Fossil  The fileedit Page

This document describes the limitations of, caveats for, and disclaimers for the /fileedit page, which provides users with checkin privileges basic editing features for files via the web interface.

Important Caveats and Disclaimers

Predictably, the ability to edit files in a repository from a web browser halfway around the world comes with several obligatory caveats and disclaimers...

/fileedit Does Nothing by Default.

In order to "activate" it, a user with the "setup" permission must set the fileedit-glob repository setting to a comma- or newline-delimited list of globs representing a whitelist of files which may be edited online. Any user with commit access may then edit files matching one of those globs. Certain pages within the UI get an "edit" link added to them when the current user's permissions and the whitelist both permit editing of that file.

CSRF & HTTP Referrer Headers

In order to protect against Cross-site Request Forgery (CSRF) attacks, Fossil UI features which write to the database require that the browser send the so-called HTTP Referer header (noting that the misspelling of "referrer" is a historical accident which has long-since been standardized!). Modern browsers, by default, include such information automatically for interactive actions which lead to a request, e.g. clicking on a link back to the same server. However, /fileedit uses asynchronous "XHR" connections, which browsers may treat differently than strictly interactive elements.

  • Firefox: configuration option network.http.sendRefererHeader specifies whether the Referer header is sent. It must have a value of 2 (which is the default) for XHR requests to get the Referer header. Purely interactive Fossil features, in which users directly activate links or forms, work with a level of 1 or higher.
  • Chrome: apparently requires an add-on in order to change this policy, so Chrome without such an add-on will not suppress this header.
  • Safari: ???
  • Other browsers: ???

If /fileedit shows an error message saying "CSRF violation," the problem is that the browser is not sending a Referer header to XHR connections. Fossil does not offer a way to disable its CSRF protections.

/fileedit Works by Creating Commits

Thus any edits made via that page become a normal part of the repository.

/fileedit is Intended for use with Embedded Docs

... and similar text files, and is most certainly not intended for editing code.

Editing files with unusual syntax requirements, e.g. hard tabs in makefiles, may break them. You Have Been Warned.

Similarly, though every effort is made to retain the end-of-line style used by being-edited files, the round-trip through an HTML textarea element may change the EOLs. The Commit section of the page offers three different options for how to treat newlines when saving changes. Files with mixed EOL styles will be normalized to a single EOL style when modified using /fileedit. When "inheriting" the EOL style from a previous version which has mixed styles, the first EOL style detected in the previous version of the file is used.

/fileedit is Not a Replacement for a Checkout

A full-featured checkout allows far more possibilities than this basic online editor permits, and the feature scope of /fileedit is intentionally kept small, implementing only the bare necessities needed for performing basic edits online. It is not, and will never be, a replacement for a checkout.

It is to be expected that users will want to do "more" with this page, and we generally encourage feature requests, but be aware that certain types of ostensibly sensible feature requests will be rejected for /fileedit. These include, but are not limited to:

  • Features which are already provided by other pages, e.g. the ability to create a new named branch or add tags.
  • Features which would require re-implementing significant capabilities provided only within a checkout (e.g. merging files).
  • The ability to edit/manipulate files which are in a local checkout. (If you have a checkout, use your local editor, not /fileedit.)
  • Editing of non-text files, e.g. images. Use a checkout and your preferred graphics editor.
  • Support for syncing/pulling/pushing of a repository before and/or after edits. Those features cannot be reliably provided via a web interface for several reasons.

Similarly, some potential features have significant downsides, abuses, and/or implementation hurdles which make the decision of whether or not to implement them subject to notable contributor debate. e.g. the ability to add new files or remove/rename older files.

/fileedit Stores Only Limited Local Edits While Working

When changes are made to a given checkin/file combination, /fileedit will, if possible, store them in window.localStorage or window.sessionStorage, if available, but...

  • Which storage is used is unspecified and may differ across environments.
  • If neither of those is available, the storage is transient and will not survive a page reload. In this case, the UI issues a clear warning in the editor tab.
  • It stores only the most recent checkin/file combinations which have been modified (exactly how many may differ - the number will be noted somewhere in the UI). Note that changing the "executable bit" is counted as a modification, but the checkin comment is not and is reset after a commit.
  • If its internal limit on the number of modified files is exceeded, it silently discards the oldest edits to keep the list at its limit.

Edits are saved whenever the editor component fires its "change" event, which essentially means as soon as it loses input focus. Thus to force the browser to save any pending changes, simply click somwhere on the page outside of the editor.

Exactly how long localStorage will survive, and how much it or sessionStorage can hold, is environment-dependent. sessionStorage will survive until the current browser tab is closed, but it survives across reloads of the same tab.

If /fileedit determines that no persistent storage is available a warning is displayed on the editor page.

The Power is Yours, but...

"With great power comes great responsibility."

Use this feature judiciously, if at all.

Now, with those warnings and caveats out of the way...


Tips and Tricks

fossil Global-scope JS Object

/fileedit is largely implemented in JavaScript, and makes heavy use of the global-scope fossil object, which provides infrastructure-level features intended for use by Fossil UI pages. (That said, that infrastructure was introduced with /fileedit, and most pages do not use it.)

The fossil.page object represents the UI's current page (on pages which make use of this API - most do not). That object supports listening to page-specific events so that JS code installed via client-side edits to the site skin's footer may react to those changes somehow. The next section describes one such use for such events...

Integrating Syntax Highlighting

Assuming a repository has integrated a 3rd-party syntax highlighting solution, it can probably (depending on its API) be told how to highlight /fileedit's wiki/markdown-format previews. Here are instructions for doing so with highlightjs:

At the very bottom of the site skin's footer, add a script tag similar to the following:

<script nonce="$<nonce>">
if(window.fossil && fossil.page && fossil.page.name==='fileedit'){
  fossil.page.addEventListener(
    'fileedit-preview-updated',
    (ev)=>{
     if(ev.detail.previewMode==='wiki'){
       ev.detail.element.querySelectorAll(
         'code[class^=language-]'
        ).forEach((e)=>hljs.highlightBlock(e));
     }
    }
  );
}
</script>

Note that the nonce="$<nonce>" part is intended to be entered literally as shown above. It will be expanded to contain the current request's nonce value when the page is rendered.

The first line of the script just ensures that the expected JS-level infrastructure is loaded. It's only loaded in the /fileedit page and possibly pages added or "upgraded" since /fileedit's introduction.

The part in the if block adds an event listener to the /fileedit app which gets called when the preview is refreshed. That event contains 3 properties:

  • previewMode: a string describing the current preview mode: wiki (which includes Fossil-native wiki and markdown), text, htmlInline, htmlIframe. We should "probably" only highlight wiki text, and thus the example above limits its work to that type of preview. It won't work with htmlIframe, as that represents an iframe element which contains a complete HTML document.
  • element: the DOM element in which the preview is rendered.
  • mimetype: the mimetype of the being-previewed content, as determined by Fossil (by its file extension).

The event listener callback shown above doesn't use the mimetype, but makes used of the other two. It fishes all code blocks out of the preview which explicitly have a CSS class named language-something, and then asks highlightjs to highlight them.

Integrating a Custom Editor Widget

(These instructions also work for the /wikiedit page by replacing "fileedit" with "wikiedit" in any strings or symbol names!)

It is possible to replace /fileedit's basic text-editing widget (a textarea element) with a fancy 3rd-party editor widget by following these instructions...

All JavaScript code which follows is assumed to be in a script tag similar to the one shown in the previous section:

<script nonce="$<nonce>">
if(window.fossil && fossil.page && fossil.page.name==='fileedit'){
  // code specific to the fileedit page goes here
}
</script>

First, install proxy functions so that fossil.page.fileContent() can get and set your content:

fossil.page.setContentMethods(
  function(){ return text-form content of your widget },
  function(content){ set text-form content of your widget }
};

Secondly, we need to alert the editor app when there are changes so that it can do things like store edits locally so that they are not lost on a page reload. How that is done is completely dependent on the 3rd-party editor widget, but it generically looks something like:

myCustomWidget.on('eventName', ()=>fossil.page.notifyOfChange());

(This feature requires fossil version 2.13 or later. In 2.12 it is possible to do this but requires making use of a "leaky abstraction".)

Lastly, if the 3rd-party editor does not hide or remove the native editor widget, and does not inject itself into the DOM on the caller's behalf, we can replace the native widget with the 3rd-party one with:

fossil.page.replaceEditorWidget(yourNewWidgetElement);

That method must be passed a DOM element and may only be called once: it removes itself the first time it is called.

That should be all there is to it. When fossil.page needs to get the being-edited content, it will call the installed content-getter function with no arguments, and when it sets the content (immediately after (re)loading a file or grabbing local edits), it will pass that content to the installed content-setter method. Those, in turn will trigger the installed proxies and fire any relevant events.

Below is an example of Fossil skin footer content which plugs in the TinyMCE HTML editor into the /wikiedit page, but the process is identical for /fileedit (noting that /fileedit may need to be able to edit multiple types of files for which a special-purpose editor like TinyMCE may not be suitable). Note that any paths to CSS and JS resources of course need to be modified to suit one's own installation.

<!-- TinyMCE CSS and JS: -->
<link href="$<home>/doc/ckout/skin.min.css" rel="stylesheet" type="text/css">
<link href="$<home>/doc/ckout/content.min.css" rel="stylesheet" type="text/css">
<script src='$<home>/doc/ckout/tinymce.min.js'></script>
<script src='$<home>/doc/ckout/theme.min.js'></script>
<script src='$<home>/doc/ckout/icons.min.js'></script>
<!-- Integrate TinyMCE into /wikiedit: -->
<script nonce="$<nonce>">
if(window.fossil && window.fossil.page.name==='wikiedit'){
  window.fossil.onPageLoad( function(){
    const elemId = 'wikiedit-content-editor';
    tinymce.init({selector: 'textarea#'+elemId});
    const widget = tinymce.get(elemId);
    fossil.page.setContentMethods(
      function(){return widget.getContent()},
      function(content){widget.setContent(content)}
    );
    widget.on('change', function(){
      if(widget.isDirty()) fossil.page.notifyOfChange();
    });
  });
}
</script>