# Skinning the Fossil Web Interface

The Fossil web interface comes with a pre-configured look and feel.  The default
look and feel works fine in many situations.  However, you may want to change
the look and feel (the "skin") of Fossil to better suite your own individual tastes.
This document provides background information to aid you in that task.

## <a id="builtin"></a>Built-in Skins

Fossil comes with [multiple built-in skins](/skins).  If the default skin does not
suite your tastes, perhaps one of the other built-in skins will work better.
If nothing else, the built-in skins can serve as examples or templates that
you can use to develop your own custom skin.

The sources to these built-ins can
be found in the Fossil source tree under the skins/ folder.  The 
[skins/](/dir?ci=trunk&name=skins)
folder contains a separate subfolder for each built-in skin, with each
subfolders holding at least these five files:

   * css.txt
   * details.txt
   * footer.txt
   * header.txt
   * js.txt

Try out the built-in skins by using the --skin option on the
[fossil ui](/help?cmd=ui) or [fossil server](/help?cmd=server) commands.

## <a id="sharing"></a>Sharing Skins

The skin of a repository is not part of the versioned state and does not
"push" or "pull" like checked-in files.  The skin is local to the
repository.  However, skins can be shared between repositories using
the [fossil config](/help?cmd=configuration) command.
The "fossil config push skin" command will send the local skin to a remote
repository and the "fossil config pull skin" command will import a skin
from a remote repository.  The "fossil config export skin FILENAME"
will export the skin for a repository into a file FILENAME.  This file
can then be imported into a different repository using the
"fossil config import FILENAME" command.  Unlike "push" and "pull",
the "export" and "import" commands are able to move skins between
repositories for different projects.  So, for example, if you have a
group of related repositories, you can develop a skin for one of them,
then get a consistent look across all the repositories by exporting
the skin from the first repository and importing into all the others.

The file generated by "fossil config export" could be checked into
one of your repositories and versioned, if desired.  This will not
automatically change the skin when looking backwards in time, but it
will provide an historical record of what the skin used to be and
allow the historical look of the repositories to be recreated if
necessary.

When cloning a repository, the skin of the new repository is initialized to
the skin of the repository from which it was cloned.

# Structure Of A Fossil Web Page

Every HTML page generated by Fossil has the same basic structure:

| Fossil-Generated HTML Header |
| Skin Header                  |
| Fossil-Generated Content     |
| Skin Footer                  |
| Fossil-Generated HTML Footer |

By default, Fossil starts every generated HTML page with this:

    <html>
    <head>
    <base href="...">
    <meta http-equiv="Content-Security-Policy" content="....">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>....</title>
    <link rel="stylesheet" href="..." type="text/css">
    </head>
    <body class="FEATURE">

Fossil used to require a static version of this in every skin’s Header
area, but over time, we have found good cause to generate multiple
elements at runtime.

One such is the `FEATURE` element, being either the top-level HTTP
request routing element (e.g. `doc`) or an aggregate feature class that
groups multiple routes under a single name. A prime example is `forum`,
which groups the `/forummain`, `/forumpost`, and `/forume2` routes,
allowing per-feature CSS. For instance, to style `<blockquote>` tags
specially for forum posts written in Markdown, leaving all other block
quotes alone, you could say:

    body.forum div.markdown blockquote {
      margin-left: 10px;
    }

You can [override this generated HTML header](#override) by including a
“`<body>`” tag somewhere in the Header area of the skin, but it is
almost always best to limit a custom skin’s Header section to something
like this:

<div class="sidebar" id="version-2.24">Prior to Fossil 2.24, we used
generic `<div>` elements to mark up these sections of the header, but we
switched to these semantic tag names to give browser accessibility
features more freedom to do intelligent things with the page content.
Those who made custom skins based on the old way of doing things will
need to track this change when upgrading, else the corresponding CSS
will mistarget the page header elements. Also, if you’re using Fossil’s
chat feature, failing to track this change will cause it to miscalculate
the message area size, resulting in double scrollbars. Simply diffing
your custom header in the skin editor against the stock version should
be sufficient to show what you need to change.</div>


    <header>
      ...
    </header>
    <nav class="mainmenu" title="Main Menu">
      ...
    </nav>
    <nav id="hbdrop" class="hbdrop" title="sitemap"></nav>

See the stock skins’ headers for ideas of what to put in place of the
ellipses.

The Fossil-generated Content section immediately follows this Header.
It will look like this:

    <div class="content">
      ... Fossil-generated content here ...
    </div>

After the Content is the custom Skin Footer section which should
follow this template:

    <footer>
      ... skin-specific stuff here ...
    </footer>

As with the `<header>` change called out above, this, too, is a breaking
change in Fossil 2.24.

Finally, Fossil always adds its own footer (unless overridden)
to close out the generated HTML:

    </body>
    </html>

## <a id="mainmenu"></a>Changing the Main Menu Contents

The actual text content of the skin’s main menu is not
part of the skin proper if you’re using one of the stock skins.
If you look at the Header section of the skin, you’ll find a
`<div class="mainmenu">` element whose contents are set by a short
[TH1](./th1.md) script from the contents of the **Main Menu** section of
the Setup → Configuration screen.

This feature allows the main menu contents to stay the same across
different skins, so you no longer have to reapply menu customizations
when trying different skins.

See the [`capexpr`](./th1.md#capexpr) section of the TH1 docs for help
on interpreting the default contents of this block.


## <a id="override"></a>Overriding the HTML Header and Footer

Notice that the `<html>`, `<head>`, and opening `<body>` 
elements at the beginning of the document,
and the closing `</body>` and `</html>` elements at the end are automatically
generated by Fossil.  This is recommended.

However, for maximum design flexibility, Fossil allows those elements to be
supplied as part of the configurable Skin Header and Skin Footer.
If the Skin Header contains the text "`<body`", then Fossil assumes that
the Skin Header and Skin Footer will handle all of the `<html>`,
`<head>`, and `<body>` text itself, and the Fossil-generated header and
footer will be blank.

When overriding the HTML Header in this way, you will probably want to use some
of the [TH1 variables documented below](#vars) such as `$stylesheet_url`
to avoid hand-writing code that Fossil can generate for you.

# Designing, Debugging, and Installing A Custom Skin

It is possible to develop a new skin from scratch.  But a better and easier
approach is to use one of the existing built-in skins as a baseline and
make incremental modifications, testing after each step, to obtain the
desired result.

The skin is controlled by five files:

<dl>
<dt><b>css.txt</b></dt>

<dd>The css.txt file is the text of the CSS for Fossil.
Fossil might add additional CSS elements after
the css.txt file, if it sees that the css.txt omits some
CSS components that Fossil needs.  But for the most part,
the content of the css.txt is the CSS for the page.</dd>

<dt><b>details.txt</b><dt>

<dd>The details.txt file is short list of settings that control
the look and feel, mostly of the timeline.  The default
details.txt file looks like this:

<pre>
pikchr-background:          ""
pikchr-fontscale:           ""
pikchr-foreground:          ""
pikchr-scale:               ""
timeline-arrowheads:        1
timeline-circle-nodes:      1
timeline-color-graph-lines: 1
white-foreground:           0
</pre>

The three "timeline-" settings in details.txt control the appearance
of certain aspects of the timeline graph.  The number on the
right is a boolean - "1" to activate the feature and "0" to
disable it.  The "white-foreground:" setting should be set to
"1" if the page color has light-color text on a darker background,
and "0" if the page has dark text on a light-colored background.

If the "pikchr-foreground" setting
is defined and is not an empty string then it specifies a
foreground color to use for [pikchr diagrams](./pikchr.md).  The
default pikchr foreground color is black, or white if the
"white-foreground" boolean is set.  The "pikchr-background"
settings does the same for the pikchr diagram background color.
If the "pikchr-fontscale" and "pikchr-scale" values are not
empty strings, then they should be floating point values (close
to 1.0) that specify relative scaling of the fonts in pikchr
diagrams and other elements of the diagrams, respectively.
</dd>

<dt><b>footer.txt</b> and <b>header.txt</b></dt>

<dd>The footer.txt and header.txt files contain the Skin Footer
and Skin Header respectively.  Of these, the Skin Header is
the most important, as it contains the markup used to generate
the banner and menu bar for each page.

Both the footer.txt and header.txt file are 
[processed using TH1](#headfoot) prior to being output as 
part of the overall web page.</dd>

<dt><b>js.txt</b></dt>

<dd>The js.txt file is optional.  It is intended to be javascript.
The complete text of this javascript might be inserted into
the Skin Footer, after being processed using TH1, using
code like the following in the "footer.txt" file:

<pre>
&lt;script nonce="$nonce"&gt;
  &lt;th1&gt;styleScript&lt;/th1&gt;
&lt;/script&gt;
</pre>

The js.txt file was originally used to insert javascript
that controls the hamburger menu in the default skin.  More
recently, the javascript for the hamburger menu was moved into
a separate built-in file.  Skins that use the hamburger menu
typically cause the javascript to be loaded by including the
following TH1 code in the "header.txt" file:

<pre>
&lt;th1&gt;builtin_request_js hbmenu.js&lt;/th1&gt;
</pre>

The difference between `styleScript` and `builtin_request_js`
is that the `styleScript` command interprets the file
using TH1 and injects the content directly into the output
stream, whereas the `builtin_request_js` command inserts the
Javascript verbatim and does so at some unspecified future time
down inside the Fossil-generated footer.
You can use either
approach in custom skins that you create.

Note that the "js.txt" file is *not* automatically inserted into
the generate HTML for a page.  You, the skin designer, must
cause the javascript to be inserted by issuing appropriate
TH1 commands in the "header.txt" or "footer.txt" files.</dd>
</dl>

Developing a new skin is simply a matter of creating appropriate
versions of these five control files.

### Skin Development Using The Web Interface

Users with admin privileges can use the Admin/Skin configuration page
on the web interface to develop a new skin.  The development of a new
skin occurs without disrupting the existing skin.  So you can work on
a new skin for a Fossil instance while the existing skin is still in
active use.

The new skin is a "draft" skin.  You initialize one of 9 draft skins
to either the current skin or to one of the built-in skins.  Then
use forms to edit the 5 control files described above.  The new
skin can be tested after each edit.  Finally, once the new skin is
working as desired, the draft skin is "published" and becomes the
new live skin that most users see.

### Skin Development Using A Local Text Editor

An alternative approach is to copy the five control files for your
baseline skin into a temporary working directory (here called
"./newskin") and then launch the [fossil ui](/help?cmd=ui) command
with the "--skin ./newskin" option.  If the argument to the --skin
option contains a "/" character, then the five control files are
read out of the directory named.  You can then edit the control
files in the ./newskin folder using you favorite text editor, and
press "Reload" on your browser to see the effects.

### Disabling The Web Browser Cache During Development

Fossil is aggressive about asking the web browser to cache 
resources.  While developing a new skin, it is often helpful to
put your web browser into developer mode and disable the cache.
If you fail to do this, then you might make some change to your skin
under development and press "Reload" only to find that the display
did not change.  After you have finished work your skin, the
caches should synchronize with your new design and you can reactivate
your web browser's cache and take it out of developer mode.

## <a id="headfoot"></a>Header and Footer Processing

The `header.txt` and `footer.txt` control files of a skin are the HTML text
of the Skin Header and Skin Footer, except that before being inserted
into the output stream, the text is run through a
[TH1 interpreter](./th1.md) that might adjust the text as follows:

  *  All text within &lt;th1&gt;...&lt;/th1&gt; is omitted from the
     output and is instead run as a TH1 script.  That TH1
     script has the opportunity to insert new text in place of itself,
     or to inhibit or enable the output of subsequent text.

  *  Text of the form "$NAME" or "$&lt;NAME&gt;" is replaced with
     the value of the TH1 variable NAME.

For example, first few lines of a typical Skin Header will look
like this:

    <div class="header">
      <div class="title"><h1>$<project_name></h1>$<title>/div>

After variables are substituted by TH1, that will look more like this:

    <div class="header">
      <div class="title"><h1>Project Name</h1>Page Title</div>

As you can see, two TH1 variable substitutions were done.

The same TH1 interpreter is used for both the header and the footer
and for all scripts contained within them both.  Hence, any global
TH1 variables that are set by the header are available to the footer.

## <a id="menu"></a>Customizing the ≡ Hamburger Menu

The menu bar of the default skin has an entry to open a drop-down menu with
additional navigation links, represented by the ≡ button (hence the name
"hamburger menu"). The Javascript logic to open and close the hamburger menu
when the button is clicked is usually handled by a script named
"hbmenu.js" that is one of the [built-in resource files](/test-builtin-files)
that are part of Fossil.

The ≡ button for the hamburger menu is added to the menu bar by the following
TH1 commands in the `header.txt` file, right before the menu bar links:

    html "<a id='hbbtn' href='$home/sitemap'>&#9776;</a>"
    builtin_request_js hbmenu.js

The hamburger button can be repositioned between the other menu links (but the
drop-down menu is always left-aligned with the menu bar), or it can be removed
by deleting the above statements.  The "html" statement inserts the appropriate
`<a>` for the hamburger menu button (some skins require something slightly
different - for example the ardoise skins wants "`<li><a>`").  The
"builtin_request_js hbmenu.js" asks Fossil to include the "hbmenu.js" 
resource files in the Fossil-generated footer.

The hbmenu.js script requires
the following `<div>` element somewhere in your header, in which to build
the hamburger menu.

    <div id='hbdrop'></div>

Out of the box, the contents of the panel is populated with the [Site
Map](/sitemap), but only if the panel does not already contain any HTML
elements (that is, not just comments, plain text or non-presentational white
space). So the hamburger menu can be customized by replacing the empty `<div
id='hbdrop'></div>` element with a menu structure knitted according to the
following template:

    <div id="hbdrop" data-anim-ms="400">
     <ul class="columns" style="column-width: 20em; column-count: auto">
      <!-- NEW GROUP WITH HEADING LINK -->
      <li>
       <a href="$home$index_page">Link: Home</a>
       <ul>
        <li><a href="$home/timeline">Link: Timeline</a></li>
        <li><a href="$home/dir?ci=tip">Link: File List</a></li>
       </ul>
      </li>
      <!-- NEW GROUP WITH HEADING TEXT -->
      <li>
       Heading Text
       <ul>
        <li><a href="$home/doc/trunk/www/customskin.md">Link: Theming</a></li>
        <li><a href="$home/doc/trunk/www/th1.md">Link: TH1 Scripts</a></li>
       </ul>
      </li>
      <!-- NEXT GROUP GOES HERE -->
     </ul>
    </div>

The custom `data-anim-ms` attribute can be added to the panel element to direct
the Javascript logic to override the default menu animation duration of 400 ms.
A faster animation duration of 80-200 ms may be preferred for smaller menus. The
animation is disabled by setting the attribute to `"0"`.


## <a id="vars"></a>TH1 Variables

Before expanding the TH1 within the header and footer, Fossil first
initializes a number of TH1 variables to values that depend on
repository settings and the specific page being generated.

   *   **`project_name`** - The project_name variable is filled with the
       name of the project as configured under the Admin/Configuration
       menu.

   *   **`project_description`** - The project_description variable is
       filled with the description of the project as configured under
       the Admin/Configuration menu.

   *   **`title`** - The title variable holds the title of the page being
       generated.

       The title variable is special in that it is deleted after
       the header script runs and before the footer script.  This is
       necessary to avoid a conflict with a variable by the same name used
       in my ticket-screen scripts.

   *   **`baseurl`** - The root of the URL namespace for this server.

   *   **`secureurl`** - The same as $baseurl except that if the scheme is
                       "http:" it is changed to "https:"

   *   **`home`** - The $baseurl without the scheme and hostname.  For example,
       if the $baseurl is "http://projectX.com/cgi-bin/fossil" then the
       $home will be just "/cgi-bin/fossil".

   *   **`index_page`** - The landing page URI as
       specified by the Admin/Configuration setup page.

   *   **`current_page`** - The name of the page currently being processed,
       without the leading "/" and without query parameters.
       Examples:  "timeline", "doc/trunk/README.txt", "wiki".

   *   **`csrf_token`** - A token used to prevent cross-site request forgery.

   *   **`default_csp`** - [Fossil’s default CSP](./defcsp.md) unless
       [overridden by custom TH1 code](./defcsp.md#th1). Useful within
       the skin for inserting the CSP into a `<meta>` tag within [a
       custom `<head>` element](#headfoot).

   *   **`nonce`** - The value of the cryptographic nonce for the request
       being processed.

   *   **`release_version`** - The release version of Fossil.  Ex: "1.31"

   *   **`manifest_version`** - A prefix on the check-in hash of the
       specific version of fossil that is running.  Ex: "\[47bb6432a1\]"

   *   **`manifest_date`** - The date of the source-code check-in for the
       version of fossil that is running.

   *   **`compiler_name`** - The name and version of the compiler used to
       build the fossil executable.

   *   **`login`** - This variable only exists if the user has logged in.
       The value is the username of the user.

   *   **`stylesheet_url`** - A URL for the internal style-sheet maintained
       by Fossil.

   *   **`logo_image_url`** - A URL for the logo image for this project, as
       configured on the Admin/Logo page.

   *   **`background_image_url`** - A URL for a background image for this
       project, as configured on the Admin/Logo page.

All of the above are variables in the sense that either the header or the
footer is free to change or erase them.  But they should probably be treated
as constants.  New predefined values are likely to be added in future
releases of Fossil.


## <a id="procedure"></a>Suggested Skin Customization Procedure

Developers are free, of course, to develop new skins using any method they
want, but the following is a technique that has worked well in the past and
can serve as a starting point for future work:

   1.  Select a built-in skin that is closest to the desired look.  Make
       copies of the css, footer, and header into files name "css.txt",
       "details.txt",
       "footer.txt", and "header.txt" in some temporary directory.

       If the Fossil source code is available, then these three files can
       be copied directly out of one of the subdirectories under skins.  If
       sources are not easily at hand, then a copy/paste out of the
       CSS, footer, and header editing screens under the Admin menu will
       work just as well.  The important point is that the three files
       be named exactly "css.txt", "footer.txt", and "header.txt" and that
       they all be in the same directory.

   2.  Run the [fossil ui](/help?cmd=ui) command with an extra
       option "--skin SKINDIR" where SKINDIR is the name of the directory
       in which the three txt files were stored in step 1.   This will bring
       up the Fossil website using the tree files in SKINDIR.

   3.  Edit the *.txt files in SKINDIR.  After making each small change,
       press Reload on the web browser to see the effect of that change.
       Iterate until the desired look is achieved.

   4.  Copy/paste the resulting css.txt, details.txt,
       header.txt, and footer.txt files
       into the CSS, details, header, and footer configuration screens
       under the Admin/Skins menu.


## See Also

*   [Customizing the Timeline Graph](customgraph.md)
