XUL element attributes

« XUL Reference home The following attributes are common to all XUL elements:

align
Type: one of the values below
The align attribute specifies how child elements of the box are aligned, when the size of the box is larger than the total size of the children.
  • For boxes that have horizontal orientation, it specifies how its children will be aligned vertically.
  • For boxes that have vertical orientation, it specifies how its children will be aligned horizontally.
start
Child elements are aligned starting from the left or top edge of the box. If the box is larger than the total size of the children, the extra space is placed on the right or bottom side.
center
Extra space is split equally along each side of the child elements, resulting in the children being placed in the center of the box.
end
Child elements are placed on the right or bottom edge of the box. If the box is larger than the total size of the children, the extra space is placed on the left or top side.
baseline
This value applies to horizontally oriented boxes only. It causes the child elements to be aligned so that their text labels are lined up.
stretch
This is the default value. The child elements are stretched to fit the size of the box. For a horizontal box, the children are stretched to be the height of the box. For a vertical box, the children are stretched to be the width of the box. If the size of the box changes, the children stretch to fit. Use the flex attribute to create elements that stretch in the opposite direction.
left
The elements are aligned on their left edges.
center
The elements are centered horizontally.
right
The elements are aligned on their right edges.
The pack attribute is related to the alignment but is used to specify the position in the opposite direction. You can also specify the value of align using the style property -moz-box-align.
allowevents
Type: boolean
If true, events are passed to children of the element. Otherwise, events are passed to the element only.
allownegativeassertions
Type: boolean
Valid on any element that has a datasources attribute. When multiple datasources are used, one may override an assertion from another. This attribute, if true, which is the default, allows a datasource to negate an earlier assertion.
class
Type: string
The style class of the element. Multiple classes may be specified by separating them with spaces.
coalesceduplicatearcs
Type: boolean
Valid on any element that has a datasources attribute. When multiple datasources are used, one may override an assertion from another. This attribute, if true, which is the default, allows a datasource to negate an earlier assertion.
collapsed
Type: boolean
If true, then the element is collapsed and does not appear. It is equivalent to setting the CSS visibility property to collapse.

 

container
Type: boolean
Set to true if the element is to act as a container which can have child elements. This would be used for folders. This will be set by the template builder as needed.
containment
Type: URI
This attribute specifies RDF properties (an RDF predicate) that indicate that a resource is a container. When generating content from a template this is used to determine which resources from the datasource are containers and thus can have child nodes and which ones are not containers.
This attribute should be placed on the same element that the datasources and the ref attribute is on. It may be set to a space-separated list of RDF properties or resources.
context
Type: id
Should be set to the value of the id of the popup element that should appear when the user context-clicks on the element. A context-click varies on each platform. Usually it will be a right click. You can use the special value '_child' to indicate the first menupopup child of the element.
contextmenu
Type: id
Alternate name for the context attribute, but also has a corresponding script property contextMenu.
datasources
Type: space separated list of datasource URIs
A space-separated list of datasources that an element's template will use for content generation. These can be either internal datasources such as rdf:bookmarks or a URL. The datasources attribute may be placed on most elements, although it will usually be found on trees and menu related elements. The element should have a template element as a child.
For RDF templates, the specified datasources are combined into a single composite datasource which holds the data from all of the datasources. This composite datasource is accesssible via a script through the database property.
For XML datasources, only one source is used, either the URL of an XML file or an anchor reference to another element within the same document. For instance, the reference '#data' refers to an element with the id 'data'.
If you plan on adding a datasource to an element but don't want one to be added right away, set this attribute to 'rdf:null'. This will make the element so that its contents can be generated from a datasource. Otherwise, you cannot add one later.
When the XUL document is contained on a remote web site, the datasources may only be loaded from the same domain as the document.
dir
Type: one of the values below
The direction in which the child elements of the element are placed.
normal
For scales, the scale's values are ordered from left to right (for horizontal scales) or from top to bottom (for vertical scales)  For other elements, the elements are placed left to right or top to bottom in the order they appear in the XUL code.
reverse
For scales, the scale's values are ordered from right to left (for horizontal scales) or from bottom to top (for vertical scales). For other elements, they are placed right to left or bottom to top. This is reverse of the order in which they appear in the XUL code.
empty
Type: boolean
Set to true if the element is a container that contains no children. This will be set by the template builder as needed.
equalsize
Type: one of the values below
This attribute can be used to make the children of the element equal in size.
always
For a horizontally oriented element, this will make all of its children have the width of the widest child. For a vertically oriented element, this will make its children all have the height of the tallest child.
never
All of the children are displayed at the size required by the content or as specified by the width and height attributes or the CSS width and height properties.
flags
Type: space-separated list of the values below
A set of flags used for miscellaneous purposes. Two flags are defined, which may be the value of this attribute.
  • dont-test-empty: For template generated content, the builder will not check that a container is empty.
  • dont-build-content: This flag may be used on a tree to indicate that content elements should not be generated. This results in a performance enhancement, but you will not be able to use the DOM functions to retrieve the tree rows.
flex
Type: string (representing an integer)
Indicates the flexibility of the element, which indicates how an element's container distributes remaining empty space among its children. Flexible elements grow and shrink to fit their given space. Elements with larger flex values will be made larger than elements with lower flex values, at the ratio determined by the two elements. The actual value is not relevant unless there are other flexible elements within the same container. Once the default sizes of elements in a box are calculated, the remaining space in the box is divided among the flexible elements, according to their flex ratios. Specifying a flex value of 0 has the same effect as leaving the flex attribute out entirely.
height
Type: string (representing an integer)
The preferred height of the element in pixels. The actual displayed height may be different if the element or its contents have a minimum or maximum height. The CSS height property may also be used.
hidden
Type: boolean
If set to true, the element is not displayed. This is similar to setting the CSS display property to 'none'.
id
Type: unique id
A unique identifier so that you can identify the element with. You can use this as a parameter to getElementById() and other DOM functions and to reference the element in style sheets.
insertafter
Type: id
When an element is in an overlay, the insertafter attribute specifies the id of the element in the base window that the element should appear after. This attribute overrides the insertbefore attribute. This value may be a comma-separated list of ids, which are scanned and the first one found in the window is used.
insertbefore
Type: id
When an element is in an overlay, the insertbefore attribute specifies the id of the element in the base window that the element should appear before. This value may be a comma-separated list of ids, which are scanned and the first one found in the window is used.
left
Type: string (representing an integer)
For elements placed directly within a stack, specifies the pixel position of the left edge of the element relative to the left edge of the stack.
maxheight
Type: string (representing an integer)
The maximum height of the element. This corresponds to the max-height CSS property.
maxwidth
Type: string (representing an integer)
The maximum width of the element. This corresponds to the max-width CSS property.
menu
Type: id
Alternate name for the popup attribute, but also has a corresponding script property 'menu'.
minheight
Type: string (representing an integer)
The minimum height of the element. This corresponds to the min-height CSS property.

 

minwidth
Type: string (representing an integer)
The minimum width of the element. This corresponds to the min-width CSS property.
mousethrough
Type: one of the values below
Determines whether mouse events are passed to the element or not. If this attribute is not specified, the value is inherited from the parent of the element. If no ancestor has the mousethrough attribute set, the default value is never.
always
Mouse events are transparent to the element. This means that the element will not receive any mouse events due to either clicking or movement. Child elements may override this if they specify mousethrough="never".
never
Mouse events are passed to the element as normal.
observes
Type: id
Set to an id of a broadcaster element that is being observed by the element. If an attribute changes in the broadcaster it is also changed in the observer.
ordinal
Type: string (representing an integer)
An integer which specifies the position of the element within its parent. By default, elements appear in the order they appear in the XUL code. The ordinal attribute can be used to change the order. Note the default ordinal for elements is 1. You can retrieve the displayed order by using the properties of the boxObject of the container.
orient
Type: one of the values below
Used to specify whether the children of the element are oriented horizontally or vertically. The default value depends on the element. You can also use the -moz-box-orient style property.
horizontal
Child elements of the element are placed next to each other in a row in the order that they appear in the XUL source.
vertical
Child elements of the element are placed under each other in a column in the order that they appear in the XUL source.
pack
Type: one of the values below
The pack attribute specifies where child elements of the box are placed when the box is larger that the size of the children. For boxes with horizontal orientation, it is used to indicate the position of children horizontally. For boxes with vertical orientation, it is used to indicate the position of children vertically. The align attribute is used to specify the position in the opposite direction. You can also specify the value of pack using the style property -moz-box-pack.
start
Child elements are placed starting from the left or top edge of the box. If the box is larger than the total size of the children, the extra space is placed on the right or bottom side.
center
Extra space is split equally along each side of the child elements, resulting the children being placed in the center of the box.
end
Child elements are placed on the right or bottom edge of the box. If the box is larger than the total size of the children, the extra space is placed on the left or top side.
persist
Type: space-separated list of attribute names
A space-separated list of attributes that are maintained when the window is closed. When the window is re-opened, the values of persistent attributes are restored. In Mozilla, persistent attributes are stored in the per-profile file localstore.rdf. Persistence can also be stored using the document.persist function. In order for persistence to work, the element must also have an id. Persistence will not remember the absence of an attribute, so for boolean attributes like checked where absence means false, you will need to explicitly set the attribute to false before the window closes (bug 15232).
popup
Type: id
Should be set to the value of the id of the popup element that should appear when the user clicks on the element.
position
Type: string (representing an integer)
When an element is in an overlay, the position is an index where the child is inserted. The position is one-based, so use a value of 1 to place the element at the beginning. This attribute is ignored if either an insertbefore or insertafter attribute matches an element.
preference-editable
Mozilla 1.8
Type: boolean
If true, the element may be used as one that modifies a preference in a prefwindow. The preference attribute may be used to connect to a preference element. This is useful for custom elements implemented in XBL. The element should fire change, command, or input event when the value is changed so that the preference will update accordingly.

See the pref system documentation for more information.
querytype
Type: string
Indicates the type of datasource used in a template. Firefox 3 provides 3 built-in datasources: 'rdf', default, 'xml' and 'storage'. Extensions may provide support for additional datasources.
ref
Type: URI
For template-generated elements, this attribute is used to specify the root RDF node where content generation begins. This will correspond to the value of an about attribute on an RDF container. This attribute should be placed alongside the datasources attribute.
removeelement
Type: id
When placed on an element in an overlay, it indicates that the element in the base file should be removed from the window.
sortDirection
Type: one of the values below
Set this attribute to set the direction that template-generated content is sorted. Use the sortResource attribute to specify the sort key.
ascending
The data is sorted in ascending order.
descending
The data is sorted in descending order.
natural
The data is sorted in natural order, which means the order that it is stored in.
sortResource
Type: URI
For template-generated content, this specifies the sort key, if you would like the content to be sorted. The key should be the full URI of the RDF resource to sort by, for example 'http://home.netscape.com/NC-rdf#Name'. Place this attribute on the same element as the datasources attribute. Use sortResource2 to specify a secondary sort key.
sortResource2
Type: URI
The value of this attribute is the URI of an RDF predicate that serves as a secondary key for sorted content.
statustext
Type: string
Used to set the text that appears on the status bar when the user moves the mouse over the element. Mozilla doesn't adjust the status bar automatically however. This attribute serves only as a place to keep the text. In Firefox, this text is automatically placed in the statusbar for menuitems on the menu bar.
style
Type: CSS inline style
CSS style rules to be applied to the element. Syntax is as in the HTML style attribute. It is preferred to put style rules in style sheets.
template
Type: id
For template generated elements, this attribute may optionally be placed on the root node (the element with the datasources attribute) to refer to a template that exists elsewhere in the XUL code. This template attribute should be set to the id of the template element. This might be used to share a single template between multiple trees or menus. If this attribute is not specified, there should be a template element directly inside the node.
tooltip
Type: id
Should be set to the value of the id of the tooltip or panel element that should be used as a tooltip window when the mouse hovers over the element for a moment. The tooltip will automatically disappear when the mouse is moved. If this attribute is set to '_child', the first tooltip child element inside the element is used.

 

tooltiptext
Type: string
Used to set the text which appears in the tooltip when the user moves the mouse over the element. This can be used instead of setting the tooltip to a popup for the common case where it contains only text. The tooltip is displayed in a default tooltip which displays only a label, however the default tooltip may be changed by setting the default attribute on a tooltip element.
top
Type: string (representing an integer)
For elements placed directly within a stack, specifies the pixel position of the top edge of the element relative to the top edge of the stack.
uri
Type: string
For template-generated content, the attribute should be placed on the element where content generation should begin. Thus, it should be placed on an element that is a descendant of a template. The value should be set to rdf:*.
Elements that appear inside the element with the attribute will be repeated for each node in the RDF datasource. Elements outside will appear only once.
wait-cursor
Type: boolean
Set this attribute to true to have the cursor switch to a waiting cursor while the mouse is hovering over the element. Usually, you would only use this on the window element or other top-level elements. In order to revert to the normal cursor state call the method removeAttribute("wait-cursor") when the process effectively has ended otherwise the wait cursor might never disappear.
width
Type: string (representing an integer)
The preferred width of the element. The value should not include a unit as all values are in pixels. The actual displayed width may be different if the element or its contents have a minimum or maximum width, or the size is adjusted by the flexibility or alignment of its parent. The CSS width property may also be used.

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