====== Common rules ======

Grouping is a way to group data by diffrent criteria. jqGrid currently supports one level of grouping.

The simple way to group in jqGrid is to enable grouping with the grid option **grouping:true** and define a field name on which grouping occurs. The name should correspond to  the name in colModel.
The definition is done with array //groupField// which is a part of another grid option **groupingView**. 

It is important to note that if you want the grouping to be correct, then the data should come from server to the grid sorted by that field. When we are in local mode (the data is an array) the data is grouped (sorted) automatically so there is no need to define any additional sort column.

In order to inform the server that we want to have a grouped data, jqGrid add to the sidx parameter the  groupField name on which we group. This done only if we have enabled the grouping and the data is remote. 

For example if the grouping configuration is defined as:

<code javascript>
jQuery("#grid").jqGrid({ 
  ...
  grouping:true, 
  groupingView : { 
     groupField : ['name'],
     groupDataSorted : true 
  }, 
  caption: "Grouping" 
});
</code>

then the request sent to the server will look like this (using FireBug)

{{:wiki:grouping.png|}}

We should get this information from the request, perform the appropriate sorting server side and return the requested data to the grid. The grid then get the data and do the grouping adding the appropriate (defined) headers and footers.

===== Limitations =====
  - When the grouping is enabled, the following options will be set explicit into the code:
  * scroll = false;
  * rownumbers = false;
  * treeGrid = false;
  * gridview = true (afterInsertRow does not fire too);

Please refer in grid [[options]] for detailed information on what these options mean


====== Options and methods ======
===== Grid Options =====
All options in grouping are set as grid options and can be changed dynamically using the setGridParam method.
Two options are related to grouping 

  - grouping
  - groupingView

The first option **grouping**  is Boolean and enables or disables the grouping feature into the grid. The default values of this option is false. To enable grouping set it to true - i.e **grouping : true**

The **groupingView** option is actually a object and consist a lot of other options. 
Below is a example on how this should be used:

<code javascript>
jQuery("#grid").jqGrid({ 
  ...
  groupingView : { 
     groupField : ['name', 'ínvdate'],
     groupOrder : ['asc', 'desc'] 
  }
  ...
});
</code>

Below is the list of the options that are part of **groupingView** option \\

^Property^Type^Description^Default^
|groupField|array|Defines the name from [[colmodel_options | colModel]] on which we group. The first value is the first lavel, the second values is the second level and etc. |empty|
|groupOrder|array|Defines the initial sort order of the group level. Can be asc for ascending or desc for descending order. If the grouping is enabled the default value is asc.|empty|
|groupText|array|Defines the grouping header text for the group level that will be displayed in the grid. By default if defined the value if {0} which means that the group value name will be displayed.  It is possible to specify another value {1} which meant the the total cont of this group will be displayed too. It is possible to set here any valid html content.|empty|
|groupColumnShow|array|Show/Hide the column on which we group. The value here should be a boolean true/false for the group level. If the grouping is enabled we set this value to true. |empty|
|groupSummary|array|Enable or disable the summary (footer) row of the current group level. If grouping is set the default value for the group is false.|empty|
|groupSummaryPos|array| Set the position of the summary row at current group level. Possible values - header or footer. If set to header the summary values are placed at the same row where the group values is. If footer is set additional row at end of the group level is builded and the summary values are placed here|footer|
|hideFirstGroupCol|boolean| If set to true the values at first column are replaced with empty ones so that we have a pretty view. This usually is set ih the first column is a group column|false|
|showSummaryOnHide|boolean|Show or hide the summary (footer) row when we collapse the group.|false|
|groupCollapse|boolean|Defines if the initially the grid should show or hide the detailed rows of the group.|false|
|plusicon|string|Set the icon from jQuery UI  Theme Roller that will be used if the grouped row is collapsed|ui-icon-circlesmall-plus|
|minusicon|string|Set the icon from jQuery UI Theme Roller that will be used if the grouped row is expanded|ui-icon-circlesmall-minus|
|isInTheSameGroup| array| The elements of the array correspond to the number of the groups. Every element of this array is a function which should return true or false. In case if it return false the element will be added in the groupt. Parameters passed to this functiona are : previous value, current value, group index, group object| null | 
|formatDisplayField| array| The elements of the array correspond to the number of the groups.Every element should return a value which will be display grouped value. Parameters passed to this function are: current value, source value, colModel option, group index and group object.|null| 

===== colModel Options =====
Additionally if the group summary footer row is enabled we use a option in column model to set the type of the summary field.
We add two options in colModel and it name is **summaryType**, **summaryTpl**, **summaryRound** and **summaryRoundType**. 

=== summaryType ===
This option can be a string with certain values or a user defined function.
Bellow is a example of using this option:

<code javascript>
jQuery("#grid").jqGrid({ 
  ...
  colModel : [
     {..},
     {name:'amount',index:'amount', width:80, align:"right", sorttype:'number',formatter:'number',summaryType:'sum'},
     ...
  ],
  ...
});
</code>

The option determines what type of calculation we should do with the current group value applied to column. Currently we support the following build in functions:

  * sum - apply the sum function to the current group value and return the result
  * count - apply the count function to the current group value and return the result
  * avg - apply the average function to the current group value and return the result
  * min - apply the min function to the current group value and return the result
  * max - apply the max function to the current group value and return the result

The option can be defined as function. If defined we pass three parameters to it - the current value, the name and the record object. The function should return value. Note that this value will be used again for the group value until it changes.

Bellow is a example on using this function - simulating the sum function.
<code javascript>

function mysum(val, name, record)
{
return parseFloat(val||0) + parseFloat((record[name]||0));
}

jQuery("#grid").jqGrid({ 
  ...
  colModel : [
     {..},
     {name:'amount',index:'amount', width:80, align:"right", sorttype:'number',formatter:'number',summaryType:mysum},
     ...
  ],
  ...
});

</code>

===summaryTpl===
This option acts as template which can be used in the summary footer row. By default its value is defined as {0} - which means that this will print the summary value. The parameter can contain any valid HTML code.

===summaryRound===
<code javascript>

{..., summaryRound: number_of_digits, ... }
</code>

By default this parameter is not defined in colModel when grouping is on.\\
The number_of_digits by default is not defined.\\
This options determines the length of the remaining part after the decimal point.

===summaryRoundType===
<code javascript>
{ summaryRoundType: 'round' | 'fixed' }
</code>

This parameter works only if the //summaryRound// is defined.

This is rounding method selector.

Parameter //round// means 'just round it and do not keep trailing zeroes'. //fixed// means 'round it and keep the given fixed number of digits even zeroes'.

The default option is set to round

===== Methods =====
Bellow are the methods that can be used with the grouping.

^Function^Parameters^Returns^Description^
|groupingToggle|groupid|none|Toggles the group identified by groupid. The groupid is a  combination of grid id plus 'ghead_' plus the current count number in the grid view. By example if the grid id is named mygrid the the second grouping value in grid will become **mygridghead_1** |
|groupingGroupBy|name,\\ options|grid object| Perform a grouping by given name. A set of additional options can be set with the option parameter. The groupingView object is extended with the options parameter.|
|groupingRemove|current|grid object|Remove the current grouping and set the grouping parameter to false. If the parameter **current** is set to true all the headers and footers are removed without triggering the grid. If the parameter is false (default) the grid is triggered.|