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93 lines
2.9 KiB
JavaScript
93 lines
2.9 KiB
JavaScript
(function() {
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// NOTE: You *must* also include this line in any test that uses this file:
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netscape.security.PrivilegeManager.enablePrivilege("UniversalXPConnect");
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var prefService = Components.classes["@mozilla.org/preferences-service;1"]
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.getService(Components.interfaces.nsIPrefService);
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function determinePrefKind(branch, prefName) {
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switch (branch.getPrefType(prefName)) {
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case branch.PREF_STRING: return "CharPref";
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case branch.PREF_INT: return "IntPref";
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case branch.PREF_BOOL: return "BoolPref";
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default: /* PREF_INVALID */ return "ComplexValue";
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}
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}
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function memoize(fn, obj) {
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var cache = {}, sep = '___',
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join = Array.prototype.join;
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return function() {
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var key = join.call(arguments, sep);
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if (!(key in cache))
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cache[key] = fn.apply(obj, arguments);
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return cache[key];
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};
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}
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var makeAccessor = memoize(function(pref) {
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var splat = pref.split('.'),
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basePref = splat.pop(),
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branch, kind;
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try {
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branch = prefService.getBranch(splat.join('.') + '.')
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} catch (e) {
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alert("Calling prefService.getBranch failed: " +
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"did you read the NOTE in mozprefs.js?");
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throw e;
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}
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kind = determinePrefKind(branch, basePref);
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return function(value) {
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var oldValue = branch['get' + kind](basePref);
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if (arguments.length > 0)
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branch['set' + kind](basePref, value);
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return oldValue;
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};
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});
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/* function pref(name[, value[, fn[, obj]]])
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* -----------------------------------------
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* Use cases:
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*
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* 1. Get the value of the dom.disable_open_during_load preference:
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*
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* pref('dom.disable_open_during_load')
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*
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* 2. Set the preference to true, returning the old value:
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*
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* var oldValue = pref('dom.disable_open_during_load', true);
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*
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* 3. Set the value of the preference to true just for the duration
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* of the specified function's execution:
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*
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* pref('dom.disable_open_during_load', true, function() {
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* window.open(this.getUrl()); // fails if still loading
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* }, this); // for convenience, allow binding
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*
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* Rationale: Unless a great deal of care is taken to catch all
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* exceptions and restore original preference values,
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* manually setting & restoring preferences can lead
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* to unpredictable test behavior. The try-finally
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* block below eliminates that risk.
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*/
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function pref(name, /*optional:*/ value, fn, obj) {
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var acc = makeAccessor(name);
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switch (arguments.length) {
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case 1: return acc();
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case 2: return acc(value);
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default:
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var oldValue = acc(value),
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extra_args = [].slice.call(arguments, 4);
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try { return fn.apply(obj, extra_args) }
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finally { acc(oldValue) } // reset no matter what
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}
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};
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window.pref = pref; // export
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})();
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