XBL Modes

Introduction

The XBL component binding defined with <xbl:binding> supports the xxbl:mode attribute, which contains an optional space-separated list of tokens. Each token enables a mode, as described below. Modes change the behavior of the component.

Example:

<xbl:binding
    id="fr-code-mirror"
    element="fr|code-mirror"
    xxbl:mode="lhha binding value external-value focus">

The binding mode

The binding mode enables an optional XForms single-item binding. This means that the component supports the XForms binding attributes:

  • model
  • context
  • ref
  • bind

When a component has a binding, UI events are dispatched depending on the bound item:

  • xforms-enabled / xforms-disabled
  • xforms-readonly / xforms-readwrite
  • xforms-optional / xforms-required
  • xforms-valid / xforms-invalid

You can access the actual bound node via the xxf:binding() function:

xxf:binding('fr-foo')

The id passed must be the id of the xbl:binding element.

The xxf:binding-context() function returns the XPath evaluation context of the binding

xxf:binding-context('fr-foo')

For an example, see Creating a single-node binding.

The value mode

The value mode makes the component hold a value through its binding. This means the component behaves like <xf:input> and other controls and dispatches xforms-value-changed events.

You use this mode in addition to binding.

For an example, see Adding support for a value.

The external-value mode

[SINCE Orbeon Forms 2016.1]

You use the external-value mode in addition to the binding and value modes.

You use this mode when the component implementation is mostly done in JavaScript and not with nested XForms controls.

By default, value doesn't expose the control's value to the client. By adding the external-value mode, the control's value is made available to the client and accessible via JavaScript.

For more details, see Support for the external-value mode.

The javascript-lifecycle mode

[SINCE Orbeon Forms 2016.1]

You use this mode when the component implementation is mostly done in JavaScript and not with nested XForms controls.

The javascript-lifecycle mode lets Orbeon Forms handle more of a JavaScript companion class's lifecycle, including initialization, destruction, and state changes. You often use it in conjunction with external-value.

For example prior to Orbeon Forms 2016.1, you would call the component's init() method from XForms event handlers. With javascript-lifecycle, this is no longer needed.

For more details, see Support for the javascript-lifecycle mode.

The lhha and custom-lhha modes

The lhha mode allows the component to support the <xh:label>, <xh:hint>, <xh:help> and <xh:alert> element, whether:

  • directly nested under the component's bound element
  • or using the for attribute

By default, markup is output for the LHHA elements. You can disable this with the additional custom-lhha mode.

For an example, see Adding LHHA elements.

[SINCE Orbeon Forms 4.5]

Sometimes, a component implementation uses HTML form controls, and you would like a <label> element pointing to it with a for attribute in the generated HTML markup.

You enable this with the xxbl:label-for attribute.

The value of the attribute must be the id of a nested XForms control or a nested HTML control element.

For examples, see some of the Orbeon Forms XBL components. https://github.com/orbeon/orbeon-forms/tree/master/form-runner/jvm/src/main/resources/xbl/orbeon

The focus mode

You use this mode when the component implementation is mostly done in JavaScript and not with nested XForms controls.

The focus mode allows the component to handle keyboard focus natively, so that the XForms engine is aware of focus.

[SINCE Orbeon Forms 2016.1]

When the component receives focus, for example following an XForms <xf:setfocus> action, the JavaScript companion class's xformsFocus() method is called if present. If the method is missing, then the legacy setFocus() method is called.

[UNTIL Orbeon Forms 4.10 included]

The JavaScript companion class's setFocus() method is called if present.

The nohandlers mode

The nohandlers mode disables automatic processing of nested event handlers. You should only need this for very special components.

For an example and more details, see Component user: attaching event handlers to the bound node.

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