Modification of cross-site linker for simple web workers

*.gwt.xml

  <define-linker name="webworker" class="com.wobastic.gwt.webworker.linker.WebWorkerLinker" />
  <add-linker name="webworker"/> 

EmptyTemplate.js

This should be an empty file

WebWorkerLinker.java

/*
 * Copyright 2010 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */

package com.wobastic.gwt.webworker.linker;

import com.google.gwt.core.ext.LinkerContext;
import com.google.gwt.core.ext.TreeLogger;
import com.google.gwt.core.ext.UnableToCompleteException;
import com.google.gwt.core.ext.linker.LinkerOrder;
import com.google.gwt.core.ext.linker.LinkerOrder.Order;
import com.google.gwt.core.ext.linker.Shardable;
import com.google.gwt.core.linker.CrossSiteIframeLinker;
import com.google.gwt.dev.About;
import com.google.gwt.dev.util.DefaultTextOutput;
import com.google.gwt.dev.util.TextOutput;

/**
 * This linker uses an iframe to hold the code and a script tag to download the
 * code. It can download code cross-site, because it uses a script tag to
 * download it and because it never uses XHR. The iframe, meanwhile, makes it
 * trivial to install additional code as the app runs.
 */
@LinkerOrder(Order.PRIMARY)
@Shardable
public class WebWorkerLinker extends CrossSiteIframeLinker {
  @Override
  public String getDescription() {
    return "WebWorker";
  }


  /**
   * Returns the name of the {@code ComputeScriptBase} script.  By default,
   * returns {@code "com/google/gwt/core/ext/linker/impl/computeScriptBase.js"}.
   *
   * @param context a LinkerContext
   */
  protected String getJsComputeScriptBase(LinkerContext context) {
    return getStringConfigurationProperty(context, "computeScriptBaseJs",
        "com/wobastic/gwt/webworker/linker/EmptyTemplate.js");
  }


  /**
   * Returns the name of the {@code JsInstallLocation} script.  By default,
   * returns {@code "com/google/gwt/core/ext/linker/impl/installLocationIframe.js"}.
   *
   * @param context a LinkerContext
   */
  protected String getJsInstallLocation(LinkerContext context) {
    return "com/wobastic/gwt/webworker/linker/EmptyTemplate.js";
  }

  /**
   * Returns the name of the {@code JsInstallScript} script.  The default is chosen
   * based on the value of {@link #shouldInstallCode}.
   *
   * <p> If you override this, verify that {@link #shouldInstallCode} is
   * set consistently or fragment loading won't work.
   */
  protected String getJsInstallScript(LinkerContext context) {
    return "com/wobastic/gwt/webworker/linker/EmptyTemplate.js";
  }


  /**
   * Returns the name of the {@code JsLoadExternalStylesheets} script.  By default,
   * returns {@code "com/google/gwt/core/ext/linker/impl/loadExternalStylesheets.js"}.
   *
   * @param context a LinkerContext
   */
  protected String getJsLoadExternalStylesheets(LinkerContext context) {
    return "com/wobastic/gwt/webworker/linker/EmptyTemplate.js";
  }


  /**
   * Returns the name of the {@code JsProcessMetas} script.  By default,
   * returns {@code "com/google/gwt/core/ext/linker/impl/processMetas.js"}.
   *
   * @param context a LinkerContext
   */
  protected String getJsProcessMetas(LinkerContext context) {
    return "com/wobastic/gwt/webworker/linker/EmptyTemplate.js";
  }


  @Override
  protected String getModulePrefix(TreeLogger logger, LinkerContext context, String strongName)
    throws UnableToCompleteException {
    TextOutput out = new DefaultTextOutput(context.isOutputCompact());

    // Note: this code is included in both the primary fragment and devmode.js

    // $wnd is the main window that the GWT code will affect and also the
    // location where the bootstrap function was defined. In iframe-based linkers,
    // $wnd is set to window.parent. Usually, in others, $wnd = window.
    // By default, $wnd is not set when the module starts, but a replacement for
    // installLocationIframe.js may set it.

    out.print("var $wnd = $wnd || self;");
    out.newlineOpt();
    out.print("var __gwtModuleFunction = $wnd." + context.getModuleFunctionName() + ";");
    out.newlineOpt();
    out.print("var $sendStats = __gwtModuleFunction.__sendStats;");
    out.newlineOpt();
    out.print("$sendStats('moduleStartup', 'moduleEvalStart');");
    out.newlineOpt();
    out.print("var $gwt_version = \"" + About.getGwtVersionNum() + "\";");
    out.newlineOpt();
    out.print("var $strongName = '" + strongName + "';");
    out.newlineOpt();
    out.print("var $gwt = {};");
    out.newlineOpt();
    //out.print("var $doc = $wnd.document;");
    //out.newlineOpt();
    out.print("var $moduleName, $moduleBase;");
    out.newlineOpt();

    // The functions for runAsync are set up in the bootstrap script so they
    // can be overridden in the same way as other bootstrap code is, however
    // they will be called from, and expected to run in the scope of the GWT code
    // (usually an iframe) so, here we set up those pointers.
    out.print("function __gwtStartLoadingFragment(frag) {");
    out.newlineOpt();
    String fragDir = getFragmentSubdir(logger, context) + '/';
    out.print("var fragFile = '" + fragDir + "' + $strongName + '/' + frag + '" + FRAGMENT_EXTENSION + "';");
    out.newlineOpt();
    out.print("return __gwtModuleFunction.__startLoadingFragment(fragFile);");
    out.newlineOpt();
    out.print("}");
    out.newlineOpt();
    out.print("function __gwtInstallCode(code) {return __gwtModuleFunction.__installRunAsyncCode(code);}");
    out.newlineOpt();

    // The functions for property access are set up in the bootstrap script however
    // they will be called from, and expected to run in the scope of the GWT code
    // (usually an iframe) so, here we set up those pointers.
    out.print("function __gwt_isKnownPropertyValue(propName, propValue) {");
    out.newlineOpt();
    out.print("return __gwtModuleFunction.__gwt_isKnownPropertyValue(propName, propValue);");
    out.newlineOpt();
    out.print("}");
    out.newlineOpt();
    out.print("function __gwt_getMetaProperty(name) {");
    out.newlineOpt();
    out.print("return __gwtModuleFunction.__gwt_getMetaProperty(name);");
    out.newlineOpt();
    out.print("}");
    out.newlineOpt();

    // Even though we call the $sendStats function in the code written in this
    // linker, some of the compilation code still needs the $stats and
    // $sessionId
    // variables to be available.
    out.print("var $stats = $wnd.__gwtStatsEvent ? function(a) {");
    out.newlineOpt();
    out.print("return $wnd.__gwtStatsEvent && $wnd.__gwtStatsEvent(a);");
    out.newlineOpt();
    out.print("} : null;");
    out.newlineOpt();
    out.print("var $sessionId = $wnd.__gwtStatsSessionId ? $wnd.__gwtStatsSessionId : null;");
    out.newlineOpt();

    return out.toString();
  }


  @Override
  protected String getSelectionScriptTemplate(TreeLogger logger, LinkerContext context) {
    return "com/wobastic/gwt/webworker/linker/WebWorkerTemplate.js";
  }

  /**
   * Determines the strategy for installing JavaScript code into the iframe.
   * If set to false, a &lt;script&gt; tag pointing to the js file is added
   * directly to the iframe. Otherwise, GWT downloads the JavaScript code
   * as a list of strings and then adds it to the iframe.
   */
  protected boolean shouldInstallCode(LinkerContext context) {
    return false;
  }

  /**
   * Returns whether to use "self" for $wnd and $doc references. Defaults to false.
   * Useful for worker threads.
   */
  protected boolean shouldUseSelfForWindowAndDocument(LinkerContext context) {
    return true;
  }
}

WebWorkerTemplate.js

/*
 * Copyright 2010 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */
__BEGIN_TRY_BLOCK__
function __MODULE_FUNC__() {
  var $wnd = __WINDOW_DEF__;
  //var $doc = __DOCUMENT_DEF__;

  sendStats('bootstrap', 'begin');

  /****************************************************************************
   * Internal Helper Functions
   ***************************************************************************/

  function isHostedMode() {
    var query = $wnd.location.search;
    return ((query.indexOf('gwt.codesvr.__MODULE_NAME__=') != -1) ||
            (query.indexOf('gwt.codesvr=') != -1));
  }

  // Helper function to send statistics to the __gwtStatsEvent function if it
  // exists.
  function sendStats(evtGroupString, typeString) {
    if ($wnd.__gwtStatsEvent) {
      $wnd.__gwtStatsEvent({
        moduleName: '__MODULE_NAME__',
        sessionId: $wnd.__gwtStatsSessionId,
        subSystem: 'startup',
        evtGroup: evtGroupString,
        millis:(new Date()).getTime(),
        type: typeString,
      });
    }
  }


  /****************************************************************************
   * Exposed Functions and Variables
   ***************************************************************************/
  // These are set by various parts of the bootstrapping code, but they always
  // need to exist, so give them all default values here.

  // Exposed for the convenience of the devmode.js and md5.js files
  __MODULE_FUNC__.__sendStats = sendStats;

  // Exposed for the call made to gwtOnLoad. Some are not figured out yet, so
  // assign them later, once the values are known.
  __MODULE_FUNC__.__moduleName = '__MODULE_NAME__';
  __MODULE_FUNC__.__errFn = null;
  __MODULE_FUNC__.__moduleBase = 'DUMMY';
  __MODULE_FUNC__.__softPermutationId = 0;

  // Exposed for devmode.js
  __MODULE_FUNC__.__computePropValue = null;
  // Exposed for super dev mode
  __MODULE_FUNC__.__getPropMap = null;
  
  // Exposed for runAsync
  __MODULE_FUNC__.__installRunAsyncCode = function() {};
  __MODULE_FUNC__.__gwtStartLoadingFragment = function() { return null; };

  // Exposed for property provider code
  __MODULE_FUNC__.__gwt_isKnownPropertyValue = function() { return false; };
  __MODULE_FUNC__.__gwt_getMetaProperty = function() { return null; };

  // Exposed for permutations code
  var __propertyErrorFunction = null;


  // Set up our entry in the page-wide registry of active modules.
  // It must be set up before calling computeScriptBase() and
  // getCompiledCodeFilename().
  var activeModules =
      ($wnd.__gwt_activeModules = ($wnd.__gwt_activeModules || {}));
  activeModules["__MODULE_NAME__"] = {moduleName: "__MODULE_NAME__"};

  __MODULE_FUNC__.__moduleStartupDone = function(permProps) {
    // Make embedded properties available to Super Dev Mode.
    // (They override any properties already exported.)
    var oldBindings = activeModules["__MODULE_NAME__"].bindings;
    activeModules["__MODULE_NAME__"].bindings = function() {
      var props = oldBindings ? oldBindings() : {};
      var embeddedProps = permProps[__MODULE_FUNC__.__softPermutationId];
      for (var i = 0; i < embeddedProps.length; i++) {
        var pair = embeddedProps[i];
        props[pair[0]] = pair[1];
      }
      return props;
    };
  };

  /****************************************************************************
   * Internal Helper functions that have been broken out into their own .js
   * files for readability and for easy sharing between linkers.  The linker
   * code will inject these functions in these placeholders.
   ***************************************************************************/
  // Provides getInstallLocationDoc() function.
  __INSTALL_LOCATION__

  // Provides the installScript() function.
  __INSTALL_SCRIPT__
  function installScript(filename) {
      sendStats('moduleStartup', 'moduleRequested');
	  importScripts(filename);
      sendStats('moduleStartup', 'scriptImported');
  }

  // Sets the __MODULE_FUNC__.__installRunAsyncCode and 
  // __MODULE_FUNC__.__startLoadingFragment functions
  __RUN_ASYNC__

  // Provides the processMetas() function which sets the __gwt_getMetaProperty
  // __propertyErrorFunction and __MODULE_FUNC__.__errFn variables if needed
  __PROCESS_METAS__

  // Provides the computeScriptBase() function
  __COMPUTE_SCRIPT_BASE__
  function computeScriptBase() {
	function getDirectoryOfFile(path){
	    var hashIndex = path.lastIndexOf('#');
	    if (hashIndex == -1) {
	      hashIndex = path.length;
	    }
	    var queryIndex = path.indexOf('?');
	    if (queryIndex == -1) {
	      queryIndex = path.length;
	    }
	    var slashIndex = path.lastIndexOf('/', Math.min(queryIndex, hashIndex));
	    return slashIndex >= 0?path.substring(0, slashIndex + 1):'';
	  }
	
	  function isLocationOk(){
	    var loc = $wnd.location;
	    return loc.href == loc.protocol + '//' + loc.host + loc.pathname + loc.search + loc.hash;
	  }
	
	  var tempBase = getDirectoryOfFile($wnd.location.href);
	  return tempBase;
  }

  // Provides the computeUrlForResource() function
  __COMPUTE_URL_FOR_RESOURCE__

  // Provides the getCompiledCodeFilename() function which sets the following
  // variables if needed:
  //   __gwt_isKnownPropertyValue
  //   __MODULE_FUNC__.__computePropValue
  //   __MODULE_FUNC__.__getPropMap
  //   __MODULE_FUNC__.__softPermutationId
  __PERMUTATIONS__

  // Provides the loadExternalStylesheets() function
  __LOAD_STYLESHEETS__

  /****************************************************************************
   * Bootstrap startup code
   ***************************************************************************/

  // Must be called before computeScriptBase() and getCompiledFilename()
  //processMetas();

  // Must be set before getCompiledFilename() is called
  __MODULE_FUNC__.__moduleBase = computeScriptBase();
  activeModules["__MODULE_NAME__"].moduleBase = __MODULE_FUNC__.__moduleBase;

  // Must be done right before the "bootstrap" "end" stat is sent
  var filename = getCompiledCodeFilename();

  __DEV_MODE_REDIRECT_HOOK__

  //loadExternalStylesheets();

  sendStats('bootstrap', 'end');

  installScript(filename);

  return true; // success
}
__MODULE_FUNC__.succeeded = __MODULE_FUNC__();

__END_TRY_BLOCK_AND_START_CATCH__
  __MODULE_FUNC_ERROR_CATCH__
__END_CATCH_BLOCK__