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Fluid Project is evaluating CSS Frameworks as a possible tool:

  • for implementing project websites, and component demos
  • to integrate in components themselves to bring additional features

After a research and evaluation period (see: CSS Framework Research Notes), Foundation and Bootstrap have emerged to be the front runners. This attempts to document in detail the requirements of the framework to be used.

Criteria Evaluation


Feature / Desired applicationBootstrapFoundation
Responsive layouts
  • Bootstrap uses fixed width containers that "snap" across breakpoints
  • Grid layout needs to follow a container-row-column hierarchy. Otherwise 15px paddings / margins don't align properly.
  • Foundation uses fluid width containers that stretch and shrink depending on the size of the client, with relevant breakpoints.
  • Foundation has a row-column hierarchy with paddings on the columns only. Row is only for containment.
Style reset
  • normalize.css is included in default package, but optional whether or not it is used in your markup.
Units in EMs

Current release (v3) uses pixels and not EMs. However, v4 (unreleased) will support EMs. See Mark Otto's January 9th response in this thread on Github.

  • Note: EMs will be supported. Unclear if REMs will be used.
  • UIO works well with Bootstrap's pixel units, although EMs are more desirable.
Foundation 5 uses REM units throughout. The exception being media queries which use EM units.
  • REMs are desirable and easier to use for CSS styling than EM because REMs always refer to the root EM and not the parent EM as with EM units.
  • REM units currently do not scale properly in UI Options. See
    serverFluid Project Issue Tracker
Ease of customizing default styles  
Ease of using default styles in a heavily customized application
  • +/-15px margin and padding on container, rows, and columns dictate a hierarchy and usage pattern. Customizing this or deviating from this pattern causes unintentional and unwanted alignment issues which can be hard to correct (involves overriding).
  • This hierarchy is required to ensure good scalable layouts.
Custom builds  
Namespacing framework classnames
  • Bootstrap uses generic classnames which may cause classname collisions.
  • A work-around is to use LESS or Sass to add a named container. See this as a possible solution:
UIO Theme generation using default build  

UIO Theme generation - can it be done using the framework's customization tool? 

UIO Theme generation using preprocessor  
Effects of custom Bootstrap build with default Bootstrap


Effects of custom Bootstrap build with default Foundation  
Effects of custom Foundation build with default FoundationN/A 
Effects of custom Foundation build with default Bootstrap  
Nice to have - tooltips  





Summary and Background

Up to version 1.5, Infusion shipped with a built-in CSS framework called the Fluid Skinning System. When the FSS was first designed, there were few viable production-scale CSS frameworks available to developers. As a community, we felt a need to provide something that had been designed with accessibility and flexibility in mind. Since then, we've experienced a massive shift in the way websites are designed and implemented. Responsive Web Design is now widely practiced, enabling web pages to adapt to different screen sizes and device form factors. CSS preprocessors such as Less and Sass have changed the way style sheets are developed and reused. Mature and widely-used CSS frameworks such as Bootstrap and Foundation are available to help ease the effort of styling responsive layouts, grids, and widgets.

Unfortunately, the Fluid Skinning System hasn't kept pace. As a result, we chose to deprecate it in version 1.5. We recommend that users of Infusion choose from any of the available third-party frameworks based on their own needs and requirements. As of Infusion 2.0, we will remove FSS entirely.

Infusion components currently don't rely on any CSS framework, and we will continue to ensure that they are styled in a way that is unlikely to conflict with popular tools like Bootstrap and Foundation. For the foreseeable future, we don't plan to include any third-party CSS framework with Infusion, nor to require that our users select a specific framework.

Who is this document for?

This document reflects the decision-making process we have undertaken as a community to select a CSS framework for some of our own websites, documentation, and demos. It may also be useful when selecting your own CSS framework to use alongside Infusion.

Recommendation Summary

Fluid Infusion components do not use a CSS framework out of the box. The motivation for this is to ensure Infusion components play nicely in whatever application is used. Integrators may choose to add their own CSS framework to Infusion components if they wish.

Using a CSS Framework within an Infusion component

  • Components shipped as part of the core Infusion package do not use a CSS framework for their styling.
  • Some CSS frameworks don't use namespaced or prefixed class names, which creates the possibility of collisions that can cause styling problems. Infusion component styles are always namespaced, which reduces the potential for Infusion to cause conflicts with non-namespaced frameworks. See Infusion Class Name Conventions for more information.
  • Because Infusion components do not use a CSS framework by default, component creators will need to create good default styles and leave it to the integrator to customize with their own CSS framework if they choose to.

Using a CSS Framework within Fluid-related demos, websites, etc.

  • A CSS framework is fine to be used for websites, demos, and other integration / non-component scenarios. We recommend Foundation because of its use of REM sizing throughout.

Using a CSS Framework for contrast themes in UI Options and the Preferences Framework

  • At this time it is difficult to create contrast themes for CSS frameworks despite the availability of custom builders. Custom builders may not be an appropriate tool as they do not cover all possible styling rules we want to affect.
  • Creating a theme manually is non-trivial (lots of values to adapt)
  • Themes would have to be tested with each major and minor framework release to ensure compatibility. This adds a maintenance burden.

Future possibilities

  • There may be an opportunity to add new features to Learner Preferences that can transform CSS framework components (like navigation bars and button links). Further discussion is encouraged.
  • Contrast theme generation using a CSS pre-processor to be investigated. Possible pre-processors include: Less, SASS, and Stylus. This will be a separate discussion.

Appropriate Use of a CSS Framework

Example: Metadata component

Choosing a CSS Framework: Why Zurb Foundation?

In deciding which framework to recommend for the Fluid project, many criteria were considered including: documentation, community support, accessibility, and scalability.

After researching and comparing 6 different CSS frameworks, Zurb Foundation is the recommended framework for the following reasons:

  • Foundation uses REMs as units which ensures scalability across clients and devices.
  • Foundation's grid system is flexible - it's fluid width and has a cleaner structure which makes integration and customization easier.
  • We typically work in highly customized environments and Foundation is light weight and doesn't get in the way (mostly).

Can I use a different framework?

Yes, you can use any framework you prefer. For Fluid-related websites and demos, we prefer frameworks that are:

  • Accessible and scalable
  • Mature and widely supported
  • Open source

Future Considerations

Better namespacing

  • At this time it is very difficult to namespace CSS framework classes. Most solutions are a manual process, or a manual process that is automated by a script. This is fragile and requires constant testing with each new framework release.
  • If a CSS framework or tool emerges to support custom name spacing easily, and satisfies our needs (i.e. scalable, accessible, widely supported, etc.) - we should revisit the topic of using a framework for Infusion components.

Add CSS framework support to the Preferences Framework

  • Since CSS frameworks share common features (such as navigation bars, link buttons, progress bars, breadcrumbs), this can lead to some new preferences.
  • For example:
    • Linearize / stack content by changing the grid layout
    • Navigation bar preferences: make tabs look like pills, make navigation pills stack
    • Pager: size, appearance, spacing
    • Alerts: change the way alerts are positioned or styled (i.e. make them bigger, put them in a floating panel etc.)
  • In order to support multiple CSS frameworks, consider using an adapter model where the Preferences framework supports a generic definition and adapters are created to map CSS framework definitions to the framework. i.e. Framework 1 may use divs for breadcrumbs, and Framework 2 may use a list. The adapter would define this configuration so that the framework can use both.



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