Preferences bindings

Work in progress See also this forum thread.

This document describes the new XBL bindings introduced in Deer Park Alpha 1 (aka Firefox 1.1a and Firefox 1.1 Developer Preview Release) and other Toolkit 1.1 applications, which allow you write Options (Preferences) UI faster, using less JavaScript code.

This is not official yet. May be incomplete, contain any kinds of mistakes and typos etc. Please, if you see one, either fix it or note it on the talk page.

To-do

Todo:

• sort alphabetically
• review the doc, do something about things marked '??'.
• describe platform specific features:
  • instant apply
  • animation
• (maybe) simple example(s)

Why

Describe the benefits of the new system:

• Use of declarative language (XUL elements/attributes) to associate UI controls with user preferences, less JS is needed
• More natural feel on Linux/Mac OS: instantapply/animation
• ...

New elements

<prefwindow>

<prefwindow> is a top-level element, like <window> or <dialog. You should use it when creating Options dialog for applications based on Toolkit 1.1 or later (e.g. Firefox 1.1 or Thunderbird 1.1).

The following attributes, properties and methods are available.

Attributes

type

Must be either "prefwindow" or "child". Use the former on the main prefwindow, and the latter for the subdialogs.
Child prefwindows read initial values for their preferences from their opener, not from the preferences service. They also don't save the preferences to the preferences service when closed - only clicking OK on the main prefwindow does that. (Can child windows have prefpanes??)

lastSelected

The id of the last selected pane. Used to reopen that pane when the Options window is opened next time.

Properties

preferencePanes (readonly)

A NodeList of <prefpane> elements.

type (readonly)

Returns the value of the type attribute.

lastSelected (readonly)

Returns the value of the lastSelected attribute.

instantApply (readonly)

Indicates whether the window is in "instant apply" mode. The value is read from browser.preferences.instantApply boolean user preference. (?? It's declared as a <field>, so you can set the value, however I don't believe it's valid to do that.)

currentPane (readonly)

Currently selected <prefpane> element. Use showPane() method to select another pane. (Same comment as for instantApply.)

Methods

showPane(aPaneElement)

Selects given pane, loading it dynamically, if necessary. aPaneElement must be a <prefpane> element from the same window.

animate(aOldPane, aNewPane)

?? is this a public method

addPane(aPaneElement)

Adds the specified <prefpane> element to the dialog. You can use this method to append dynamically created panes to the dialog.

openSubDialog(aURL, aFeatures, aParams)

Opens a modal sub-dialog. Similar to window.openDialog, except you don't have to specify modal and centerscreen features when using this method, they are added automatically. Use this method to open a modal subdialog, like Connection Settings in Firefox.

openWindow(aWindowType, aURL, aFeatures, aParams)

Opens the specified window or focuses an already open one with given window type. Use this method to open a non-modal window, like Exceptions window in Firefox Options.

Note that you can define an initWithParams() function in your window - to handle parameters passed using openWindow() in case the window was already open. For example the Permissions Manager UI in Firefox uses the same window for three dialogs: Images, Software installation and Popups. It uses initWithParams() to change the dialog type without closing and re-opening it.

The suggested pattern is as follows:

function onLoad(ev) {
  // do some initialization...

  initWithParams(arguments[0]); // we expect a single parameter to be passed to the window
}

function initWithParams(aParams) {
  // this will also get called when an already open window is activated using openWindow()
}

<prefpane>

<prefpane> is an element representing a pane (tab) in the Options window. It must be a child of the <prefwindow> element.

<prefpane> can have a src attribute specifying the overlay which provides the real content for it, or it can contain arbitrary XUL elements as its content. Using the first method can reduce time needed to load your Options window, if it's very large, as only a single pane needs to be loaded before the window can be shown to user.

Attributes

id

The id of the pane. This may be used to match the element from a dynamic overlay, but you must provide an id for all your <prefpane> elements, even if you don't use dynamic pane loading.

image

Specifies the URL of an image to be used on the pane button. (does setting this at runtime have any effect??)

label

The label for the pane button.

selected

Indicates whether the pane is currently selected (active). (?? Setting this at design-time doesn't work, use lastSelected attribute of <prefwindow> instead.)

src

See above, the URL of the overlay which provides content for the pane.

Properties

(todo: figure out what happens if you set these attributes/properties at runtime. I don't think all of them have effect at runtime.)

src

Gets and sets the value of the src attribute.

selected

Gets and sets the value of the selected attribute.

image

Gets and sets the value of the image attribute.

label

Gets and sets the value of the label attribute.

preferenceElements (readonly)

A NodeList of child elements with preference attribute.

preferences (readonly)

A NodeList of all child <preference> elements.

loaded (readonly)

Indicates whether the pane is fully loaded. (?? while it's possible to set the value of the property, it's not recommended to do so. The property really ought to be readonly)

contentHeight (readonly)

The height (in pixels) of current pane's content.

Methods

writePreferences(flushToDisk)

Saves all <preference>s of the pane in user preferences, optionally flushes to the disk (updating prefs.js) if aFlushToDisk is true.

preferenceForElement(element)

Returns the <preference> element, which is being observed by the supplied element (i.e. which is specified in aElement's preference attribute.)

getPreferenceElement(startElement)

??

userChangedValue(element)

??

Events

paneload

This event is fired on the pane element when the pane is loaded (e.g. after the overlay is merged.) You can put the handler for the event in onpaneload attribute on the element.

<preferences>

<preferences> is a container element for <preference> elements. It's supposed to be a child of <prefpane> element.

<preferences> element should contain one or more <preference> elements.

Attributes

This element doesn't offer any additional attributes over those common to all XUL elements.

Methods

fireChangedEvent(preference)

Creates and dispatches a changed (non-bubbling) event to the specified preference element. Also executes code specified in onchanged attribute of the element. See also the description of change event of <preference>.

Fields

service

The preferences service (nsIPrefService).

rootBranch

The root prefs branch (nsIPrefBranch).

defaultBranch

The root branch with default values (nsIPrefBranch).

rootBranchInternal

The root prefs branch (nsIPrefBranch2).

<preference>

<preference> is an element that is used as an intermediary between UI elements and items in user preferences. It must be a direct child of <preferences>.

Attributes

id

The id of the element, it's used as a value of preference attribute on UI elements.

name

The preference it controls (e.g. browser.preferences.instantApply).

type

The type of the preference. Possible values are: int, bool, string (for non-unicode (ASCII) strings), wstring (like nsIPrefLocalizedString), unichar (unicode string), file (nsIFile).

inverted

(Applies only to prefs with type="bool".) When this is set to true, the value on the associated UI element is a negation of the value stored in user preferences.

readonly

??

instantApply

You can set this attribute to true to make the preference apply instantly, even when the global setting is not to use instant apply.

Properties

instantApply (readonly)

Whether to use instant apply for this preference. This is true if either the element has an instantApply attribute set to true, or the <prefwindow>'s instantApply property is true. (But note bug 293439.)

preferences (readonly)

Parent <preferences> element.

name

Gets and sets the value of the name attribute.

type

Gets and sets the value of the type attribute.

inverted

Gets and sets the value of the inverted attribute.

readonly

Gets and sets the value of the readonly attribute.

value

The current value of the preference. If instantApply is on, this is always equal to valueFromPreferences. Otherwise, it's the current value of associated UI elements, i.e. what user currently sees.

locked (readonly)

Returns true if the preference is locked.

disabled

Gets/sets the value of disabled attribute, also updating disabled property of associated UI elements. (but initial value of attribute doesn't seem to have any effect??)

tabIndex

Gets/sets the value of tabindex attribute, also updating tab index of associated UI elements. (?? same comment as for disabled)

hasUserValue (readonly)

Returns true if the preference has a user value set.

defaultValue (readonly)

Returns the default value of the preference.

valueFromPreferences

Gets and sets the value stored in the user preference, specified in name.

Methods

getElementValue(element)

Retrieves the value that should be written to preferences based on the current state of the supplied element. This function calls onpreferencewrite.

isElementEditable(element)

Returns true, if the given element is "editable" (see below).

reset()

Resets the preference to its default value. Note: this method throws an exception if the preference doesn't have a user value set yet. (Is this intended behavior??)

setElementValue(element)

Initializes the supplied element from the value stored in the preference. This function calls onpreferenceread.

updateElements()

Update all elements that observe this preference.

Events

change

This event is dispatched to the <preference> element, when its value (according to preferences service) changes. The onchange attribute may be used to handle the event.

New attributes

The following attributes may be put on any element in the prefwindow:

• onpreferenceread/write [1]
• preference-editable
• preference

Example(s)

See the forum thread for now.