Irrlicht_0.1源码学习（4）—include/irrTypes.h & include/IeventReceiver.h

irrTypes.h这个文件做的事很简单，通过一系列typedef操作定义了Irrlicht引擎中的所有基本数据类型，以保证引擎的可移植性。

IeventReceiver.h则定义了一些用于事件系统中的枚举和结构/类。其中包含了EEVENT_TYPE、EMOUSE_INPUT_EVENT、EGUI_EVENT_TYPE三种枚举类型以及SEvent结构和IEventReceiver类。

EEVENT_TYPE：用于枚举irrlicht引擎中所有的事件类型（gui事件、鼠标事件、键盘事件）

    //! Enumeration for all event types there are.
    enum EEVENT_TYPE
    {
        //! An event of the graphical user interface.
        EET_GUI_EVENT = 0,

        //! A mouse input event.
        EET_MOUSE_INPUT_EVENT,

        //! A key input evant.
        EET_KEY_INPUT_EVENT
    };

EMOUSE_INPUT_EVENT：用于枚举所有的鼠标输入事件

    //! Enumeration for all mouse input events
    enum EMOUSE_INPUT_EVENT
    {
        //! Left mouse button was pressed down.
        EMIE_LMOUSE_PRESSED_DOWN = 0,
        //! Right mouse button was pressed down.
        EMIE_RMOUSE_PRESSED_DOWN,
        //! Middle mouse button was pressed down.
        EMIE_MMOUSE_PRESSED_DOWN,
        //! Left mouse button was left up.
        EMIE_LMOUSE_LEFT_UP,
        //! Right mouse button was left up.
        EMIE_RMOUSE_LEFT_UP,
        //! Middle mouse button was left up.
        EMIE_MMOUSE_LEFT_UP,
        //! The mouse cursor changed its position.
        EMIE_MOUSE_MOVED
    };

EGUI_EVENT_TYPE：用于枚举所有由gui系统投递出的事件

   //! Enumeration for all events which are sendable by the gui system
   enum EGUI_EVENT_TYPE
   {
       //! A gui element has lost its key focus.
       EGET_ELEMENT_KEY_FOCUS_LOST = 0,
       //! A gui element has lost its mouse focus.
       EGET_ELEMENT_MOUSE_FOCUS_LOST,
       //! A gui element was hovered.
       EGET_ELEMENT_HOVERED,
       //! A button was clicked.
       EGET_BUTTON_CLICKED,
       //! A scrollbar has changed its position.
       EGET_SCROLL_BAR_CHANGED,
       //! A checkbox has changed its check state.
       EGET_CHECKBOX_CHANGED,
       //! A new item in a listbox was seleted.
       EGET_LISTBOX_CHANGED, 
       /! An item in the listbox was selected, which was already selected.
       EGET_LISTBOX_SELECTED_AGAIN, 
   };

SEvent：用于储存各类事件相关数据的结构体，其实现中使用union优化内存占用情况

//! Struct for holding event data. An event can be a gui, mouse or keyboard event.
struct SEvent
{
    EEVENT_TYPE EventType;

    union
    {
        struct 
        {
            gui::IGUIElement* Caller;
            gui::EGUI_EVENT_TYPE EventType;            
        } GUIEvent;

        struct
        {
            s32 X, Y; // mouse positions;
            EMOUSE_INPUT_EVENT Event;
        } MouseInput;

        struct
        {
            s32 Key; // TODO key
            bool PressedDown; // if not pressed, then left up
        } KeyInput;

    };

};

IEventReceiver：所有能够接收事件的对象必须实现的接口类，内部声明了一个处理各类事件的纯虚函数（OnEvent）

//! Interface of an object wich can receive events.
class IEventReceiver
{
public:

    //! called if an event happened. returns true if event was processed
    virtual bool OnEvent(SEvent event) = 0;
};