+ * <p>Validates a value according to the field's validation rules and marks the field as invalid
+ * if the validation fails. Validation rules are processed in the following order:</p>
+ * <div class="mdetail-params"><ul>
+ *
+ * <li><b>1. Field specific validator</b>
+ * <div class="sub-desc">
+ * <p>A validator offers a way to customize and reuse a validation specification.
+ * If a field is configured with a <code>{@link #validator}</code>
+ * function, it will be passed the current field value. The <code>{@link #validator}</code>
+ * function is expected to return either:
+ * <div class="mdetail-params"><ul>
+ * <li>Boolean <tt>true</tt> if the value is valid (validation continues).</li>
+ * <li>a String to represent the invalid message if invalid (validation halts).</li>
+ * </ul></div>
+ * </div></li>
+ *
+ * <li><b>2. Basic Validation</b>
+ * <div class="sub-desc">
+ * <p>If the <code>{@link #validator}</code> has not halted validation,
+ * basic validation proceeds as follows:</p>
+ *
+ * <div class="mdetail-params"><ul>
+ *
+ * <li><code>{@link #allowBlank}</code> : (Invalid message =
+ * <code>{@link #emptyText}</code>)<div class="sub-desc">
+ * Depending on the configuration of <code>{@link #allowBlank}</code>, a
+ * blank field will cause validation to halt at this step and return
+ * Boolean true or false accordingly.
+ * </div></li>
+ *
+ * <li><code>{@link #minLength}</code> : (Invalid message =
+ * <code>{@link #minLengthText}</code>)<div class="sub-desc">
+ * If the passed value does not satisfy the <code>{@link #minLength}</code>
+ * specified, validation halts.
+ * </div></li>
+ *
+ * <li><code>{@link #maxLength}</code> : (Invalid message =
+ * <code>{@link #maxLengthText}</code>)<div class="sub-desc">
+ * If the passed value does not satisfy the <code>{@link #maxLength}</code>
+ * specified, validation halts.
+ * </div></li>
+ *
+ * </ul></div>
+ * </div></li>
+ *
+ * <li><b>3. Preconfigured Validation Types (VTypes)</b>
+ * <div class="sub-desc">
+ * <p>If none of the prior validation steps halts validation, a field
+ * configured with a <code>{@link #vtype}</code> will utilize the
+ * corresponding {@link Ext.form.VTypes VTypes} validation function.
+ * If invalid, either the field's <code>{@link #vtypeText}</code> or
+ * the VTypes vtype Text property will be used for the invalid message.
+ * Keystrokes on the field will be filtered according to the VTypes
+ * vtype Mask property.</p>
+ * </div></li>
+ *
+ * <li><b>4. Field specific regex test</b>
+ * <div class="sub-desc">
+ * <p>If none of the prior validation steps halts validation, a field's
+ * configured <code>{@link #regex}</code> test will be processed.
+ * The invalid message for this test is configured with
+ * <code>{@link #regexText}</code>.</p>
+ * </div></li>
+ *