[Adminhtml] add Events to Widget Grid

app/code/core/Mage/Adminhtml/Block/Cache/Grid.php

@@ -47,7 +47,7 @@ protected function _prepareCollection()
      */
     protected function _afterLoadCollection()
     {
-        return $this;
+        return parent::_afterLoadCollection();
     }
 
     /**

app/code/core/Mage/Adminhtml/Block/Catalog/Product/Attribute/Set/Grid.php

@@ -45,7 +45,7 @@ protected function _prepareColumns()
             'index'     => 'attribute_set_name',
         ]);
 
-        return $this;
+        return parent::_prepareColumns();
     }
 
     /**

app/code/core/Mage/Adminhtml/Block/Newsletter/Template/Grid.php

@@ -114,7 +114,7 @@ protected function _prepareColumns()
             ],
         );
 
-        return $this;
+        return parent::_prepareColumns();
     }
 
     public function getRowUrl($row)

app/code/core/Mage/Adminhtml/Block/Review/Product/Grid.php

@@ -86,7 +86,7 @@ protected function _prepareColumns()
             );
         }
 
-        return $this;
+        return Mage_Adminhtml_Block_Widget_Grid::_prepareColumns();
     }
 
     /**

app/code/core/Mage/Adminhtml/Block/System/Email/Template/Grid.php

@@ -106,7 +106,7 @@ protected function _prepareColumns()
                 'renderer'  => 'adminhtml/system_email_template_grid_renderer_action',
             ],
         );
-        return $this;
+        return parent::_prepareColumns();
     }
 
     public function getRowUrl($row)

app/code/core/Mage/Adminhtml/Block/Urlrewrite/Product/Grid.php

@@ -65,7 +65,7 @@ protected function _prepareColumns()
                 'options' => Mage::getSingleton('catalog/product_status')->getOptionArray(),
             ],
         );
-        return $this;
+        return Mage_Adminhtml_Block_Widget_Grid::_prepareColumns();
     }
 
     /**

app/code/core/Mage/Adminhtml/Block/Widget/Grid.php

@@ -315,6 +315,11 @@ public function getMainButtonsHtml()
      */
     public function setCollection($collection)
     {
+        Mage::dispatchEvent('adminhtml_grid_set_collection', [
+            'grid' => $this,
+            'collection' => $collection,
+        ]);
+
         $this->_collection = $collection;
     }
 
@@ -697,6 +702,7 @@ protected function _preparePage()
      */
     protected function _prepareColumns()
     {
+        Mage::dispatchEvent('adminhtml_grid_prepare_columns_after', ['grid' => $this]);
         $this->sortColumnsByOrder();
         return $this;
     }
@@ -766,6 +772,7 @@ protected function _prepareMassactionColumn()
      */
     protected function _prepareGrid()
     {
+        Mage::dispatchEvent('adminhtml_grid_prepare_columns_before', ['grid' => $this]);
         $this->_prepareColumns();
         $this->_prepareMassactionBlock();
         $this->_prepareCollection();
@@ -793,6 +800,11 @@ protected function _beforeToHtml()
      */
     protected function _afterLoadCollection()
     {
+        Mage::dispatchEvent('adminhtml_grid_after_load_collection', [
+            'grid' => $this,
+            'collection' => $this->getCollection(),
+        ]);
+
         return $this;
     }
 
@@ -801,6 +813,11 @@ protected function _afterLoadCollection()
      */
     protected function _beforeLoadCollection()
     {
+        Mage::dispatchEvent('adminhtml_grid_before_load_collection', [
+            'grid' => $this,
+            'collection' => $this->getCollection(),
+        ]);
+
         return $this;
     }
 

app/code/core/Mage/Index/Block/Adminhtml/Process/Grid.php

@@ -78,7 +78,7 @@ protected function _afterLoadCollection()
             }
         }
 
-        return $this;
+        return parent::_afterLoadCollection();
     }
 
     /**