Add viewer.getLayerAtLevel method and rename getLayerLevel to getLevelOfLayer.

Add layers unit test.

src/viewer.js

@@ -1071,13 +1071,25 @@ $.extend( $.Viewer.prototype, $.EventSource.prototype, $.ControlDock.prototype,
         return this;
     },
 
+    /**
+     * Get the layer at the specified level.
+     * @param {Number} level The layer to retrieve level.
+     * @returns {OpenSeadragon.Drawer} The layer at the specified level.
+     */
+    getLayerAtLevel: function( level ) {
+        if ( level >= this.drawers.length ) {
+            throw new Error( "Level bigger than number of layers." );
+        }
+        return this.drawers[ level ];
+    },
+
     /**
      * Get the level of the layer associated with the given drawer or -1 if not
      * present.
      * @param {OpenSeadragon.Drawer} drawer The underlying drawer of the layer.
      * @returns {Number} The level of the layer or -1 if not present.
      */
-    getLayerLevel: function( drawer ) {
+    getLevelOfLayer: function( drawer ) {
         return $.indexOf( this.drawers, drawer );
     },
 
@@ -1098,7 +1110,7 @@ $.extend( $.Viewer.prototype, $.EventSource.prototype, $.ControlDock.prototype,
      * @fires OpenSeadragon.Viewer.event:layer-level-changed
      */
     setLayerLevel: function( drawer, level ) {
-        var oldLevel = this.getLayerLevel( drawer );
+        var oldLevel = this.getLevelOfLayer( drawer );
         if ( level === 0 || oldLevel === 0 ) {
             throw new Error( "Cannot reassign base level." );
         }

test/layers.js

@@ -0,0 +1,129 @@
+/* global module, asyncTest, $, ok, equal, notEqual, start, test, Util, testLog */
+
+( function() {
+    var viewer;
+
+    module( 'Layers', {
+        setup: function() {
+            $( '<div id="layersexample"></div>' ).appendTo( "#qunit-fixture" );
+
+            testLog.reset();
+
+            viewer = OpenSeadragon( {
+                id: 'layersexample',
+                prefixUrl: '/build/openseadragon/images/',
+                springStiffness: 100 // Faster animation = faster tests
+            });
+        },
+        teardown: function() {
+            if ( viewer && viewer.close ) {
+                viewer.close();
+            }
+
+            viewer = null;
+            $("#layersexample").remove();
+        }
+    } );
+
+    // ----------
+    asyncTest( 'Layers operations', function() {
+        expect( 22 );
+
+        viewer.addHandler( "open", function() {
+            equal( 0, viewer.getNumberOfLayers(),
+                "No layer should be present after opening." );
+
+            var options = {
+                tileSource: {
+                    type: 'legacy-image-pyramid',
+                    levels: [ {
+                            url: "test/data/A.png",
+                            width: 1000,
+                            height: 1000
+                        } ]
+                }
+            };
+            viewer.addLayer( options );
+            viewer.addHandler( "add-layer", function addFirstLayerHandler( event ) {
+                viewer.removeHandler( "add-layer", addFirstLayerHandler );
+                var layer1 = event.drawer;
+
+                equal( viewer.getNumberOfLayers(), 1,
+                    "1 layer should be present after adding a layer." );
+                equal( options, event.options,
+                    "The options should be transmitted via the event." );
+                equal( viewer.getLevelOfLayer( layer1 ), 1,
+                    "The first added layer should have a level of 1" );
+                equal( viewer.getLayerAtLevel( 1 ), layer1,
+                    "The layer at level 1 should be the first added layer." );
+
+                viewer.addLayer( options );
+                viewer.addHandler( "add-layer", function addSecondLayerHandler( event ) {
+                    viewer.removeHandler( "add-layer", addSecondLayerHandler );
+                    var layer2 = event.drawer;
+
+                    equal( viewer.getNumberOfLayers(), 2,
+                        "2 layers should be present after adding a second layer." );
+                    equal( viewer.getLevelOfLayer( layer2 ), 2,
+                        "If not specified, a layer should be added with the highest level." );
+                    equal( viewer.getLayerAtLevel( 2 ), layer2,
+                        "The layer at level 2 should be the second added layer." );
+
+                    viewer.addHandler( "layer-level-changed",
+                        function layerLevelChangedHandler( event ) {
+                            viewer.removeHandler( "layer-level-changed",
+                                layerLevelChangedHandler );
+                            equal( event.drawer, layer2,
+                                "The layer which changed level should be layer2" );
+                            equal( event.previousLevel, 2, "Previous level should be 2." );
+                            equal( event.newLevel, 1, "New level should be 1." );
+                        });
+                    viewer.setLayerLevel( layer2, 1 );
+                    equal( viewer.getLevelOfLayer( layer2 ), 1,
+                        "Layer2 level should be 1 after setLayerLevel." );
+                    equal( viewer.getLevelOfLayer( layer1 ), 2,
+                        "Layer1 level should be 2 after setLayerLevel." );
+                    equal( viewer.getLayerAtLevel( 1 ), layer2,
+                        "The layer at level 1 should be layer2." );
+                    equal( viewer.getLayerAtLevel( 2 ), layer1,
+                        "The layer at level 2 should be layer1." );
+
+                    options.level = 2;
+                    options.tileSource.levels[0].url = "test/data/CCyan.png";
+                    options.opacity = 0.5;
+                    viewer.addLayer( options );
+                    viewer.addHandler( "add-layer", function addThirdLayerHandler( event ) {
+                        viewer.removeHandler( "add-layer", addThirdLayerHandler );
+                        var layer3 = event.drawer;
+
+                        equal( viewer.getNumberOfLayers(), 3,
+                            "3 layers should be present after adding a third layer." );
+                        equal( viewer.getLevelOfLayer( layer3 ), 2,
+                            "Layer 3 should be added with level 2." );
+                        equal( viewer.getLevelOfLayer( layer2 ), 1,
+                            "Layer 2 should stay at level 1." );
+
+                        viewer.addHandler( "remove-layer", function removeLayerHandler( event ) {
+                            viewer.removeHandler( "remove-layer", removeLayerHandler );
+
+                            equal( layer2, event.drawer, "Removed layer should be layer2." );
+
+                            equal( viewer.getLevelOfLayer( layer1 ), 2,
+                                "Layer 1 should be at level 2." );
+                            equal( viewer.getLevelOfLayer( layer2 ), -1,
+                                "Layer 2 should be at level -1." );
+                            equal( viewer.getLevelOfLayer( layer3 ), 1,
+                                "Layer 3 should be at level 1." );
+
+                        });
+                        viewer.removeLayer( layer2 );
+                        start();
+                    });
+                });
+            });
+        });
+        viewer.open( '/test/data/testpattern.dzi' );
+    });
+
+
+})();

test/test.css

@@ -17,3 +17,8 @@
     height: 500px;
     width: 500px;
 }
+
+#layersexample {
+    height: 500px;
+    width: 500px;
+}

test/test.html

@@ -27,5 +27,6 @@
     <script src="/test/utils.js"></script>
     <script src="/test/events.js"></script>
     <script src="/test/units.js"></script>
+    <script src="/test/layers.js"></script>
 </body>
 </html>