Question

I have been trying to use follow scroll to move dialog together with user scroll but no success

<script>
$(function() {
    $( "#dialog:ui-dialog" ).dialog( "destroy" );
    $( "#dialog-report-problem-form" ).dialog({
        autoOpen: true,
        height: 550,
        width: 700,
        modal: true,
        buttons: {
            "<?= $this->translate('REPORT_PROBLEM'); ?>": function() {
                reportProblem();
            },
            "<?= $this->translate('CANCEL'); ?>": function() {
                $( this ).dialog( "close" );
            }
        },
        close: function() {
        }
    });
    $.scrollFollow("#dialog-report-problem-form",{speed: 10}); 
});
</script>

.

<div id="dialog-report-problem-form" title="<?= $this->translate('REPORT_PROBLEM'); ?>">
    <?= $this->form ?>
</div>

I have been receiving the error

 box.cont.offset() is null

Does anyone knows how could fix or another jquery based solution to follow user scroll?

Answer 1

The plugin scrollFollow seems to be pretty buggy and development discontinued (last update in 2008)

• when you use it with $.scrollFollow(), the default option values are not set so you get a lot of errors like the one you got.
• when using it with $(...).scrollFollow, the main option container is not obtained correctly so it does not really work…

Here is a small script that will move the dialog around when the window is scrolled:

(function(wnd, $) {

        // query for elements once
    var $dlg = $("#dialog-report-problem-form").parent(),
        $wnd = $(wnd),
        // get the initial position of dialog
        initialTop = $dlg.offset().top - $wnd.scrollTop();

    $wnd.scroll(function() {
            // when qscrolling, animate the 'top' property
            $dlg.stop()
                .animate({
                    "top": ($wnd.scrollTop() + initialTop) + "px"
                }, "slow");
        })
        .resize(function() {
            // in case of resize, re-set the initial top position of the dialog
            initialTop =  $dlg.offset().top - $wnd.scrollTop();
        });

    // if you close/open the dialog, it will mess up the 'initialTop'
    // this will re-set the correct 'initialTop' when the dialog opens again
    $dlg.bind('dialogcreate dialogopen', function(e) {
        initialTop = $dlg.offset().top - $wnd.scrollTop();
    });

})(window, jQuery);

Working example on jsfiddle.