想用SDL的按键检测，网上找了半天都没找到SDL中按键的值的定义，索性自己去看头文件，在SDL_keysym.h中。
其实很多键的值和它们的ASCII码是相同的。
其他更多的用法，可以参考这篇博客：http://blog.chinaunix.net/uid-28482676-id-3444915.html/
typedef enum {
/** @name ASCII mapped keysyms
* The keyboard syms have been cleverly chosen to map to ASCII
*/
/*@{*/
SDLK_UNKNOWN = ,
SDLK_FIRST = ,
SDLK_BACKSPACE = ,
SDLK_TAB = ,
SDLK_CLEAR = ,
SDLK_RETURN = ,
SDLK_PAUSE = ,
SDLK_ESCAPE = ,
SDLK_SPACE = ,
SDLK_EXCLAIM = ,
SDLK_QUOTEDBL = ,
SDLK_HASH = ,
SDLK_DOLLAR = ,
SDLK_AMPERSAND = ,
SDLK_QUOTE = ,
SDLK_LEFTPAREN = ,
SDLK_RIGHTPAREN = ,
SDLK_ASTERISK = ,
SDLK_PLUS = ,
SDLK_COMMA = ,
SDLK_MINUS = ,
SDLK_PERIOD = ,
SDLK_SLASH = ,
SDLK_0 = ,
SDLK_1 = ,
SDLK_2 = ,
SDLK_3 = ,
SDLK_4 = ,
SDLK_5 = ,
SDLK_6 = ,
SDLK_7 = ,
SDLK_8 = ,
SDLK_9 = ,
SDLK_COLON = ,
SDLK_SEMICOLON = ,
SDLK_LESS = ,
SDLK_EQUALS = ,
SDLK_GREATER = ,
SDLK_QUESTION = ,
SDLK_AT = ,
/*
Skip uppercase letters
*/
SDLK_LEFTBRACKET = ,
SDLK_BACKSLASH = ,
SDLK_RIGHTBRACKET = ,
SDLK_CARET = ,
SDLK_UNDERSCORE = ,
SDLK_BACKQUOTE = ,
SDLK_a = ,
SDLK_b = ,
SDLK_c = ,
SDLK_d = ,
SDLK_e = ,
SDLK_f = ,
SDLK_g = ,
SDLK_h = ,
SDLK_i = ,
SDLK_j = ,
SDLK_k = ,
SDLK_l = ,
SDLK_m = ,
SDLK_n = ,
SDLK_o = ,
SDLK_p = ,
SDLK_q = ,
SDLK_r = ,
SDLK_s = ,
SDLK_t = ,
SDLK_u = ,
SDLK_v = ,
SDLK_w = ,
SDLK_x = ,
SDLK_y = ,
SDLK_z = ,
SDLK_DELETE = ,
/* End of ASCII mapped keysyms */
/*@}*/ /** @name International keyboard syms */
/*@{*/
SDLK_WORLD_0 = , /* 0xA0 */
SDLK_WORLD_1 = ,
SDLK_WORLD_2 = ,
SDLK_WORLD_3 = ,
SDLK_WORLD_4 = ,
SDLK_WORLD_5 = ,
SDLK_WORLD_6 = ,
SDLK_WORLD_7 = ,
SDLK_WORLD_8 = ,
SDLK_WORLD_9 = ,
SDLK_WORLD_10 = ,
SDLK_WORLD_11 = ,
SDLK_WORLD_12 = ,
SDLK_WORLD_13 = ,
SDLK_WORLD_14 = ,
SDLK_WORLD_15 = ,
SDLK_WORLD_16 = ,
SDLK_WORLD_17 = ,
SDLK_WORLD_18 = ,
SDLK_WORLD_19 = ,
SDLK_WORLD_20 = ,
SDLK_WORLD_21 = ,
SDLK_WORLD_22 = ,
SDLK_WORLD_23 = ,
SDLK_WORLD_24 = ,
SDLK_WORLD_25 = ,
SDLK_WORLD_26 = ,
SDLK_WORLD_27 = ,
SDLK_WORLD_28 = ,
SDLK_WORLD_29 = ,
SDLK_WORLD_30 = ,
SDLK_WORLD_31 = ,
SDLK_WORLD_32 = ,
SDLK_WORLD_33 = ,
SDLK_WORLD_34 = ,
SDLK_WORLD_35 = ,
SDLK_WORLD_36 = ,
SDLK_WORLD_37 = ,
SDLK_WORLD_38 = ,
SDLK_WORLD_39 = ,
SDLK_WORLD_40 = ,
SDLK_WORLD_41 = ,
SDLK_WORLD_42 = ,
SDLK_WORLD_43 = ,
SDLK_WORLD_44 = ,
SDLK_WORLD_45 = ,
SDLK_WORLD_46 = ,
SDLK_WORLD_47 = ,
SDLK_WORLD_48 = ,
SDLK_WORLD_49 = ,
SDLK_WORLD_50 = ,
SDLK_WORLD_51 = ,
SDLK_WORLD_52 = ,
SDLK_WORLD_53 = ,
SDLK_WORLD_54 = ,
SDLK_WORLD_55 = ,
SDLK_WORLD_56 = ,
SDLK_WORLD_57 = ,
SDLK_WORLD_58 = ,
SDLK_WORLD_59 = ,
SDLK_WORLD_60 = ,
SDLK_WORLD_61 = ,
SDLK_WORLD_62 = ,
SDLK_WORLD_63 = ,
SDLK_WORLD_64 = ,
SDLK_WORLD_65 = ,
SDLK_WORLD_66 = ,
SDLK_WORLD_67 = ,
SDLK_WORLD_68 = ,
SDLK_WORLD_69 = ,
SDLK_WORLD_70 = ,
SDLK_WORLD_71 = ,
SDLK_WORLD_72 = ,
SDLK_WORLD_73 = ,
SDLK_WORLD_74 = ,
SDLK_WORLD_75 = ,
SDLK_WORLD_76 = ,
SDLK_WORLD_77 = ,
SDLK_WORLD_78 = ,
SDLK_WORLD_79 = ,
SDLK_WORLD_80 = ,
SDLK_WORLD_81 = ,
SDLK_WORLD_82 = ,
SDLK_WORLD_83 = ,
SDLK_WORLD_84 = ,
SDLK_WORLD_85 = ,
SDLK_WORLD_86 = ,
SDLK_WORLD_87 = ,
SDLK_WORLD_88 = ,
SDLK_WORLD_89 = ,
SDLK_WORLD_90 = ,
SDLK_WORLD_91 = ,
SDLK_WORLD_92 = ,
SDLK_WORLD_93 = ,
SDLK_WORLD_94 = ,
SDLK_WORLD_95 = , /* 0xFF */
/*@}*/ /** @name Numeric keypad */
/*@{*/
SDLK_KP0 = ,
SDLK_KP1 = ,
SDLK_KP2 = ,
SDLK_KP3 = ,
SDLK_KP4 = ,
SDLK_KP5 = ,
SDLK_KP6 = ,
SDLK_KP7 = ,
SDLK_KP8 = ,
SDLK_KP9 = ,
SDLK_KP_PERIOD = ,
SDLK_KP_DIVIDE = ,
SDLK_KP_MULTIPLY = ,
SDLK_KP_MINUS = ,
SDLK_KP_PLUS = ,
SDLK_KP_ENTER = ,
SDLK_KP_EQUALS = ,
/*@}*/ /** @name Arrows + Home/End pad */
/*@{*/
SDLK_UP = ,
SDLK_DOWN = ,
SDLK_RIGHT = ,
SDLK_LEFT = ,
SDLK_INSERT = ,
SDLK_HOME = ,
SDLK_END = ,
SDLK_PAGEUP = ,
SDLK_PAGEDOWN = ,
/*@}*/ /** @name Function keys */
/*@{*/
SDLK_F1 = ,
SDLK_F2 = ,
SDLK_F3 = ,
SDLK_F4 = ,
SDLK_F5 = ,
SDLK_F6 = ,
SDLK_F7 = ,
SDLK_F8 = ,
SDLK_F9 = ,
SDLK_F10 = ,
SDLK_F11 = ,
SDLK_F12 = ,
SDLK_F13 = ,
SDLK_F14 = ,
SDLK_F15 = ,
/*@}*/ /** @name Key state modifier keys */
/*@{*/
SDLK_NUMLOCK = ,
SDLK_CAPSLOCK = ,
SDLK_SCROLLOCK = ,
SDLK_RSHIFT = ,
SDLK_LSHIFT = ,
SDLK_RCTRL = ,
SDLK_LCTRL = ,
SDLK_RALT = ,
SDLK_LALT = ,
SDLK_RMETA = ,
SDLK_LMETA = ,
SDLK_LSUPER = , /**< Left "Windows" key */
SDLK_RSUPER = , /**< Right "Windows" key */
SDLK_MODE = , /**< "Alt Gr" key */
SDLK_COMPOSE = , /**< Multi-key compose key */
/*@}*/ /** @name Miscellaneous function keys */
/*@{*/
SDLK_HELP = ,
SDLK_PRINT = ,
SDLK_SYSREQ = ,
SDLK_BREAK = ,
SDLK_MENU = ,
SDLK_POWER = , /**< Power Macintosh power key */
SDLK_EURO = , /**< Some european keyboards */
SDLK_UNDO = , /**< Atari keyboard has Undo */
/*@}*/ /* Add any other keys here */ SDLK_LAST
} SDLKey;
