OpenLayers.TileManager - OpenLayers

# OpenLayers.TileManager

Provides queueing of image requests and caching of image elements.

Queueing avoids unnecessary image requests while changing zoom levels quickly, and helps improve dragging performance on mobile devices that show a lag in dragging when loading of new images starts. zoomDelay and moveDelay are the configuration options to control this behavior.

Caching avoids setting the src on image elements for images that have already been used. Several maps can share a TileManager instance, in which case each map gets its own tile queue, but all maps share the same tile cache.

Summary

OpenLayers.TileManager | Provides queueing of image requests and caching of image elements.
Properties |
cacheSize | {Number} Number of image elements to keep referenced in this instance’s cache for fast reuse.
tilesPerFrame | {Number} Number of queued tiles to load per frame (see frameDelay).
frameDelay | {Number} Delay between tile loading frames (see tilesPerFrame) in milliseconds.
moveDelay | {Number} Delay in milliseconds after a map’s move event before loading tiles.
zoomDelay | {Number} Delay in milliseconds after a map’s zoomend event before loading tiles.
maps | {Array(OpenLayers.Map)} The maps to manage tiles on.
tileQueueId | {Object} The ids of the drawTilesFromQueue loop, keyed by map id.
tileQueue | {Object(Array(OpenLayers.Tile))} Tiles queued for drawing, keyed by map id.
tileCache | {Object} Cached image elements, keyed by URL.
tileCacheIndex | {Array(String)} URLs of cached tiles.
Constructor |
OpenLayers.TileManager | Constructor for a new OpenLayers.TileManager instance.
Functions |
addMap | Binds this instance to a map
removeMap | Unbinds this instance from a map
move | Handles the map’s move event
zoomEnd | Handles the map’s zoomEnd event
changeLayer | Handles the map’s changeLayer event
addLayer | Handles the map’s addlayer event
removeLayer | Handles the map’s preremovelayer event
updateTimeout | Applies the moveDelay or zoomDelay to the drawTilesFromQueue loop, and schedules more queue processing after frameDelay if there are still tiles in the queue.
addTile | Listener for the layer’s addtile event
unloadTile | Listener for the tile’s unload event
queueTileDraw | Adds a tile to the queue that will draw it.
drawTilesFromQueue | Draws tiles from the tileQueue, and unqueues the tiles
manageTileCache | Adds, updates, removes and fetches cache entries.
addToCache |
clearTileQueue | Clears the tile queue from tiles of a specific layer
destroy |

### Properties

### cacheSize

{Number} Number of image elements to keep referenced in this instance’s cache for fast reuse. Default is 256.

### tilesPerFrame

{Number} Number of queued tiles to load per frame (see frameDelay). Default is 2.

### frameDelay

{Number} Delay between tile loading frames (see tilesPerFrame) in milliseconds. Default is 16.

### moveDelay

{Number} Delay in milliseconds after a map’s move event before loading tiles. Default is 100.

### zoomDelay

{Number} Delay in milliseconds after a map’s zoomend event before loading tiles. Default is 200.

### maps

{Array(OpenLayers.Map)} The maps to manage tiles on.

### tileQueueId

{Object} The ids of the drawTilesFromQueue loop, keyed by map id.

### tileQueue

{Object(Array(OpenLayers.Tile))} Tiles queued for drawing, keyed by map id.

### tileCache

{Object} Cached image elements, keyed by URL.

### tileCacheIndex

{Array(String)} URLs of cached tiles. First entry is the least recently used.

### Constructor

### OpenLayers.TileManager

Constructor for a new OpenLayers.TileManager instance.

#### Parameters

options | {Object} Configuration for this instance.

### Functions

### addMap

> addMap: function( | map | )

Binds this instance to a map

#### Parameters

map | {OpenLayers.Map}

### removeMap

> removeMap: function( | map | )

Unbinds this instance from a map

#### Parameters

map | {OpenLayers.Map}

### move

> move: function( | evt | )

Handles the map’s move event

#### Parameters

evt | {Object} Listener argument

### zoomEnd

> zoomEnd: function( | evt | )

Handles the map’s zoomEnd event

#### Parameters

evt | {Object} Listener argument

### changeLayer

> changeLayer: function( | evt | )

Handles the map’s changeLayer event

#### Parameters

evt | {Object} Listener argument

### addLayer

> addLayer: function( | evt | )

Handles the map’s addlayer event

#### Parameters

evt | {Object} The listener argument

### removeLayer

> removeLayer: function( | evt | )

Handles the map’s preremovelayer event

#### Parameters

evt | {Object} The listener argument

### updateTimeout

> updateTimeout: function( | map,
> | delay,
> | nice | )

Applies the moveDelay or zoomDelay to the drawTilesFromQueue loop, and schedules more queue processing after frameDelay if there are still tiles in the queue.

#### Parameters

map | {OpenLayers.Map} The map to update the timeout for
delay | {Number} The delay to apply
nice | {Boolean} If true, the timeout function will only be created if the tilequeue is not empty. This is used by the move handler to avoid impacts on dragging performance. For other events, the tile queue may not be populated yet, so we need to set the timer regardless of the queue size.

### addTile

> addTile: function( | evt | )

Listener for the layer’s addtile event

#### Parameters

evt | {Object} The listener argument

### unloadTile

> unloadTile: function( | evt | )

Listener for the tile’s unload event

#### Parameters

evt | {Object} The listener argument

### queueTileDraw

> queueTileDraw: function( | evt | )

Adds a tile to the queue that will draw it.

#### Parameters

evt | {Object} Listener argument of the tile’s beforedraw event

### drawTilesFromQueue

> drawTilesFromQueue: function( | map | )

Draws tiles from the tileQueue, and unqueues the tiles

### manageTileCache

> manageTileCache: function( | evt | )

Adds, updates, removes and fetches cache entries.

#### Parameters

evt | {Object} Listener argument of the tile’s beforeload event

### addToCache

> addToCache: function( | evt | )

#### Parameters

evt | {Object} Listener argument for the tile’s loadend event

### clearTileQueue

> clearTileQueue: function( | evt | )

Clears the tile queue from tiles of a specific layer

#### Parameters

evt | {Object} Listener argument of the layer’s retile event

### destroy

> destroy: function()

{Number} Delay between tile loading frames (see tilesPerFrame) in milliseconds.
{Number} Number of queued tiles to load per frame (see frameDelay).
Instances of OpenLayers.Map are interactive maps embedded in a web page.

> drawTilesFromQueue: function( | map | )

Draws tiles from the tileQueue, and unqueues the tiles
Constructor for a new OpenLayers.TileManager instance.

> addMap: function( | map | )

Binds this instance to a map

> removeMap: function( | map | )

Unbinds this instance from a map

> move: function( | evt | )

Handles the map’s move event

> zoomEnd: function( | evt | )

Handles the map’s zoomEnd event

> changeLayer: function( | evt | )

Handles the map’s changeLayer event

> addLayer: function( | evt | )

Handles the map’s addlayer event

> removeLayer: function( | evt | )

Handles the map’s preremovelayer event

> updateTimeout: function( | map,
> | delay,
> | nice | )

Applies the moveDelay or zoomDelay to the drawTilesFromQueue loop, and schedules more queue processing after frameDelay if there are still tiles in the queue.
{Number} Delay in milliseconds after a map’s move event before loading tiles.
{Number} Delay in milliseconds after a map’s zoomend event before loading tiles.

> addTile: function( | evt | )

Listener for the layer’s addtile event

> unloadTile: function( | evt | )

Listener for the tile’s unload event

> queueTileDraw: function( | evt | )

Adds a tile to the queue that will draw it.

> manageTileCache: function( | evt | )

Adds, updates, removes and fetches cache entries.

> addToCache: function( | evt | )

> clearTileQueue: function( | evt | )

Clears the tile queue from tiles of a specific layer

> destroy: function()

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