# Class: Scroller

Scroller v1.0.0 documentation

new Scroller( oDT:object, [oOpts:object] )

  Scroller is a virtual rendering plug-in for DataTables which allows large datasets to be drawn on screen every quickly. What the virtual rendering means is that only the visible portion of the table (and a bit to either side to make the scrolling smooth) is drawn, while the scrolling container gives the visual impression that the whole table is visible. This is done by making use of the pagination abilities of DataTables and moving the table around in the scrolling container DataTables adds to the page. The scrolling container is forced to the height it would be for the full table display using an extra element.
  Note that rows in the table MUST all be the same hight. Information in a cell which expands on to multiple lines will cause some odd behaviour in the scrolling.
  Scroller is initialised by simply including the letter 'S' in the sDom for the table you want to have this feature enabled on. Note that the 'S' must come AFTER the 't' parameter in sDom.
  Key features include:

  - Speed! The aim of Scroller for DataTables is to make rendering large data sets fast
  - Full compatibility with deferred rendering in DataTables 1.8 for maximum speed
  - Correct visual scrolling implementation, similar to "infinite scrolling" in DataTable core
  - Integration with state saving in DataTables (scrolling position is saved)
  - Easy to use

  ### Constructor

  ##### Parameters:

  | Name | Type | Attributes | Default | Description
  --- | --- | --- | --- | --- | ---
  1 | oDT | object |  |  | DataTables settings object
  2 | oOpts | object | Optional | {} | Configuration object for FixedColumns. Options are defined by Scroller.oDefaults

  ##### Example:

      		$(document).ready(function() {
      			$('#example').dataTable( {
      				"sScrollY": "200px",
      				"sAjaxSource": "media/dataset/large.txt",
      				"sDom": "frtiS",
      				"bDeferRender": true
      			} );
      		} );

### Requires

- jQuery 1.4+
- DataTables 1.8.0+

## Summary

### Namespaces

dom
  DOM elements used by the class instance
oDefaults
  Scroller default settings for initialisation
s
  Settings object which contains customisable information for the Scroller instance

### Methods

fnPixelsToRow( iPixels:int ):int
  Calculate the row number that will be found at the given pixel position (y-scroll)
fnRowToPixels( iRow:int ):int
  Calculate the pixel position from the top of the scrolling container for a given row
fnScrollToRow( iRow:int, [bAnimate:bool] ):void
  Calculate the row number that will be found at the given pixel position (y-scroll)
<private> _fnCalcRowHeight( ):void
  Automatic calculation of table row height. This is just a little tricky here as using initialisation DataTables has tale the table out of the document, so we need to create a new table and insert it into the document, calculate the row height and then whip the table out.
<private> _fnConstruct( ):void
  Initialisation for Scroller
<private> _fnDrawCallback( ):void
  Draw callback function which is fired when the DataTable is redrawn. The main function of this method is to position the drawn table correctly the scrolling container for the rows that is displays as a result of the scrolling position.
<private> _fnInfo( ):void
  Update any information elements that are controlled by the DataTable based on the scrolling viewport and what rows are visible in it. This function basically acts in the same way as _fnUpdateInfo in DataTables, and effectively replaces that function.
<private> _fnScroll( ):void
  Scrolling function - fired whenever the scrolling position is changed. This method needs to use the stored values to see if the table should be redrawn as we are moving towards the end of the information that is currently drawn or not. If needed, then it will redraw the table based on the new position.

## Details

### Methods

fnPixelsToRow( iPixels:int ):int

  Calculate the row number that will be found at the given pixel position (y-scroll)

  ##### Parameters:

  | Name | Type | Attributes | Default | Description
  --- | --- | --- | --- | --- | ---
  1 | iPixels | int |  |  | Offset from top to caluclate the row number of

  ##### Returns:

  Row index

  ##### Example:

       	$(document).ready(function() {
       		$('#example').dataTable( {
       			"sScrollY": "200px",
       			"sAjaxSource": "media/dataset/large.txt",
       			"sDom": "frtiS",
       			"bDeferRender": true,
       			"fnInitComplete": function () {
       				// Find what row number is at 500px
       				alert( this.oScroller.fnPixelsToRow( 500 ) );
       			}
       		} );
       	} );

fnRowToPixels( iRow:int ):int

  Calculate the pixel position from the top of the scrolling container for a given row

  ##### Parameters:

  | Name | Type | Attributes | Default | Description
  --- | --- | --- | --- | --- | ---
  1 | iRow | int |  |  | Row number to calculate the position of

  ##### Returns:

  Pixels

  ##### Example:

       	$(document).ready(function() {
       		$('#example').dataTable( {
       			"sScrollY": "200px",
       			"sAjaxSource": "media/dataset/large.txt",
       			"sDom": "frtiS",
       			"bDeferRender": true,
       			"fnInitComplete": function () {
       				// Find where row 25 is
       				alert( this.oScroller.fnRowToPixels( 25 ) );
       			}
       		} );
       	} );

fnScrollToRow( iRow:int, [bAnimate:bool] ):void

  Calculate the row number that will be found at the given pixel position (y-scroll)

  ##### Parameters:

  | Name | Type | Attributes | Default | Description
  --- | --- | --- | --- | --- | ---
  1 | iRow | int |  |  | Row index to scroll to
  2 | bAnimate | bool | Optional | true | Animate the transision or not

  ##### Example:

       	$(document).ready(function() {
       		$('#example').dataTable( {
       			"sScrollY": "200px",
       			"sAjaxSource": "media/dataset/large.txt",
       			"sDom": "frtiS",
       			"bDeferRender": true,
       			"fnInitComplete": function () {
       				// Immediately scroll to row 1000
       				this.oScroller.fnScrollToRow( 1000 );
       			}
       		} );
       	} );

<private> _fnCalcRowHeight( ):void

  Automatic calculation of table row height. This is just a little tricky here as using initialisation DataTables has tale the table out of the document, so we need to create a new table and insert it into the document, calculate the row height and then whip the table out.

<private> _fnConstruct( ):void

  Initialisation for Scroller

<private> _fnDrawCallback( ):void

  Draw callback function which is fired when the DataTable is redrawn. The main function of this method is to position the drawn table correctly the scrolling container for the rows that is displays as a result of the scrolling position.

<private> _fnInfo( ):void

  Update any information elements that are controlled by the DataTable based on the scrolling viewport and what rows are visible in it. This function basically acts in the same way as _fnUpdateInfo in DataTables, and effectively replaces that function.

<private> _fnScroll( ):void

  Scrolling function - fired whenever the scrolling position is changed. This method needs to use the stored values to see if the table should be redrawn as we are moving towards the end of the information that is currently drawn or not. If needed, then it will redraw the table based on the new position.