType)type
timeStamp:(CFTimeInterval)timeStamp
location:(CGPoint)point
modifiers:(WebEventFlags)modifiers
touchCount:(unsigned)touchCount
touchLocations:(NSArray *)touchLocations
touchIdentifiers:(NSArray *)touchIdentifiers
touchPhases:(NSArray *)touchPhases isGesture:(BOOL)isGesture
gestureScale:(float)gestureScale
gestureRotation:(float)gestureRotation;
- (WebEvent *)initWithKeyEventType:(WebEventType)type
timeStamp:(CFTimeInterval)timeStamp
characters:(NSString *)characters
charactersIgnoringModifiers:(NSString *)charactersIgnoringModifiers
modifiers:(WebEventFlags)modifiers
isRepeating:(BOOL)repeating
isPopupVariant:(BOOL)popupVariant
keyCode:(uint16_t)keyCode
isTabKey:(BOOL)tabKey
characterSet:(WebEventCharacterSet)characterSet;
@property(nonatomic,readonly) WebEventType type;
@property(nonatomic,readonly) CFTimeInterval timestamp;
// Mouse
@property(nonatomic,readonly) CGPoint locationInWindow;
// Keyboard
@property(nonatomic,readonly,retain) NSString *characters;
@property(nonatomic,readonly,retain) NSString *charactersIgnoringModifiers;
@property(nonatomic,readonly) WebEventFlags modifierFlags;
@property(nonatomic,readonly,getter=isKeyRepeating) BOOL keyRepeating;
@property(nonatomic,readonly,getter=isPopupVariant) BOOL popupVariant;
@property(nonatomic,readonly) uint16_t keyCode;
@property(nonatomic,readonly,getter=isTabKey) BOOL tabKey;
@property(nonatomic,readonly) WebEventCharacterSet characterSet;
// Scroll Wheel
@property(nonatomic,readonly) float deltaX;
@property(nonatomic,readonly) float deltaY;
// Touch
@property(nonatomic,readonly) unsigned touchCount;
@property(nonatomic,readonly,retain) NSArray *touchLocations;
@property(nonatomic,readonly,retain) NSArray *touchIdentifiers;
@property(nonatomic,readonly,retain) NSArray *touchPhases;
// Gesture
@property(nonatomic,readonly) BOOL isGesture;
@property(nonatomic,readonly) float gestureScale;
@property(nonatomic,readonly) float gestureRotation;
@end
WebEvent封装了4种事件：鼠标（手指）、键盘、滚轮、触摸，主要通过属性WebEventType type来区分。
鼠标事件主要由单击手势来触发，会产生mouseup，mousemove和mousedown事件。其中单击就是同一RunLoop内连贯的mousedown和mouseup，而mousemove是模拟事件，可触发mouseover消息。
键盘事件发生在编辑框内，按下iOS虚拟键盘的按键就会触发。
滚轮由双指平移手势触发，在输入框内有效。
触摸特指JavaScript监听的touchstart、gesturestart等消息，由UIWebTouchEventsGestureRecognizer来计算。
这些事件触发后，都会在主线程创建WebEvent，然后用GCD技术转到WebThread执行。
开源码的EventHandler.h中有如下几行：
#if PLATFORM(MAC) && defined(__OBJC__)
void mouseDown(WebEvent *);
void mouseUp(WebEvent *);
void mouseMoved(WebEvent *);
bool keyEvent(WebEvent *);
bool wheelEvent(WebEvent *);
void touchEvent(WebEvent *);
static WebEvent *currentEvent();
#endif使用xdb也能找到，可是在EventHandler的实现中却找不到，所以
Apple是没有完全公开iOS源码的。
另有一个PlatformEventFactoryIOS.h的文件有如下声明：
class PlatformEventFactory {
public:
static PlatformMouseEvent createPlatformMouseEvent(WebEvent *);
static PlatformWheelEvent createPlatformWheelEvent(WebEvent *);
static PlatformKeyboardEvent createPlatformKeyboardEvent(WebEvent *);
static PlatformTouchEvent createPlatformTouchEvent(WebEvent *);
};这些函数的作用就是把Objective-C类封装的WebEvent转换成WebCore里C++的PlatformEvent。可以猜测，接受WebEvent型参数的EventHandler函数也就只是简单做这个工作，转换后再直接调用通用的函数就ok了。如：
bool handleMousePressEvent(const PlatformMouseEvent&);
bool handleMouseMoveEvent(const PlatformMouseEvent&, HitTestResult* hoveredNode = 0, bool onlyUpdateScrollbars = false);
bool handleMouseReleaseEvent(const PlatformMouseEvent&);
bool handleWheelEvent(const PlatformWheelEvent&);
void defaultWheelEventHandler(Node*, WheelEvent*);
#if ENABLE(GESTURE_EVENTS)
bool handleGestureEvent(const PlatformGestureEvent&);
bool handleGestureTap(const PlatformGestureEvent&, Node* preTargetedNode = 0);
bool handleGestureScrollUpdate(const PlatformGestureEvent&);
#endif
一个堆栈示例：
Thread 4 WebThread, Queue : (null) #0 0x03385790 in WebCore::EventHandler::mouseMoved(WebCore::PlatformMouseEvent const&) () #1 0x0338ae0f in WebCore::EventHandler::mouseMoved(WebEvent*) () #2 0x02efd822 in -[WebHTMLView(WebPrivate) mouseMoved:] () #3 0x03f6c6ac in -[WAKView _selfHandleEvent:] () #4 0x03f6c603 in -[WAKView handleEvent:] () #5 0x03f6f94d in -[WAKWindow sendEventSynchronously:] () #6 0x03f6f75b in __23-[WAKWindow sendEvent:]_block_invoke () #7 0x03f83fe2 in _WebThreadRun () #8 0x03f83ee0 in WebThreadRun () #9 0x03f6f71c in -[WAKWindow sendEvent:] () #10 0x03f6fa0c in __46-[WAKWindow sendMouseMoveEvent:contentChange:]_block_invoke () #11 0x03f83fe2 in _WebThreadRun () #12 0x03f83ee0 in WebThreadRun () #13 0x03f6f9d2 in -[WAKWindow sendMouseMoveEvent:contentChange:] () #14 0x0023609d in __64-[UIWebDocumentView(Interaction) _sendMouseMoveAndAttemptClick:]_block_invoke () #15 0x03f844ea in HandleRunSource () #16 0x0226e33f in __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ () #17 0x0226dd95 in __CFRunLoopDoSources0 () #18 0x0228b124 in __CFRunLoopRun () #19 0x0228a59f in CFRunLoopRunSpecific () #20 0x0228a3eb in CFRunLoopRunInMode () #21 0x03f83c30 in RunWebThread(void*) () #22 0x05a5c65c in _pthread_body () #23 0x05a5c4e6 in _pthread_start ()
其它的Event都差不多，不再赘述了。
