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RootWidget and Rendering Startup

 17th July 2014 at 6:23pm

The previous parts of this chapter showed how WikiText is transformed to DOM nodes which dynamically react to tiddler changes and a way to compose tiddlers from other tiddlers. This last part describes how the TiddlyWiki core plug-in starts up a UI build from tiddlers and WikiText.

After the microkernel has loaded it starts executing Startup Modules. The core plug-in contains two startup modules which are responsible to kick off the UI:

rootwidget.js is a startup module and creates an instance of the base widget. This widget is globally accessible $tw.rootWidget. The DOM node associated to this widget is the current browser window's DOM (document).

At first, the root widget has no children but provides some basic event handlers (Messages) like:

  • tm-notify: Displays the message given in param as a notification.
  • tm-save-wiki: Triggered by a save button, the user can click. This handler uses the syncer module described in Extended Persistence to save the current wiki.
  • tm-auto-save-wiki: Similar to tm-save-wiki but not triggered directly by the user but automatically triggered when a wiki page is edited and saved. A Saver implementation which starts a download of the updated wiki file would not support the auto-save method and would only be used when the tm-save-wiki message is used.
  • tm-download-file: This message also uses the syncer module described in Extended Persistence but explicitly demands to choose a saver with the download-method to start downloading a single tiddler.

After the root widget is loaded another startup module $:/core/modules/startup/render.js creates a transclude widget which contains the contents of $:/core/ui/PageTemplate which is now bound to the browsers DOM document. The render function of the transclude widget is initially executed and a listener is registered at the store which executes the refresh function of the transclude widget to trigger the Selective Update process.

Techniques for including other tiddlers and Templates are finally used in $:/core/ui/PageTemplate to build the TiddlyWiki UI only from tiddlers written in WikiText (with widgets implemented in javascript):

For example to implement the list of open wiki pages the $:/core/ui/PageTemplate contains a navigator widget which maintains a list of open tiddlers in a field of $:/StoryList and handles events like tm-navigate by adding a tiddler specified as parameter to the top of the list in $:/StoryList. The story tiddler transcluded in $:/core/ui/PageTemplate then uses a ListWidget to transclude all tiddlers in $:/StoryList through a special template $:/core/ui/ViewTemplate. A event of the type tm-close-tiddler would remove a specified tiddler from $:/StoryList. The Event Mechanism would trigger a changed event which triggers a call of the ListWidget's refresh function which would remove the tiddler from the list, closing the tiddler.