Make tile pre-loading a per-layer option

src/objectliterals.exports

@@ -100,6 +100,16 @@
 @exportObjectLiteralProperty ol.layer.LayerOptions.source ol.source.Source
 @exportObjectLiteralProperty ol.layer.LayerOptions.visible boolean|undefined
 
+@exportObjectLiteral ol.layer.TileLayerOptions
+@exportObjectLiteralProperty ol.layer.TileLayerOptions.brightness number|undefined
+@exportObjectLiteralProperty ol.layer.TileLayerOptions.contrast number|undefined
+@exportObjectLiteralProperty ol.layer.TileLayerOptions.hue number|undefined
+@exportObjectLiteralProperty ol.layer.TileLayerOptions.opacity number|undefined
+@exportObjectLiteralProperty ol.layer.TileLayerOptions.preload boolean|undefined
+@exportObjectLiteralProperty ol.layer.TileLayerOptions.saturation number|undefined
+@exportObjectLiteralProperty ol.layer.TileLayerOptions.source ol.source.Source
+@exportObjectLiteralProperty ol.layer.TileLayerOptions.visible boolean|undefined
+
 @exportObjectLiteral ol.layer.VectorLayerOptions
 @exportObjectLiteralProperty ol.layer.VectorLayerOptions.opacity number|undefined
 @exportObjectLiteralProperty ol.layer.VectorLayerOptions.source ol.source.Source

src/ol/layer/tilelayer.exports

@@ -1 +1 @@
-@exportClass ol.layer.TileLayer ol.layer.LayerOptions
+@exportClass ol.layer.TileLayer ol.layer.TileLayerOptions

src/ol/layer/tilelayer.js

@@ -4,21 +4,58 @@ goog.require('ol.layer.Layer');
 goog.require('ol.source.TileSource');
 
 
+/**
+ * @enum {string}
+ */
+ol.layer.TileLayerProperty = {
+  PRELOAD: 'preload'
+};
+
+
 
 /**
  * @constructor
  * @extends {ol.layer.Layer}
- * @param {ol.layer.LayerOptions} layerOptions Layer options.
+ * @param {ol.layer.TileLayerOptions} options Options.
  */
-ol.layer.TileLayer = function(layerOptions) {
-  goog.base(this, layerOptions);
+ol.layer.TileLayer = function(options) {
+
+  goog.base(this, options);
+
+  this.setPreload(
+      goog.isDef(options.preload) ? options.preload : false);
+
 };
 goog.inherits(ol.layer.TileLayer, ol.layer.Layer);
 
 
+/**
+ * @return {boolean} Preload.
+ */
+ol.layer.TileLayer.prototype.getPreload = function() {
+  return /** @type {boolean} */ (this.get(ol.layer.TileLayerProperty.PRELOAD));
+};
+goog.exportProperty(
+    ol.layer.TileLayer.prototype,
+    'getPreload',
+    ol.layer.TileLayer.prototype.getPreload);
+
+
 /**
  * @return {ol.source.TileSource} Source.
  */
 ol.layer.TileLayer.prototype.getTileSource = function() {
   return /** @type {ol.source.TileSource} */ (this.getSource());
 };
+
+
+/**
+ * @param {boolean} preload Preload.
+ */
+ol.layer.TileLayer.prototype.setPreload = function(preload) {
+  this.set(ol.layer.TileLayerProperty.PRELOAD, preload);
+};
+goog.exportProperty(
+    ol.layer.TileLayer.prototype,
+    'setPreload',
+    ol.layer.TileLayer.prototype.setPreload);

src/ol/renderer/canvas/canvastilelayerrenderer.js

@@ -285,8 +285,8 @@ ol.renderer.canvas.TileLayer.prototype.renderFrame =
   }
 
   this.updateUsedTiles(frameState.usedTiles, tileSource, z, tileRange);
-  this.manageTilePyramid(
-      frameState, tileSource, tileGrid, projection, extent, z);
+  this.manageTilePyramid(frameState, tileSource, tileGrid, projection, extent,
+      z, tileLayer.getPreload());
   this.scheduleExpireCache(frameState, tileSource);
 
   var transform = this.transform_;

src/ol/renderer/dom/domtilelayerrenderer.js

@@ -218,8 +218,8 @@ ol.renderer.dom.TileLayer.prototype.renderFrame =
   }
 
   this.updateUsedTiles(frameState.usedTiles, tileSource, z, tileRange);
-  this.manageTilePyramid(
-      frameState, tileSource, tileGrid, projection, extent, z);
+  this.manageTilePyramid(frameState, tileSource, tileGrid, projection, extent,
+      z, tileLayer.getPreload());
   this.scheduleExpireCache(frameState, tileSource);
 
 };

src/ol/renderer/layerrenderer.js

@@ -17,12 +17,6 @@ goog.require('ol.layer.LayerState');
 goog.require('ol.source.TileSource');
 
 
-/**
- * @define {boolean} Preemptively load low resolution tiles.
- */
-ol.PREEMPTIVELY_LOAD_LOW_RESOLUTION_TILES = true;
-
-
 
 /**
  * @constructor
@@ -297,13 +291,15 @@ ol.renderer.Layer.prototype.snapCenterToPixel =
  * @param {ol.Projection} projection Projection.
  * @param {ol.Extent} extent Extent.
  * @param {number} currentZ Current Z.
+ * @param {boolean} preload Preload low resolution tiles.
  * @param {function(this: T, ol.Tile)=} opt_tileCallback Tile callback.
  * @param {T=} opt_obj Object.
  * @protected
  * @template T
  */
-ol.renderer.Layer.prototype.manageTilePyramid = function(frameState, tileSource,
-    tileGrid, projection, extent, currentZ, opt_tileCallback, opt_obj) {
+ol.renderer.Layer.prototype.manageTilePyramid = function(
+    frameState, tileSource, tileGrid, projection, extent, currentZ, preload,
+    opt_tileCallback, opt_obj) {
   var tileSourceKey = goog.getUid(tileSource).toString();
   if (!(tileSourceKey in frameState.wantedTiles)) {
     frameState.wantedTiles[tileSourceKey] = {};
@@ -317,7 +313,7 @@ ol.renderer.Layer.prototype.manageTilePyramid = function(frameState, tileSource,
     tileResolution = tileGrid.getResolution(z);
     for (x = tileRange.minX; x <= tileRange.maxX; ++x) {
       for (y = tileRange.minY; y <= tileRange.maxY; ++y) {
-        if (ol.PREEMPTIVELY_LOAD_LOW_RESOLUTION_TILES || z == currentZ) {
+        if (preload || z == currentZ) {
           tile = tileSource.getTile(z, x, y, tileGrid, projection);
           if (tile.getState() == ol.TileState.IDLE) {
             wantedTiles[tile.tileCoord.toString()] = true;

src/ol/renderer/webgl/webgltilelayerrenderer.js

@@ -269,6 +269,7 @@ ol.renderer.webgl.TileLayer.prototype.renderFrame =
   var tileTextureQueue = mapRenderer.getTileTextureQueue();
   this.manageTilePyramid(
       frameState, tileSource, tileGrid, projection, extent, z,
+      tileLayer.getPreload(),
       function(tile) {
         if (tile.getState() == ol.TileState.LOADED &&
             !mapRenderer.isTileTextureLoaded(tile) &&