X-Git-Url: https://adrianiainlam.tk/git/?a=blobdiff_plain;f=auto_tests%2Ftests%2FUtil.js;h=53a83f8130515a86bfc8264c3eb609e65d706d7d;hb=378194819965ebefef3b6c93e180cf343dcff997;hp=2b308b36df08b6e0a017ec6ff64410488367f240;hpb=20bb4e9d1e3da5bedaee7584a9e91aefd9e3a6d4;p=dygraphs.git

diff --git a/auto_tests/tests/Util.js b/auto_tests/tests/Util.js
index 2b308b3..53a83f8 100644
--- a/auto_tests/tests/Util.js
+++ b/auto_tests/tests/Util.js
@@ -79,3 +79,57 @@ Util.makeNumbers = function(ary) {
   }
   return ret;
 };
+
+
+/**
+ * Sample a pixel from the canvas.
+ * Returns an [r, g, b, a] tuple where each values is in [0, 255].
+ */
+Util.samplePixel = function(canvas, x, y) {
+  var ctx = canvas.getContext("2d");  // bypasses Proxy if applied.
+
+  // TODO(danvk): Any performance issues with this?
+  var imageData = ctx.getImageData(0, 0, canvas.width, canvas.height);
+
+  var scale = Dygraph.getContextPixelRatio(ctx);
+
+  var i = 4 * (x * scale + imageData.width * y * scale);
+  var d = imageData.data;
+  return [d[i], d[i+1], d[i+2], d[i+3]];
+};
+
+/**
+ * Overrides the browser's built-in XMLHttpRequest with a mock.
+ * Usage:
+ *
+ * var mockXhr = Util.overrideXMLHttpRequest(your_data);
+ * ... call code that does an XHR ...
+ * mockXhr.respond();  // restores default behavior.
+ * ... do your assertions ...
+ */
+Util.overrideXMLHttpRequest = function(data) {
+  var originalXMLHttpRequest = XMLHttpRequest;
+
+  var requests = [];
+  var FakeXMLHttpRequest = function () {
+    requests.push(this);
+  };
+  FakeXMLHttpRequest.prototype.open = function () {};
+  FakeXMLHttpRequest.prototype.send = function () {
+    this.readyState = 4;
+    this.status = 200;
+    this.responseText = data;
+  };
+  FakeXMLHttpRequest.restore = function() {
+    XMLHttpRequest = originalXMLHttpRequest;
+  };
+  FakeXMLHttpRequest.respond = function() {
+    for (var i = 0; i < requests.length; i++) {
+      requests[i].onreadystatechange();
+    }
+    FakeXMLHttpRequest.restore();
+  };
+  XMLHttpRequest = FakeXMLHttpRequest;
+  return FakeXMLHttpRequest;
+};
+