Add defines for certain reprojection constants

src/ol/ol.js

@@ -28,6 +28,13 @@ ol.DEFAULT_MAX_ZOOM = 42;
 ol.DEFAULT_MIN_ZOOM = 0;
 
 
+/**
+ * @define {number} Default maximum allowed threshold  (in pixels) for
+ *     reprojection triangulation. Default is `0.5`.
+ */
+ol.DEFAULT_RASTER_REPROJ_ERROR_THRESHOLD = 0.5;
+
+
 /**
  * @define {number} Default high water mark.
  */
@@ -166,6 +173,39 @@ ol.OVERVIEWMAP_MAX_RATIO = 0.75;
 ol.OVERVIEWMAP_MIN_RATIO = 0.1;
 
 
+/**
+ * @define {number} Maximum number of source tiles for raster reprojection.
+ *     If too many source tiles are determined to be loaded to create a single
+ *     reprojected tile the browser can become unresponsive or even crash.
+ *     This can happen if the developer defines projections improperly and/or
+ *     with unlimited extents.
+ *     If too many tiles are required, no tiles are loaded and
+ *     `ol.TileState.ERROR` state is set. Default is `100`.
+ */
+ol.RASTER_REPROJ_MAX_SOURCE_TILES = 100;
+
+
+/**
+ * @define {number} Maximum number of subdivision steps during raster
+ *     reprojection triangulation. Prevents high memory usage and large
+ *     number of proj4 calls when for certain transformations and areas.
+ *     At most `2*(4^this)` triangles are created. Default is `5`.
+ */
+ol.RASTER_REPROJ_MAX_SUBDIVISION = 5;
+
+
+/**
+ * @define {number} Maximum allowed size of triangle relative to world width.
+ *     When transforming corners of world extent between certain projections,
+ *     The resulting triangulation seems to have zero error and no subdivision
+ *     is performed.
+ *     If the triangle width is more than this (relative to world width; 0-1),
+ *     subdivison is forced (respecting `ol.RASTER_REPROJ_MAX_SUBDIVISION`).
+ *     Default is `0.25`.
+ */
+ol.RASTER_REPROJ_MAX_TRIANGLE_WIDTH = 0.25;
+
+
 /**
  * @define {number} Tolerance for geometry simplification in device pixels.
  */

src/ol/reproj/image.js

@@ -63,7 +63,7 @@ ol.reproj.Image = function(sourceProj, targetProj,
    * @type {!ol.reproj.Triangulation}
    */
   this.triangulation_ = new ol.reproj.Triangulation(
-      sourceProj, targetProj, limitedTargetExtent, this.maxSourceExtent_);
+      sourceProj, targetProj, limitedTargetExtent, this.maxSourceExtent_, 0);
 
   /**
    * @private

src/ol/reproj/tile.js

@@ -99,7 +99,7 @@ ol.reproj.Tile = function(sourceProj, sourceTileGrid,
 
   var targetResolution = targetTileGrid.getResolution(z);
 
-  var errorThresholdInPixels = 0.5;
+  var errorThresholdInPixels = ol.DEFAULT_RASTER_REPROJ_ERROR_THRESHOLD;
 
   // in source units
   var errorThreshold = targetResolution * errorThresholdInPixels *
@@ -111,7 +111,7 @@ ol.reproj.Tile = function(sourceProj, sourceTileGrid,
    */
   this.triangulation_ = new ol.reproj.Triangulation(
       sourceProj, targetProj, limitedTargetExtent, maxSourceExtent,
-      5, errorThreshold);
+      errorThreshold);
 
   if (this.triangulation_.getTriangles().length === 0) {
     // no valid triangles -> EMPTY
@@ -166,11 +166,11 @@ ol.reproj.Tile = function(sourceProj, sourceTileGrid,
       xRange = goog.array.range(srcRange.minX, srcRange.maxX + 1);
     }
 
-    if (xRange.length * srcRange.getHeight() > 100) {
-      // Too many source tiles are needed -- something probably went wrong
-      // This sometimes happens for certain non-global projections
-      // if no extent is specified.
-      // TODO: detect somehow better? or at least make this a define
+    var tilesRequired = xRange.length * srcRange.getHeight();
+    goog.asserts.assert(tilesRequired < ol.RASTER_REPROJ_MAX_SOURCE_TILES,
+        'reasonable number of tiles is required');
+
+    if (tilesRequired > ol.RASTER_REPROJ_MAX_SOURCE_TILES) {
       this.state = ol.TileState.ERROR;
       return;
     }

src/ol/reproj/triangulation.js

@@ -20,13 +20,12 @@ ol.reproj.Triangle;
  * @param {ol.proj.Projection} sourceProj
  * @param {ol.proj.Projection} targetProj
  * @param {ol.Extent} targetExtent
- * @param {ol.Extent=} opt_maxSourceExtent
- * @param {number=} opt_maxSubdiv Maximal subdivision.
- * @param {number=} opt_errorThreshold Acceptable error (in source units).
+ * @param {ol.Extent} maxSourceExtent
+ * @param {number} errorThreshold Acceptable error (in source units).
  * @constructor
  */
 ol.reproj.Triangulation = function(sourceProj, targetProj, targetExtent,
-    opt_maxSourceExtent, opt_maxSubdiv, opt_errorThreshold) {
+    maxSourceExtent, errorThreshold) {
 
   /**
    * @type {ol.proj.Projection}
@@ -50,11 +49,8 @@ ol.reproj.Triangulation = function(sourceProj, targetProj, targetExtent,
    * @type {ol.Extent}
    * @private
    */
-  this.maxSourceExtent_ = goog.isDef(opt_maxSourceExtent) ?
-                          opt_maxSourceExtent : null;
+  this.maxSourceExtent_ = maxSourceExtent;
 
-  var errorThreshold = goog.isDef(opt_errorThreshold) ?
-                       opt_errorThreshold : 0; //TODO: define
   /**
    * @type {number}
    * @private
@@ -99,7 +95,7 @@ ol.reproj.Triangulation = function(sourceProj, targetProj, targetExtent,
 
   this.addQuadIfValid_(tlDst, trDst, brDst, blDst,
                        tlDstSrc, trDstSrc, brDstSrc, blDstSrc,
-                       opt_maxSubdiv || 0);
+                       ol.RASTER_REPROJ_MAX_SUBDIVISION);
 };
 
 
@@ -155,7 +151,7 @@ ol.reproj.Triangulation.prototype.addQuadIfValid_ = function(a, b, c, d,
 
   if (maxSubdiv > 0) {
     var needsSubdivision = !wrapsX && this.sourceProj_.isGlobal() &&
-                           srcCoverageX > 0.25; //TODO: define
+                           srcCoverageX > ol.RASTER_REPROJ_MAX_TRIANGLE_WIDTH;
 
     var center = [(a[0] + c[0]) / 2, (a[1] + c[1]) / 2];
     var centerSrc = this.transformInv_(center);