SDL学习笔记(2)——事件处理

SDL事件是诸如按键，鼠标移动，操纵按钮按下之类的东西。

在内部，SDL将所有等待处理的事件存储在事件队列中。首选方式是使用SDL_PollEvent()接收系统事件。它可以从主循环完成，并且在等待事件发布时不会挂起主循环。如果队列上没有事件，则返回0，否则返回1。

1. 定义是否退出的标志isQuit初始值设置为0，表示不退出。
2. 我们使用while循环依次处理每个事件，直到遇到SDL_QUIT事件，退出循环结束进程。

int isQuit = 0;
while (!isQuit) {
	SDL_PollEvent(&test_event)
	switch (test_event.type) {
	    case SDL_QUIT:
	    	isQuit = 1;
			printf("We got a quit event.\n");
			break;
		default:
	      	//printf("Unhandled Event!\n");
	      	break;
	}
}
printf("Event queue empty.\n");

除了从SDL中取事件外，我们也可以自定义事件，放到时间处理队列中。

SDL_Event user_event;

user_event.type = SDL_USEREVENT;
user_event.user.code = 2;
user_event.user.data1 = NULL;
user_event.user.data2 = NULL;
SDL_PushEvent(&user_event);

SDL_Event是SDL中使用的所有事件结构的并集。 使用它很简单，只需知道哪种事件类型对应于哪个联合成员即可。 下表列出了这些关系

Event Type	Event Structure	SDL_Event Field
SDL_AUDIODEVICEADDED SDL_AUDIODEVICEREMOVED	SDL_AudioDeviceEvent	adevice
SDL_CONTROLLERAXISMOTION	SDL_ControllerAxisEvent	caxis
SDL_CONTROLLERBUTTONDOWN SDL_CONTROLLERBUTTONUP	SDL_ControllerButtonEvent	cbutton
SDL_CONTROLLERDEVICEADDED SDL_CONTROLLERDEVICEREMOVED SDL_CONTROLLERDEVICEREMAPPED	SDL_ControllerDeviceEvent	cdevice
SDL_DOLLARGESTURE SDL_DOLLARRECORD	SDL_DollarGestureEvent	dgesture
SDL_DROPFILE SDL_DROPTEXT SDL_DROPBEGIN SDL_DROPCOMPLETE	SDL_DropEvent	drop
SDL_FINGERMOTION SDL_FINGERDOWN SDL_FINGERUP	SDL_TouchFingerEvent	tfinger
SDL_KEYDOWN SDL_KEYUP	SDL_KeyboardEvent	key
SDL_JOYAXISMOTION	SDL_JoyAxisEvent	jaxis
SDL_JOYBALLMOTION	SDL_JoyBallEvent	jball
SDL_JOYHATMOTION	SDL_JoyHatEvent	jhat
SDL_JOYBUTTONDOWN SDL_JOYBUTTONUP	SDL_JoyButtonEvent	jbutton
SDL_JOYDEVICEADDED SDL_JOYDEVICEREMOVED	SDL_JoyDeviceEvent	jdevice
SDL_MOUSEMOTION	SDL_MouseMotionEvent	motion
SDL_MOUSEBUTTONDOWN SDL_MOUSEBUTTONUP	SDL_MouseButtonEvent	button
SDL_MOUSEWHEEL	SDL_MouseWheelEvent	wheel
SDL_MULTIGESTURE	SDL_MultiGestureEvent	mgesture
SDL_QUIT	SDL_QuitEvent	quit
SDL_SYSWMEVENT	SDL_SysWMEvent	syswm
SDL_TEXTEDITING	SDL_TextEditingEvent	edit
SDL_TEXTINPUT	SDL_TextInputEvent	text
SDL_USEREVENT	SDL_UserEvent	user
SDL_WINDOWEVENT	SDL_WindowEvent	window
Other events	SDL_CommonEvent	none, use .type