Packt Publishing Drupal 5 Themes reviewed

A first release candidate of Drupal 6 was made available on December 20, 2007, that is, two days prior to the publication of this theming guide... which covers Drupal 5! Drupal 6.1 has since been released, and many of Drupal’s most popular add-on modules are now ready for use on production web sites. The author mentioned on his blog that an updated version of his book will be published, but Packt Publishing is not yet listing 'Drupal 6 Themes' among its upcoming publications. Still, I read the book, and worked through its examples on a Drupal 6 install. As a somewhat seasoned Drupal developer, I still found the book helpful. I recommend it, provided that, as you read along, you refer yourself to the concise (and well-put-together) Drupal 6 theming guide available on Drupal.org. Theming has definitely taken a leap forward in D6. For instance, intercepting and overriding theming functions is a lot easier now.

What this book covers

Chapter 1 ("The Elements of a Drupal Theme") presents the theming terminology used in Drupal — and that stuff hasn’t changed in Drupal 6.

Chapter 2 explains how to set up and configure a theme in Drupal in the admin interface. By way of example, we download the theme 'Gagarin' from Drupal.org and install it. We also configure 'Garland', which still is the default theme shipped with Drupal. Surprisingly, I learned quite a handful of tricks in this chapter. All of it is applicable to Drupal 6; even the neat PHP snippets used for the content & visibility of custom 'blocks' work as is. For fun, I ported the Gagarin theme to Drupal 6 in less than 10 minutes, using a porting guide put together by Wesley Tanaka. Your milage may vary (you may do it faster than I).

Chapter 3 explains how the PHPTemplate 'engine' works. Wordy as this chapter is, the definition of a theming engine remains... somewhat ambiguous. But the rest of the book will clear that out. You may download this chapter from the publisher’s web site. Take note that the default PHPTemplate 'template' files have been moved to their respective core module folder in Drupal 6. For example, you’ll find the default page.tpl.php file under /modules/system, and node.tpl.php under modules/node.

Chapter 4 is a reference guide to stylesheets and themable (ie: overridable) functions. Only a brief description (ie: one sentence) is provided for each function. The author gives us a snippet of PHP code that produces a list of the theming functions used on the page, but it’s somewhat useless because with it we don’t know which function produces what markup. In Drupal 6, a neat & sexy add-on module, 'Theme developer', part of the 'Devel' kit of modules, tells us which function to override — and so much more: using Firebug-style point-and-click, we can select the DOM element we wish to theme, and we learn how to do so (that is, which theming function to intercept & override) by reading a tooltip. See the screenshot and screencast.

Chapter 5 presents different ways to intercept & override themable functions. In Drupal 6, one of these ways has been simplified, that of "placing overrides in dedicated [template] files" for which no default file exists. One needs to tell the theming engine about the presence of the template file by way of a preprocess function, setting either $vars['template_file'] or $vars['template_files']. In the instance where we want additional variables to become available inside the template, we use that same preprocess function, ie: engineName_preprocess_hook.

In Drupal 6, adding stylesheets (besides the default style.css) is as easy as adding a few lines to a new *.info file for the theme. Same with creating new regions on the page: the themeName.info file takes care of that. One needs not add any PHP code to template.php.

In chapter 6, we modify a theme, 'Zen'. Be warned: even the Drupal 5 version of this theme has undergone significant change between the time that chapter was written and the publication of the book.

In chapter 7, we learn how to create a theme from scratch — and so much more (this chapter definitely should have been broken down). We’re finally presented with a list of the variables available in each template file. In Drupal 6, many variables have been renamed (for example, $sidebar_left has become… $left), and new handy ones have been created which are available in all templates, for exampe $logged_in and $is_admin. Note that we should use the new D6 variable $body_classes to apply dynamic CSS styling, instead of the ol’ $layout (still available).

In chapter 8, we learn how to theme forms. I had to do some research to find how to apply the author’s solutions within Drupal 6. Some change is trivial, for example the handy hook_ form_alter function has different parameters passed to it in D6, the function’s signature has changed...

From that in D5 : function formmod_form_alter($form_id, &$form){

To this in D6 : function formmod_form_alter(&$form, $form_state, $form_id){

In D6, some form-theming solutions are easier to implement... or more difficult: I still haven’t figured how to use images for the forms submit button. However, to achieve this, imo, a CSS solution is preferred in both Drupal 5 and 6. No need to change the markup. (Use the CSS property background-image in other words, and 'indent' the submit button text far-far to the left.)

What this book does not cover, though I wish it did

• How to use jquery, the wondrous javascript library shipped with Drupal (there is no mention of it, really).
• How to create a theme with a configurable color scheme, using the Color Module. A simple tutorial where we create a theme for which we can change the color of the header and links through the 'setttings' UI would have been awesome. By the way, it was brought to my attention that a patch is available to make the theme 'Bluemarine' (shipped with Drupal 6) colorable.
• Related to the last point, we’re not shown how to modify the theme’s settings page — to add to it, for example.
• How to theme Views pages, and nodes created with the Content Construction Kit (CCK). Although it becomes easy to figure it out. To theme a view, we need to know the 'internal path' of the view, and create a template file for it. For example, if the internal path is 'view/comments', then the template file to drop in our theme folder would be page-view-comments.tpl.php. (By the way, the explanation for the order of precedence among template files, ie: the working of the variable $suggestions, has moved to /includes/theme.inc. in Drupal 6.) When it comes to theming a node with a particular node type, we need to know the machine-readable name of the content type. Hence, to theme nodes created with CCK that are of the type 'news', we drop a template with name node-news.tpl.php in our theme folder.
• How to commit a theme to Drupal.org CVS (using a freeware utility like TortoiseCVS, for example).

This book is particulary successful at breaking down information into bits and steps. It is extremely well-written, quite technical and in-depth, and provides a handful of screen captures in most places. Lists of To-Do’s, in the form of "client’s requirements", make it all the more fun to work through the longer exercises. Finally, we can theme it _all_ in Drupal, and the author drives that point home.

Where the book falls somewhat short in its delivery

• Although the author comes from a "design background" (so it says in the book’s preface), he fails to inspire. The theme created from scratch is particularly unappealing. Check it out:



• When it comes to designing Drupal themes, in chapters 6 and 7, we’re faced with basically copying and pasting CSS rules scattered throughout a set of *.txt source files (that you can download from the publisher’s web site) into one stylesheet, ie: style.css.

Although, to be fair, this is not a book on CSS, nor web design...