devextreme/dist/transpiled/ui/scroll_view/ui.scroll_view.native.slide_down.js

HTML5 JavaScript Component Suite for Responsive Web Development

"use strict";

var Callbacks = require("../../core/utils/callbacks"),
    NativeStrategy = require("./ui.scrollable.native"),
    Deferred = require("../../core/utils/deferred").Deferred;

var STATE_RELEASED = 0,
    STATE_READY = 1,
    STATE_LOADING = 2,
    LOADING_HEIGHT = 80;

var SlideDownNativeScrollViewStrategy = NativeStrategy.inherit({

    _init: function _init(scrollView) {
        this.callBase(scrollView);
        this._$topPocket = scrollView._$topPocket;
        this._$bottomPocket = scrollView._$bottomPocket;

        this._initCallbacks();
    },

    _initCallbacks: function _initCallbacks() {
        this.pullDownCallbacks = Callbacks();
        this.releaseCallbacks = Callbacks();
        this.reachBottomCallbacks = Callbacks();
    },

    render: function render() {
        this.callBase();
        this._renderPullDown();
        this._renderBottom();
        this._releaseState();
        this._updateDimensions();
    },

    _renderPullDown: function _renderPullDown() {
        this._$topPocket.empty();
    },

    _renderBottom: function _renderBottom() {
        this._$bottomPocket.empty().append("<progress>");
    },

    _releaseState: function _releaseState() {
        if (this._state === STATE_RELEASED) {
            return;
        }

        this._state = STATE_RELEASED;
    },

    _updateDimensions: function _updateDimensions() {
        this._scrollOffset = this._$container.prop("scrollHeight") - this._$container.prop("clientHeight");
        this._containerSize = {
            height: this._$container.prop("clientHeight"),
            width: this._$container.prop("clientWidth")
        };
        this._contentSize = this._componentContentSize = {
            height: this._$container.prop("scrollHeight"),
            width: this._$container.prop("scrollWidth")
        };
    },

    handleScroll: function handleScroll(e) {
        this.callBase(e);
        if (this._isReachBottom(this._lastLocation.top)) {
            this._reachBottom();
        }
    },

    _isReachBottom: function _isReachBottom(location) {
        this._scrollContent = this._$container.prop("scrollHeight") - this._$container.prop("clientHeight");
        return this._reachBottomEnabled && location < -this._scrollContent + LOADING_HEIGHT;
    },

    _reachBottom: function _reachBottom() {
        if (this._state === STATE_LOADING) {
            return;
        }
        this._state = STATE_LOADING;
        this.reachBottomCallbacks.fire();
    },

    pullDownEnable: function pullDownEnable(enabled) {
        this._pullDownEnabled = enabled;
    },

    reachBottomEnable: function reachBottomEnable(enabled) {
        this._reachBottomEnabled = enabled;
        this._$bottomPocket.toggle(enabled);
    },

    pendingRelease: function pendingRelease() {
        this._state = STATE_READY;
    },

    release: function release() {
        var deferred = new Deferred();

        this._state = STATE_RELEASED;
        this.releaseCallbacks.fire();
        this.update();

        return deferred.resolve().promise();
    }
});

module.exports = SlideDownNativeScrollViewStrategy;