FontListCombobox.html

<script>
    jQuery.widget( "custom.combobox", {
      _create: function() {
        this.wrapper = jQuery( "<span>" )
          .addClass( "custom-combobox" )
          .attr( "title", this.element.attr('title') )
          .insertAfter( this.element );
        this.element.hide();
        this._createAutocomplete();
        this._createShowAllButton();
      },
 
      _createAutocomplete: function() {
        var selected = this.element.children( ":selected" ),
            //thistitle = this.element.title,
            value = selected.val() ? selected.text() : "",
            $wrapper = this.wrapper;
        this.input = jQuery( "<input>" )
          .appendTo( this.wrapper )
          .val( value )
          //.attr( "title", thistitle )
          .addClass( "custom-combobox-input ui-widget ui-widget-content ui-corner-left" )
          .autocomplete({
            delay: 0,
            minLength: 0,
            source: jQuery.proxy( this, "_source" ),
            open: function(event, ui){
              let $btnwidth = $wrapper.find('.custom-combobox-toggle').length > 0 ? $wrapper.find('.custom-combobox-toggle').width() : 0; 
              $(this).autocomplete("widget").css({"width": (($wrapper.width() + $btnwidth) + "px")});
            }
          })
          .tooltip({
            classes: {
              "ui-tooltip": "ui-state-highlight"
            }
          });
          //input.width(getwid);
        this._on( this.input, {
          autocompleteselect: function( event, ui ) {
            ui.item.option.selected = true;
            this._trigger( "select", event, {
              item: ui.item.option
            });
            this.element.trigger("change");
          },
 
          autocompletechange: function( event, ui ) {
            this.element.val(this.input.val());
            this.element.trigger("change");
            this._removeIfInvalid(event,ui);
          }
        });
      },
 
      _createShowAllButton: function() {
        var input = this.input,
          wasOpen = false;
 
        jQuery( "<a>" )
          .attr( "tabIndex", -1 )
          .attr( "title", "Show All Items" )
          .tooltip()
          .appendTo( this.wrapper )
          .button({
            icons: {
              primary: "ui-icon-triangle-1-s"
            },
            text: false
          })
          .removeClass( "ui-corner-all" )
          .addClass( "custom-combobox-toggle ui-corner-right" )
          .on( "mousedown", function() {
            wasOpen = input.autocomplete( "widget" ).is( ":visible" );
          })
          .on( "click", function() {
            input.trigger( "focus" );
 
            // Close if already visible
            if ( wasOpen ) {
              return;
            }
 
            // Pass empty string as value to search for, displaying all results
            input.autocomplete( "search", "" );
          });
      },
 
      _source: function( request, response ) {
        var matcher = new RegExp( jQuery.ui.autocomplete.escapeRegex(request.term), "i" );
        response( this.element.children( "option" ).map(function() {
          var text = jQuery( this ).text();
          if ( this.value && ( !request.term || matcher.test(text) ) )
            return {
              label: text,
              value: text,
              option: this
            };
        }) ); //.slice(0, 15) applied to map() will limit results to 15
      },
 
      _removeIfInvalid: function( event, ui ) {
 
        // Selected an item, nothing to do
        if ( ui.item ) {
          return;
        }
 
        // Search for a match (case-insensitive)
        var value = this.input.val(),
          valueLowerCase = value.toLowerCase(),
          valid = false;
        this.element.children( "option" ).each(function() {
          if ( jQuery( this ).text().toLowerCase() === valueLowerCase ) {
            this.selected = valid = true;
            return false;
          }
        });
 
        // Found a match, nothing to do
        if ( valid ) {
          return;
        }
 
        // Remove invalid value
        this.input
          .val( "" )
          .attr( "title", value + " didn't match any item" )
          .tooltip( "open" );
        this.element.val( "" );
        this._delay(function() {
          this.input.tooltip( "close" ).attr( "title", "" );
        }, 2500 );
        this.input.autocomplete().term = "";
      },
 
      _destroy: function() {
        this.wrapper.remove();
        this.element.show();
      },
      widget: function() {
        return this.input;
      }
    });
</script>