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Important!: because of move from the to this new home, not everything is updated or fully working yet... stay tuned...

What's New in the Tcl Plugin 2.0

New Features

  • The Tcl Plugin is now based on Tcl/Tk 8.0. This means that you get the benefits of Tcl's just-in-time bytecode compiler, and some scripts will execute significantly faster, especially compute-intensive ones.

  • Native look and feel for Tclets on each platform, because the plugin now uses Tk 8.0.

  • First source release: the complete source for the plugin and all Tcl files is included!

  • The plugin is now free for any use, including redistribution, derivation, commercial use, etc. Please let us know if you redistribute it or derive another piece of software from it - this is just to satisfy our own curiosity, not obligatory.

  • New installation locations:
    • On Unix the plugin installs by default into the Netscape hierarchy, in yourhome/.netscape/tclplug.
    • On Win32, it installs by default into c: clplug.

  • Comprehensive documentation is provided in your-install/doc. Read those manual pages to find out all the nitty gritty details about what's possible with this feature-rich plugin. Use 'nroff -man' or similar to produce a printed copy of the manual pages or use the online version.

  • New "policy" command instead of overloading the "package require" mechanism.

    The 2.0.3b release includes a new command "policy" that can be used by Tclets to request the use of a policy. Previously the same was achieved by issuing a "package require" command in a Tclet. See the policy manual page.

  • Several new security policies: inside, outside, home.

    These policies provide similar functionality to what used to be in Browser, Tempfile and Safesock combined. Each policy provides the same functions, with the only difference being which resources a Tclet can access. The features provides:

    • Communication with the hosting browser to fetch and post URLs.
    • Access to remote servers through sockets.
    • Local persistent storage that can be shared with other Tclets loaded from the same site.
    All policy names are now lower-case.

    All policies are documented in manual pages included in the 'doc' directory of the plugin runtime library. All policies are configurable through settings in a separate configuration file for each policy.

    At this time, site administrators are required to edit the configuration files. A future version of the Tcl plugin will come with an admin tool that will let site administrators control these settings from a GUI without having to edit text files.

  • Javascript communication is moved into its own policy: javascript. The facilities for communicating with Javascript and for generating HTML on the fly into new or existing frames has been moved into its own policy called Javascript. The reason for this was security: it is impossible to restrict access to any URLs when these functions are available, therefore they cannot be available in Home, Inside and Outside.

  • The capabilities provided by the plugin are organized into logical packages called "features".

    All the features are stored in <your-install>/safetcl. The capabilities provided by the plugin have been organized into several features:

    • "url" allows a Tclet to fetch and post to URLs, display URLs, etc.
    • "network" allows a Tclet to open network sockets.
    • "persist" enables a Tclet to use local persistent storage.
    • "stream" allows a Tclet to generate output streams to frames managed by the browser.
    • "unsafe" restores the unsafe commands that were removed by the Safe Base.

  • Flexible configuration package, configuration syntax is "English"-like.

    All configurable parameters of the plugin are controlled from a central configuration file, <your-install>/config/plugin.cfg. The configuration is organized in easy to understand sections and the configuration itself is written in a human readable form.

  • Policies are now "codeless", that is, you don't have to know (a lot) of Tcl to write a policy.

    Policies are just named configurations, so you don't need to write a lot of Tcl code to implement a new policy. Policy configurations specify which features they enable and under what circumstances, and they do not contain implementations for those features -- that is left for the features themselves.

    Settings in the plugin.cfg file control which policies are enabled and under what circumstances.

  • The plugin now uses namespaces for partitioning its functionality.
    • safe:: for the Safe Base.
    • cfg:: for the configuration package.
    • browser:: for the procedures to communicate with the hosting browser.
    • safefeature:: for procedures implementing feature packages.
    • rpi:: for remote procedure invocations between the plugin and an external process hosting Tclets (see below).

  • Tclets can appear inline in the web page by giving their source as the value of a "script" tag in the embed statement. Both a "script" tag and an "src" tag can appear within the same embed statement.

  • Tclets can now execute without display, by specifying "tk=0" in the embed statement. You should also use the "hidden" tag to tell the browser not to reserve space for this instance on the page.

  • A Tcl Plugin "how to" web site.
    At present the web site is somewhat skeletal, it will fill out quickly now that we're done with 2.0. If you want to contribute let us know by email at, or to the developers direct at or

  • The Tcl Plugin now supports use of an external process to host Tclets, in addition to being able to host Tclets directly within the browser. The external process must contain on Tk 8.0 or later. A default executable is supplied with the plugin and will be used if the user didn't specify which executable to use.

    In this release, the plugin hosts Tclets inside the browser by default. In a future release the default will be to host Tclets in an external process.

    For information on how to use the external process facility in the plugin, see the plugin manual page.

  • Lots of information about the Tclet is now available inside the Tclet itself, e.g. the URL from which it was loaded and the text of the Tclet.

  • Many bug fixes related to initialization and de-initialization. Previously these bugs would cause the plugin to eventually fail.

  • Much better support for fonts, using both X11 fonts and portable font name specification. See the Tk 8.0 documentation.

  • Much better support for focus propagation on Unix: the Tclet has a chance to get the focus when the mouse enters, and the Tclet loses focus when the mouse leaves.

  • Faster loading of Tclets due to smarter use of streaming and the browser cache. Reloading of a previously used Tclet is much faster. A splash screen is provided for slow-loading Tclets to give the user an indication that the plugin is alive and simply slow because the Tclet code hasn't arrived yet.

  • The browser::openStream API now supports mime types other than text/html, allowing the Tclet to write image data, for example.

  • Most APIs have been made binary-safe. They can now handle data that contains embedded \0's.

  • The browser::getForm and browser::displayForm APIs now take unencoded data to submit to the remote service, and do the proper encoding to protect the data in transit.

  • The browser::javascript API now accepts arbitrary JavaScript code. As long as you enclose it in curly braces, the right thing will happen.

  • The APIs to communicate with the browser have all been enhanced to take callbacks that get called when the appropriate event happens. This allows a Tclet to find out for example when a requested stream of data starts to arrive from a URL. These APIs also take an integer specifying the number of milliseconds to wait before timing out. Finally, they are all non-blocking if callbacks are specified, to allow a Tclet to continue computing or responding to user input while it is waiting for a requested URL's contents to arrive.

  • Dynamic loading of Tcl extensions is now supported when the plugin uses an external process to host Tclets. If you need to use a special executable that contains the extension statically linked you can do that too, with the TCL_PLUGIN_WISH environment variable. See the plugin manual page.

  • Auto-loading now works in Tclets and packages work just as in regular Tcl.

  • Supports a console for debugging, and event logging to a window and/or to a file. See the plugin manual page.

  • Supports logging of significant events to a file or to a window. See the plugin manual entry for details.

  • (Unix) Supports debugging of external process hosting Tclets with gdb. Note that this overwrites .gdbinit in your home directory without asking, which may not be what you want.

  • The plugin is now extensible because most of it was rewritten in Tcl. The relevant scripts are provided in the plugin runtime library. This will also make it much easier to support the Mac version in a timely manner in future releases.

  • The plugin now works well with Netscape Navigator 3.0 and 4.0 on Unix and Win32.

  • The plugin now works well with IE 3.0 and IE 4.0 on Win32.

  • The plugin also works with the Opera 3.0 beta 5 release on Win32, although not perfectly.

  • The plugin also works with the Amaya browser from the W3C on Linux 2.0. We have not tested whether the Win32 version works or whether it works with Amaya on other versions of Unix.

  • Security enhancements:
    • Tclets no longer see the auto_path and instead use symbolic tokens. Likewise, tcl_library, tk_library and other paths are symbols now.
    • vwait and tkwait have been restored so Tclets can now use them.
    • fixed several security holes in the local persistent storage feature.

  • Many bug fixes:
    • Color maps now work better.
    • More robust if many Tclets are being used at the same time.
    • Event mechanism overhauled, now more responsive and robust.
    • Sockets now work reliably, and the plugin uses a reliable efficient RPC package to communicate with the external executable.
    • Commands that crash IE 3.0 or 4.0 are now disabled if the plugin detects that it's being used in those browsers.

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Last modified: Wed Feb 11 1998, 18:04, hosted by