Club Drupal

ZEN'S STYLESHEETS

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Don't panic!

There are 11 CSS files in this sub-theme, but it's not as bad as it first seems:

- There are 5 CSS files whose names end in "-rtl.css". Those are CSS files

  needed to style content written in Right-to-Left languages, such as Arabic and

  Hebrew. If your website doesn't use such languages, you can safely delete all

  of those CSS files.

- There are 2 example layout stylesheets inside the "layouts" folder,

  "responsive.css" and "fixed.css", but only one of them is used at any time.

- One is just a print stylesheet!

That leaves just 4 CSS files!

- styles.css

- normalize.css

- layouts/responsive.css

- components/misc.css

Now go look in the styles.css file. That file simply includes (via @import) the

other files. It also shows how the files in your sub-theme can be categorized

with the SMACSS technique. http://smacss.com

Why not just one stylesheet?

- For performance reasons you should always have all of your CSS in a single

  file to minimize the number of HTTP requests the user's browser needs to do.

  Fortunately, Drupal has a "Aggregate and compress CSS" feature that will

  automatically combine all the CSS files from its modules and themes into one

  file. You can turn on that feature under "Bandwidth Optimization" on the page:

    Administration > Configuration > Development > Performance

  So Drupal allows us (if we want) to use more than one stylesheet file, but

  still serves all the styles in one file to our users.

- When developing a site using a single stylesheet, it can become unwieldy to

  scroll and find the place you need to edit. As a deadline becomes imminent,

  developers often start stuffing new styles at the bottom of the stylesheet,

  completely destroying any stylesheet organization.

- Instead of one monolithic stylesheet, Zen sub-themes' CSS files are organized

  into several smaller stylesheets. Once you learn the organization (described

  below) it becomes easier to find the right place to add new styles.

- Stylesheets are added in the order specified in the styles.css file. The

  default order of the stylesheets is designed to allow CSS authors to use the

  lowest specificity possible to achieve the required styling, with more general

  stylesheets being added first and more specific stylesheets added later.

ORDER AND PURPOSE OF DEFAULT STYLESHEETS

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First off, if you find you don't like this organization of stylesheets, you are

free to change it; simply edit the @import declarations in your sub-theme's

styles.css file. This structure was crafted based on several years of experience

theming Drupal websites.

- styles.css:

  This is the only CSS file listed in your sub-theme's .info file. Its purpose

  is to @include all the other stylesheets in your sub-theme. When CSS

  aggregation is off, this file will be loaded by web browsers first before they

  begin to load the @include'd stylesheets; this results in a delay to load all

  the stylesheets, a serious front-end performance problem. However, it does

  make it easy to debug your website during development. To remove this

  performance problem, turn on Drupal's CSS aggregation after development is

  completed. See the note above about "Bandwidth Optimization".

- normalize.css:

  This is the place where you should set the default styling for all HTML

  elements and standardize the styling across browsers. If you prefer a specific

  HTML reset method, feel free to use it instead of normalize; just make sure

  you set all the styles for all HTML elements after you reset them. In SMACSS,

  this file contains all the "base rules". http://smacss.com/book/type-base

- layouts/responsive.css:

  Zen's default layout is based on the Zen Grids layout method. Despite the

  name, it is an independent project from the Zen theme. Zen Grids is an

  intuitive, flexible grid system that leverages the natural source order of

  your content to make it easier to create fluid responsive designs. You can

  learn more about Zen Grids at http://zengrids.com

  The responsive.css file is used by default, but these files are

  designed to be easily replaced. If you are more familiar with a different CSS

  layout method, such as GridSetApp, 960.gs, etc., you can replace the default

  layout with your choice of layout CSS file.

  In SMACSS, this file contains the "layout rules".

  http://smacss.com/book/type-layout

- layouts/fixed.css:

  This layout is based on the Zen Grids layout method, but uses a fixed pixel

  width. It is not included by default in your theme's .info file, but is

  provided as an option.

  In SMACSS, this file contains the "layout rules".

  http://smacss.com/book/type-layout

- components/misc.css:

  This file contains some common component styles needed for Drupal, such as:

  - Tabs: contains actual styling for Drupal tabs, a common Drupal element that

    is often neglected by site designers. Zen provides some basic styling which

    you are free to use or to rip out and replace.

  - Various page elements: page styling for the markup in page.tpl.php.

  - Blocks: styling for the markup in block.tpl.php.

  - Menus: styling for your site's menus.

  - Comments: styling for the markup in comment-wrapper.tpl.php and

    comments.tpl.php.

  - forms: styling for the markup in various Drupal forms.

  - fields: styling for the markup produced by theme_field().

  In SMACSS, this file contains "module rules". You can add additional files

  if you'd like to further refine your stylesheet organization. Just add them

  to the styles.css file. http://smacss.com/book/type-layout

- print.css:

  The print styles for all markup.

  In SMACSS, this file contains a media query state that overrides modular

  styles. This means it most closely related to "module rules".

  http://smacss.com/book/type-module

In these stylesheets, we have included just the classes and IDs needed to apply

a minimum amount of styling. To learn many more useful Drupal core selectors,

check Zen's online documentation: https://drupal.org/node/1707736

STYLES FOR INTERNET EXPLORER

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Zen allows IE-specific styles using a method first described by Paul Irish at:

http://paulirish.com/2008/conditional-stylesheets-vs-css-hacks-answer-neither/

If you look at Zen's templates/html.tpl.php file, you will see the HTML tag that

will be used by your site. Using Microsoft's conditional comment syntax,

different HTML tags will be used for different versions of Internet Explorer.

For example, IE6 will see the HTML tag that has these classes: lt-ie7 lt-ie8

lt-ie9. If you need to write an IE6-specific rule, you can simply prefix the

selector with ".lt-ie7 " (should be read as "less than IE 7"). To write a rule

that applies to both IE6 and IE7, use ".lt-ie8 ":

  .someRule { /* Styles for all browsers */ }

  .lt-ie8 .someRule { /* Styles for IE6 and IE7 only. */ }

Many CSS authors prefer using IE "conditional stylesheets", which are

stylesheets added via conditional comments. If you would prefer that method, you

should check out the Conditional Stylesheets module:

https://drupal.org/project/conditional_styles

DRUPAL CORE'S STYLESHEETS

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Note: Many of Zen's styles are overriding Drupal's core stylesheets, so if you

remove a declaration from them, the styles may still not be what you want since

Drupal's core stylesheets are still styling the element.