Theming, Part 2: Sidebar Templates and Plugins

It's time for part 2 of the LnBlog themes tutorial series. In this episode, we'll cover modifying your sidebar. This will include a brief discussion of how theme templates work as well as an introduction to the plugin system. In the process, we will also create a very simple and extremely unimpressive plugin. Note that in this tutorial, unlike the last one, I will assume that you have a basic knowledge of HTML and CSS. This tutorial will also include some PHP code, although I will nto assume a working knowledge of PHP (although if you have one, it will help).

As you may recall from last time, LnBlog's theme system has a concept of paths. This applies not only to images and style sheets, as we saw before, but also to template. In other words, LnBlog will look for a given template first in your blog's templates directory, second in the templates directory of your current theme, and lastly in the templates for the default theme. This means that you can easily modify the templates for each of your blogs individually or for all of them at a time.

Modifying the template

Let's start by making a copy of your LnBlog/themes/default/templates/include_sidebar.php file and saving it on your local hard drive so we can play with it. If you open up the file in a text editor, you'll notice that there's almost nothing in it. It should just look like this: activateEventFull($tmp=false, "sidebar", "OnOutput"); $EVENT_REGISTER->activateEventFull($tmp=false, "sidebar", "OutputComplete"); ?> Of course, if you don't know PHP, that's probably doesn't mean anything to you. In fact, it probably doesn't mean much even if you do know PHP. That's because this code is part of LnBlog's event system

As you may already know, the default page banner, menubar, and sidebar in LnBlog are all implemented as plugins. If you open up your include_banner.php or include_menubar.php, they'll contain similar code. Basically, this code raises an event, i.e. it tells LnBlog's event manager that something interesting is happening and any plugin that's interested in this event better get it's act together. The event manager them checks a list of plugins that signed up to be notified when this event happens and tells them to do their thing.

Now, since this is a template, we can actually ad HTML code right into it. For illustrative purposes, I'll add some of my favorite links to the sidebar. Here's what the resulting code looks like: <?php global $EVENT_REGISTER; $EVENT_REGISTER->activateEventFull($tmp=false, "sidebar", "OnOutput"); ?> <h3>Recommended Links</h3> <ul> <li><a href="">The Old New Thing</a></li> <li><a href="">Security Focus</a></li> <li><a href="">The Daily Grind</a></li> </ul> <?php $EVENT_REGISTER->activateEventFull($tmp=false, "sidebar", "OutputComplete"); ?> Notice that I broke the PHP code into two blocks and put the HTML in between them. Since tempaltes are actually PHP files, anything inside the <?php ?> tags is treated as PHP code, and anything outside them is treated as HTML. If you're sharp, you probably noticed that I did this because of the event code: I put my markup between the OnOutput and OutputComplete events.

If you save this file and upload it to your blog's templates directory, you'll see your list of links in the sidebar. However, you'll notice that the links are at the bottom of the sidebar. That's because all the plugins are loaded by the OnOutput event. If you move the HTML code above that event, then all your links will end up at the top of the sidebar. But what if you want your links in the middle somewhere? Maybe you want your links between your articles and your RSS feeds. Well, that's why this isn't the recommended way to add to the sidebar.

A simple sidebar plugin

However, there is good news. Writing a simple plugin to display some links in the sidebar is easy. Really easy. In fact, it's about a dozen lines of boiler-plate PHP code with your HTML inserted in the middle. And once you have the plugin written, it will be detected by the plugin manager and you will be able to change where it appears in the sidebar by changing its load order in the plugin loading configuration page.

Here's a plugin version of the links in the example above: <?php class MyLinks extends Plugin { function MyLinks() { $this->plugin_desc = "Shows my favorite links in the sidebar"; $this->plugin_version = "0.1.0"; } function show_links() { ?> <h3>Recommended Links</h3> <ul> <li><a href="">The Old New Thing</a></li> <li><a href="">Security Focus</a></li> <li><a href="">The Daily Grind</a></li> </ul> <?php } } $plug = new MyLinks(); $plug->registerEventHandler("sidebar", "OnOutput", "show_links"); ?> This is about the simplest plugin you can have. It is a simple PHP class with a constructor that defines the version number and a short description, and a single method that dumps some HTML output to the screen. Note at the bottom that you have to create an instance of the class and register the method with the event manager.

Now is probably a good time to mention that plugins use a path mechanism too. In other words, you can have plugins that apply only to a single blog, just like you can with theme template and style sheet. Just make a "plugins" directory in the blog's directory and put the plugins there. They will be treated just like a regular plugin, but no other blog will be able to see them.

So, now let's install your new plugin. Copy the above code and paste it into a new file named sidebar_mylinks.php. Note that it is very important that you not have any blank lines or spaces outside the PHP <?php >> tags, as this will cause error messages due to the way PHP handles output. Now, create that plugins directory in you blog's directory on the server and upload the sidebar_mylinks.php file into it. If you open up your blog in a web browser, you should see the new links. If you change the load order of your sidebar_mylinks plugin from the plugin loading page, then the link section will move in the sidebar.

If you want to have several independant sidebar sections, you can make copies of this plugin to achieve that. Just change the HTML code, the plugin_desc on the fourth line, and change all three instances of the name MyLinks to MyOtherLinks, or something like that (the exact name doesn't matter, so long as no two plugins have the same name). If you're feeling adventurous, you can also adapt this to add markup to the banner or menubar by changing the "sidebar" parameter in the registerEventHandler line to "banner" or "menubar".

You can download files for this tutorial here. In the next installment, we'll go into theming the content areas of a page, including templates for blog entries. We'll also cover modifying the associated style sheets and possibly adding some images.

Theming, Part 1: Custom Banner

It's been a long time since I posted anything, so I figured I'd put up a little informal documentation on the theme system. After all, who wants to be stuck with just the default themes? The answer is: me, because I'm the one who designed them. But I'm sure other people would like to personalize the look of their site a bit.

Today, let's talk about setting a custom page banner. That seems to be one of the first things most people change on their blog. Plus it's fairly easy to do in LnBlog and doesn't require a great deal of HTML or CSS knowledge. So let's get started!

For this exercise, you'll need two things. The first is a banner image. It can be anything you want, so long as a web browser can display it and it's a suitable size. Since I'll be assuming you use the default LnBlog theme, which is not fixed-width, I'd recommend a JPEG image that's at least 1024 pixels wide and around 160 pixels high. For illustrative purposes, I'll use this picture of the hills. If you have a moderately high resolution digital camera, you can probably take a decent picture yourself and use the GIMP or some other image editor to cut out an appropriately sized image.

The second thing you'll need is a copy of your banner style sheet to work on. This one is easy: just go into your LnBlog/themes folder, find the directory for your theme, and copy the styles/banner.css file to someplace on your local hard drive so that you can edit it.

Now that we've got a stylesheet and an image, setting the banner background is easy. Just open up your copy of the banner.css file, find the #banner section, and change it so it looks like this: #banner { width: 100%; border: 1px solid black; background-image: url(../images/horizon.jpg); background-repeat: no-repeat; max-width: 1281px; max-height: 160px; } This gives us a banner box with a thin border and our horizon image as the background. Note that the max-width and max-height are set to the width and height of the image. This keeps the box from expanding to larger than the size of the picture and looking funny.

As long as we're in the style sheet, we might as well consider the text. Let's say, for the sake of argument, that you wanted to change the alignment of the default banner text. Let's say you want to put the blog name on the left side of the banner and the description on the right. Well, in that case, you would look for the #banner h1 style for the name and the #banner h3 style for the description. If you look just below the section we just modified, you'll see something like this: #banner h1, #banner h2, #banner h3 { text-align: center; vertical-align: middle; color: white; } This sets the default style for the first three levels of heading. We can override the alignment by simply creating additional styles below that section, because in CSS, styles later in the file take precedence over earlier ones. So, let's add the following: #banner h1 { text-align: left; margin-left: 10%; } #banner h3 { text-align: right; font-style: italic; margin-right: 10%; } This gives us a left-aligned heading, and a right-aligned, italicized description. (If you don't see a blog description, you can turn it on in the plugin configuration page, under the "pageheader" plugin option.) Note the margins are set so that the text doesn't bump up against the edge of the banner.

So at this point, we have our image and our stylesheet. Now what? Well, we install them on the server, of course! But where to put them?

This is where the flexibility of LnBlog's theme system come in. You see, we actually have several options. First, we can always put them in our theme directory, overwriting the old style sheet. The second possibility is creating a new theme. The third is applying this only to a single blog. Changing the files for the default themes isn't really recommended, so we'll stick to the second and third options.

Creating a new theme, especially one this simple, is quite easy. Just go into your LnBlog/themes directory and create a new folder with whatever name you want the theme to have. Then, inside that folder, create four more folders with the following names: images, styles, scripts, and templates. Now copy your banner image into the images directory you just made and put the banner.css file in the styles directory. Now, if you edit your blog setting and change the theme to the one you just created, you should see your new banner.

The process for applying your custom banner to a single weblog is very similar. You would simply open up the directory for that weblog and create an images directory and a styles directory. Copy your image and style sheet to the corresponding directories and the changes will automatically take effect for that blog.

By now, you've probalby noticed the pattern here. When constructing a page to send to the client web browser, LnBlog uses a search path mechanism to find files. There are four kinds of files: images, styles, scripts, and templates. LnBlog looks for each type of file in a directory of the same name, located in the current blog's folder, the current theme's folder, or the default theme's folder. The search takes place in that order, so if you don't have a particular file in your blog or in your theme, the default will always be there. The idea is to make it easy to create small variations on existing themes. The down side, of course, is that it's somewhat more difficult to create custom themes from scratch. But, then again, given that you have to get all the template variable right in order for things to work, it's usually easier to just start from an existing theme anyway.

Next time, we'll talk about templates and how the enevt-driven plugin system interacts with them.