testing/mochitest/mozprefs.js

   1 (function() {
   2
   3   // NOTE: You *must* also include this line in any test that uses this file:
   4   netscape.security.PrivilegeManager.enablePrivilege("UniversalXPConnect");
   5
   6   var prefService = Components.classes["@mozilla.org/preferences-service;1"]
   7                               .getService(Components.interfaces.nsIPrefService);
   8
   9   function determinePrefKind(branch, prefName) {
  10     switch (branch.getPrefType(prefName)) {
  11     case branch.PREF_STRING:    return "CharPref";
  12     case branch.PREF_INT:       return "IntPref";
  13     case branch.PREF_BOOL:      return "BoolPref";
  14     default: /* PREF_INVALID */ return "ComplexValue";
  15     }
  16   }
  17
  18   function memoize(fn, obj) {
  19     var cache = {}, sep = '___',
  20         join = Array.prototype.join;
  21     return function() {
  22       var key = join.call(arguments, sep);
  23       if (!(key in cache))
  24         cache[key] = fn.apply(obj, arguments);
  25       return cache[key];
  26     };
  27   }
  28
  29   var makeAccessor = memoize(function(pref) {
  30     var splat = pref.split('.'),
  31         basePref = splat.pop(),
  32         branch, kind;
  33
  34     try {
  35       branch = prefService.getBranch(splat.join('.') + '.')
  36     } catch (e) {
  37       alert("Calling prefService.getBranch failed: " +
  38         "did you read the NOTE in mozprefs.js?");
  39       throw e;
  40     }
  41
  42     kind = determinePrefKind(branch, basePref);
  43
  44     return function(value) {
  45       var oldValue = branch['get' + kind](basePref);
  46       if (arguments.length > 0)
  47         branch['set' + kind](basePref, value);
  48       return oldValue;
  49     };
  50   });
  51
  52   /* function pref(name[, value[, fn[, obj]]])
  53    * -----------------------------------------
  54    * Use cases:
  55    *
  56    *   1. Get the value of the dom.disable_open_during_load preference:
  57    *
  58    *      pref('dom.disable_open_during_load')
  59    *
  60    *   2. Set the preference to true, returning the old value:
  61    *
  62    *      var oldValue = pref('dom.disable_open_during_load', true);
  63    *
  64    *   3. Set the value of the preference to true just for the duration
  65    *      of the specified function's execution:
  66    *
  67    *      pref('dom.disable_open_during_load', true, function() {
  68    *        window.open(this.getUrl()); // fails if still loading
  69    *      }, this); // for convenience, allow binding
  70    *
  71    *      Rationale: Unless a great deal of care is taken to catch all
  72    *                 exceptions and restore original preference values,
  73    *                 manually setting & restoring preferences can lead
  74    *                 to unpredictable test behavior.  The try-finally
  75    *                 block below eliminates that risk.
  76    */
  77   function pref(name, /*optional:*/ value, fn, obj) {
  78     var acc = makeAccessor(name);
  79     switch (arguments.length) {
  80     case 1: return acc();
  81     case 2: return acc(value);
  82     default:
  83       var oldValue = acc(value),
  84           extra_args = [].slice.call(arguments, 4);
  85       try { return fn.apply(obj, extra_args) }
  86       finally { acc(oldValue) } // reset no matter what
  87     }
  88   };
  89
  90   window.pref = pref; // export
  91
  92 })();