在键盘输入期间测试活动标志

Question

我正在使用 SDL2 轮询事件并将键盘按下转发给游戏对象。我从 SDL_KEYDOWN 事件类型传入 SDL_KeyBoardEvent 变量。我似乎无法理解如何管理在输入过程中按住修饰键的情况。

我比较了 MODK_Keys 枚举和 SDL_KeyBoardEvent 的 key.keysym.mod 值，它似乎不应该进入顶部 if 循环，但确实如此。如果我只按住 shift 并按任何键，如 a，输出是第一个 if 语句中的意外输出。它显示

1 0
Ctrl + Alt + Shift + 97

这个( key.keysym.mod & ( KMOD_LCTRL | KMOD_RCTRL ) )在输出的时候等于0，但是是通过逻辑表达式吗？下面是 if 语句

void KeyDown(SDL_KeyboardEvent key) {

    if( !( key.keysym.sym == SDLK_LSHIFT || key.keysym.sym == SDLK_RSHIFT || key.keysym.sym == SDLK_LCTRL || key.keysym.sym == SDLK_RCTRL || key.keysym.sym == SDLK_LALT || key.keysym.sym == SDLK_RALT )) {

        if( ( key.keysym.mod & ( KMOD_LSHIFT | KMOD_RSHIFT ) > 0 ) && ( key.keysym.mod & ( KMOD_LCTRL | KMOD_RCTRL ) > 0 ) && ( key.keysym.mod & ( KMOD_LALT | KMOD_RALT )  > 0  )) {
            std::cout << ( key.keysym.mod & ( KMOD_LSHIFT | KMOD_RSHIFT ) ) << " " << ( key.keysym.mod & ( KMOD_LCTRL | KMOD_RCTRL ) ) << std::endl;
            std::cout << "Ctrl + Alt + Shift + " << key.keysym.sym  << std::endl;
        }
        else if ( ( key.keysym.mod & ( KMOD_LSHIFT |  KMOD_RSHIFT ) > 0 ) && ( key.keysym.mod & ( KMOD_LCTRL | KMOD_RCTRL ) > 0 )) {
            std::cout << "Shift + Ctrl + " << key.keysym.sym << std::endl;
        }
        else if ( ( key.keysym.mod & ( KMOD_LSHIFT |  KMOD_RSHIFT ) > 0 ) && ( key.keysym.mod & ( KMOD_LALT | KMOD_RALT )  > 0 )) {
            std::cout << "Shift + Alt + " << key.keysym.sym << std::endl;
        }
        else if ( ( key.keysym.mod & ( KMOD_LCTRL | KMOD_RCTRL ) > 0 ) && ( key.keysym.mod & ( KMOD_LALT | KMOD_RALT )  > 0 )) {
            std::cout << "Ctrl + Alt + " << key.keysym.sym << std::endl;
        }
        else if ( key.keysym.mod & ( KMOD_LSHIFT |  KMOD_RSHIFT ) > 0 ) {
            std::cout << "Shift + " << key.keysym.sym << std::endl;
        }
        else if ( key.keysym.mod & ( KMOD_LALT | KMOD_RALT ) > 0 ) {
            std::cout << "Alt + " << key.keysym.sym << std::endl;
        }
        else if ( key.keysym.mod & ( KMOD_LCTRL | KMOD_RCTRL ) > 0 ) {
            std::cout << "Ctrl + " << key.keysym.sym << std::endl;
        }
        else {
            std::cout << "Unmodded " << key.keysym.sym << " MODS: " << key.keysym.mod << std::endl;
        }

    }
}

Answer 1

睡在上面并尝试了一件不同的事情。显然我的操作顺序有误。

使以下开关起作用（更改所有表达式）

( key.keysym.mod & ( KMOD_LSHIFT | KMOD_RSHIFT ) > 0 )

(( key.keysym.mod & ( KMOD_LSHIFT | KMOD_RSHIFT )) > 0 )

有效的函数是

void KeyDown(SDL_KeyboardEvent key) {

    if( !( key.keysym.sym == SDLK_LSHIFT || key.keysym.sym == SDLK_RSHIFT || key.keysym.sym == SDLK_LCTRL || key.keysym.sym == SDLK_RCTRL || key.keysym.sym == SDLK_LALT || key.keysym.sym == SDLK_RALT )) {

        if( (( key.keysym.mod & ( KMOD_LSHIFT | KMOD_RSHIFT )) > 0 ) && (( key.keysym.mod & ( KMOD_LCTRL | KMOD_RCTRL )) > 0 ) && (( key.keysym.mod & ( KMOD_LALT | KMOD_RALT ))  > 0  )) {
            std::cout << "Ctrl + Alt + Shift + " << key.keysym.sym  << std::endl;
        }
        else if ( (( key.keysym.mod & ( KMOD_LSHIFT |  KMOD_RSHIFT )) > 0 ) && (( key.keysym.mod & ( KMOD_LCTRL | KMOD_RCTRL )) > 0 )) {
            std::cout << "Shift + Ctrl + " << key.keysym.sym << std::endl;
        }
        else if ( (( key.keysym.mod & ( KMOD_LSHIFT |  KMOD_RSHIFT )) > 0 ) && (( key.keysym.mod & ( KMOD_LALT | KMOD_RALT ))  > 0 )) {
            std::cout << "Shift + Alt + " << key.keysym.sym << std::endl;
        }
        else if ( (( key.keysym.mod & ( KMOD_LCTRL | KMOD_RCTRL )) > 0 ) && (( key.keysym.mod & ( KMOD_LALT | KMOD_RALT ))  > 0 )) {
            std::cout << "Ctrl + Alt + " << key.keysym.sym << std::endl;
        }
        else if (( key.keysym.mod & ( KMOD_LSHIFT |  KMOD_RSHIFT )) > 0 ) {
            std::cout << "Shift + " << key.keysym.sym << std::endl;
        }
        else if (( key.keysym.mod & ( KMOD_LALT | KMOD_RALT )) > 0 ) {
            std::cout << "Alt + " << key.keysym.sym << std::endl;
        }
        else if (( key.keysym.mod & ( KMOD_LCTRL | KMOD_RCTRL )) > 0 ) {
            std::cout << "Ctrl + " << key.keysym.sym << std::endl;
        }
        else {
            std::cout << "Unmodded " << key.keysym.sym << " MODS: " << key.keysym.mod << std::endl;
        }

    }
}

在键盘输入期间测试活动标志

Testing for active flags during keyboard input

c++

keyboard-events

sdl-2