modularize the display of diffs for skpdiff

experimental/skpdiff/diff_viewer.js

-function DiffViewController($scope) {
+angular.module('diff_viewer', []).
+config(['$routeProvider', function($routeProvider) {
+    // Show the list of differences by default
+    $routeProvider.
+    otherwise({ templateUrl: '/diff_list.html', controller: DiffListController});
+}]).
+directive('swapImg', function() {
+    // Custom directive for showing an image that gets swapped my mouseover.
+    return {
+        restrict: 'E', // The directive can be used as an element name
+        replace: true, // The directive replaces itself with the template
+        template: '<canvas ng-mouseenter="swap()" ng-mouseleave="swap()"></canvas>',
+        scope: { // The attributes below are bound to the scope
+            leftSrc: '@',
+            rightSrc: '@',
+            side: '@'
+        },
+        link: function(scope, elm, attrs, ctrl) {
+            var leftImage = new Image();
+            var rightImage = new Image();
+            var ctx = elm[0].getContext('2d');
+
+            scope.render = function() {
+                var image;
+                if (scope.side == "left") {
+                    image = leftImage;
+                } else {
+                    image = rightImage;
+                }
+
+                // Make it so the maximum size of an image is 500, and the images are scaled
+                // down in halves.
+                var divisor = 1;
+                while ((image.width / divisor) > 500) {
+                    divisor *= 2;
+                }
+
+                // Set canvas to correct size and draw the image into it
+                elm[0].width = image.width / divisor;
+                elm[0].height = image.height / divisor;
+                ctx.drawImage(image, 0, 0, elm[0].width, elm[0].height);
+            };
+
+            // When the leftSrc attribute changes, load the image and then rerender
+            attrs.$observe('leftSrc', function(value) {
+                leftImage.src = value;
+                leftImage.onload = function() {
+                    if (scope.side == "left") {
+                        scope.render();
+                    }
+                };
+            });
+
+            // When the rightSrc attribute changes, load the image and then rerender
+            attrs.$observe('rightSrc', function(value) {
+                rightImage.src = value;
+                rightImage.onload = function() {
+                    if (scope.side == "right") {
+                        scope.render();
+                    }
+                };
+            });
+
+            // Swap which side to draw onto the canvas and then rerender
+            scope.swap = function() {
+                if (scope.side == "left") {
+                    scope.side = "right";
+                } else {
+                    scope.side = "left";
+                }
+                scope.render();
+            };
+        }
+    };
+});
+
+function DiffListController($scope) {
+    // Label each kind of differ for the sort buttons.
     $scope.differs = [
         {
             "title": "Different Pixels"
         },
         {
             "title": "Perceptual Difference"
         }
     ];
+
+    // Puts the records within AngularJS scope
+    $scope.records = SkPDiffRecords.records;
+
+    // Indicates which diff metric is used for sorting
     $scope.sortIndex = 1;
-    $scope.records = SkPDiffRecords.records;
-    $scope.highlight = function(differName) {
-        console.debug(differName);
-    }
-    $scope.setSortIndex = function(a) {
-        $scope.sortIndex = a;
-    }
-    $scope.sortingDiffer = function(a) {
-        console.debug($scope.sortIndex);
-        return a.diffs[$scope.sortIndex].result;
-    }
-}
+
+    // Called by the sort buttons to adjust the metric used for sorting
+    $scope.setSortIndex = function(idx) {
+        $scope.sortIndex = idx;
+    };
+
+    // A predicate for pulling out the number used for sorting
+    $scope.sortingDiffer = function(record) {
+        return record.diffs[$scope.sortIndex].result;
+    };
+}