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Diffstat (limited to 'toolkit/modules/Preferences.sys.mjs')
| -rw-r--r-- | toolkit/modules/Preferences.sys.mjs | 451 |
1 files changed, 451 insertions, 0 deletions
diff --git a/toolkit/modules/Preferences.sys.mjs b/toolkit/modules/Preferences.sys.mjs new file mode 100644 index 0000000000..619087aa67 --- /dev/null +++ b/toolkit/modules/Preferences.sys.mjs @@ -0,0 +1,451 @@ +/* This Source Code Form is subject to the terms of the Mozilla Public + * License, v. 2.0. If a copy of the MPL was not distributed with this + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ + +// The minimum and maximum integers that can be set as preferences. +// The range of valid values is narrower than the range of valid JS values +// because the native preferences code treats integers as NSPR PRInt32s, +// which are 32-bit signed integers on all platforms. +const MAX_INT = 0x7fffffff; // Math.pow(2, 31) - 1 +const MIN_INT = -0x80000000; + +export function Preferences(args) { + this._cachedPrefBranch = null; + if (isObject(args)) { + if (args.branch) { + this._branchStr = args.branch; + } + if (args.defaultBranch) { + this._defaultBranch = args.defaultBranch; + } + if (args.privacyContext) { + this._privacyContext = args.privacyContext; + } + } else if (args) { + this._branchStr = args; + } +} + +/** + * Get the value of a pref, if any; otherwise return the default value. + * + * @param prefName {String|Array} + * the pref to get, or an array of prefs to get + * + * @param defaultValue + * the default value, if any, for prefs that don't have one + * + * @param valueType + * the XPCOM interface of the pref's complex value type, if any + * + * @returns the value of the pref, if any; otherwise the default value + */ +Preferences.get = function (prefName, defaultValue, valueType = null) { + if (Array.isArray(prefName)) { + return prefName.map(v => this.get(v, defaultValue)); + } + + return this._get(prefName, defaultValue, valueType); +}; + +Preferences._get = function (prefName, defaultValue, valueType) { + switch (this._prefBranch.getPrefType(prefName)) { + case Ci.nsIPrefBranch.PREF_STRING: + if (valueType) { + let ifaces = ["nsIFile", "nsIPrefLocalizedString"]; + if (ifaces.includes(valueType.name)) { + return this._prefBranch.getComplexValue(prefName, valueType).data; + } + } + return this._prefBranch.getStringPref(prefName); + + case Ci.nsIPrefBranch.PREF_INT: + return this._prefBranch.getIntPref(prefName); + + case Ci.nsIPrefBranch.PREF_BOOL: + return this._prefBranch.getBoolPref(prefName); + + case Ci.nsIPrefBranch.PREF_INVALID: + return defaultValue; + + default: + // This should never happen. + throw new Error( + `Error getting pref ${prefName}; its value's type is ` + + `${this._prefBranch.getPrefType(prefName)}, which I don't ` + + `know how to handle.` + ); + } +}; + +/** + * Set a preference to a value. + * + * You can set multiple prefs by passing an object as the only parameter. + * In that case, this method will treat the properties of the object + * as preferences to set, where each property name is the name of a pref + * and its corresponding property value is the value of the pref. + * + * @param prefName {String|Object} + * the name of the pref to set; or an object containing a set + * of prefs to set + * + * @param prefValue {String|Number|Boolean} + * the value to which to set the pref + * + * Note: Preferences cannot store non-integer numbers or numbers outside + * the signed 32-bit range -(2^31-1) to 2^31-1, If you have such a number, + * store it as a string by calling toString() on the number before passing + * it to this method, i.e.: + * Preferences.set("pi", 3.14159.toString()) + * Preferences.set("big", Math.pow(2, 31).toString()). + */ +Preferences.set = function (prefName, prefValue) { + if (isObject(prefName)) { + for (let [name, value] of Object.entries(prefName)) { + this.set(name, value); + } + return; + } + + this._set(prefName, prefValue); +}; + +Preferences._set = function (prefName, prefValue) { + let prefType; + if (typeof prefValue != "undefined" && prefValue != null) { + prefType = prefValue.constructor.name; + } + + switch (prefType) { + case "String": + this._prefBranch.setStringPref(prefName, prefValue); + break; + + case "Number": + // We throw if the number is outside the range, since the result + // will never be what the consumer wanted to store, but we only warn + // if the number is non-integer, since the consumer might not mind + // the loss of precision. + if (prefValue > MAX_INT || prefValue < MIN_INT) { + throw new Error( + `you cannot set the ${prefName} pref to the number ` + + `${prefValue}, as number pref values must be in the signed ` + + `32-bit integer range -(2^31-1) to 2^31-1. To store numbers ` + + `outside that range, store them as strings.` + ); + } + this._prefBranch.setIntPref(prefName, prefValue); + if (prefValue % 1 != 0) { + console.error( + "Warning: setting the ", + prefName, + " pref to the non-integer number ", + prefValue, + " converted it " + + "to the integer number " + + this.get(prefName) + + "; to retain fractional precision, store non-integer " + + "numbers as strings." + ); + } + break; + + case "Boolean": + this._prefBranch.setBoolPref(prefName, prefValue); + break; + + default: + throw new Error( + `can't set pref ${prefName} to value '${prefValue}'; ` + + `it isn't a String, Number, or Boolean` + ); + } +}; + +/** + * Whether or not the given pref has a value. This is different from isSet + * because it returns true whether the value of the pref is a default value + * or a user-set value, while isSet only returns true if the value + * is a user-set value. + * + * @param prefName {String|Array} + * the pref to check, or an array of prefs to check + * + * @returns {Boolean|Array} + * whether or not the pref has a value; or, if the caller provided + * an array of pref names, an array of booleans indicating whether + * or not the prefs have values + */ +Preferences.has = function (prefName) { + if (Array.isArray(prefName)) { + return prefName.map(this.has, this); + } + + return ( + this._prefBranch.getPrefType(prefName) != Ci.nsIPrefBranch.PREF_INVALID + ); +}; + +/** + * Whether or not the given pref has a user-set value. This is different + * from |has| because it returns true only if the value of the pref is a user- + * set value, while |has| returns true if the value of the pref is a default + * value or a user-set value. + * + * @param prefName {String|Array} + * the pref to check, or an array of prefs to check + * + * @returns {Boolean|Array} + * whether or not the pref has a user-set value; or, if the caller + * provided an array of pref names, an array of booleans indicating + * whether or not the prefs have user-set values + */ +Preferences.isSet = function (prefName) { + if (Array.isArray(prefName)) { + return prefName.map(this.isSet, this); + } + + return this.has(prefName) && this._prefBranch.prefHasUserValue(prefName); +}; + +/** + * Whether or not the given pref has a user-set value. Use isSet instead, + * which is equivalent. + * @deprecated + */ +Preferences.modified = function (prefName) { + return this.isSet(prefName); +}; + +Preferences.reset = function (prefName) { + if (Array.isArray(prefName)) { + prefName.map(v => this.reset(v)); + return; + } + + this._prefBranch.clearUserPref(prefName); +}; + +/** + * Lock a pref so it can't be changed. + * + * @param prefName {String|Array} + * the pref to lock, or an array of prefs to lock + */ +Preferences.lock = function (prefName) { + if (Array.isArray(prefName)) { + prefName.map(this.lock, this); + } + + this._prefBranch.lockPref(prefName); +}; + +/** + * Unlock a pref so it can be changed. + * + * @param prefName {String|Array} + * the pref to lock, or an array of prefs to lock + */ +Preferences.unlock = function (prefName) { + if (Array.isArray(prefName)) { + prefName.map(this.unlock, this); + } + + this._prefBranch.unlockPref(prefName); +}; + +/** + * Whether or not the given pref is locked against changes. + * + * @param prefName {String|Array} + * the pref to check, or an array of prefs to check + * + * @returns {Boolean|Array} + * whether or not the pref has a user-set value; or, if the caller + * provided an array of pref names, an array of booleans indicating + * whether or not the prefs have user-set values + */ +Preferences.locked = function (prefName) { + if (Array.isArray(prefName)) { + return prefName.map(this.locked, this); + } + + return this._prefBranch.prefIsLocked(prefName); +}; + +/** + * Start observing a pref. + * + * The callback can be a function or any object that implements nsIObserver. + * When the callback is a function and thisObject is provided, it gets called + * as a method of thisObject. + * + * @param prefName {String} + * the name of the pref to observe + * + * @param callback {Function|Object} + * the code to notify when the pref changes; + * + * @param thisObject {Object} [optional] + * the object to use as |this| when calling a Function callback; + * + * @returns the wrapped observer + */ +Preferences.observe = function (prefName, callback, thisObject) { + let fullPrefName = this._branchStr + (prefName || ""); + + let observer = new PrefObserver(fullPrefName, callback, thisObject); + Preferences._prefBranch.addObserver(fullPrefName, observer, true); + observers.push(observer); + + return observer; +}; + +/** + * Stop observing a pref. + * + * You must call this method with the same prefName, callback, and thisObject + * with which you originally registered the observer. However, you don't have + * to call this method on the same exact instance of Preferences; you can call + * it on any instance. For example, the following code first starts and then + * stops observing the "foo.bar.baz" preference: + * + * let observer = function() {...}; + * Preferences.observe("foo.bar.baz", observer); + * new Preferences("foo.bar.").ignore("baz", observer); + * + * @param prefName {String} + * the name of the pref being observed + * + * @param callback {Function|Object} + * the code being notified when the pref changes + * + * @param thisObject {Object} [optional] + * the object being used as |this| when calling a Function callback + */ +Preferences.ignore = function (prefName, callback, thisObject) { + let fullPrefName = this._branchStr + (prefName || ""); + + // This seems fairly inefficient, but I'm not sure how much better we can + // make it. We could index by fullBranch, but we can't index by callback + // or thisObject, as far as I know, since the keys to JavaScript hashes + // (a.k.a. objects) can apparently only be primitive values. + let [observer] = observers.filter( + v => + v.prefName == fullPrefName && + v.callback == callback && + v.thisObject == thisObject + ); + + if (observer) { + Preferences._prefBranch.removeObserver(fullPrefName, observer); + observers.splice(observers.indexOf(observer), 1); + } else { + console.error( + `Attempt to stop observing a preference "${prefName}" that's not being observed` + ); + } +}; + +Preferences.resetBranch = function (prefBranch = "") { + this.reset(this._prefBranch.getChildList(prefBranch)); +}; + +/** + * A string identifying the branch of the preferences tree to which this + * instance provides access. + * @private + */ +Preferences._branchStr = ""; + +/** + * The cached preferences branch object this instance encapsulates, or null. + * Do not use! Use _prefBranch below instead. + * @private + */ +Preferences._cachedPrefBranch = null; + +/** + * The preferences branch object for this instance. + * @private + */ +Object.defineProperty(Preferences, "_prefBranch", { + get: function _prefBranch() { + if (!this._cachedPrefBranch) { + let prefSvc = Services.prefs; + this._cachedPrefBranch = this._defaultBranch + ? prefSvc.getDefaultBranch(this._branchStr) + : prefSvc.getBranch(this._branchStr); + } + return this._cachedPrefBranch; + }, + enumerable: true, + configurable: true, +}); + +// Constructor-based access (Preferences.get(...) and set) is preferred over +// instance-based access (new Preferences().get(...) and set) and when using the +// root preferences branch, as it's desirable not to allocate the extra object. +// But both forms are acceptable. +Preferences.prototype = Preferences; + +/** + * A cache of pref observers. + * + * We use this to remove observers when a caller calls Preferences::ignore. + * + * All Preferences instances share this object, because we want callers to be + * able to remove an observer using a different Preferences object than the one + * with which they added it. That means we have to identify the observers + * in this object by their complete pref name, not just their name relative to + * the root branch of the Preferences object with which they were created. + */ +var observers = []; + +function PrefObserver(prefName, callback, thisObject) { + this.prefName = prefName; + this.callback = callback; + this.thisObject = thisObject; +} + +PrefObserver.prototype = { + QueryInterface: ChromeUtils.generateQI([ + "nsIObserver", + "nsISupportsWeakReference", + ]), + + observe(subject, topic, data) { + // The pref service only observes whole branches, but we only observe + // individual preferences, so we check here that the pref that changed + // is the exact one we're observing (and not some sub-pref on the branch). + if (data != this.prefName) { + return; + } + + if (typeof this.callback == "function") { + let prefValue = Preferences.get(this.prefName); + + if (this.thisObject) { + this.callback.call(this.thisObject, prefValue); + } else { + this.callback(prefValue); + } + } else { + // typeof this.callback == "object" (nsIObserver) + this.callback.observe(subject, topic, data); + } + }, +}; + +function isObject(val) { + // We can't check for |val.constructor == Object| here, since the value + // might be from a different context whose Object constructor is not the same + // as ours, so instead we match based on the name of the constructor. + return ( + typeof val != "undefined" && + val != null && + typeof val == "object" && + val.constructor.name == "Object" + ); +} |