static/ext/src/ux/form/field/ClearButton.js
function() {
            if (this.hideClearButtonWhenEmpty && Ext.isEmpty(this.textField.getValue())) {
                return false;
            }

            var clearButtonEl = this.clearButtonEl;
            //noinspection RedundantIfStatementJS
            if (this.hideClearButtonWhenMouseOut
                && !clearButtonEl.hasCls(this.clearButtonCls + '-mouse-over-button')
                && !clearButtonEl.hasCls(this.clearButtonCls + '-mouse-over-input')) {
                return false;
            }

            return true;
        }
function() {
            if (this.hideClearButtonWhenEmpty && Ext.isEmpty(this.textField.getValue())) {
                return false;
            }

            var clearButtonEl = this.clearButtonEl;
            //noinspection RedundantIfStatementJS
            if (this.hideClearButtonWhenMouseOut
                && !clearButtonEl.hasCls(this.clearButtonCls + '-mouse-over-button')
                && !clearButtonEl.hasCls(this.clearButtonCls + '-mouse-over-input')) {
                return false;
            }

            return true;
        }
Checks config options and current mouse status to determine if the clear button should be visible.