Essentials of Javascript - Cultural View

Lively Kernel 113
Lively has been used to build simple web sites, including its own tutorial, and also a client-side Wiki system that
stores its pages in an SVN repository. Lively content varies from relatively static pages of text to fully dynamic
models that look and behave like flash simulations. The Lively Kernel achieves complex dynamic behavior without
any specific animation support (it does not use the animation features of SVG), but by simple scheduling of multiple
green-thread processes in JavaScript.
Lively Text and Transformations
The Lively Kernel includes its own multifont text editor written in JavaScript. It includes support for centering,
justification and similar rudimentary text composition capabilities. Working in Lively thus has much the same feel as
working in a web page design program, except that the on-the-fly text layout is not being done in an offline
composition program, but it is in fact the built-in dynamic behavior of text in the Lively Kernel.
The liveliness of Lively graphics becomes even more apparent when you manipulate the scale and rotation handles
for objects and text. The entire code browser can be used when tilted 20 degrees on its side. Because the text editor is
made up entirely of lively graphics, it works perfectly well when rotated or scaled, just as do the scroll bars, clipping
frames, and the rest of the entire lively user interface.
Cross-Browser Compatibility
The Lively Kernel depends on browser support for JavaScript and SVG or Canvas graphics, all now part of the W3C
standards. At the time of writing, this means that it runs in Safari, Firefox, Chrome and Opera browsers.
While this requirement might seem less compatible than HTML, Lively is actually more compatible across the
browsers on which it runs than is HTML. This is because there is greater uniformity among JavaScript, SVG and
Canvas implementations than there is from one HTML implementation to another. Except for one small initial file,
the Lively Kernel code base is entirely free of tests for which client browser is being used.
The Lively IDE
Lively includes an integrated development environment of considerable power, designed to work via WebDAV with
a local set of a dozen or so source JavaScript files synchronizable with an SVN repository. If the user opens a
SystemBrowser, all the JavaScript source files are listed in the file pane of the browser. If the user clicks on one of
these files, it will be read, parsed (by an OMeta JavaScript parser) and displayed similar to a Smalltalk browser with
functions or class definitions listed and, for each class, all the method names are shown. The user can click on a
method name, edit its code in the bottom pane, and then save the new definition. The new definition will be checked
for syntax and, if correct, it will be stored back in the .JS file. Moreover, if in "eval mode" (the usual case), the
method will be redefined in the system that is running. This allows non-critical changes to be made without any need
to restart Lively or any of the applications being developed. When all the source files are loaded, a rapid scan will
find every reference to a selected text, and present all the code bodies that match in a separate sub-browser.
The Lively IDE includes object inspectors and morph style panels for controlling fills, borders, and text styles. There
are also facilities for debugging at error points and profiling for performance tuning, but these have not been pushed,
owing to the improving quality of such run-time support in all the major browsers.