added Form::beforeRender()

Author: dg

src/Bridges/FormsLatte/Runtime.php

@@ -26,6 +26,7 @@ class Runtime
 	 */
 	public static function renderFormBegin(Form $form, array $attrs, $withTags = TRUE)
 	{
+		$form->beforeRender();
 		foreach ($form->getControls() as $control) {
 			$control->setOption('rendered', FALSE);
 		}

src/Forms/Form.php

@@ -578,6 +578,15 @@ public function getRenderer()
 	}
 
 
+	/**
+	 * Must be called before form is rendered.
+	 * @return void
+	 */
+	public function beforeRender()
+	{
+	}
+
+
 	/**
 	 * Renders form.
 	 * @return void
@@ -587,6 +596,7 @@ public function render(...$args)
 		if ($args) {
 			trigger_error('Arguments in ' . __METHOD__ . ' are deprecated.', E_USER_DEPRECATED);
 		}
+		$this->beforeRender();
 		echo $this->getRenderer()->render($this, ...$args);
 	}