zulip/frontend_tests/node_tests/scroll_util.js

zrequire('scroll_util');

(function test_scroll_delta() {
    // If we are entirely on-screen, don't scroll
    assert.equal(0, scroll_util.scroll_delta({
        elem_top: 1,
        elem_bottom: 9,
        container_height: 10,
    }));

    assert.equal(0, scroll_util.scroll_delta({
        elem_top: -5,
        elem_bottom: 15,
        container_height: 10,
    }));

    // The top is offscreen.
    assert.equal(-3, scroll_util.scroll_delta({
        elem_top: -3,
        elem_bottom: 5,
        container_height: 10,
    }));

    assert.equal(-3, scroll_util.scroll_delta({
        elem_top: -3,
        elem_bottom: -1,
        container_height: 10,
    }));

    assert.equal(-11, scroll_util.scroll_delta({
        elem_top: -150,
        elem_bottom: -1,
        container_height: 10,
    }));

    // The bottom is offscreen.
    assert.equal(3, scroll_util.scroll_delta({
        elem_top: 7,
        elem_bottom: 13,
        container_height: 10,
    }));

    assert.equal(3, scroll_util.scroll_delta({
        elem_top: 11,
        elem_bottom: 13,
        container_height: 10,
    }));

    assert.equal(11, scroll_util.scroll_delta({
        elem_top: 11,
        elem_bottom: 99,
        container_height: 10,
    }));

}());

(function test_scroll_element_into_container() {
    const container = (function () {
        var top = 3;
        return {
            height: () => 100,
            scrollTop: (arg) => {
                if (arg === undefined) {
                    return top;
                }
                top = arg;
            },
        };
    }());

    const elem1 = {
        height: () => 25,
        position: () => {
            return {
                top: 0,
            };
        },
    };
    scroll_util.scroll_element_into_container(elem1, container);
    assert.equal(container.scrollTop(), 3);

    const elem2 = {
        height: () => 15,
        position: () => {
            return {
                top: 250,
            };
        },
    };
    scroll_util.scroll_element_into_container(elem2, container);
    assert.equal(container.scrollTop(), 250 - 100 + 3 + 15);
}());