From 6278f6fe69767cf21c1d3361bc141321a282d9ef Mon Sep 17 00:00:00 2001
From: Dan Vanderkam <dan@dygraphs.com>
Date: Thu, 8 Mar 2012 19:34:08 -0500
Subject: [PATCH] Check for balanced context.save() and context.restore() calls

---
 auto_tests/tests/CanvasAssertions.js | 30 ++++++++++++++++++++++++++----
 auto_tests/tests/error_bars.js       |  1 +
 auto_tests/tests/simple_drawing.js   | 12 +++++++++++-
 3 files changed, 38 insertions(+), 5 deletions(-)

diff --git a/auto_tests/tests/CanvasAssertions.js b/auto_tests/tests/CanvasAssertions.js
index 8b52155..6481c60 100644
--- a/auto_tests/tests/CanvasAssertions.js
+++ b/auto_tests/tests/CanvasAssertions.js
@@ -83,7 +83,29 @@ CanvasAssertions.assertLineDrawn = function(proxy, p1, p2, attrs) {
   };
   fail("Can't find a line drawn between " + p1 +
       " and " + p2 + " with attributes " + toString(attrs));
-}
+};
+
+/**
+ * Verifies that every call to context.save() has a matching call to
+ * context.restore().
+ */
+CanvasAssertions.assertBalancedSaveRestore = function(proxy) {
+  var depth = 0;
+  for (var i = 0; i < proxy.calls__.length; i++) {
+    var call = proxy.calls__[i];
+    if (call.name == "save") depth++
+    if (call.name == "restore") {
+      if (depth == 0) {
+        fail("Too many calls to restore()");
+      }
+      depth--;
+    }
+  }
+
+  if (depth > 0) {
+    fail("Missing matching 'context.restore()' calls.");
+  }
+};
 
 /**
  * Checks how many lines of the given color have been drawn.
@@ -98,7 +120,7 @@ CanvasAssertions.numLinesDrawn = function(proxy, color) {
     }
   }
   return num_lines;
-}
+};
 
 CanvasAssertions.matchPixels = function(expected, actual) {
   // Expect array of two integers. Assuming the values are within one
@@ -106,7 +128,7 @@ CanvasAssertions.matchPixels = function(expected, actual) {
   // who knows what pixel a value of 5.8888 results in.
   return Math.abs(expected[0] - actual[0]) < 1 &&
       Math.abs(expected[1] - actual[1]) < 1;
-}
+};
 
 CanvasAssertions.matchAttributes = function(expected, actual) {
   for (var attr in expected) {
@@ -115,4 +137,4 @@ CanvasAssertions.matchAttributes = function(expected, actual) {
     }
   }
   return true;
-}
+};
diff --git a/auto_tests/tests/error_bars.js b/auto_tests/tests/error_bars.js
index 8bc20e3..c9e3a38 100644
--- a/auto_tests/tests/error_bars.js
+++ b/auto_tests/tests/error_bars.js
@@ -86,5 +86,6 @@ errorBarsTestCase.prototype.testErrorBarsDrawn = function() {
     xy2 = g.toDomCoords(data[i + 1][0], data[i + 1][1][1]);
     CanvasAssertions.assertLineDrawn(htx, xy1, xy2, attrs);
   }
+  CanvasAssertions.assertBalancedSaveRestore(htx);
 };
 
diff --git a/auto_tests/tests/simple_drawing.js b/auto_tests/tests/simple_drawing.js
index 0ea13a4..8f3b0c5 100644
--- a/auto_tests/tests/simple_drawing.js
+++ b/auto_tests/tests/simple_drawing.js
@@ -55,7 +55,16 @@ SimpleDrawingTestCase.prototype.testDrawSimpleRangePlusOne = function() {
     strokeStyle: "#008080",
     lineWidth: 1
   });
-}
+  CanvasAssertions.assertBalancedSaveRestore(htx);
+};
+
+SimpleDrawingTestCase.prototype.testDrawWithAxis = function() {
+  var graph = document.getElementById("graph");
+  var g = new Dygraph(graph, ZERO_TO_FIFTY);
+
+  var htx = g.hidden_ctx_;
+  CanvasAssertions.assertBalancedSaveRestore(htx);
+};
 
 /**
  * Tests that it is drawing dashes, and it remember the dash history between
@@ -79,4 +88,5 @@ SimpleDrawingTestCase.prototype.testDrawSimpleDash = function() {
   htx = g.hidden_ctx_;
 
   assertEquals(29, CanvasAssertions.numLinesDrawn(htx, "#ff0000"));
+  CanvasAssertions.assertBalancedSaveRestore(htx);
 };
-- 
2.7.4