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Susy - Compass Plugin

Susy is a semantic CSS framework creator entirely native to Compass. Susy is an expert at fluid grids in an elastic (or fluid, or fixed) shell that will never activate that bloody side-scroll bar. Susy sets your width on the outer element (container), adds a max-width of 100% and builds the rest of your grid in percentages. The philosophy and technique are based on Natalie Downe's "CSS Systems" - which introduces difficult math in the service of beautiful structure. With the power of Compass/Sass, Susy will do that math for you.

Using simple mixins, columns can be created, suffixed, prefixed, and nested easily - and always in flexible percentages.

Install

sudo gem sources --add http://gems.github.com/ 
sudo gem install chriseppstein-compass 
sudo gem install ericam-compass-susy-plugin

Create a Susy-based Compass Project

compass -r susy -f susy <project name>

Then edit your _base.sass, screen.sass and print.sass files accordingly. A reset is added automatically.

Philosophy and Goals

The method comes from Natalie Downe's "CSS Systems", but I'll cover it here.

It is important for accessibility and usability that we are:

  • Responsive to text sizing: In order for our site to be accessible we need to allow different font-sizes to be set by the client. In order to maintain design integrity of proportions and line-lengths, the grid needs to respond to those sizes.

  • Responsive to window sizing: In order to maintain usability across platforms/monitors, our grid needs to respond to the size of the viewport. This is mainly an issue as the viewport shrinks and we are given a side-scroll bar. No one likes that. On the large end our design integrity and line lengths are more important than taking up all the possible space.

In order to achieve both we need to combine the best of the elastic (em-based) and fluid (%-based) models. The solution is simple: First we build a fluid grid, then place it inside an elastic shell, and apply a maximum width to that shell so that it never exceeds the size of the viewport. It's simple in theory, but daunting in practice, as you constantly have to adjust your math based on the context.

But Susy harnesses the power of Compass and Sass to do all the math for you.

Grid Basics

  • Set up your default grid values (total columns, column width, gutter width, side gutter width), your base font size, and other style defaults in _base.sass.

  • Create your grid in screen.sass: apply the +susy mixin to the body element and the +container mixin to the element that contains the page grid.

  • Use the +columns mixin to declare the width in columns of an element, or +full for any element spanning the full width of its context.

  • Use +alpha and +omega to declare elements which include the first or last column within their parent element (+full to declare both +alpha and +omega). Note: +alpha is actually only needed in the very top level, and does nothing in nested contexts. Neither is needed on a +full element.

  • Use +prefix or +suffix to give the width (in columns) of an elements left or right margin, or +pad to give both +prefix and +suffix at once.

  • In nested contexts, all of these mixins take an extra final argument, the width in columns of the parent (nesting) element.

That's it for the basics! Here's a sample Susy grid layout:

body
  +susy
 
#page
  +container
 
#brand
  +full
  +pad(1,1)
  h1
    +full(8)
    +pad(1,2,8)
    
#nav
  +columns(2)
  +alpha
 
#content
  +columns(8)
  +omega
  #description
    +columns(5,8)
  #credit
    +columns(3,8)
    +omega(8)

Tutorial

For more details, read the tutorial.
It's also included with Susy in the docs/ folder.

Extra Utility Mixins

Extra utilities are included in Susy's utils.sass file, with additional list options, experimental (CSS3/proprietary) CSS, and more.

  • +show-grid(!src) will remove all your backgrounds and repeat the specified grid image on an element. Good for testing your baseline grid.

  • +inline-block-list([!horizontalpadding]) for making lists inline-block when floating just won't do the trick.

  • +hide for hiding content from visual browsers while keeping accessability intact.

  • +skip-link([!top = 0, !right, !bottom, !left]) hide a link, and then show it again on focus. the TRBL settings allow you to place it absolutely on display. Default will be top left of the positioning context.

And then the fun stuff:

  • +opacity(!opacity) adds cross-browser opacity settings (takes a range of 0 to 1).

  • +border-radius(!radius) (+border-bottom-left-radius etc. all work) for rounded corners in supporting browsers.

  • +box-sizing(!model) for setting the box sizing model in supporting browsers.

  • +box-shadow(!verticaloffset, !horizontaloffset, !blur, !color) for box-shadow in webkit, mozilla and CSS3.

  • +column-count(!number), +column-gap(!length), +column-width(!length), and +column-rule(!width, !style, !color) for CSS columns in webkit, mozilla and CSS3.

Advanced Options

Susy is built for flexibility, so that you always write the code you want to write. While everything should 'just work' out of the box, there are plenty of advanced options hidden inside. Here's a few:

  • !hacks is a boolean constant that you can set in your base.sass file to choose between using targeted hacks for IE (a variation of the star hack in most cases) in your screen.css, or using a conditional-comment targeted ie.css. All the needed mixins are available for either setting. !hacks is true by default so there is no extra work maintaining multiple files unless you want to.

    Example 1:

      !hacks = true

  #nav
    +inline-block-list

    Example 2:

      !hacks = false

  (in screen.sass)
  #nav
    +inline-block-list

  (in ie.sass)
  #nav li
    +ie-inline-block

    It requires more maintenance on your part, but the result is a hack-free output.

    The susy mixins that use either hacks or targeted mixins are +omega ('+ie-omega([!right-floated = false])'), +inline-block (+ie-inline-block), and +inline-block-list which sets +inline-block on the list items.

    These ie-specific mixins only add the needed ie-specific adjustments, so they need to be used in addition to their counterparts, not on their own.

  • gutter(!context) is a function that you can call at any time to return the size of a gutter in your given context using percentages. The number is returned without units so that you can perform math on it. In order to use it, you will have to add "%" to it.

    Example:

      #nav
    :padding-right= gutter(5) + "%"

  • columns(!number, !context) returns the span of !number columns in !context as a percentage (again without the units declared). This span includes any gutters between the columns spanned.

    Example:

      #nav
    :padding-left= columns(3,5) + "%"

  • side_gutter() is also available and takes no arguments since it is always used at the top nesting level.

  • px2em() takes one numeric argument representing the number of pixels you want to mimic. The return is an em value (with no units declared) that approximates that number of pixels. Useful for keeping your entire design fluid.

    Example:

    #nav
  :border-bottom= px2em(2) + "em"