Index: modules/field/modules/text/text.js
===================================================================
RCS file: modules/field/modules/text/text.js
diff -N modules/field/modules/text/text.js
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ modules/field/modules/text/text.js	16 Aug 2009 22:51:30 -0000
@@ -0,0 +1,69 @@
+// $Id$
+
+(function ($) {
+
+/**
+ * Auto-hide summary textarea if empty and show hide and unhide links.
+ */
+Drupal.behaviors.textareaSummary = {
+  attach: function (context, settings) {
+    $('textarea.text-textarea-summary:not(.text-textarea-summary-processed)', context).addClass('text-textarea-summary-processed').each(function () {
+      var $fieldset = $(this).closest('fieldset');
+      var $div = $(this).closest('div.text-summary-wrapper');
+
+      // If no summary is set, hide the summary field.
+      if ($(this).val() == '') {
+        $div.hide();
+        // If the 'edit summary' link is present, just display it.
+        if ($fieldset.find('div.text-full-wrapper').prev('label > span.field-edit-link').length) {
+          $fieldset.find('div.text-full-wrapper span.field-edit-link').show();
+        }
+        // Otherwise append the link and configure the click event action.
+        else {
+          $fieldset.find('div.text-full-wrapper div.form-item-textarea label').append($('<span class="field-edit-link">(<a class="link-edit-summary" href="#">' + Drupal.t('Edit summary') + '</a>)</span>')).end().find('a.link-edit-summary').click(function () {
+            $fieldset.find('div.text-summary-wrapper').show().end().find('label span.field-edit-link').hide();
+            var $edit_link = $fieldset.find('div.text-summary-wrapper span.field-edit-link');
+            if ($edit_link.length) {
+              $edit_link.show();
+            }
+            else {
+              $fieldset.find('div.text-summary-wrapper div.form-item-textarea label').append($('<span class="field-edit-link">(<a class="link-hide-summary" href="#">' + Drupal.t('Hide summary') + '</a>)</span>')).end().find('a.link-hide-summary').click(function () {
+                $fieldset.find('label span.field-edit-link').show();
+                $div.hide();
+                return false;
+              });
+            }
+            return false;
+          });
+        }
+      }
+      // If there is a summary set, don't hide the summary field.
+      else {
+        // If the 'hide summary' link is present, just display it.
+        if ($div.prev('label > span.field-edit-link').length) {
+          $div.prev('label > span.field-edit-link').show();
+        }
+        // Otherwise append the link and configure the click event action.
+        else {
+          $fieldset.find('div.text-summary-wrapper div.form-item-textarea label').append($('<span class="field-edit-link">(<a class="link-hide-summary field-edit-link" href="#">' + Drupal.t('Hide summary') + '</a>)</span>')).end().find('a.link-hide-summary').click(function () {
+            var $edit_link = $fieldset.find('div.text-full-wrapper span.field-edit-link');
+            if ($edit_link.length) {
+              $edit_link.show();
+            }
+            else {
+              $fieldset.find('div.text-full-wrapper div.form-item-textarea label').append($('<span class="field-edit-link">(<a class="link-edit-summary field-edit-link" href="#">' + Drupal.t('Edit summary') + '</a>)</span>')).end().find('a.link-edit-summary').click(function () {
+                $fieldset.find('div.text-full-wrapper').find('label span.field-edit-link').hide().end().end().find('div.text-summary-wrapper').show();;
+                return false;
+              });
+            }
+            $div.hide();
+            return false;
+          });
+        }
+      }
+    });
+  }
+};
+
+})(jQuery);
+
Index: modules/field/modules/text/text.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/field/modules/text/text.module,v
retrieving revision 1.17
diff -u -p -r1.17 text.module
--- modules/field/modules/text/text.module	4 Aug 2009 06:38:56 -0000	1.17
+++ modules/field/modules/text/text.module	16 Aug 2009 22:51:31 -0000
@@ -664,6 +664,10 @@ function text_textarea_with_summary_proc
     '#description' => t('Leave blank to use trimmed value of full text as the summary.'),
     '#required' => $element['#required'],
     '#display' => $display,
+    '#attached_js' => array(drupal_get_path('module', 'text') . '/text.js'), 
+    '#attributes' => array('class' => 'text-textarea-summary'),
+    '#prefix' => '<div class="text-summary-wrapper">',
+    '#suffix' => '</div>',
   );
 
   $field_key = $element['#columns'][0];
@@ -676,6 +680,9 @@ function text_textarea_with_summary_proc
     '#description' => $element['#description'],
     '#required' => $element['#required'],
     '#required' => $instance['required'],
+    '#attributes' => array('class' => 'text-full-textarea'),
+    '#prefix' => '<div class="text-full-wrapper">',
+    '#suffix' => '</div>',
   );
 
   if (!empty($instance['settings']['text_processing'])) {