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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">

<html>

<head>

    <title>The AWT Modality</title>

</head>

<body bgcolor="white">

    <h1 align="center">The AWT Modality</h1>

    <p>
      This document, together with the API documentation for modality-related
      classes (such as <code>java.awt.Dialog</code>), briefly describes the new
      modality features and how to use them. It contains the following sections:
    </p><ul>
      <li><a href="#Definitions">Definitions</a></li>
      </li><li><a href="#ModalityTypes">Modality types</a></li>
      <li><a href="#ShowHideBlocking">Show/hide blocking</a></li>
      <li><a href="#ModalExclusion">Modal exclusion</a></li>
      <li><a href="#Related">Related AWT features</a></li>
      <li><a href="#Security">Security</a></li>
      <li><a href="#PlatformSupport">Platform support</a></li>
      <li><a href="#Compatibility">Compatibility</a></li>
      <li><a href="#Examples">Examples</a></li>
    </ul>

    <a name="Definitions"></a>
    </p><h3>Definitions</h3>

    <p>
      <u>Document</u> - a window without an owner that, together with
      all its child hierarchy, may be operated on as a single self-contained
      document.
      Every window belongs to some document &#151; its root can be found as
      the closest ancestor window without an owner.
    </p><p>
      <a name="ModalBlocked"></a>
      <u>Modal blocked window</u> - a window, that:
      </p><ul>
        <li>doesn't receive any user input events
        </li><li>doesn't receive input focus
        </li><li>keeps its Z-order below the modal dialog that blocks it
      </li></ul>
      <blockquote>
        <hr>
          <b>Warning!</b> Some window managers allow users to change the window
          Z-order in an arbitrary way &#151; in that case the last requirement 
          may not be met.
        <hr>
      </blockquote>
    <p>
      <u>Modal dialog</u> - a dialog that blocks some windows while it is
      visible. The blocked windows are determined according to the dialog's
      scope of blocking.
    </p><p>
      <u>Modal excluded window</u> - a window that stays unblocked
      while the modal dialog is visible. If a window is modal excluded
      then all its owned windows and child components are also excluded.
    </p><p>
      <u>Scope of blocking (SB)</u> - the set of windows (instances of
      <code>java.awt.Window</code> and all derived classes) that are blocked by 
      the modal dialog while it is visible.
    </p><p>
     <blockquote><hr>
      <b>Note</b>: Everywhere in this document the notion of "window" is equal
      to a top-level window in the Java programming language &#151; in other words
      an instance of <code>java.awt.Window</code> or any descendant class.
      <hr></blockquote>

    <a name="ModalityTypes"></a>
    </p><h3>Modality types</h3>

    <p>
      There are four supported modality types :
      </p><ul>
        <li>toolkit
        </li><li>application
        </li><li>document
        </li><li>modeless
      </li></ul>
      A dialog is, by default, modeless.  A modal dialog is, by default,
      application-modal.
    <p>
    </p><ol>
      <li><u>Modeless dialogs</u><br>
        A modeless dialog doesn't block any windows while visible.
      </li><li><u>Document-modal dialogs</u><br>
        A document-modal dialog blocks all windows from the same
        document except those from its child hierarchy. The document root
        is determined as the closest ancestor window without an
        owner.
      </li><li><u>Application-modal dialogs</u><br>
        An application-modal dialog blocks all windows from the same
        application except for those from its child hierarchy.
        If there are several applets launched in a browser, they can be
        treated either as separate applications or a single application.
	This behavior is implementation-dependent.
      </li><li><u>Toolkit-modal dialogs</u><br>
        A toolkit-modal dialog blocks all windows that run in the same
        toolkit except those from its child hierarchy. If there
        are several applets launched all of them run with the same toolkit,
        so a toolkit-modal dialog shown from an applet may affect other
        applets and all windows of the browser instance which embeds the
        Java runtime environment for this toolkit.
        See the security section below.
    </li></ol>
    <p>
      Modality priority is arranged by the strength of blocking: modeless,
      document-modal, application-modal and toolkit-modal. This arrangement
      is used when determining what dialog should remain unblocked if two
      are visible and block each other. It naturally reflects the nesting
      of a dialog's scope of blocking (SB): a modeless dialog has an empty SB,
      a document-modal dialog's SB is complete in some applications,
      and all the applications are run in one toolkit.  </p><p>
      Notes about owners:
      </p><ul>
        <li>Creating a document-modal dialog without an owner:<br>
          Since <code>Dialog</code> is a class derived from
	  <code>Window</code>, a <code>Dialog</code> instance automatically
          becomes the root of the document if it has no owner. Thus, if
          such a dialog is document-modal, its scope of blocking is empty
          and it behaves the same way as a modeless dialog.
        </li><li>Creating an application-modal or toolkit-modal dialog with an
	  owner:<br>
          The scope of blocking for an application- or toolkit-modal
          dialog, as opposed to a document-modal dialog, doesn't depend on
          its owner. Thus, in this case the only thing that the owner
          affects is the Z-order: the dialog always stays on top of its owner.
      </li></ul>
    <p>
    <blockquote><hr>
      <b>Implementation note</b>: Changing the modality type for a visible
      dialog may have no effect until it is hidden and then shown again.
      <hr></blockquote>

    <a name="ShowHideBlocking"></a>
    </p><h3>Show/hide blocking</h3>

    <p>
      <u>Showing the window or modeless dialog: "F"</u><br>
      All the visible modal dialogs are looked through &#151; if F is from the SB
      of one of them, it becomes blocked by it. If there are several such
      dialogs, the first shown is used. If no such dialogs exist, F remains
      unblocked.
    </p><p>
      <u>Showing the modal dialog: "M"</u><br>
      When modal dialog M is shown, all the visible windows fall into one of
      three distinct groups: 
      <ul>
      <li>Blockers of M (modal dialogs that block M and
      either are in M's child hierarchy, or are not blocked by M, or have
      a greater mode of modality, or block some other blocker of M)
      <li>Blocked by M (windows from M's SB that are not blockers and are
      not in child hierarchy of any blocker)
      <li>All other windows (windows or modeless
      dialogs outside M's SB and modal dialogs outside M's SB that do not
      block M).
      </ul>
      </p><p>
      After the modal dialog M is shown, it becomes blocked by the first shown
      dialog from the first group (if there are any), all the windows from the
      second one become blocked by M, and all the windows from the third group
      remain untouched.
    </p><p>
      <u>In typical cases</u>, when no child dialogs are shown before their owners,
      this rule can be simplified. (The following, simplified case, may
      leave out some details).
      </p><p>
      <u>Showing the document-modal dialog: "M"</u><br>
      All the visible application- and toolkit-modal dialogs are looked
      through &#151; if M is from the SB of one of them,
      it becomes blocked by it. If there are several such dialogs,
      the first shown is used. If no such dialogs exist, M remains unblocked.
      </p><p>
      <u>Showing the application-modal dialog: "M"</u><br>
      All the visible toolkit-modal dialogs are looked through &#151;
      if M is from the SB of one of them, it becomes blocked by it.
      If there are several such dialogs, the first shown is used.
      If no such dialogs exist, M remains unblocked.
      </p><p>
      <u>Showing the toolkit-modal dialog: "M"</u><br>
      M remains unblocked.
      </p><p>
<!--        <center> -->
          </p>
          <table border="1" cols="5" rows="5">
	  <caption>The Standard Blocking Matrix</caption>
            <tbody><tr align="center">
              <td align="center">current/shown</td>
              <td align="center">frame &amp; modeless</td>
              <td align="center">document</td>
              <td align="center">application</td>
              <td align="center">toolkit</td>
            </tr>
            <tr align="center">
              <td align="center">-</td>
              <td align="center">-</td>
              <td align="center">-</td>
              <td align="center">-</td>
              <td align="center">-</td>
            </tr>
            <tr align="center">
              <td align="center">document</td>
              <td align="center">blocked</td>
              <td align="center">-</td>
              <td align="center">-</td>
              <td align="center">-</td>
            </tr>
            <tr align="center">
              <td align="center">application</td>
              <td align="center">blocked</td>
              <td align="center">blocked</td>
              <td align="center">-</td>
              <td align="center">-</td>
            </tr>
            <tr align="center">
              <td align="center">toolkit</td>
              <td align="center">blocked</td>
              <td align="center">blocked</td>
              <td align="center">blocked</td>
              <td align="center">-</td>
            </tr>
          </tbody></table>
<!--        </center> -->
      <p>
      After the modal dialog is shown, all the windows from its SB are blocked,
      except those that block this modal dialog.
    </p><p>
      <u>Hiding the window or modeless dialog: "F"</u><br>
      If F was blocked by any modal dialog M, it becomes unblocked and is
      removed from M's blocked windows list.
    </p><p>
      <u>Hiding the modal dialog: "M"</u><br>
      If M was blocked by any other modal dialog, for example, "N",
      it becomes unblocked and
      is removed from N's blocked windows list. Then, all the windows and dialogs
      blocked by M become unblocked, and after that the same checks 
      (as in Showing the modal dialog: "M")
      are performed for each of them in the order they were initially shown.

    <a name="ModalExclusion"></a>
    </p><h3>Modal exclusion</h3>

    <p>
      There are two modal exclusion types introduced as of JDK 6
      </p><ul>
        <li>Exclusion from blocking of toolkit-modal dialogs
        </li><li>Exclusion from blocking of application-modal dialogs
      </li></ul>
      By default, a window's modal exclusion property is turned off.
    <p>
      </p><ol>
        <li><u>Application-modal exclusion</u><br>
          If a window is application-modal excluded, it is not blocked by any
          application-modal dialogs. Also, it is not blocked by document-modal
          dialogs from outside of its child hierarchy.
        </li><li><u>Toolkit-modal exclusion</u><br>
          If a window is toolkit-modal excluded, it is not blocked
          by any application- or toolkit-modal dialogs. Also, it is not
          blocked by document-modal dialogs from outside of their child hierarchy.
      </li></ol>
    <p>
    <blockquote>
      <hr>
        <b>Implementation note</b>: Changing the modal exclusion type for a visible window
        may have no effect until it is hidden and then shown again.
      </hr>
    </blockquote>

    <a name="Related"</a>
    </p><h3>Related AWT features</h3>

    <p>
      <u>Always-On-Top</u><br>
      When a modal dialog that is not always-on-top blocks an always-on-top window,
      their relative Z-order is unspecified and platform-dependent.
    </p>
    <p>
      <u>The <code>toFront()</code> and <code>toBack()</code> methods</u><br>
      A modal dialog should always be above all its blocked windows. Thus, if a blocked
      window is brought to the front, its blocking dialog, if any, is also brought to the
      front and remains above the blocked window. Likewise, if a modal dialog is sent to
      the back, all of its blocked windows are sent to the back to keep them below the
      blocking dialog.
    </p>
    <p>
      <u>Minimizing, maximizing and closing blocked windows</u><br>
      When a modal dialog blocks a window, the user may not be able to maximize or
      minimize the blocked window&#151; however, the actual behavior is unspecified
      and platform-dependent. In any case, the user can't close the blocked window
      interactively&#151; but it can be closed programmatically by calling the
      <code>setVisible(false)</code> or <code>dispose()</code> methods on the blocked
      window.
    </p>
    <p>
      <u>Blocked windows activations</u><br>
      When the user selects a blocked window, it may be brought to the front, along
      with the blocking modal dialog which would then become the active window&#151;
      however, the actual behavior is unspecified and platform-dependent.
    </p>
    <p>
      <u>Hiding a modal dialog</u><br>
      When the modal dialog that currently has focus is hidden, it is unspecified
      and platform-dependent, which other window will become the active window.
      Any of the following may become the active window:
      <ol>
        <li>The owner of the modal dialog - if the owner is unblocked.
        </li><li>The <code>Window</code>, which was active before this modal dialog gained
        focus - if the owner of the modal dialog is absent or is blocked.
      </li></ol>
      If the modal dialog to be hidden does not have focus, the active window remains
      unchanged.
    </p>
    <a name="Security"></a>
    </p><h3>Security</h3>

    <p>
      A special <code>AWTPermission</code>, <code>"toolkitModality"</code>,
      is required to show toolkit-modal
      dialogs. This would prevent, for example, blocking a browser or 
      Java Web Start (JWS) by modal dialogs shown from applets.
    </p><p>
      The same permission is required to exclude a window from toolkit modality.
      This would prevent, for example, a dialog shown from an applet not to be
      blocked by a browser's or JWS's modal dialog.

    <a name="PlatformSupport"></a>
    </p><h3>Platform support</h3>

    <p>
      Two <code>java.awt.Toolkit</code> methods allow you to check whether
      the current platform supports specific modality features:
      </p><ul>
        <li><code>isModalityTypeSupported(modalityType)</code><br>
          Returns whether the specified modality type is supported on
	  the current platform.
          If mode "M" is not supported and a dialog is set to M-modal,
          it behaves as modeless.
        </li>
	<li><code>isModalExclusionTypeSupported(modalExclusionType)</code><br>
          Returns whether the given modal exclusion type is supported on
	  the current platform. If exclusion type "E" is not supported
	  and a window is marked as E-excluded, this has no effect.
      </li></ul>

    <a name="Compatibility"></a>
    <h3>Compatibility</h3>

    <p>
      The default modality type is application-modal. It is used by the API
      calls: <code>Dialog.setModal(true)</code>, 
      <code>Dialog(owner, true)</code>, etc. Prior to JDK 6
      the default type was toolkit-modal,
      but the only distinction between application- and toolkit-modality is for
      applets and applications launched from Java Web Start.

    <a name="Examples"></a>
    </p><h3>Examples</h3>

    <table cols="2" border="0">
      <tbody><tr>
        <td align="left" valign="center">
	<ol>
          <li>Frame "F" is shown<br>
          <li>Document-modal dialog "D<sub>i</sub>" is shown<br>
          <li>F becomes blocked by D<sub>i</sub> &#151; it's in the same document<br>
          <li>Document-modal dialog "D<sub>ii</sub>" is shown<br>
          <li>D<sub>i</sub> becomes blocked by D<sub>ii</sub> &#151; it's in the
	      same document<br>
	  </ol>
          <br>
        </td>
        <td align="center" valign="center">
          <img src="modal-example1.gif">
          <br>
        </td>
      </tr>
      <tr>
        <td align="left" valign="center">
	<ol>
         <li>Frame "F" is shown<br>
         <li>Document-modal dialog "D<sub>i</sub>" is shown<br>
         <li>F becomes blocked by D<sub>i</sub> &#151; it's in the same document<br>
         <li>Document-modal dialog "D<sub>ii</sub>" is shown<br>
         <li>D<sub>i</sub> becomes blocked by D<sub>ii</sub> &#151;
	     it's in the same document<br>
         <li>D<sub>i</sub> is hidden<br>
         <li>F becomes blocked by D<sub>ii</sub> &#151; it's in the same document<br>
         </ol>
	 <br>
        </td>
        <td align="center">
          <img src="modal-example2.gif">
          <br>
        </td>
      </tr>
      <tr>
        <td align="left" valign="center">
	<ol>
          <li>Frame "F" is shown<br>
          <li>Toolkit-modal dialog "D<sub>i</sub>" is created, but not shown<br>
          <li>Document-modal dialog "D<sub>ii</sub>" is shown<br>
          <li>F becomes blocked by D<sub>ii</sub> &#151; it's in the same document<br>
          <li>Application-modal dialog "D<sub>iii</sub>" is shown<br>
          <li>D<sub>ii</sub> becomes blocked by D<sub>iii</sub> &#151;
	      it's in the same application<br>
          <li>D<sub>i</sub> is shown<br>
          <li>D<sub>i</sub> becomes blocked by D<sub>ii</sub> &#151; it's its owner<br>
          <li>D<sub>iii</sub> remains unblocked &#151; it blocks D<sub>ii</sub> and 
	      D<sub>ii</sub> blocks D<sub>i</sub><br>
	  </ol>
          <br>
        </td>
        <td align="center" valign="center">
          <img src="modal-example3.gif">
          <br>
        </td>
      </tr>
      <tr>
        <td align="left" valign="center">
	<ol>
          <li>Frame "F" is shown<br>
          <li>Toolkit-modal dialog "D<sub>i</sub>" is created, but not shown<br>
          <li>Document-modal dialog "D<sub>ii</sub>" is shown<br>
          <li>F becomes blocked by D<sub>ii</sub> &#151; it's in the same document<br>
          <li>Application-modal dialog "D<sub>iii</sub>" is shown<br>
          <li>D<sub>ii</sub> becomes blocked by D<sub>iii</sub> &#151; it's in the
	      same application<br>
          <li>D<sub>i</sub> is shown<br>
          <li>D<sub>iii</sub> becomes blocked by D<sub>i</sub> &#151; D<sub>i</sub>
	      is not blocked<br>
          <li>D<sub>i</sub> remains unblocked<br>
	  </ol>
          <br>
        </td>
        <td align="center" valign="center">
          <img src="modal-example4.gif">
          <br>
        </td>
      </tr>
    </tbody></table>

</body></html>