Added lots of documentation for table and particularly totals. added afterRow hook

Author: romaninsh

docs/table.rst

@@ -451,8 +451,7 @@ Table Totals
 
 .. php:attr:: totals_plan
 .. php:attr:: totals
-.. php:method:: addTotals()
-
+.. php:method:: addTotals($plan, $plan_id = null)
 
 Table implements a built-in handling for the "Totals" row. Simple usage would be::
 
@@ -467,6 +466,16 @@ but here is what actually happens:
 .. important:: addTotals() will only calculate based on rendered rows. If your table has limit
     or uses :php:class:`Paginator` you should calculate totals differently. See :php:meth:`Grid::addGrandTotals`
 
+Method addTotals() can be executed multiple times and every time it defines a new plan and
+will be reflected as an extra row for totals.
+
+To illustrate the need for multiple totals plans, here are some the scenarios which Table allows
+you to cover:
+
+ - Add "subtotal" then "tax" and then "total" row to your table.
+ - Create "group totals" which will appear in the middle of the table.
+ - Display per-page total and grand totals (for entire table).
+
 Definition of a "totals plan"
 -----------------------------
 
@@ -495,20 +504,118 @@ is set. The above example can therefore be shortened::
 
     $table->addTotals(['client' => 'Totals for {$clients} client(s)']);
 
+In addition to the plans you define, there is also going to be `{$_row_count}` which automatically counts
+number of rows in your table.
+
 Possible values for total plan stages
 -------------------------------------
 
 `init` value is typically a number, but can be any value, especially if you are going to control it's
 increment / formatting.
 
-`update` can be string - either "sum" or "increment". Other values are not supported. You can also pass
-a callable which gives you an option to perform update yourself.
+`update` can be string. Supported built-ins are:
+
+ - min
+ - inc
+ - max
+ - sum
+ - avg
+
+You can use a callable which gives you an option to perform update yourself. Also, make note that `inc`
+will ONLY increment when value of the column it's associated with is not empty. If you need to get
+total number of rows, use a special value `{$_row_count}`
+
+Update can also be set to `false` if you don't want update to take place. If not set, or set to `null`
+then default action (based on column type) will be invoked.
 
 `format` uses a template in a format suitable for :php:class:`Template`. Within the template you can
 reference other fields too. A benefit for using template is that type formatting is done automatically
 for you.
 
+If `format` set to `null` or omitted then default action will be used which is to display totals only
+`money` / `numeric` and title column ("Totals for 123 record(s)")
+
+
+Using Callbacks
+---------------
+
+Value of any stage may also be a callback. Callbacks will be executed during the appropriate stage execution
+and the value will be used:
+
+`init` defines callback like this::
+
+    function($model) {
+
+        // $model is not loaded yet!!
+
+        return 0; // initial value
+    }
+
+`update` defines callback like this::
+
+    function($total, $value, $model) {
+
+        // $total is previous value 
+        // $value is value of the column
+        // $model will be loaded to current column
+    }
+
+Here is example how you can implement "longest value" function::
+
+    function ($total, $value) {
+        return strlen($value) > strlen($total) ? $value : $total;
+    }
 
+`format` defines callback like this::
+
+    function ($total, $model) {
+        return 'Total is: '.$total;
+    }
+
+.. important:: when defining format as a string, template engine performs value
+    formatting. If you define it through the callback, it's up to you.
+
+Some examples
+-------------
+
+Calculate total salary yourself::
+
+
+    $salary_value = my_calc_salary();
+
+    $table->addTotals(['salary'=> money_format($salary_value]));
+
+.. important:: The value for the format above is passed through Template, so if user has control over
+    the value, he may reference model field you don't want him to see. Keep your security tight!!
+
+Safer version of the above code would be::
+
+    $salary_value = my_calc_salary();
+
+    $table->addTotals(['salary'=> function() use($salary_value) { money_format($salary_value]); });
+
+Here is another alternative::
+
+    $salary_value = my_calc_salary();
+
+    $table->addTotals(['salary'=> [
+        'init'=> $salary_value,
+        'update'=>false,
+    ]);
+
+Combine output into single column::
+
+    $table->addTotals([
+        'name'=>['update'=>'increment', 'format'=>'Total salary for {$name} employees is {$salary}'],
+        'salary'=>['update'=>'sum', 'format'=>false]
+    ]);
+
+With introduciton of callbacks you can show average value too::
+
+    $table->addTotals([
+        'name'=>['update'=>'increment', 'format'=>'Total salary for {$name} employees is {$salary}'],
+        'salary'=>['update'=>'sum', 'format'=>false]
+    ]);
 
 
 Advanced Usage

src/Table.php

@@ -440,6 +440,8 @@ public function renderView()
             $this->renderRow();
 
             $rows++;
+
+            $this->hook('afterRow');
         }
 
         // Add totals rows or empty message