Add HiDPI support to ol.source.TileWMS

src/objectliterals.jsdoc

@@ -737,10 +737,15 @@
  *     edges" issues by properly configuring the WMS service. For example, MapServer
  *     has a `tile_map_edge_buffer` configuration parameter for this. See
  *     http://mapserver.org/output/tile_mode.html.
+ * @property {boolean|undefined} hidpi Use the `ol.Map#pixelRatio` value when
+ *     requesting the image from the remote server. Default is `true`.
  * @property {string|undefined} logo Logo.
  * @property {ol.tilegrid.TileGrid|undefined} tileGrid Tile grid.
  * @property {number|undefined} maxZoom Maximum zoom.
  * @property {ol.proj.ProjectionLike} projection Projection.
+ * @property {ol.source.wms.ServerType|undefined} serverType The type of the remote WMS
+ *     server: `mapserver`, `geoserver` or `qgis`. Only needed if `hidpi` is `true`.
+ *     Default is `undefined`.
  * @property {ol.TileLoadFunctionType|undefined} tileLoadFunction Optional
  *     function to load a tile given a URL.
  * @property {string|undefined} url WMS service URL.

src/ol/source/tilewmssource.js

@@ -4,6 +4,7 @@
 goog.provide('ol.source.TileWMS');
 
 goog.require('goog.array');
+goog.require('goog.asserts');
 goog.require('goog.math');
 goog.require('goog.object');
 goog.require('goog.string');
@@ -13,6 +14,7 @@ goog.require('ol.TileUrlFunction');
 goog.require('ol.extent');
 goog.require('ol.source.TileImage');
 goog.require('ol.source.wms');
+goog.require('ol.source.wms.ServerType');
 
 
 
@@ -71,6 +73,18 @@ ol.source.TileWMS = function(opt_options) {
    */
   this.v13_ = true;
 
+  /**
+   * @private
+   * @type {ol.source.wms.ServerType|undefined}
+   */
+  this.serverType_ = options.serverType;
+
+  /**
+   * @private
+   * @type {boolean}
+   */
+  this.hidpi_ = goog.isDef(options.hidpi) ? options.hidpi : true;
+
   /**
    * @private
    * @type {string}
@@ -117,6 +131,23 @@ ol.source.TileWMS.prototype.getParams = function() {
 };
 
 
+/**
+ * @param {number} z Z.
+ * @param {number} pixelRatio Pixel ratio.
+ * @param {ol.proj.Projection} projection Projection.
+ * @return {number} Size.
+ */
+ol.source.TileWMS.prototype.getTilePixelSize =
+    function(z, pixelRatio, projection) {
+  var tileSize = goog.base(this, 'getTilePixelSize', z, pixelRatio, projection);
+  if (pixelRatio == 1 || !this.hidpi_ || !goog.isDef(this.serverType_)) {
+    return tileSize;
+  } else {
+    return (tileSize * pixelRatio + 0.5) | 0;
+  }
+};
+
+
 /**
  * @private
  */
@@ -166,17 +197,21 @@ ol.source.TileWMS.prototype.tileUrlFunction_ =
   goog.object.extend(params, this.params_);
 
   var tileResolution = tileGrid.getResolution(tileCoord.z);
+  if (pixelRatio != 1 && (!this.hidpi_ || !goog.isDef(this.serverType_))) {
+    pixelRatio = 1;
+  }
   var tileSize = tileGrid.getTileSize(tileCoord.z);
   var gutter = this.gutter_;
-  if (gutter === 0) {
-    goog.object.set(params, 'WIDTH', tileSize);
-    goog.object.set(params, 'HEIGHT', tileSize);
-  } else {
-    goog.object.set(params, 'WIDTH', tileSize + 2 * gutter);
-    goog.object.set(params, 'HEIGHT', tileSize + 2 * gutter);
+  if (gutter !== 0) {
+    tileSize += 2 * gutter;
     tileExtent =
         ol.extent.buffer(tileExtent, tileResolution * gutter, this.tmpExtent_);
   }
+  if (pixelRatio != 1) {
+    tileSize = (tileSize * pixelRatio + 0.5) | 0;
+  }
+  goog.object.set(params, 'WIDTH', tileSize);
+  goog.object.set(params, 'HEIGHT', tileSize);
 
   params[this.v13_ ? 'CRS' : 'SRS'] = projection.getCode();
 
@@ -184,6 +219,24 @@ ol.source.TileWMS.prototype.tileUrlFunction_ =
     goog.object.set(params, 'STYLES', new String(''));
   }
 
+  if (pixelRatio != 1) {
+    switch (this.serverType_) {
+      case ol.source.wms.ServerType.GEOSERVER:
+        var dpi = (90 * pixelRatio + 0.5) | 0;
+        goog.object.set(params, 'FORMAT_OPTIONS', 'dpi:' + dpi);
+        break;
+      case ol.source.wms.ServerType.MAPSERVER:
+        goog.object.set(params, 'MAP_RESOLUTION', 90 * pixelRatio);
+        break;
+      case ol.source.wms.ServerType.QGIS:
+        goog.object.set(params, 'DPI', 90 * pixelRatio);
+        break;
+      default:
+        goog.asserts.fail();
+        break;
+    }
+  }
+
   var axisOrientation = projection.getAxisOrientation();
   var bbox;
   if (this.v13_ && axisOrientation.substr(0, 2) == 'ne') {