Glimmer DSL for CSS 1.5.2

Ruby Programmable Cascading Style Sheets

Glimmer DSL for CSS provides Ruby syntax for building CSS (Cascading Style Sheets), included in Glimmer DSL for Web (Ruby in the Browser Web Frontend Framework) to use in Rails Frontend Development. It used to be part of the Glimmer library (created in 2007), but eventually got extracted into its own project. The Ruby gem also includes a CSS to Glimmer converter (css_to_glimmer) to automatically convert legacy CSS code into Glimmer DSL syntax.

Example (you can try in IRB):

require 'glimmer-dsl-css'

include Glimmer

@css = css {
  body {
    font_size 1.1.em
    background 'white'
    width 90.%
    height 100.%
  }
  
  rule('body > h1') {
    background_color :red
    font_size 24
  }
  
  media('screen and (min-width: 30em) and (orientation: landscape)') {
    rule('body#app h1#title') {
      font_size 16
      font_family '"Times New Roman", Times, serif'
    }
  }
}

puts @css

Output (minified CSS):

body{font-size:1.1em;background:white;width:90%;height:100%}body > h1{background-color:red;font-size:24px}@media screen and (min-width: 30em) and (orientation: landscape){body#app h1#title{font-size:16px;font-family:"Times New Roman", Times, serif}}

The key reason for using the CSS DSL instead of actual CSS is Ruby programmability without getting lost in string concatenations. The CSS DSL helps in including conditional CSS with if or ternery expressions as well as looping from lists while building CSS.

  rule('body > h1') {
    background_color is_error ? :red : :green
    font_size new_user ? 24 : 20
  }

Within the context of Glimmer app development, Glimmer DSL for CSS is useful in providing CSS for Glimmer DSL for Web, Glimmer DSL for Opal, and the SWT Browser widget.

Learn more about the differences between various Glimmer DSLs by looking at the Glimmer DSL Comparison Table.

Setup

Please follow these instructions to make the glimmer command available on your system.

Option 1: Direct Install

Run this command to install directly:

gem install glimmer-dsl-css -v 1.5.2

Note: In case you are using JRuby, jgem is JRuby's version of the gem command. RVM allows running gem as an alias in JRuby. Otherwise, you may also run jruby -S gem install ...

Add require 'glimmer-dsl-css' to your code.

When using with Glimmer DSL for SWT or Glimmer DSL for Opal, make sure it is added after require glimmer-dsl-swt and require glimmer-dsl-opal to give it a lower precedence than them when processed by the Glimmer DSL engine.

That's it! Requiring the gem activates the Glimmer CSS DSL automatically.

Option 2: Bundler

Add the following to Gemfile (after glimmer-dsl-swt and/or glimmer-dsl-opal if included too):

gem 'glimmer-dsl-css', '~> 1.5.2'

And, then run:

bundle install

Note: When using JRuby, prefix with jruby -S

Require in your code via Bundler (e.g. require 'bundler'; Bundler.require) or add require 'glimmer-dsl-css' to your code.

When using with Glimmer DSL for SWT or Glimmer DSL for Opal, make sure it is loaded after glimmer-dsl-swt and glimmer-dsl-opal to give it a lower precedence than them when processed by the Glimmer DSL engine.

That's it! Requiring the gem activates the Glimmer CSS DSL automatically.

CSS DSL

  _('body > h1') {
    background_color is_error ? :red : :green
    font_size new_user ? 24 : 20
  }

Simply start with css keyword and add stylesheet rule sets inside its block using Glimmer DSL syntax. Once done, you may call to_s or to_css to get the formatted CSS output.

css is the only top-level keyword in the Glimmer CSS DSL

Selectors may be specified by any of _, s, r, ru, rul, rule keywords or HTML element keyword directly (e.g. body) Rule property values may be specified by underscored property name directly (e.g. font_size), which is auto-translated to CSS property name by replacing underscores with dashes (e.g. font-size)

Example (you can try in IRB):

require 'glimmer-dsl-css'

include Glimmer

@css = css {
  body {
    font_size '1.1em'
    background 'white'
  }
  
  r('body > h1') {
    background_color :red
    font_size 24
  }
}

puts @css

Output (minified CSS):

body{font-size:1.1em;background:white}body > h1{background-color:red;font-size:24px}

The body > h1 rule could have been written in any other alternative way:

  rule('body > h1') {
    background_color :red
    font_size 24
  }

  rul('body > h1') {
    background_color :red
    font_size 24
  }

  _('body > h1') {
    background_color :red
    font_size 24
  }

  _ 'body > h1' do
    background_color :red
    font_size 24
  end

Numeric Values and Unit Types

All CSS unit types are supported by invoking methods matching them on Numeric objects (e.g. 3.em produces '3em'):

px (default if not specified)
pt
pc
Q
in
cm
mm
em
rem
vh
vw
vmin
vmax
%

For example:

require 'glimmer-dsl-css'

include Glimmer

@css = css {
  body {
    font_size 1.1.em
    width 80.%
    height 100.%
    background 'white'
  }
  
  r('body > h1') {
    font_size 24.px
    background_color :red
  }
}

puts @css

Output (minified CSS):

body{font-size:1.1em;width:80%;height:100%;background:white}body > h1{font-size:24px;background-color:red}

Also, as you saw above, numeric values (e.g. 24 in font_size 24) automatically get suffixed with px by convention (e.g. 24px).

require 'glimmer-dsl-css'

include Glimmer

@css = css {
  body {
    font_size 14
    background 'white'
  }
  _ 'body > h1' do
    background_color :red
    font_size 24
  end
}

puts @css

Output (minified CSS):

body{font-size:14px;background:white}body > h1{background-color:red;font-size:24px}

Raw CSS

You can mix in raw CSS with Glimmer CSS DSL syntax by using the raw keyword and passing it an argument that is the raw CSS String. That enables adding programmability (e.g. if/else statements) to some parts of a CSS document while leaving the others as raw CSS.

Example (you can try in IRB):

require 'glimmer-dsl-css'

include Glimmer

color = 'black'
size = 8

@css = css {
  # Programmable CSS
  body {
    font_size size < 10 ? "0.#{size}em" : '1.1em'
    background color.nil? ? 'white' : color
  }
  
  # Non-Programmable CSS
  raw '
  body > h1 {
    background-color: red;
    font-size: 24px;
  }
  
  body > section {
    font-size: 16px;
  }
  '
}

puts @css

Output (minified CSS):

body{font-size:0.8em;background:black}body > h1 {background-color: red;font-size: 24px;}body > section {font-size: 16px;}

CSS to Glimmer Converter

The Ruby gem includes a CSS to Glimmer converter (css_to_glimmer) to automatically convert legacy CSS code into Glimmer DSL syntax.

Script:

bin/css_to_glimmer

Usage:

css_to_glimmer [-r=rule_keyword] path_to_css_file

Example:

Suppose we have a CSS file called input.css:

html, body {
  margin:0;
  padding:0;
}

@media (max-width: 430px) {
  .footer {
    height:50px;
  }

  .filters {
    bottom:10px;
  }
}

We can run this command:

css_to_glimmer input.css

Printout:

Converting from CSS syntax to Glimmer DSL Ruby syntax for input file: input.css
Converted output file: input.css.glimmer.rb

Output file (input.css.glimmer.rb) is a runnable Ruby file containing Glimmer DSL for CSS syntax:

require 'glimmer-dsl-css'

include Glimmer

style_sheet = css {
  rule('html,body') {
    margin '0'
    padding '0'
  }
  
  media('(max-width: 430px)') {
    rule('.footer') {
      height '50px'
    }
    
    rule('.filters') {
      bottom '10px'
    }
  }
}

puts style_sheet.to_s

If you would rather customize the rule keyword with a shorter alias like rul, ru, r, s (for selector), or _, you can run the following command:

css_to_glimmer -r=ru input.css

Output file (input.css.glimmer.rb) is a runnable Ruby file containing Glimmer DSL for CSS syntax:

require 'glimmer-dsl-css'

include Glimmer

style_sheet = css {
  ru('html,body') {
    margin '0'
    padding '0'
  }
  
  media('(max-width: 430px)') {
    ru('.footer') {
      height '50px'
    }
    
    ru('.filters') {
      bottom '10px'
    }
  }
}

puts style_sheet.to_s