Fix update event when hide/show element

[Indigo744]

I identified a regression with both PR #87 and #85
Function createLegends() shall be called only if new legends elements are given.
Otherwise, it is not possible to use the opt.setLegendElemsState option (since legend is always redrawn).

[neveldo]

Hello,

I agree that createLegends() should be called only if new legends elements are given in the parameter, and that the "update legends" part should be surrounded by the condition :

if (typeof updatedOptions != "undefined" && typeof updatedOptions.legend === "object") {

But, regarding the 'setLegendElemsState' behaviour :

            // Set showlegendElems variable
            // If not defined, or badly defined, revert to TRUE
            if (typeof opt != "undefined" && typeof opt.setLegendElemsState === "string") {
                showlegendElems = (opt.setLegendElemsState === "hide") ? false : true;
            }

            // Hide/Show all elements based on showlegendElems
            //      Toggle (i.e. click) only if:
            //          - slice legend is shown AND we want to hide
            //          - slice legend is hidden AND we want to show
            $("[data-type='elem']", $(this)).each(function() {
                if (($(this).attr('data-hidden') === "0" && showlegendElems === false) || 
                    ($(this).attr('data-hidden') === "1" && showlegendElems === true)) {
                    // Toggle state of element by clicking
                    $(this).trigger('click', false);
                }
            });

Why not simply move this part of code at the end of the event ? It will allow users to update map legends AND to initialize them with a hidden state at the same time. And it will be unnecessary to check for "updateLegend === false" in order to change the legend elements state. What do you think about it ?

[Indigo744]

Really good idea! I was so focus on putting this call at the beginning, I forgot I could just move it around :-)

[neveldo]

Thank you for the code update, I merge your pull request !