auto_tests/tests/CanvasAssertions.js

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  20
  21 /**
  22  * @fileoverview Assertions and other code used to test a canvas proxy.
  23  *
  24  * @author konigsberg@google.com (Robert Konigsberg)
  25  */
  26
  27 var CanvasAssertions = {};
  28
  29 /**
  30  * Updates path attributes to match fill/stroke operations.
  31  *
  32  * This sets fillStyle to undefined for stroked paths,
  33  * and strokeStyle to undefined for filled paths, to simplify
  34  * matchers such as numLinesDrawn.
  35  *
  36  * @private
  37  * @param {Array.<Object>} List of operations.
  38  */
  39 CanvasAssertions.cleanPathAttrs_ = function(calls) {
  40   var isStroked = true;
  41   for (var i = calls.length - 1; i >= 0; --i) {
  42     var call = calls[i];
  43     var name = call.name;
  44     if (name == 'stroke') {
  45       isStroked = true;
  46     } else if (name == 'fill') {
  47       isStroked = false;
  48     } else if (name == 'lineTo') {
  49       if (isStroked) {
  50         call.properties.fillStyle = undefined;
  51       } else {
  52         call.properties.strokeStyle = undefined;
  53       }
  54     }
  55   }
  56 };
  57
  58
  59 /**
  60  * Assert that a line is drawn between the two points
  61  *
  62  * This merely looks for one of these four possibilities:
  63  * moveTo(p1) -> lineTo(p2)
  64  * moveTo(p2) -> lineTo(p1)
  65  * lineTo(p1) -> lineTo(p2)
  66  * lineTo(p2) -> lineTo(p1)
  67  *
  68  * predicate is meant to be used when you want to track things like
  69  * color and stroke width. It can either be a hash of context properties,
  70  * or a function that accepts the current call.
  71  */
  72 CanvasAssertions.assertLineDrawn = function(proxy, p1, p2, predicate) {
  73   CanvasAssertions.cleanPathAttrs_(proxy.calls__);
  74   // found = 1 when prior loop found p1.
  75   // found = 2 when prior loop found p2.
  76   var priorFound = 0;
  77   for (var i = 0; i < proxy.calls__.length; i++) {
  78     var call = proxy.calls__[i];
  79
  80     // This disables lineTo -> moveTo pairs.
  81     if (call.name == "moveTo" && priorFound > 0) {
  82       priorFound = 0;
  83     }
  84
  85     var found = 0;
  86     if (call.name == "moveTo" || call.name == "lineTo") {
  87       var matchp1 = CanvasAssertions.matchPixels(p1, call.args);
  88       var matchp2 = CanvasAssertions.matchPixels(p2, call.args);
  89       if (matchp1 || matchp2) {
  90         if (priorFound == 1 && matchp2) {
  91           if (CanvasAssertions.match(predicate, call)) {
  92             return;
  93           }
  94         }
  95         if (priorFound == 2 && matchp1) {
  96           if (CanvasAssertions.match(predicate, call)) {
  97             return;
  98           }
  99         }
 100         found = matchp1 ? 1 : 2;
 101       }
 102     }
 103     priorFound = found;
 104   }
 105
 106   var toString = function(x) {
 107     var s = "{";
 108     for (var prop in x) {
 109       if (x.hasOwnProperty(prop)) {
 110         if (s.length > 1) {
 111           s = s + ", ";
 112         }
 113         s = s + prop + ": " + x[prop];
 114       }
 115     }
 116     return s + "}";
 117   };
 118   fail("Can't find a line drawn between " + p1 +
 119       " and " + p2 + " with attributes " + toString(predicate));
 120 };
 121
 122 /**
 123  * Return the lines drawn with specific attributes.
 124  *
 125  * This merely looks for one of these four possibilities:
 126  * moveTo(p1) -> lineTo(p2)
 127  * moveTo(p2) -> lineTo(p1)
 128  * lineTo(p1) -> lineTo(p2)
 129  * lineTo(p2) -> lineTo(p1)
 130  *
 131  * attrs is meant to be used when you want to track things like
 132  * color and stroke width.
 133  */
 134 CanvasAssertions.getLinesDrawn = function(proxy, predicate) {
 135   CanvasAssertions.cleanPathAttrs_(proxy.calls__);
 136   var lastCall;
 137   var lines = [];
 138   for (var i = 0; i < proxy.calls__.length; i++) {
 139     var call = proxy.calls__[i];
 140
 141     if (call.name == "lineTo") {
 142       if (lastCall != null) {
 143         if (CanvasAssertions.match(predicate, call)) {
 144           lines.push([lastCall, call]);
 145         }
 146       }
 147     }
 148
 149     lastCall = (call.name === "lineTo" || call.name === "moveTo") ? call : null;
 150   }
 151   return lines;
 152 };
 153
 154 /**
 155  * Verifies that every call to context.save() has a matching call to
 156  * context.restore().
 157  */
 158 CanvasAssertions.assertBalancedSaveRestore = function(proxy) {
 159   var depth = 0;
 160   for (var i = 0; i < proxy.calls__.length; i++) {
 161     var call = proxy.calls__[i];
 162     if (call.name == "save") depth++
 163     if (call.name == "restore") {
 164       if (depth == 0) {
 165         fail("Too many calls to restore()");
 166       }
 167       depth--;
 168     }
 169   }
 170
 171   if (depth > 0) {
 172     fail("Missing matching 'context.restore()' calls.");
 173   }
 174 };
 175
 176 /**
 177  * Checks how many lines of the given color have been drawn.
 178  * @return {Integer} The number of lines of the given color.
 179  */
 180 // TODO(konigsberg): change 'color' to predicate? color is the
 181 // common case. Possibly allow predicate to be function, hash, or
 182 // string representing color?
 183 CanvasAssertions.numLinesDrawn = function(proxy, color) {
 184   CanvasAssertions.cleanPathAttrs_(proxy.calls__);
 185   var num_lines = 0;
 186   for (var i = 0; i < proxy.calls__.length; i++) {
 187     var call = proxy.calls__[i];
 188
 189     // note: Don't simplify these two conditionals into one. The
 190     // separation simplifies debugging tricky tests.
 191     if (call.name == "lineTo") {
 192       if (call.properties.strokeStyle == color) {
 193         num_lines++;
 194       }
 195     }
 196   }
 197   return num_lines;
 198 };
 199
 200 /**
 201  * Asserts that a series of lines are connected. For example,
 202  * assertConsecutiveLinesDrawn(proxy, [[x1, y1], [x2, y2], [x3, y3]], predicate)
 203  * is shorthand for
 204  * assertLineDrawn(proxy, [x1, y1], [x2, y2], predicate)
 205  * assertLineDrawn(proxy, [x2, y2], [x3, y3], predicate)
 206  */
 207 CanvasAssertions.assertConsecutiveLinesDrawn = function(proxy, segments, predicate) {
 208   for (var i = 0; i < segments.length - 1; i++) {
 209     CanvasAssertions.assertLineDrawn(proxy, segments[i], segments[i+1], predicate);
 210   }
 211 }
 212
 213 CanvasAssertions.matchPixels = function(expected, actual) {
 214   // Expect array of two integers. Assuming the values are within one
 215   // integer unit of each other. This should be tightened down by someone
 216   // who knows what pixel a value of 5.8888 results in.
 217   return Math.abs(expected[0] - actual[0]) < 1 &&
 218       Math.abs(expected[1] - actual[1]) < 1;
 219 };
 220
 221 /**
 222  * For matching a proxy call against defined conditions.
 223  * predicate can either by a hash of items compared against call.properties,
 224  * or it can be a function that accepts the call, and returns true or false.
 225  * If it's null, this function returns true.
 226  */
 227 CanvasAssertions.match = function(predicate, call) {
 228   if (predicate === null) {
 229     return true;
 230   }
 231   if (typeof(predicate) === "function") {
 232     return predicate(call);
 233   } else {
 234     for (var attr in predicate) {
 235       if (predicate.hasOwnProperty(attr) && predicate[attr] != call.properties[attr]) {
 236         return false;
 237       }
 238     }
 239   }
 240   return true;
 241 };