Merge pull request #1757 from twpayne/interim-tiles-on-error

Add option to use interim tiles on tile errors

src/objectliterals.jsdoc

@@ -539,6 +539,8 @@
  *      (inclusive) at which this layer will be visible.
  * @property {number|undefined} maxResolution The maximum resolution
  *      (exclusive) below which this layer will be visible.
+ * @property {boolean|undefined} useInterimTilesOnError Use interim tiles on
+ *      error.  Default is `true`.
  * @todo stability experimental
  */
 

src/ol/layer/tilelayer.js

@@ -7,7 +7,8 @@ goog.require('ol.layer.Layer');
  * @enum {string}
  */
 ol.layer.TileProperty = {
-  PRELOAD: 'preload'
+  PRELOAD: 'preload',
+  USE_INTERIM_TILES_ON_ERROR: 'useInterimTilesOnError'
 };
 
 
@@ -51,3 +52,32 @@ goog.exportProperty(
     ol.layer.Tile.prototype,
     'setPreload',
     ol.layer.Tile.prototype.setPreload);
+
+
+/**
+ * @return {boolean|undefined} Use interim tiles on error.
+ * @todo stability experimental
+ */
+ol.layer.Tile.prototype.getUseInterimTilesOnError = function() {
+  return /** @type {boolean|undefined} */ (
+      this.get(ol.layer.TileProperty.USE_INTERIM_TILES_ON_ERROR));
+};
+goog.exportProperty(
+    ol.layer.Tile.prototype,
+    'getUseInterimTilesOnError',
+    ol.layer.Tile.prototype.getUseInterimTilesOnError);
+
+
+/**
+ * @param {boolean|undefined} useInterimTilesOnError Use interim tiles on error.
+ * @todo stability experimental
+ */
+ol.layer.Tile.prototype.setUseInterimTilesOnError =
+    function(useInterimTilesOnError) {
+  this.set(
+      ol.layer.TileProperty.USE_INTERIM_TILES_ON_ERROR, useInterimTilesOnError);
+};
+goog.exportProperty(
+    ol.layer.Tile.prototype,
+    'setUseInterimTilesOnError',
+    ol.layer.Tile.prototype.setUseInterimTilesOnError);

src/ol/renderer/canvas/canvastilelayerrenderer.js

@@ -266,6 +266,11 @@ ol.renderer.canvas.TileLayer.prototype.prepareFrame =
   var findLoadedTiles = goog.bind(tileSource.findLoadedTiles, tileSource,
       tilesToDrawByZ, getTileIfLoaded);
 
+  var useInterimTilesOnError = tileLayer.getUseInterimTilesOnError();
+  if (!goog.isDef(useInterimTilesOnError)) {
+    useInterimTilesOnError = true;
+  }
+
   var tmpExtent = ol.extent.createEmpty();
   var tmpTileRange = new ol.TileRange(0, 0, 0, 0);
   var childTileRange, fullyLoaded, tile, tileState, x, y;
@@ -276,7 +281,7 @@ ol.renderer.canvas.TileLayer.prototype.prepareFrame =
       tileState = tile.getState();
       if (tileState == ol.TileState.LOADED ||
           tileState == ol.TileState.EMPTY ||
-          tileState == ol.TileState.ERROR) {
+          (tileState == ol.TileState.ERROR && !useInterimTilesOnError)) {
         tilesToDrawByZ[z][tile.tileCoord.toString()] = tile;
         continue;
       }
@@ -331,7 +336,7 @@ ol.renderer.canvas.TileLayer.prototype.prepareFrame =
           y = tilePixelSize * (canvasTileRange.maxY - tile.tileCoord.y);
           tileState = tile.getState();
           if (tileState == ol.TileState.EMPTY ||
-              tileState == ol.TileState.ERROR ||
+              (tileState == ol.TileState.ERROR && !useInterimTilesOnError) ||
               !opaque) {
             context.clearRect(x, y, tilePixelSize, tilePixelSize);
           }

src/ol/renderer/dom/domtilelayerrenderer.js

@@ -122,6 +122,11 @@ ol.renderer.dom.TileLayer.prototype.prepareFrame =
   var findLoadedTiles = goog.bind(tileSource.findLoadedTiles, tileSource,
       tilesToDrawByZ, getTileIfLoaded);
 
+  var useInterimTilesOnError = tileLayer.getUseInterimTilesOnError();
+  if (!goog.isDef(useInterimTilesOnError)) {
+    useInterimTilesOnError = true;
+  }
+
   var tmpExtent = ol.extent.createEmpty();
   var tmpTileRange = new ol.TileRange(0, 0, 0, 0);
   var childTileRange, fullyLoaded, tile, tileState, x, y;
@@ -133,8 +138,9 @@ ol.renderer.dom.TileLayer.prototype.prepareFrame =
       if (tileState == ol.TileState.LOADED) {
         tilesToDrawByZ[z][tile.tileCoord.toString()] = tile;
         continue;
-      } else if (tileState == ol.TileState.ERROR ||
+      } else if (tileState == ol.TileState.EMPTY ||
-                 tileState == ol.TileState.EMPTY) {
+                 (tileState == ol.TileState.ERROR &&
+                  !useInterimTilesOnError)) {
         continue;
       }
 

src/ol/renderer/webgl/webgltilelayerrenderer.js

@@ -200,6 +200,11 @@ ol.renderer.webgl.TileLayer.prototype.prepareFrame =
     var findLoadedTiles = goog.bind(tileSource.findLoadedTiles, tileSource,
         tilesToDrawByZ, getTileIfLoaded);
 
+    var useInterimTilesOnError = tileLayer.getUseInterimTilesOnError();
+    if (!goog.isDef(useInterimTilesOnError)) {
+      useInterimTilesOnError = true;
+    }
+
     var allTilesLoaded = true;
     var tmpExtent = ol.extent.createEmpty();
     var tmpTileRange = new ol.TileRange(0, 0, 0, 0);
@@ -214,8 +219,9 @@ ol.renderer.webgl.TileLayer.prototype.prepareFrame =
             tilesToDrawByZ[z][tile.tileCoord.toString()] = tile;
             continue;
           }
-        } else if (tileState == ol.TileState.ERROR ||
+        } else if (tileState == ol.TileState.EMPTY ||
-                   tileState == ol.TileState.EMPTY) {
+                   (tileState == ol.TileState.ERROR &&
+                    !useInterimTilesOnError)) {
           continue;
         }