Map is inactive if parent is hidden

[brunodegoyrans]

Symptom: If the img/map is inside a hidden parent, for example in a bootstrap tab, then the map is not working when the parent becomes visible.

Cause: Plugin uses functions width() and height() that are known to mis-work if the parent is hidden. So the wPercent and hPercent have wrong value that might resize the map very small. Then the map seems inoperant.

var wPercent = $that.width()/100,
    hPercent = $that.height()/100,

Solution: Make parents visible just before calling width() then restore invisibility.

Modified code:

/*
* rwdImageMaps jQuery plugin v1.6.x
*
* Allows image maps to be used in a responsive design by recalculating the area coordinates to match the actual image size on load and window.resize
*
* Copyright (c) 2016 Matt Stow
* https://github.com/stowball/jQuery-rwdImageMaps
* http://mattstow.com
* Licensed under the MIT license
*/
;(function($) {
$.fn.rwdImageMaps = function() {
    var $img = this;

    var rwdImageMap = function() {

        $img.each(function() {
            if (typeof($(this).attr('usemap')) == 'undefined')
                return;

            var that = this,
                $that = $(that);

                // Since WebKit doesn't know the height until after the image has loaded, perform everything in an onload copy
            $('<img />').on('load', function() {

                // Modif BC : make ancestors visible so .width() can return the right value
                //************************************************
                var hidden_ancestors = [];
                $that.parents().each(function() {
                    if ($(this).css('display') == 'none')
                    {

                $(this).show();
                        hidden_ancestors.push($(this));
                    };
                });
                // END Modif BC

                var attrW = 'width',
                    attrH = 'height',
                    w = $that.attr(attrW),
                    h = $that.attr(attrH);

                if (!w || !h) {
                    var temp = new Image();
                    temp.src = $that.attr('src');
                    if (!w)
                        w = temp.width;
                    if (!h)
                        h = temp.height;
                }

                var wPercent = $that.width()/100,
                    hPercent = $that.height()/100,
                    map = $that.attr('usemap').replace('#', ''),
                    c = 'coords';

                $('map[name="' + map + '"]').find('area').each(function() {
                    var $this = $(this);
                    if (!$this.data(c))
                        $this.data(c, $this.attr(c));

                    var coords = $this.data(c).split(','),
                        coordsPercent = new Array(coords.length);

                    for (var i = 0; i < coordsPercent.length; ++i) {
                        if (i % 2 === 0)
                            coordsPercent[i] = parseInt(((coords[i]/w)*100)*wPercent);
                        else
                            coordsPercent[i] = parseInt(((coords[i]/h)*100)*hPercent);
                    }
                    $this.attr(c, coordsPercent.toString());
                });

                // Modif BC : Restore invisibility on ancestors
                //*********************************************
                jQuery.each(hidden_ancestors, function(index, value)
                {
                    $(value).css({display: ''});
                });
                // END Modif BC

            }).attr('src', $that.attr('src'));
        });
    };
    $(window).resize(rwdImageMap).trigger('resize');

    return this;
};
})(jQuery);

[kangTaehee]

w = $that.attr(attrW),h = $that.attr(attrH); ↓ w = $that[0].naturalWidth,h = $that[0].naturalHeight; I made this correction.

[abmultimedia]

I needed to change: $(value).css({display: ''}); ↓ $(value).css({display: 'none'});

...but I found this useful. Thanks!