Tao of the Machine

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Laszlo Presentation Server

Laszlo Presentation Server is a system to develop rich web-based applications. It works with Flash, but because of its system-independent .lzx file format (which is based on XML), it will be capable of supporting other display formats as well.

For a quick guide, see Laszlo in Ten Minutes. In the meantime, here are my first impressions:

  • Writing applications using XML is straightforward and simple. I'm not really a fan of XML, but in this case it seems a natural fit. Your components are represented by XML tags. Child controls are easily added by child tags. For example, here's "hello world" in LZX format.

<canvas height="100" width="500" >
      Hello, World!

  • Running an .lzx application is easy. Simply drop the file where LPS can see it, and point your browser to it. (Of course the application server needs to be running.)

  • There are some nice features, like floating windows, easy drag & drop, easy editing, debugger, etc.

  • There are data-aware controls, but most of the examples use XML datasets. Attaching them to a "real" database is possible, but not very straightforward. I would like to connect to a database directly; Laszlo however seems to depend on server-side techniques, like JSP, ASP or CGI. Also, whatever tool or technique is used, it still needs to pass data as XML.

  • For more programming power, you can define classes and methods (in XML). You can also mix LZX code with JavaScript etc.

  • While most of the GUI stuff is as you would expect it, there are some unusual features. For example, let's say you have a list of addresses. You edit the address by clicking it, after which an edit view appears under the original line, moving all the following addresses down. To see what I mean, see the section about data-driven applications.

  • The application server output window sometimes gives helpful hints. For example, I tried modified the "hello world" example so it would show a bigger font. Without looking up the reference for the text tag, I changed it to <text size="10">. When running it, the program ran as usual (without errors), but this appeared in the output window:

hello.lzx:2:20: attribute "size" not allowed at this point; ignored
hello.lzx:2:20: found an unknown attribute named "size" on element "text", however there is an attribute named "fontsize" on class "text", did you mean to use that?

  • It's just too slow for my computer. Granted, I don't have a high-end box (900 MHz Intel Celeron, 256 Mb), but still. Apparently a lot of horsepower is necessary to run this smoothly, which you would expect from a server, I guess. Running it with IE seems faster and more stable than with Firebird, but loading times are often very slow with both browsers. Not to mention the fact that it hogs memory. (These problems might be related to the fact that it uses Java.)

All in all, a promising system. It's easy to write powerful programs that are pleasing to the eye. You'll need something better than my computer, though. :-)

Posted by Hans Nowak on 2004-04-05 20:39:16   {link} (see old comments)
Categories: internet, programming

Wax 0.2.0 released

I just finished updating Wax to work with wxPython As the migration notes warn, this new wxPython version breaks some existing code, and I did indeed have to change a number of things in Wax, although the breakage wasn't *extremely* bad. Some of the things I noticed:

  • Using wx.NULL to indicate that a Frame has no parent does not work anymore. Use None instead. This affected Frame, FlexGridFrame and GridFrame.
  • Some DC methods broke; use a (x, y) tuple or the methods ending in *XY.
  • wx.TreeView.GetFirstChild apparently changed its number of parameters.
  • wx.Sizer.Add now takes a tuple (width, height) or a component, which actually made the Wax code a bit easier.
  • Something strange: in a Notebook, when you change the page or open a new one, the window in that tab does not automatically take focus anymore. Maybe this is a problem in my own code, maybe not.
  • The "choose directory" dialog has changed. (Don't know if this affects the interface; are there additional flags?)

It's possible that some of these things, like the wx.NULL issue, have been deprecated for a while... I don't know. :-)

It's also quite possible that I've overlooked some changes, so use this version with caution, and don't be too surprised if 0.2.1 will be released quickly. Also note that Wax 0.2.0 will not work with wxPythons older than (I suppose you could hack it to make it work, but that is not recommended... in fact, the whole point of this 0.2.0 release is compatibility with

Downloads in the usual place. Bug reports welcome at the usual address.

Posted by Hans Nowak on 2004-04-03 01:19:47   {link} (see old comments)
Categories: Wax

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