SDL鼠标事件

鼠标事件有这么多种，手柄的可以忽视，Sdl.SDL_KEYDOWN，Sdl.SDL_KEYUP，Sdl.SDL_MOUSEMOTION，Sdl.SDL_MOUSEBUTTONDOWN，Sdl.SDL_MOUSEBUTTONUP应该是常用的。

public enum EventTypes
 
    {
 
        /// <summary>
 
        /// No event
 
        /// </summary>
 
        None = Sdl.SDL_NOEVENT,
 
        /// <summary>
 
        /// Active event
 
        /// </summary>
 
        ActiveEvent = Sdl.SDL_ACTIVEEVENT,
 
        /// <summary>
 
        /// Key down event
 
        /// </summary>
 
        KeyDown = Sdl.SDL_KEYDOWN,
 
        /// <summary>
 
        /// Key up event
 
        /// </summary>
 
        KeyUp = Sdl.SDL_KEYUP,
 
        /// <summary>
 
        /// Mouse Motion event
 
        /// </summary>
 
        MouseMotion = Sdl.SDL_MOUSEMOTION,
 
        /// <summary>
 
        /// Mouse button down event
 
        /// </summary>
 
        MouseButtonDown = Sdl.SDL_MOUSEBUTTONDOWN,
 
        /// <summary>
 
        /// Mouse button up event
 
        /// </summary>
 
        MouseButtonUp = Sdl.SDL_MOUSEBUTTONUP,
 
        /// <summary>
 
        /// Joystick Axis motion event
 
        /// </summary>
 
        JoystickAxisMotion = Sdl.SDL_JOYAXISMOTION,
 
        /// <summary>
 
        /// Joystick ball motion event
 
        /// </summary>
 
        JoystickBallMotion = Sdl.SDL_JOYBALLMOTION,
 
        /// <summary>
 
        /// Joystick hat motion event
 
        /// </summary>
 
        JoystickHatMotion = Sdl.SDL_JOYHATMOTION,
 
        /// <summary>
 
        /// Joystick button down event
 
        /// </summary>
 
        JoystickButtonDown = Sdl.SDL_JOYBUTTONDOWN,
 
        /// <summary>
 
        /// joystick button up event
 
        /// </summary>
 
        JoystickButtonUp = Sdl.SDL_JOYBUTTONUP,
 
        /// <summary>
 
        /// Video resize event
 
        /// </summary>
 
        VideoResize = Sdl.SDL_VIDEORESIZE,
 
        /// <summary>
 
        /// Video expose event
 
        /// </summary>
 
        VideoExpose = Sdl.SDL_VIDEOEXPOSE,
 
        /// <summary>
 
        /// Quit event
 
        /// </summary>
 
        Quit = Sdl.SDL_QUIT,
 
        /// <summary>
 
        /// Window manager event
 
        /// </summary>
 
        WindowManagerEvent = Sdl.SDL_SYSWMEVENT,
 
        /// <summary>
 
        /// user-defined event
 
        /// </summary>
 
        UserEvent = Sdl.SDL_USEREVENT
 
    }

鼠标点击后的button：

public enum MouseButton
 
    {
 
        /// <summary>
 
        /// None
 
        /// </summary>
 
        None = ,
 
        /// <summary>
 
        /// Primary button. Typically the left button
 
        /// </summary>
 
        PrimaryButton = Sdl.SDL_BUTTON_LEFT,
 
        /// <summary>
 
        /// Secondary button. typically the right button
 
        /// </summary>
 
        SecondaryButton = Sdl.SDL_BUTTON_RIGHT,
 
        /// <summary>
 
        /// Middle button
 
        /// </summary>
 
        MiddleButton = Sdl.SDL_BUTTON_MIDDLE,
 
        /// <summary>
 
        /// Wheel up
 
        /// </summary>
 
        WheelUp = Sdl.SDL_BUTTON_WHEELUP,
 
        /// <summary>
 
        /// Wheel down
 
        /// </summary>
 
        WheelDown = Sdl.SDL_BUTTON_WHEELDOWN
 
    }

常用的代码写法

while (!quit) //建立事件主循环
 
            {
 
                    while (Sdl.SDL_PollEvent(out ev) == )//从队列里取出事件
 
                    {
 
                        Sdl.SDL_WaitEvent(out ev); //必须等待
 
                        if (ev.type == Sdl.SDL_MOUSEBUTTONDOWN)
 
                        {
 
                            if (ev.button.button == Sdl.SDL_BUTTON_LEFT)
 
                            {
 
                                MouseDown(ev.button);
 
                            }
 
                            else
 
                                if (ev.button.button ==Sdl.SDL_BUTTON_RIGHT)
 
                                {
 
                                }
 
                        }
 
                        else
 
                            if (ev.type == Sdl.SDL_MOUSEMOTION)
 
                            {
 
                                MouseMove (ev.button);
 
                            }
 
                            else
 
                                if (ev.type == Sdl.SDL_MOUSEBUTTONUP)
 
                                {
 
                                    if (ev.button.button ==Sdl.SDL_BUTTON_LEFT)
 
                                    {
 
                                        MouseUp (ev.button);
 
                                    }
 
                                }
 
                                else
 
                                    if (ev.type ==Sdl.SDL_VIDEORESIZE)
 
                                    {
 
                                    }
 
                                    else
 
                                        if (ev.type ==Sdl.SDL_QUIT)
 
                                        {
 
                                            quit = true;
 
                                            break;
 
                                        }
 
                    }
 
                }

在处理SDL的事件有两种模式，一种是等待 SDL_WaitEvent,另一种是轮询SDL_PollEvent

目前，在网上可以查到的文章，大多数都使用了轮询，还有人指出等待有时会导致事件处理延迟。但是我在实际coding中，使用SDL_PollEvent，一运行就风扇不停的转，用top看了下，cpu占用到了99%。

实际上，使用wait已经足够，我不大清楚这种轮询机制在什么时候会用到。

以下是一个SDL_PollEvent的原型。分析一下这段程序：

在while(quit!=1)这个循环中，如果没有发生任何事件，quit始终为0,那么在用户没有任何操作的情况下，这里会无限循环，直到event发生，进入了SDL_PollEvent的循环中。

这就导致了cpu占用率达到了100%. 因此，这种方法是不可取的。

在外层有循环时，SDL_PollEvent论询是不能用的。如果单独使用，用户无操作的时候，又无法进入处理事件的部分。实在不能明白它有什么用。

我考虑是不是这个应该用在非实时处理的时候，比如while(quit!=1)循环中嵌入一个sleep(1)之类。

void WaitKeyboard(SubWin sw){
 
    int quit = ;
 
    SDL_Event event;
 
    KEYBOARDMODE kmode = COMMAND;
 
    while(quit!=){
 
        //        printf ( "waiting for keyboard action\n" );
 
     while( SDL_PollEvent(&event)){
 
        printf ( "WaitKeyboard: caught keyboard %x\n", event.key.keysym.sym );
 
        switch (event.type){
 
            case SDL_KEYDOWN:
 
                printf ( "tracking keydown\n" );
 
                kmode = TrackKeyDown(sw, event.key.keysym.sym, kmode);
 
                break;
 
            case SDL_QUIT:
 
                printf("Stop !\n");
 
                quit = ;
 
                break;
 
        }
 
          }
 
    }
 
    endSDL();
 
}

接下来是SDL_WaitEvent的原型

在while(quit!=1)的循环中，由于SDL_WaitEvent语句，在用户未发生任何操作前，程序处于等待状态，不会进入下一次循环，这样就避免了cpu占用的问题。

这样的做法才是正确处理SDL事件的方法。

void WaitKeyboard(SubWin sw){
 
    int quit = ;
 
    SDL_Event event;
 
    KEYBOARDMODE kmode = COMMAND;
 
    while(quit!=){
 
        //        printf ( "waiting for keyboard action\n" );
 
        //        while( SDL_PollEvent(&event)){
 
        SDL_WaitEvent(&event);
 
        printf ( "WaitKeyboard: caught keyboard %x\n", event.key.keysym.sym );
 
        switch (event.type){
 
            case SDL_KEYDOWN:
 
                printf ( "tracking keydown\n" );
 
                kmode = TrackKeyDown(sw, event.key.keysym.sym, kmode);
 
                break;
 
            case SDL_QUIT:
 
                printf("stop !\n");
 
                quit = ;
 
                break;
 
        }
 
    }
 
    endSDL();
 
}

http://blog.chinaunix.net/uid-26456800-id-3337795.html