The Kino Widget Class

Features

• Main tasks: parsing, formatting and rendering of source-text.
• Make most of the widget's internals extensible through the X Toolkit's callback mechanism.
• Provide a uniform interface for adding custom extensions:
  • Application can register callbacks for every tag
  • Application can supply arbitrary child widgets (insets) as response to unknown tags
  • Application can rewrite the source text as response to unknown tags

Internal Components of the Kino Widget

• The Parser
  ... builds a list of parsed text elements (PData objects), which can also be modified by an extension. Examples for PData objects are words, style data, tables or insets.

• The Layouter
  ... arranges the elements to displayable lines (Line objects) whenever new PData objects are added, the geometry or the default style changes.

• The Painter
  ... handles mostly exposure events from the window system and translates screen coordinates to PData elements.

Example: Using Wafe and the Kino widget

#!/usr/bin/X11/mofe --f


w3AddConverter text/html {MemoryWriter {XkAppendText k "%d"}}





XmRowColumn rc topLevel


  HtmlKino k rc


  XmRowColumn bar rc orientation horizontal


  XmPushButton load bar activateCallback {


    XkStartText k


    w3LoadAnchor [w3GetAnchor http://www.wu-wien.ac.at/wafe/] \


                 [w3RequestNew postCb {XkFinishText k; sV msg labelString "done"}]


    sV msg labelString "loading ..." 


  }


  XmLabel msg bar labelString " "





realize

• A Presenter for text/html is registered with Wafe's libwww module.
• Every time new data arrives, the incremental presenter forwards it to the Kino widget's parser by using the command XkAppendText.
• The command XkFinishText, invoked from the termination handler, tells the Kino widget to stop expecting data.

Example continued: Extending the Kino widget's capabilities

proc handleTag {w tag atts} { switch -exact $tag { CLOCK { XkAddInset $w [Clock c $w width 100 height 100 background pink] bottom } } sV k tagCallback {handleTag %W %t "%A"}

<H1>Clock Example:</H1> If you are using the Kino widget, you should see here <CLOCK> a clock!

• The tagCallback attribute of the Kino widget class can be used to register a handler which is invoked by the parser whenever a tag is ecountered.
• The name of the tag and all attributes are passed to the handler.
• The XkAddInset command can be used from within a tag callback in order to create complex compound documents.
• In the example above, a Clock widget is added whenever the CLOCK tag is encountered.
• This is a simplified example, we have more efficient mechanisms for handling one single additional tag.

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