Bug 1090950 - Properly bound fillRect call for Graphs with selections that start or end out of bounds. r=vporof

browser/devtools/shared/test/browser.ini

@@ -56,6 +56,7 @@ support-files =
 [browser_graphs-07a.js]
 [browser_graphs-07b.js]
 [browser_graphs-07c.js]
+[browser_graphs-07d.js]
 [browser_graphs-08.js]
 [browser_graphs-09a.js]
 [browser_graphs-09b.js]

browser/devtools/shared/test/browser_graphs-07d.js

@@ -0,0 +1,49 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+// Tests that selections are drawn onto the canvas.
+
+const TEST_DATA = [{ delta: 112, value: 48 }, { delta: 213, value: 59 }, { delta: 313, value: 60 }, { delta: 413, value: 59 }, { delta: 530, value: 59 }, { delta: 646, value: 58 }, { delta: 747, value: 60 }, { delta: 863, value: 48 }, { delta: 980, value: 37 }, { delta: 1097, value: 30 }, { delta: 1213, value: 29 }, { delta: 1330, value: 23 }, { delta: 1430, value: 10 }, { delta: 1534, value: 17 }, { delta: 1645, value: 20 }, { delta: 1746, value: 22 }, { delta: 1846, value: 39 }, { delta: 1963, value: 26 }, { delta: 2080, value: 27 }, { delta: 2197, value: 35 }, { delta: 2312, value: 47 }, { delta: 2412, value: 53 }, { delta: 2514, value: 60 }, { delta: 2630, value: 37 }, { delta: 2730, value: 36 }, { delta: 2830, value: 37 }, { delta: 2946, value: 36 }, { delta: 3046, value: 40 }, { delta: 3163, value: 47 }, { delta: 3280, value: 41 }, { delta: 3380, value: 35 }, { delta: 3480, value: 27 }, { delta: 3580, value: 39 }, { delta: 3680, value: 42 }, { delta: 3780, value: 49 }, { delta: 3880, value: 55 }, { delta: 3980, value: 60 }, { delta: 4080, value: 60 }, { delta: 4180, value: 60 }];
+const TEST_REGIONS = [{ start: 320, end: 460 }, { start: 780, end: 860 }];
+let {LineGraphWidget} = Cu.import("resource:///modules/devtools/Graphs.jsm", {});
+let {Promise} = devtools.require("resource://gre/modules/Promise.jsm");
+
+add_task(function*() {
+  yield promiseTab("about:blank");
+  yield performTest();
+  gBrowser.removeCurrentTab();
+});
+
+function* performTest() {
+  let [host, win, doc] = yield createHost();
+  let graph = new LineGraphWidget(doc.body, "fps");
+  yield graph.once("ready");
+
+  testGraph(graph);
+
+  yield graph.destroy();
+  host.destroy();
+}
+
+function testGraph(graph) {
+  graph.setData(TEST_DATA);
+  graph.setRegions(TEST_REGIONS);
+
+  // Measure the color of the first pixel before any selection is made.
+  graph._onAnimationFrame();
+  let pixelNoSelection = graph._ctx.getImageData(1, 1, 1, 1).data;
+
+  graph.setSelection({ start: 0, end: 10 });
+  graph._onAnimationFrame();
+  let pixelNormalSelection = graph._ctx.getImageData(1, 1, 1, 1).data;
+
+  Assert.notDeepEqual(pixelNormalSelection, pixelNoSelection,
+    "The first pixel is part of the drawn selection.");
+
+  graph.setSelection({ start: graph.width + 100, end: -100 });
+  graph._onAnimationFrame();
+  let pixelFullSelection = graph._ctx.getImageData(1, 1, 1, 1).data;
+
+  Assert.deepEqual(pixelFullSelection, pixelNormalSelection,
+    "The first pixel is still part of the drawn selection.");
+}

browser/devtools/shared/widgets/Graphs.jsm

@@ -826,7 +826,9 @@ AbstractCanvasGraph.prototype = {
       stripesColor: this.selectionStripesColor
     });
     ctx.fillStyle = pattern;
-    ctx.fillRect(start, 0, end - start, this._height);
+    let rectStart = Math.min(this._width, Math.max(0, start));
+    let rectEnd = Math.min(this._width, Math.max(0, end));
+    ctx.fillRect(rectStart, 0, rectEnd - rectStart, this._height);
 
     // Draw left boundary.