Other event extensions

Creating keyboard shortcuts with the keypress event

Filtering on the event phase

XML Events 1 only supports filtering event handlers on a subset of the DOM Level 2 Events phases. Orbeon Forms extends that behavior and supports registering handlers that match on one of the 3 main event phases specified by DOM Level 2 Events: capture, target, and bubbling.

Orbeon Forms supports the following values for the phase attribute:

capture: only activate the handler during the capture phase (this is compatible with all the specifications)
default or unspecified: only activate the handler during the target or bubbling phase (this is compatible with XML Events 1 but not included in the current XBL 2 proposal)
target: only activate the handler during the target phase (this is not present in XML Events 1)
bubbling: only activate the handler during the bubbling phase (this is not present in XML Events 1)

NOTE: In the future, the XBL 2 default action phase could be integrated if considered desirable. It is hoped that the target and bubbling values will be supported in XML Events 2.

NOTE: In most cases, the phase attribute can be omitted, in which case the target or bubbling phase is matched. This allows placing a handler directly within a target element, or any of its ancestors, which are the most common use cases in XForms.

Adding context information to events

Orbeon Forms supports passing event context attributes with the XForms 2.0 <xf:property> child element. The actions supported are actions which directly cause an event to be dispatched:

<xf:dispatch>
<xf:send>
<xxf:show>
<xxf:hide>

Here is how you pass context attributes when executing an action:

<xf:dispatch name="rename-control" target="my-model">
    <xf:property name="control"      value="my/control"/>
    <xf:property name="control-name" value="'beverage-selection'"/>
</xf:dispatch>

NOTE: Prior to standard XForms support, the <xxf:context> child element was introduced for the same purpose and can still be used for backward compatibility. The select attribute can also be used in place of value.

<xf:property> supports the following two attributes:

name

Mandatory

Name of the context attribute.

value

Mandatory

XPath 2.0 expression determining the value of the context attribute.

Note that the context attribute name cannot be a qualified name (QName), because this would not be compatible with DOM 2 Events. However, a QName can be used as custom event name.

In order to avoid confusion with standard XForms names, we recommend you use prefixed names if you use custom context information with standard event names (when supported). However, with custom event names, prefixing is not necessary.

Context attributes passed this way can be retrieved using the event() function:

<xf:action event="rename-control">
    <xf:setvalue ref="event('control')/@name" value="event('control-name')"/>
</xf:action>

NOTE: At the moment, with, <xf:dispatch>, only custom events support passing context attributes this way. Built-in events, such as xforms-value-changed, or DOMActivate, ignore nested <xf:property> elements.

Tunnelling of events properties

[SINCE Orbeon Forms 2023.1]

The xxf:tunnel="true attribute on <xf:property> allows the propagation, or tunnelling, of event properties in the following cases:

<xf:send>: the properties are tunneled to event handlers for the xforms-submit-error and xforms-submit-done events as well as event handlers for xxforms-action-error event dispatched while processing event handlers for those events
<xf:dispatch>: the properties are tunneled to event handlers for the xxforms-action-error event dispatched while processing event handlers for the event dispatched

Example with xforms-submit-done:

<xf:send submission="my-submission">
    <xf:property name="my-tunnel-property" value="42" xxf:tunnel="true"/>
</xf:send>
<xf:submission id="my-submission">
    <xf:action event="xforms-submit-done">
        <xf:message value="event('my-tunnel-property')"/>
    </xf:action>
</xf:submission>

Example with xxforms-action-error:

<xf:dispatch name="my-event" target="my-target">
    <xf:property name="divisor" value="0" xxf:tunnel="true"/>
</xf:dispatch>
<xf:group id="my-target">
    <xf:action event="my-event">
        <!-- Cause an action error -->
        <xf:setvalue ref="title" value="42 div event('divisor')"/>
    </xf:action>
    <xf:action event="xxforms-action-error">
        <xf:message value="event('divisor')"/>
    </xf:action>
</xf:group>

Allowing duplicate event in the event queue

[SINCE Orbeon Forms 2017.1]

Prior to Orbeon Forms 2017.1, the <xf:dispatch> action used with a delay value would always add all events to the event queue. This was not per the XForms specification, which says that events with the same name and effective target as ones already in the event queue are skipped.

Orbeon Forms 2017.1 rectifies that to follow XForms and skips duplicates. This change of default is usually not a problem.

To allow duplicates, the xxf:allow-duplicates="true" attribute is supported:

<xf:dispatch
    name="my-event"
    targetid="my-targetid"
    delay="10"
    xxf:allow-duplicates="true"/>

xxf:allow-duplicates is an AVT.

Enhanced support for xforms-select and xforms-deselect

[TODO: describe support for these events on xf:upload]

Targeting effective controls within repeat iterations

The following actions all support attributes resolving to a particular control:

<xf:dispatch> (target attribute)
<xf:setfocus> (control attribute)
<xf:toggle> (case attribute)
<xxf:show> (neighbor attribute)

When that control is within a repeat iteration, the actual control targetted is chosen based on the current set of repeat indexes. However, in some cases, it is useful to be able to target the control within a particular iteration. This is achieved with the xxf:repeat-indexes extension attribute on these actions. This attribute takes a space-separated list of repeat indexes, starting with the outermost repeat. Example:

<!-- Repeat hierarchy -->
<xf:repeat ref="todo-list">
    <xf:repeat ref="todo-item">
        <xf:switch>
             <xf:case id="edit-case">...</xf:case>
             <xf:case id="view-case">...</xf:case>
        </xf:switch>
    </xf:repeat>
</xf:repeat>

<xf:trigger>
    <xf:label>Toggle Me!</xf:label>
    <!-- Toggle the case within the 5th todo item of the 3rd todo list -->
    <xf:toggle event="DOMActivate" case="edit-case" xxf:repeat-indexes="3 5"/>
</xf:trigger>

Multiple event names, observers and targets on event handlers

The event, observer and target attributes, defined by the XML Events specification, only support one event name, observer, or target respectively. Orbeon Forms supports as an extension a list of space-separated values. The behavior is as follows:

For event: the handler is called if any of the specified events matches.

<xf:action event="DOMFocusIn DOMFocusOut">
    <!-- Reacting to either the "DOMFocusIn" and "DOMFocusOut" events -->
    ...
</xf:action>

For observer: the event handler is attached to all the observers specified.

<xf:action event="DOMActivate" observer="my-input my-trigger">
    <!-- Observing both the "my-input" and "my-trigger" controls -->
    ...
</xf:action>

For target: the handler is called if any of the specified targets matches.

<xf:action event="xforms-submit-done" target="create-submission update-submission">
    <!-- Checking that either the "create-submission" and "update-submission" controls is a target -->
    ...
</xf:action>

The extensions above have been requested for inclusion in XML Events 2.

Catching all events

The special #all event name on event can be used to catch all events:

<xf:group>
    <!-- Stop propagation of all events -->
    <xf:action event="#all" propagate="stop"/>
    ...
</xf:group>

Specifying the current observer as target restriction

The special #observer target name on target can be used to specify that the listener must be activated only if the event target is the listener's observer:

<xf:group>
    <!-- Restrict activation to events dispatched to the group -->
    <xf:action event="my-event" target="#observer"/>
    ...
</xf:group>

In this example, this is identical to:`

<xf:group>
    <!-- Restrict activation to events dispatched to the group -->
    <xf:action event="my-event" phase="target"/>
    ...
</xf:group>

Observing the preceding sibling element

The observer attribute can be set to the value #preceding-sibling:

<xf:repeat ref="...">
    ...
</xf:repeat

<xf:action
  event="xforms-enabled xforms-disabled xxforms-index-changed xxforms-ref-changed"
  observer="#preceding-sibling"
  target="#observer">
    
</xf:action>

In this example, we observe events targeted to the repeat element just before the event handler.

This is useful in situations where it is not possible to explicitly set an id on a control, for example when doing complex things with XBL.

Phantom handlers

Event handler support the xxf:phantom="true" attribute to specify that the event handler is listening to events flowing across XBL scopes.

XForms events flow along XBL boundaries and are fully encapsulated. This attribute allows special consumers of events to have a global view of events flowing in the XForms page. Example:

<xf:action
  observer="my-observer"
  event="xforms-enabled"
  xxf:phantom="true">

In this example, the handler will catch events that happen not only in the current XBL scope, but also those in nested XBL scopes.

This is an advanced feature and should be used wisely. It is used in Orbeon Forms by the error summary (fr:error-summary) and by Form Builder.

[SINCE Orbeon Forms 2020.1]

xxf:phantom="true" handlers can be placed within repeats. This was not previously allowed.