OpenLayers.Layer.Grid

Base class for layers that use a lattice of tiles. Create a new grid layer with the OpenLayers.Layer.Grid constructor.

Inherits from

OpenLayers.Layer.HTTPRequest

Summary

OpenLayers.Layer.Grid	Base class for layers that use a lattice of tiles.
Properties
tileSize	{OpenLayers.Size}
tileOriginCorner	{String} If the tileOrigin property is not provided, the tile origin will be derived from the layer’s maxExtent.
tileOrigin	{OpenLayers.LonLat} Optional origin for aligning the grid of tiles.
tileOptions	{Object} optional configuration options for OpenLayers.Tile instances created by this Layer, if supported by the tile class.
grid	{Array(Array(OpenLayers.Tile))} This is an array of rows, each row is an array of tiles.
singleTile	{Boolean} Moves the layer into single-tile mode, meaning that one tile will be loaded.
ratio	{Float} Used only when in single-tile mode, this specifies the ratio of the size of the single tile to the size of the map.
buffer	{Integer} Used only when in gridded mode, this specifies the number of extra rows and colums of tiles on each side which will surround the minimum grid tiles to cover the map.
numLoadingTiles	{Integer} How many tiles are still loading?
tileLoadingDelay
timerId
Constructor
OpenLayers.Layer.Grid	Create a new grid layer
Functions
removeMap	Called when the layer is removed from the map.
destroy	Deconstruct the layer and clear the grid.
clearGrid	Go through and remove all tiles from the grid, calling destroy() on each of them to kill circular references
clone	Create a clone of this layer
moveTo	This function is called whenever the map is moved.
moveByPx	Move the layer based on pixel vector.
scheduleMoveGriddedTiles	Schedule the move of tiles.
setTileSize	Check if we are in singleTile mode and if so, set the size as a ratio of the map size (as specified by the layer’s ‘ratio’ property).
getGridBounds	Deprecated.
getTilesBounds	Return the bounds of the tile grid.
initSingleTile
calculateGridLayout	Generate parameters for the grid layout.
getTileOrigin	Determine the origin for aligning the grid of tiles.
initGriddedTiles
getMaxExtent	Get this layer’s maximum extent.
spiralTileLoad	Starts at the top right corner of the grid and proceeds in a spiral towards the center, adding tiles one at a time to the beginning of a queue.
addTile	Create a tile, initialize it, and add it to the layer div.
addTileMonitoringHooks	This function takes a tile as input and adds the appropriate hooks to the tile so that the layer can keep track of the loading tiles.
removeTileMonitoringHooks	This function takes a tile as input and removes the tile hooks that were added in addTileMonitoringHooks()
moveGriddedTiles
shiftRow	Shifty grid work
shiftColumn	Shift grid work in the other dimension
removeExcessTiles	When the size of the map or the buffer changes, we may need to remove some excess rows and columns.
onMapResize	For singleTile layers, this will set a new tile size according to the dimensions of the map pane.
getTileBounds	Returns The tile bounds for a layer given a pixel location.

Properties

tileSize

{OpenLayers.Size}

tileOriginCorner

{String} If the tileOrigin property is not provided, the tile origin will be derived from the layer’s maxExtent. The corner of the maxExtent used is determined by this property. Acceptable values are “tl” (top left), “tr” (top right), “bl” (bottom left), and “br” (bottom right). Default is “bl”.

tileOrigin

{OpenLayers.LonLat} Optional origin for aligning the grid of tiles. If provided, requests for tiles at all resolutions will be aligned with this location (no tiles shall overlap this location). If not provided, the grid of tiles will be aligned with the layer’s maxExtent. Default is ``null``.

tileOptions

{Object} optional configuration options for OpenLayers.Tile instances created by this Layer, if supported by the tile class.

grid

{Array(Array(OpenLayers.Tile))} This is an array of rows, each row is an array of tiles.

singleTile

{Boolean} Moves the layer into single-tile mode, meaning that one tile will be loaded. The tile’s size will be determined by the ‘ratio’ property. When the tile is dragged such that it does not cover the entire viewport, it is reloaded.

ratio

{Float} Used only when in single-tile mode, this specifies the ratio of the size of the single tile to the size of the map.

buffer

{Integer} Used only when in gridded mode, this specifies the number of extra rows and colums of tiles on each side which will surround the minimum grid tiles to cover the map. For very slow loading layers, a larger value may increase performance somewhat when dragging, but will increase bandwidth use significantly.

numLoadingTiles

{Integer} How many tiles are still loading?

tileLoadingDelay

{Integer}

Number of milliseconds before we shift and load tiles. Default is 100.

timerId

{Number}

The id of the tileLoadingDelay timer.

Constructor

OpenLayers.Layer.Grid

Create a new grid layer

Parameters

name	{String}
url	{String}
params	{Object}
options	{Object} Hashtable of extra options to tag onto the layer

Functions

removeMap

removeMap: function( map )

Called when the layer is removed from the map.

Parameters

map	{OpenLayers.Map} The map.

destroy

destroy: function()

Deconstruct the layer and clear the grid.

clearGrid

clearGrid:function()

Go through and remove all tiles from the grid, calling destroy() on each of them to kill circular references

clone

clone: function ( obj )

Create a clone of this layer

Parameters

obj	{Object} Is this ever used?

Returns

{OpenLayers.Layer.Grid} An exact clone of this OpenLayers.Layer.Grid

moveTo

moveTo:function( bounds,
zoomChanged,
dragging )

This function is called whenever the map is moved. All the moving of actual ‘tiles’ is done by the map, but moveTo’s role is to accept a bounds and make sure the data that that bounds requires is pre-loaded.

Parameters

bounds	{OpenLayers.Bounds}
zoomChanged	{Boolean}
dragging	{Boolean}

moveByPx

moveByPx: function( dx,
dy )

Move the layer based on pixel vector.

Parameters

dx	{Number}
dy	{Number}

scheduleMoveGriddedTiles

scheduleMoveGriddedTiles: function()

Schedule the move of tiles.

setTileSize

setTileSize: function( size )

Check if we are in singleTile mode and if so, set the size as a ratio of the map size (as specified by the layer’s ‘ratio’ property).

Parameters

size	{OpenLayers.Size}

getGridBounds

getGridBounds: function()

Deprecated. This function will be removed in 3.0. Please use getTilesBounds() instead.

Returns

{OpenLayers.Bounds} A Bounds object representing the bounds of all the currently loaded tiles (including those partially or not at all seen onscreen)

getTilesBounds

getTilesBounds: function()

Return the bounds of the tile grid.

Returns

{OpenLayers.Bounds} A Bounds object representing the bounds of all the currently loaded tiles (including those partially or not at all seen onscreen).

initSingleTile

initSingleTile: function( bounds )

Parameters

bounds

{OpenLayers.Bounds}

calculateGridLayout

calculateGridLayout: function( bounds,
origin,
resolution )

Generate parameters for the grid layout.

Parameters

bounds	{<OpenLayers.Bound>}
origin	{OpenLayers.LonLat}
resolution	{Number}

Returns

Object containing properties tilelon, tilelat, tileoffsetlat, tileoffsetlat, tileoffsetx, tileoffsety

getTileOrigin

getTileOrigin: function()

Determine the origin for aligning the grid of tiles. If a tileOrigin property is supplied, that will be returned. Otherwise, the origin will be derived from the layer’s maxExtent property. In this case, the tile origin will be the corner of the maxExtent given by the tileOriginCorner property.

Returns

{OpenLayers.LonLat} The tile origin.

initGriddedTiles

initGriddedTiles:function( bounds )

Parameters

bounds

{OpenLayers.Bounds}

getMaxExtent

getMaxExtent: function()

Get this layer’s maximum extent. (Implemented as a getter for potential specific implementations in sub-classes.)

Returns

{OpenLayers.Bounds}

spiralTileLoad

spiralTileLoad: function()

Starts at the top right corner of the grid and proceeds in a spiral towards the center, adding tiles one at a time to the beginning of a queue.

Once all the grid’s tiles have been added to the queue, we go back and iterate through the queue (thus reversing the spiral order from outside-in to inside-out), calling draw() on each tile.

addTile

addTile:function( bounds,
position )

Create a tile, initialize it, and add it to the layer div.

Parameters bounds - {OpenLayers.Bounds} position - {OpenLayers.Pixel}

Returns

{OpenLayers.Tile} The added OpenLayers.Tile

addTileMonitoringHooks

addTileMonitoringHooks: function( tile )

This function takes a tile as input and adds the appropriate hooks to the tile so that the layer can keep track of the loading tiles.

Parameters

tile	{OpenLayers.Tile}

removeTileMonitoringHooks

removeTileMonitoringHooks: function( tile )

This function takes a tile as input and removes the tile hooks that were added in addTileMonitoringHooks()

Parameters

tile	{OpenLayers.Tile}

moveGriddedTiles

moveGriddedTiles: function()

shiftRow

shiftRow:function( prepend )

Shifty grid work

Parameters

prepend

{Boolean} if true, prepend to beginning. if false, then append to end

shiftColumn

shiftColumn: function( prepend )

Shift grid work in the other dimension

Parameters

prepend

{Boolean} if true, prepend to beginning. if false, then append to end

removeExcessTiles

removeExcessTiles: function( rows,
columns )

When the size of the map or the buffer changes, we may need to remove some excess rows and columns.

Parameters

rows	{Integer} Maximum number of rows we want our grid to have.
columns	{Integer} Maximum number of columns we want our grid to have.

onMapResize

onMapResize: function()

For singleTile layers, this will set a new tile size according to the dimensions of the map pane.

getTileBounds

getTileBounds: function( viewPortPx )

Returns The tile bounds for a layer given a pixel location.

Parameters

viewPortPx

{OpenLayers.Pixel} The location in the viewport.

Returns

{OpenLayers.Bounds} Bounds of the tile at the given pixel location.