74 lines
2.2 KiB
Markdown
74 lines
2.2 KiB
Markdown
---
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title: Extending Compass
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layout: tutorial
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crumb: Extending Compass
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classnames:
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- tutorial
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---
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# Extending Compass
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## Sprite engine
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The sprite engine is the work horse of sprite generation it's the interface for assembling and writing the image file to disk.
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### Requirements
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A sprite engine requires two methods `construct_sprite`, and `save(filename)`
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Once inside the class you have access to `images` which is a collection of [Compass::SassExtensions::Sprites::Image](http://rdoc.info/github/chriseppstein/compass/dda7c9/Compass/SassExtensions/Sprites/Image)
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### Configuration
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To enable your sprite engine from the config file set
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sprite_engine = :<engine name>
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The example below will load `Compass::SassExtension::Sprites::ChunkyPngEngine.new(width, height, images)`
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sprite_engine = :chunky_png
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### Class Definition
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module Compass
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module SassExtensions
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module Sprites
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class ChunkyPngEngine < Compass::SassExtensions::Sprites::Engine
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def construct_sprite
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#do something
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end
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def save(filename)
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#save file
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end
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end
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end
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end
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end
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<a name="adding-configuration-properties"></a>
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## Adding Configuration Properties to Compass
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To add a new configuration property to Compass:
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Compass::Configuration.add_configuration_property(:foobar, "this is a foobar") do
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if environment == :production
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"foo"
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else
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"bar"
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end
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end
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This will do several things:
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1. make it possible for users to set the `foobar` configuration property in their
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configuration file.
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2. Ruby code can read and write the `foobar` attribute from any configuration object.
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3. It will add the comment `# this is a foobar` above the property in the configuration file.
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A comment is not required, you can simply omit this argument if you like.
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4. The block of code provided allows you to assign a sensible default value according to other
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settings in the configuration or by using arbitrary code to determine what the value should
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be. For instance it could read from another configuration file or it could change based on
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the user's operating system. |