XUL improvements in Firefox 3

Firefox 3 provides a number of new XUL elements, as well as improvements to existing elements. While this material is documented in detail elsewhere, this article provides a convenient list of these improvements as well as links to the detailed documentation.

New elements

Numeric controls:
- The new <scale> element lets you create sliding scales that let the user select any value in a specified range. This widget would typically be used, for example, to create a volume control.
- A new value, number, for the type attribute of textboxes creates a textbox in which only numbers may be entered. In addition, arrow buttons appear to one side which may be used to step through values. More information about numeric textboxes (bug 345510)
- A <spinbuttons> element is added which can be used when creating widgets using XBL bindings. (bug 155053)
- Two widgets, <datepicker> and <timepicker>, can be used to allow the entry of dates and times. The datepicker is available in a number of styles by setting the type attribute, to allow entry with textboxes or a calendar grid. More information about date pickers Datepicker Reference Timepicker Reference
A guide has been created for menus and popups describing new features available:
- A <dropmarker> element is added which is useful when creating menu-like widgets using XBL bindings. (bug 348614)
- The <panel> element is new and designed for popups that are not menus. They can support any type of content. The <menupopup> element should be used for menus. Menus provide keyboard navigation and support opening and closing submenus.

Improvements to trees

Trees can now be scrolled horizontally. If the columns don't fit into the available width, a horizontal scrollbar appears. This happens if the columns' specified widths add up to more than the available space. See bug 212789 for details.
A new selection style allows cells to be selected individually, instead of entire rows. To use this selection style, set the tree's seltype attribute to cell.
Trees now support editing of individual cells. When the user double-clicks an editable cell, a text field appears in which the user can edit the contents of the cell. See these notes for details.
<treecol> elements now support an overflow attribute which may be set to true to allow the text of cells within that column to expand to neighbouring blank cells if the text is too large to fit into that single cell.

Improvements to menus

The image attribute is now used consistently for setting images.
Menulists fire the select event when selecting an item.
The inputField and editable properties have been added to menulist
The <menu>, <menuitem> and <menuseparator> elements now have a readonly selected property which retrieves whether the item is selected in a <menulist>
The <menu>, <menuitem> and <menuseparator> elements now have a readonly control property which returns the enclosing <menulist>
The <menu>, <menuitem> and <menuseparator> elements now support the accessKey, disabled, crop, image and label properties which set the corresponding attribute
The <menu> element now has methods to append, insert and remove menuitems. (bug 372552)
Editable menulists now offer an editor property to get the internal nsIEditor for its text field.
Menus may now be made translucent on platforms that support it (bug 70798).

Improvements to textboxes

Setting a textbox's spellcheck attribute to true enables inline spellchecking for that textbox.
The <textbox> now has a reset() method to reset the value of the textbox to the default value. The defaultValue property may be used to retrieve and modify the default value of the textbox.
An editor property is now offered, which lets you get the internal nsIEditor for the text field.
textbox now supports a newlines attribute which specifies how line breaks in pasted text are handled. Possible values are:
- pasteintact - paste everything as is
- pastetofirst - (default value) paste only up to the first line break
- replacewithspaces - replace line breaks with spaces
- replacewithcommas - replace line breaks with commas
- strip - strip out all line breaks
- stripsurroundingwhitespace - strip out all line breaks and surrounding whitespace

Other improvements

The type attribute on a <button> may be set to repeat to create buttons which fire their command event repeatedly while the mouse button is held down.
The buttondisabledaccept attribute can now be used on the <dialog> element to have the accept (OK) button initially disabled.
The <titlebar> element now supports the allowevents attribute to allow events to be passed to the children of the titlebar.
The <splitter> now supports an additional value for the collapse attribute of 'both' which indicates that the splitter can collapse elements on both sides of it when dragged. The substate attribute will set to either before or after when one is collapsed. (bug 337955)
The <richlistbox> element now supports multiple selection. Set the seltype attribute to 'multiple' to enable this.
The <radio> element has a group attribute which may be set to the id of a <radiogroup> element which the radio button belongs to. This allows the radio buttons to arranged in a manner that may not be as suitable when placing them all inside a radiogroup.
Menus, panels and tooltips support two additional methods, openPopup() and openPopupAtScreen(). These methods should be used instead of showPopup() which was found to be confusing to use.
Handling of the <key> element improved for non-Latin keyboard layout users. See Gecko Keypress Event.
On Mac OS X, the activetitlebarcolor and inactivetitlebarcolor attributes of the root elements (<window>, <dialog>, <prefwindow> and <wizard>) are available to customize the color of the windows' title bars.