Back at the very beginning of the book, in Tiddlers, we learned that everything is a tiddler. And in Field Transclusions, we mentioned in passing that the entire interface of TiddlyWiki is created by transcluding special tiddlers.
This means that, essentially, we can change anything in TiddlyWiki just by modifying these tiddlers, using the same tools we already know. (Only a tiny piece of TiddlyWiki, called the microkernel, can't be directly modified from within the wiki. But the only function of the microkernel is to load the JavaScript code and wikitext that is stored in tiddlers, so it's hard to imagine having a reason to customize it.) Completely changing the look and feel of TiddlyWiki and implementing custom JavaScript code are beyond the scope of this book, but in this chapter we will look at changing the sidebar, adding custom interface elements, and some more fun and useful things that will help you make any wiki you create with TiddlyWiki exactly fit your needs. Along the way, you'll also learn how you can poke around and discover how these tiddlers work, so you can make your own changes that we haven't talked about.
If your entire wiki is made up of these special tiddlers, you may be wondering why you don't see all of them in the list of tiddlers when you click the All section of the More tab in the sidebar of a new TiddlyWiki. The answer is that they're system tiddlers. A system tiddler is a tiddler whose title begins with $:/. System tiddlers are hidden in search results and most tabs of the sidebar.
Aside from their names and the fact that tiddlers with those names are hidden from most views, there is nothing special or different about system tiddlers as compared to “normal” tiddlers.
System tiddlers are organized into a hierarchy by giving them names with slashes separating each folder, much like a computer's file system. For instance, the default height of the text box presented when you edit a tiddler is stored in a tiddler called $:/config/TextEditor/EditorHeight/Height. (It's worth noting that no actual object representing these “folders” is created within your wiki; your wiki is just one big pile of tiddlers, and some of them happen to have slashes in their names which TiddlyWiki uses to display them in a tree. But folder is a useful way to describe each level of the hierarchy.)
Important top-level folders in this hierarchy include:
config– every setting in the control panel has a tiddler here holding your choice of value (there are other settings here that aren't displayed in the control panel as well)core– most of the code of TiddlyWiki, in both JavaScript and wikitext, is kept in herelanguage– contains translations for TiddlyWiki elements into your local languagepalettes– contains tables from names to colors used to draw the interfaceplugins– any plugins you've installed go herestate– contains temporary tiddlers that describe what you currently have open and selected in the user interfacetags– for the parts of TiddlyWiki's interface and functionality people most frequently want to add parts to, TiddlyWiki provides these special tags; by adding the tag to a new tiddler, that tiddler appears in TiddlyWiki's interfacetemp– contains miscellaneous temporary tiddlersthemes– contains CSS and configuration tweaks describing how to draw the interface
Many people like to create a top-level folder titled with their name or initials (e.g., I use $:/sib), so that when they create their own custom system tiddlers, they can see them all in the same place and remember what they've added. You don't have to make your custom tiddlers system tiddlers – you could just make them normal tiddlers with whatever names you like – but if you make them system tiddlers, you won't struggle to find them in among your wiki's content.
You can see a list of all system tiddlers in the System section of the More tab. However, the Explorer tab is usually a better way to look – this will show them in a tree view.
As noted earlier, system tiddlers are not shown in the results provided by the standard search box. If you want to find one, perhaps so you can edit it or inspect how it works, you can search in system tiddlers using the System tab of Advanced Search. On the other hand, system tiddlers are not hidden from filters. Often this isn't noticeable at all since filters typically look for things with a particular tag or field or link, and system tiddlers typically do not share tags, field values, or links with non-system tiddlers. However, some filters, both those built into TiddlyWiki and ones you compose yourself, will need to use the !is[system] filter step to remove system tiddlers from the list.
Note that neither Advanced Search, nor filters you may write, nor the System section of the More tab includes system tiddlers that are also shadow tiddlers (we'll discuss those in a moment). To find those, you'll need to use the Shadows tab of either interface.
Exercises
Create a new system tiddler, then close it and go locate it again.
Take a few minutes to poke around in the Explorer section of the More sidebar tab and look into a few system tiddlers to see how they're organized. You can safely edit a system tiddler to look at its wikitext if you like, notwithstanding the scary warning about editing a shadow tiddler; just be sure to click the X button to discard changes when you're done.