1 files changed, 90 insertions, 0 deletions
diff --git a/guidelines/wikipedia/src/color.js b/guidelines/wikipedia/src/color.js
new file mode 100644
index 0000000..b9eb31b
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+++ b/guidelines/wikipedia/src/color.js
@@ -0,0 +1,90 @@
+exports.name = "Color use";
+exports.description = "Use colors that have sufficient contrast and avoid issues with common forms of color blindness.";
+
+var fc = fiveui.color;
+var AA_NORMAL = 4.5;
+var AA_BIG = 3;
+var AAA_NORMAL = 7;
+var AAA_BIG = 4.5;
+
+
+/**
+ * Compute the font size in points, assuming 96dpi.
+ */
+var fontSizePt = function(elt) {
+  var px = $(elt).css('font-size');
+  return parseInt(px) * 72 / 96;
+};
+
+var isBold = function(elt) {
+  return $(elt).css('font-weight') == 'bold';
+};
+
+/**
+ * See if the text counts as "large scale" according to the W3C:
+ * (http://www.w3.org/TR/2008/REC-WCAG20-20081211/#larger-scaledef)
+ */
+var isLargeScale = function(elt) {
+  var size = fontSizePt(elt);
+  var bld = isBold(elt);
+  return (18 <= size || (14 <= size && bld));
+};
+
+var getAARatio = function(elt) {
+  if (isLargeScale(elt)) {
+    return AA_BIG;
+  }
+  return AA_NORMAL;
+};
+
+var getAAARatio = function(elt) {
+  if (isLargeScale(elt)) {
+    return AAA_BIG;
+  }
+  return AAA_NORMAL;
+};
+
+exports.rule = function (report) {
+
+  $5('#mw-content-text *')
+    // filter for lowest level elts having non-empty text
+    .filter(function () {
+      var $this = $(this);
+      return $this.children().length === 0 && $.trim($this.text()).length > 0;
+    })
+    .filter(exceptions)
+    .each(function (i, elt) {
+      var fg = fc.colorToRGB($(this).css('color'));
+      var bg = fc.findBGColor($(this));
+      if (fg && bg) {
+        var ratio = fc.contrast(fc.luminance(fg), fc.luminance(bg));
+        if (ratio < getAARatio(elt)) {
+          report.error('Element has poor contrast: ' + ratio +
+                       " ratio should be greater than " + getAARatio(elt), elt);
+        } else if (ratio < getAAARatio(elt)){
+          report.warning('Element has poor contrast: ' + ratio +
+                      " ratio should be greater than " + getAAARatio(elt), elt);
+        }
+      }
+  });
+};
+
+function exceptions() {
+  var $elem = $(this);
+  return !isStandardLink($elem) &&
+    !isNavboxLink($elem);
+}
+
+function isStandardLink($elem) {
+  var standard = ['new', 'external', 'extiw'];
+  var $a = $elem.closest('a');
+  return $a.is('a') && standard.some(function(klass) {
+    return $a.hasClass(klass);
+  });
+}
+
+function isNavboxLink($elem) {
+  var $a = $elem.closest('a');
+  var $nav = $a.closest('th.navbox-group');
+  return $a.length > 0 && $nav.length > 0;
+}