Package org.zkoss.zk.ui.ext.render

## Interface PrologAllowed

- All Known Implementing Classes:
    `Audio.ExtraCtrl`, `Chosenbox.ExtraCtrl`, `Combobox.ExtraCtrl`, `Cropper.ExtraCtrl`, `Datebox.ExtraCtrl`, `Grid.ExtraCtrl`, `HtmlBasedComponent.ExtraCtrl`, `HtmlNativeComponent.ExtraCtrl`, `Iframe.ExtraCtrl`, `Image.ExtraCtrl`, `Jasperreport.ExtraCtrl`, `LabelImageElement.ExtraCtrl`, `Lineitem.ExtraCtrl`, `Listbox.ExtraCtrl`, `Listitem.ExtraCtrl`, `Pdfviewer.ExtraCtrl`, `Row.ExtraCtrl`, `Rows.ExtraCtrl`, `Selectbox.ExtraCtrl`, `Treechildren.ExtraCtrl`, `Video.ExtraCtrl`

      public interface PrologAllowed

  Implemented by the object returned by `ComponentCtrl.getExtraCtrl()` if it is able to generate the specified prolog before its real content.

  It is used by ZK to minimize the output. Currently, `HtmlBasedComponent` supports it. If a ZUML page has a string consisting of whitespaces, it will ask the following component to generate them if `PrologAllowed` is implemented.

  For example, in the following codes, the whitespace between textbox and datebox won't be converted to a label component. Rather, it will ask datebox to generate by calling datebox's `setPrologContent(java.lang.String)`.

      <textbox/> <datebox/>

  Since:
    3.5.0
  Author:
    tomyeh

- - ### Method Summary

    All Methods Instance Methods Abstract Methods
    Modifier and Type | Method | Description
    --- | --- | ---
    `void` | `setPrologContent​(java.lang.String prolog)` | Sets the prolog content.

- - ### Method Detail

    - #### setPrologContent

          void setPrologContent​(java.lang.String prolog)

      Sets the prolog content. It is the content generated before the child components, if any.

      Default: none.

      Note: the prolog is one-shot only. Once the component is generated, the prolog is gone.