WhyCan Forum(哇酷开发者社区)

    while(1) {
        /* Periodically call the lv_task handler.
         * It could be done in a timer interrupt or an OS task too.*/
        lv_task_handler();

        usleep(5 * 1000);       /*Just to let the system breath*/

        #ifdef SDL_APPLE
            SDL_Event event;
            
            while(SDL_PollEvent(&event)) {
                #if USE_MOUSE != 0
                    mouse_handler(&event);
                #endif

                #if USE_KEYBOARD
                    keyboard_handler(&event);
                #endif

                #if USE_MOUSEWHEEL != 0
                    mousewheel_handler(&event);
                #endif
            }
        #endif

    }

bool keyboard_read(lv_indev_data_t * data)
{
    data->state = state;
    data->key = keycode_to_ascii(last_key);

    return false;       /*No more data to read so return false*/
}

void keyboard_handler(SDL_Event * event)
{
    /* We only care about SDL_KEYDOWN and SDL_KEYUP events */
    switch(event->type) {
        case SDL_KEYDOWN:                       /*Button press*/
            last_key = event->key.keysym.sym;   /*Save the pressed key*/
            state = LV_INDEV_STATE_PR;          /*Save the key is pressed now*/
            break;
        case SDL_KEYUP:                         /*Button release*/
            state = LV_INDEV_STATE_REL;         /*Save the key is released but keep the last key*/
            break;
        default:
            break;

    }
}

static uint32_t keycode_to_ascii(uint32_t sdl_key)
{
    /*Remap some key to LV_GROUP_KEY_... to manage groups*/
    switch(sdl_key) {
        case SDLK_RIGHT:
        case SDLK_KP_PLUS:
            return LV_GROUP_KEY_RIGHT;

        case SDLK_LEFT:
        case SDLK_KP_MINUS:
            return LV_GROUP_KEY_LEFT;

        case SDLK_UP:
            return LV_GROUP_KEY_UP;

        case SDLK_DOWN:
            return LV_GROUP_KEY_DOWN;

        case SDLK_ESCAPE:
            return LV_GROUP_KEY_ESC;

#ifdef  LV_GROUP_KEY_BACKSPACE        /*For backward compatibility*/
        case SDLK_BACKSPACE:
            return LV_GROUP_KEY_BACKSPACE;
#endif

#ifdef  LV_GROUP_KEY_DEL        /*For backward compatibility*/
        case SDLK_DELETE:
            return LV_GROUP_KEY_DEL;
#endif
        case SDLK_KP_ENTER:
        case '\r':
            return LV_GROUP_KEY_ENTER;

        default:
            return sdl_key;
    }
}

 
# Line892 @matplotlib/_init_.py
class RcParams(MutableMapping, dict):
    ...
    def __getitem__(self, key):
        ...
       elif key == "backend":
            val = dict.__getitem__(self, key)
            if val is rcsetup._auto_backend_sentinel:
                from matplotlib import pyplot as plt
                plt.switch_backend(rcsetup._auto_backend_sentinel)

# Line177 @matplotlib/pyplot.py
def switch_backend(newbackend):
    """
    Close all open figures and set the Matplotlib backend.

    The argument is case-insensitive.  Switching to an interactive backend is
    possible only if no event loop for another interactive backend has started.
    Switching to and from non-interactive backends is always possible.

    Parameters
    ----------
    newbackend : str
        The name of the backend to use.
    """
    close("all")

    if newbackend is rcsetup._auto_backend_sentinel:
        for candidate in ["macosx", "qt5agg", "qt4agg", "gtk3agg", "gtk3cairo",
                          "tkagg", "wxagg", "agg", "cairo"]:
            try:
                switch_backend(candidate)
            except ImportError:
                continue
            else:
                rcParamsOrig['backend'] = candidate
                return
    ....