db-lgtv-focus-engine/event/keydown.js

the Best TV focus engine

function throttle(fn, wait) {
    var pre = Date.now();
    return function () {
        var context = this;
        var args = arguments;
        var now = Date.now();
        if (now - pre >= wait) {
            fn.apply(context, args);
            pre = Date.now();
        }
    };
}

export function bindKeydownListener(focus_engine) {
    let throttle_key_down = throttle((e) => {
        focus_engine.last_key_down = e
        if (window['焦点框架-loading-加载中']) return
        let focused_leaf = focus_engine.findFocusedLeaf()
        if (!focused_leaf) return
        let code_enum = {}
        for (let key in focus_engine.options.KEYS) {
            for (let code of focus_engine.options.KEYS[key]) {
                code_enum[code] = key
            }
        }
        let _e = new Event("keydown")
        let _default = true
        _e.code = e.which
        _e.preventDefault = () => {
            _default = false
        }
        focused_leaf.el.dispatchEvent(_e)
        if (!_default) return
        if (!code_enum[e.which]) return
        e.preventDefault()
        switch (code_enum[e.which]) {
            case 'left':
            case 'right':
            case 'top':
            case 'bottom': {
                focused_leaf.el.dispatchEvent(new Event(code_enum[e.which]))
                let will_focus_leaf = focused_leaf[code_enum[e.which]]
                if (!will_focus_leaf) {
                    // 找不到邻居 => 重新定位 => 避免落焦误差
                    focus_engine.leaf_pool.forEach(leaf => leaf.rect = leaf.el.getBoundingClientRect())
                    focus_engine.trunk_pool.forEach(trunk => trunk.rect = trunk.el.getBoundingClientRect())
                    focused_leaf.findAllNeighbor()
                    will_focus_leaf = focused_leaf[code_enum[e.which]]
                    if (!will_focus_leaf) break
                }
                if (will_focus_leaf.parent && will_focus_leaf.parent !== focused_leaf.parent) {
                    if (will_focus_leaf.parent.cacheable && will_focus_leaf.parent.cache) {
                        // 若命中父元素缓存 则不需要聚焦叶子
                        will_focus_leaf.parent.cache.focus()
                    } else {
                        // 父元素无缓存
                        will_focus_leaf.focus()
                    }
                } else {
                    will_focus_leaf.focus()
                }
                break
            }
            case 'ok': {
                setTimeout(() => {
                    if (focus_engine.options.KEY_TYPE !== 'down') return
                    focused_leaf.ok()
                }, 0)
                break
            }
        }
    }, focus_engine.options.KEY_SPEED)
    document.onkeydown = throttle_key_down
}

export function unbindKeydownListener(focus_engine) {
    document.onkeydown = (e) => {}
}