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Laszlo Eclipse Frameworks


The Laszlo Eclipse Frameworks Project is a proposed open source project to be incubated under the Eclipse Technology Project.

The proposal is posted here to solicit community feedback, additional project participation, and ways the project can be leveraged from the Eclipse membership-at-large. You are invited to comment on and/or join the project. Please send all feedback to the newsgroup.


Rich internet client platforms are becoming increasingly popular, as witnessed by the success of the OpenLaszlo platform, an open source, XML-native platform for developing rich Internet applications that run in any modern Web browser. OpenLaszlo has become a reliable platform for thousands of developers, creating applications with the rich user interface capabilities of desktop client software and the instantaneous no-download Web deployment of HTML. To date, millions of users are have used applications developed for the OpenLaszlo platform. See the OpenLaszlo project page for more information

It is important to have the proper eclipse frameworks in place to support the OpenLaszlo platform, and other rich internet client platforms. These frameworks would allow integration of the client development and the server development, or allow integration of various rich internet client technologies.


The Laszlo Frameworks subproject's goal will be to develop a framework for development of the OpenLaszlo platform, and other rich client platforms, with full support for editing, refactoring, and debugging. The Frameworks would be an extensible such that new language features can easily be added, or other xml/script based Rich Internet Markup Languages, such as XUL or XForms could be plugged in.

Another goal of this project will be to provide the ability to easily and quickly define Eclipse UI Plugins (extension point for views,wizards,dialogs,property/preference pages) using the LZX (Laszlo xml) markup, without writing any Java code. While this is not the primary goal of the project, it has several advantages:

  • Provides added productivity to framework developers such that more functionality can quickly and easily be added.
  • Could possibly benefits the entire eclipse developer community with the added productivity .

The frameworks would allow creation and testing of OpenLaszlo and other rich client applications . Laszlo frameworks would also provide a rich editing environment for the LZX mark-up language. The editing features would provide content assistance, syntax highlighting, and code formatting for both XML and script.

In addition, the Laszlo frameworks would provide visual editing (WSYIWYG) frameworks. It would support markers for reflecting compilation and syntactical errors.

In addition to the editor, the following views would aslo be provided:

  • The Palette View would enable developers to drag and drop new XML/LZX elements into the editor.
  • The Properties View would be used to edit the attributes of the selected element in the editor.
  • The Outline View would the document as a tree, allowing the developer to make changes to the document's structure.

The frameworks would provide typical debugging capabilities to the extent allowed by the runtime. This include variable inspection, expression evaluation, and console output.

A major focus of this project will be to bring the broader community of tool developers, application specialists, testers, and day-to-day OpenLaszlo programmers into the development and refinement of this tool.

Proposed Design

The Laszlo Frameworks would be be based on the WebTools project, specifically the Structured Editor capabilities (XML Editing). A schema-like XML file would define the xml language grammar (such as lzx). This file would contain the necessary information to provide rich editing capabilities on that grammar. This would include such information such as what icon is associated with a tag, what kind of edit field should be used to edit an attribute, and what are the valid drag drop combinations. Different versions of this file could be used to provide editing of different grammars, such as XUL, or XForms.

The frameworks would tightly integrate XML tags and scripting, such as JavaScript. It would know what parts of a document are script, vs what parts are XML. It would maintain an internal model of the script, similar to the way the JDT models the Java model. This script model would be kept in sync with the XML Model.

One part of the frameworks would be an SWT renderer of LZX. This would allows certain plugins or extension points to be implmented in XML (LZX). For instance, a "view" extension-point would point to the LZX view renderer class, and contain the LZX to define the view. As an example:

            name="A LZX View"
              <checkbox>a option</checkbox>

The LZX renderer would interpet LZX tags, generate the corresponding SWT controls, and handle actions appropriately. The renderer would possibly use the rhino JavaScript engine for it's JavaScript support. It could also use the Bean Scripting Framework to expose eclipse Java objects (i.e. IResource) to the script.

Extension Points

The project will define appropriate extension points that would enable others to provide value-added functionality. These include:

  • ability to "plug-in" a different grammer other than LZX, such as XForms or XUL. The grammar would be defined in an xml file, so this would not involve writing Java code.
  • ability to "plug in" a different language. This would enable the suppor for scripting languages other than JavaScript.
  • ability to integrate language validators. This would allow for inline validation as well as syntax highlighting for pluggable models of other languages.
  • ability to extend the communication protocol for moving visual elements. By opening the protocol that exists to communicate between the running laszlo application and the framework, this allows other kinds of embedded applications to communicate state change information to and from Eclipse, and keep the editor's data model in sync. This could be extended for use by many kinds of information, not limited to visual state.
  • ability to create debugging tools based on the remote debugger protocol, and to connect romotely to an application for debugging in real time. The framework includes a debugging protocol for communicating debug state information between Eclipse and a running Laszlo application. By extending this portocol, other kinds of applications can provide debugging information to Eclipse. For example, an applet, even one residing on another machine, could be debugged if it was compiled with a small stub using the Eclipse remote debugging protocol.
  • ability to "plug-in" third-party debugging tools. The debugging protocol can also be extended to define interfaces that allow third-party vendors to plug in existing debugging tools.
  • ability to "plug-in" compiler implementations or versions.
  • ability for a third party vendor to add visual components and component libraries, by extending the framework to accept UI representations of new components.
  • ability to create custom property editors for runtime visual components, by extending the framework to allow control over which properties and what types of properties are available.
  • ability to include listeners for runtime events and logging operations, etc.


IBM is offering its IBM technology preview IDE for Laszlo as an initial code base (see IDE for Laszlo is a technology preview of an Eclipse-based development environment for creating, editing, debugging, and testing applications based on the LZX declarative mark-up language.

IBM has produced two technology preview releases. The first release was based upon the IBM initial contribution to the Eclipse web tools project, and Eclipse 3.0. The second release added the visual editing of OpenLaszlo Applications. The latest release (2.1) was based on the WebTools 0.7.

A demonstration and a gallery of screenshots can be found at:

Development Plan

The goals up to the point of this technology preview have been to develop a functional feature and plug-in set that supports editing and debugging. These goals have been met.

A formal development plan is being formulated, which includes:

  • Eclipse (Swt) rendering of LZX, implement UI plugins in LZX markup, possibly within the plugin.xml itself
  • refactoring support
  • define extension points for plugging in other xml/script based UI markups.
  • compiler performance improvements
  • improved debug support - JavaScript code stepping, breakpoints, live code update, http request monitoring, extending the debugging protocol
  • Quick navigation to named elements ("meta-dot")
  • WYSIWYG interface to performance tools

Relationships to other projects

This subproject is built on top of the Web Tools project (and thus it's prereqs).

Interested Parties

Prospective Interim Leads

  • Phil Berkland, IBM (berkland at
  • Amy Muntz, (amuntz at
Interested Organizations

Potential Committers / Contributors

  • Max Carlson, (max at
  • Phil Berkland, IBM (
  • Gino Bustelo, IBM (
  • Don Sedota, IBM (
  • Henry Minsky, (hqm at
  • Amy Muntz, (amuntz at
  • Oliver Steele, (osteele at
  • P.T. Withington, (ptw at