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	15 Aug 2009 00:33:14 -0000
@@ -0,0 +1,62 @@
+// $Id$
+
+(function ($) {
+
+Drupal.behaviors.bodySummary = {
+  attach: function () {
+    // If summary does not contains text or the text equals the body value (at least the beginning of it).
+    $('textarea.summary-textarea').each(function () { 
+      if ($(this).val() === '') {
+        $(this).closest('div.summary-wrapper').hide();
+        if ($(this).closest('fieldset').find('div.full-text-wrapper').prev('label > span.field-edit-link').size()) {
+          $(this).closest('fieldset').find('div.full-text-wrapper span.field-edit-link').show();
+        }
+        else {
+          $(this).closest('fieldset').find('div.full-text-wrapper div.form-item-textarea label').append($('<span class="field-edit-link">(<a class="link-edit-summary" href="#">' + Drupal.t('Edit summary') + '</a>)</span>'));
+          $(this).closest('fieldset').find('a.link-edit-summary').click(function () {
+            $(this).closest('fieldset').find('div.summary-wrapper').show();
+            $(this).closest('fieldset').find('label span.field-edit-link').hide();
+            if ($(this).closest('fieldset').find('div.summary-wrapper span.field-edit-link').size()) {
+              $(this).closest('fieldset').find('div.summary-wrapper span.field-edit-link').show();
+            }
+            else {
+              $(this).closest('fieldset').find('div.summary-wrapper div.form-item-textarea label').append($('<span class="field-edit-link">(<a class="link-hide-summary" href="#">' + Drupal.t('Hide summary') + '</a>)</span>'));
+              $(this).closest('fieldset').find('a.link-hide-summary').click(function () {
+                $(this).closest('fieldset').find('label span.field-edit-link').show();
+                $(this).closest('div.summary-wrapper').hide();
+                return false;
+              });
+            }
+            return false;
+          });
+        }
+      }
+      else {
+        if ($(this).closest('div.summary-wrapper').prev('label > span.field-edit-link').size()) {
+          $(this).closest('div.summary-wrapper').prev('label > span.field-edit-link').show();
+        }
+        else {
+          $(this).closest('fieldset').find('div.summary-wrapper div.form-item-textarea label').append($('<span class="field-edit-link">(<a class="link-hide-summary field-edit-link" href="#">' + Drupal.t('Hide summary') + '</a>)</span>'));
+          $(this).closest('fieldset').find('a.link-hide-summary').click(function () {
+            if ($(this).closest('fieldset').find('div.full-text-wrapper span.field-edit-link').size()) {
+              $(this).closest('fieldset').find('div.full-text-wrapper span.field-edit-link').show();
+            }
+            else {
+              $(this).closest('fieldset').find('div.full-text-wrapper div.form-item-textarea label').append($('<span class="field-edit-link">(<a class="link-edit-summary field-edit-link" href="#">' + Drupal.t('Edit summary') + '</a>)</span>'));
+              $(this).closest('fieldset').find('a.link-edit-summary').click(function () {
+                $(this).closest('fieldset').find('div.full-text-wrapper').find('label span.field-edit-link').hide();
+                $(this).closest('fieldset').find('div.summary-wrapper').show();
+                return false;
+              });
+            }
+            $(this).parents('div.summary-wrapper').hide();
+            return false;
+          });
+        }
+      }
+    });
+  }
+};
+
+})(jQuery);
+
Index: modules/field/modules/text/text.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/field/modules/text/text.module,v
retrieving revision 1.17
diff -u -p -r1.17 text.module
--- modules/field/modules/text/text.module	4 Aug 2009 06:38:56 -0000	1.17
+++ modules/field/modules/text/text.module	15 Aug 2009 00:33:14 -0000
@@ -537,6 +537,7 @@ function text_elements() {
  *   the form item for a single element for this field
  */
 function text_field_widget(&$form, &$form_state, $field, $instance, $items, $delta = 0) {
+  drupal_add_js(drupal_get_path('module', 'text') . '/text.js');
   $element = array(
     '#type' => $instance['widget']['type'],
     '#default_value' => isset($items[$delta]) ? $items[$delta] : '',
@@ -664,6 +665,9 @@ 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,
+    '#attributes' => array('class' => 'summary-textarea'),
+    '#prefix' => '<div class="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' => 'full-text-textarea'),
+    '#prefix' => '<div class="full-text-wrapper">',
+    '#suffix' => '</div>',
   );
 
   if (!empty($instance['settings']['text_processing'])) {