How to create a Roller 4.0 theme

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This is part one of a two part series:

How to create a Roller 4.0 theme, part 1 : directory structure and required files
How to create a Roller 4.0 theme, part 2 : the theme.xml file

The Roller 4.0 Template Author Guide explains how to customize your Roller theme by editing the page templates that define it. It tells you how to use Roller's template language (Velocity ), what objects are available to your template code and what macros you can use to generate HTML and other content. You can download it here in PDF form.

But the template guide does not tell you how to create a complete new Roller theme, one that you can share with other Roller site admins. That's a problem because I'd really like to see more themes, so I'm going to rough-out some docs right here on my blog. In part one I'll explain how to get started, what files you must provide and the new Roller 4.0 Stylesheet Override feature. In part two I'll explain how to create the new theme.xml theme definition file that you must include in your theme. Let's roll.

Getting started

Just as before, a Roller theme is a directory of files, some page templates and some "resource" files, which are typically images. So, your first step in creating a new theme is to create a directory to hold those files. Give it a simple one word alphanumeric name with no spaces.

In the next sections, I'll explain what files you need and I'll show some example templates from a minimal theme called "example1." This example theme is made up of seven files, including three Velocity templates (.vm files), a couple of images and a theme.xml file. Here's the directory layout of example1.

Add Weblog and _day templates

A theme must have at least a weblog template with the name "Weblog" and you'll find an example of one below. It's advisable to also have a _day template, which is responsble for displaying one day's worth of blog entries.

Here's the Weblog.vm file for the example1 theme, with

<html>

<head>

  <title>$model.weblog.name #if($model.permalink) 

     : $model.weblogEntry.title #end</title> 

  #showAutodiscoveryLinks($model.weblog)

  <style type="text/css">

  h1 { color:red; } 

  h2 { color:orange; }

  a { color:orange; text-decoration:none; font-weight: bold; }

  </style>

  <link rel="stylesheet" type="text/css" media="all" href="$model.weblog.stylesheet">

</head>

<body>

  <table width="80%" align="center">

    <tr>

      <td valign="top">

        <h1>$model.weblog.name</h1>

        #set($rootCategory = $model.weblog.getWeblogCategory("nil"))

        #showWeblogCategoryLinksList($rootCategory false false)

        #set($pager = $model.getWeblogEntriesPager()) 

        #showNextPrevEntriesControl($pager)

        #showWeblogEntriesPager($pager)

      </td>

      <td valign="top">

        #showPageMenu($model.weblog)

        #showAuthorMenu(true)

      </td>

    </tr>

  </table>

</body>

</html>

And here's the corresponding _day template:

<h2 class="dayheading">$utils.formatDate($day, "MMM dd, yyyy")</h2> 

#foreach($entry in $entries)

  <h2 class="entryheading">

    <img src=$url.resource("images/aquadot.jpg") />&nbsp;

    <a href="$url.entry($entry.anchor)">$entry.title</a>

  </h2>

  <p>$utils.formatDate($entry.pubTime, "HH:MMa z") by $entry.creator.fullName</p>  

  <p>

  #if($model.permalink)

    $entry.displayContent

  #else

    $entry.displayContent($url.entry($entry.anchor))

  #end

  </p>

#end

You can read more about the Weblog and _day templates in the Roller Template Guide, what I'd like to highlight now is a new 4.0 feature called the Stylesheet Override . Notice that the Weblog.vm file above includes some CSS styles, followed by a to a CSS file with URL $model.weblog.stylesheet , that's the Stylesheet Override file. Let me explain.

Add a Stylesheet Override file

Roller 4.0's new Stylesheet Override feature makes it possible for users of your theme to to change font, colors and other things without having to edit any of the templates that define the blog. Instead, they edit a CSS file known as the override file and that file is included in the right places when the blog is displayed.

To support Stylesheet Override your theme must provide an 1) override file, 2) an entry its theme.xml file and 3) must reference the override file in the right place as shown above in the example Weblog.vm file.

When you create your override file, keep in mind that your theme should stand-alone without the override file. The override file is for specifying additional styles above and beyond what your theme already provides. It's perfectly OK and even a good idea for your theme's override file to be empty, or containing a comment like this:

  /* add your own custom CSS here */

Add other resources required by your theme

If your theme requires any static resources, i.e. images for the banner or for the background, then include them in the theme directory or its sub-directories. You must reference each one in your theme.xml definition file.

Your theme must also provide a Preview Image , an image (recommended size ~350x400) that will be shown to users as they browse possible themes within Roller. To satisfy this requirement, you include a preview image file in your theme directory and reference it from your theme.xml file.

In part 2, I'll explain how to create that theme.xml file with references to all the tempate files and images that make up a theme.

In part one I explained how to create a theme directory and add the required template and resource files. Now I'll wrap things up by explaining what goes into a theme.xml theme definition file and how to deploy your new theme.

Create a theme.xml file

The example1 theme that I discussed in part one has a preview image, a Stylesheet Override file, a weblog template, a _day template, a custom template that displays an about page and a single image called aquadot.jpg . The theme.xml theme definition file below includes each of those items.

<?xml version="1.0" encoding="UTF-8"?>

<weblogtheme>    

  <id>example1</id> 

  <name>Example1: minimal theme</name>

  <author>Dave Johnson</author>     

  <preview-image path="preview.jpg" />


  <stylesheet>

    <name>Override</name>

    <description>Stylesheet override</description>

    <link>override.css</link>

    <templateLanguage>velocity</templateLanguage>

    <contentsFile>override.css</contentsFile>

  </stylesheet>


  <template action="weblog">

    <name>Weblog</name>

    <description>Main template of weblog</description>

    <link>weblog</link>

    <navbar>false</navbar>

    <hidden>true</hidden>

    <templateLanguage>velocity</templateLanguage>

    <contentType>text/html</contentType>

    <contentsFile>weblog.vm</contentsFile>

  </template>


  <template action="custom">

    <name>_day</name>

    <description>Displays one day of entries</description>

    <link>_day</link>

    <navbar>false</navbar>

    <hidden>true</hidden>

    <templateLanguage>velocity</templateLanguage>

    <contentType>text/html</contentType>

    <contentsFile>day.vm</contentsFile>

  </template>


  <template action="custom">

    <name>About</name>

    <description>About this weblog...</description>

    <link>about</link>

    <navbar>true</navbar>

    <hidden>false</hidden>

    <templateLanguage>velocity</templateLanguage>

    <contentType>text/html</contentType>

    <contentsFile>about.vm</contentsFile>

  </template>


  <resource path="images/aquadot.jpg" />   

</weblogtheme>

Now I'll break it down and explain each element.

Inside

The root element of the XML file contains some theme meta-data, an optional stylesheet, one or more templates and zero or more resources. Here's a run-down of the meta-data you must include in each theme:

- the unique ID, by convention this is the same as directory name
- name of the theme
- name of theme author
- path to image preview file, relative to theme directory

The override

Following the theme meta-data is the stylesheet declaration, including all of the required elements:

- name of stylesheet
- description of stylesheet
- value used in stylesheet URI (e.g. ~http://example.com/../page/styles.css )
- in 4.0, this must be 'velocity'
- path to theme file containing stylesheet, relative to theme directory

The elements

Next are the template elements, one for each page template. Each element must have an 'action' attribute that declares on which action the template will be invoked. Here are the possible values of the action attribute:

weblog: Each theme must have a weblog template, which displays the main page of the blog
permalink: (optional) template which will be used when displaying individual entries
searchIndex: (optional) template to be invoked to display search results
tagsIndex: (optional) template to be used when displaying entries by tag
custom: (optional) You can add as many custom templates as you want.

And here are the elements that must be included in a :

- name of the template
- description of template
- value used in stylesheet URI (e.g. ~http://example.com/../page/mypage )
- true if page should be include in navigation menus generated by standard macros
- true if page not to be called directly and only used as an include
- in 4.0, this must be 'velocity'
- the content-type to be generated by the template
- path to theme file containing template, relative to theme directory

Including resources

After the template elements, we include the one element we need for the one image that is included in the theme. The path is relative to the theme directory.

Deploying your theme to Roller

To make your theme available to Roller, copy the theme directory into the Roller themes directory. Restart Roller and watch the logs to see that your theme is deployed correctly. If there is an error in your theme.xml file you should see an XML parser error in your roller.log file. You can also turn on additional theme debugging by adding the following to your roller-custom.properties override file.

log4j.category.org.apache.roller.weblogger.business.themes=DEBUG

If you want to share your theme with an even wider audience, then consider contributing it to the Roller Support project, a site that hosts additional themes that are not included in the official Apache Roller release because Roller ships with only four core themes.

That's all

I think that covers all the bases. Let me know if it works for you or what parts of the doc could be improved. I hope to get this into the next rev of the Roller Template Guide (which you can get from the Roller download page in PDF form).

Here's the example1 theme that I discussed in this post:

转自【http://rollerweblogger.org/roller/entry/how_to_create_a_roller 】

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