Building Progressive UIs with Grails
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This document discusses progressive enhancement and how to build progressive user interfaces with Grails. It provides examples of using Grails features like request.xhr and withFormat to vary output for AJAX requests. It also covers techniques like separating markup and behavior, reading and enhancing markup with JavaScript, form enhancements, and test-driven progressive enhancement using Modernizr and yepnope.
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Building Progressive UIs with Grails
- 1. Building Progressive UIs with Grails Rob Fletcher Energized Work
- 2. Who am I?
- 4. What is Progressive Enhancement? Approach to building web UIs that emphasizes: • Semantic markup • Separation of markup, appearance, behaviour • Rich appearance and behaviour applied selectively • Adaptive design for cross-browser & cross- device support • Distinct from 'graceful degradation’
- 5. Designing with Progressive Enhancement http://filamentgroup.com/dwpe/
- 6. Is this worth the effort? • Cross-browser compatibility • SEO compliance • Mobile device support • Support for assistive devices e.g. screenreaders • Low bandwidth environments • Maintainable structure • Testability
- 7. Fundamentals • JavaScript and CSS separated from markup • Script reads and enhances markup • Presentational markup injected by script
- 9. Don’t Break The Web!
- 10. Separation of markup & behaviour Markup: <a href="/foo” class="profile">Click me</a> <a href="/foo" onclick="return doSomething()"> Click me External script file: </a> $('a.profile').click(doSomething);
- 11. Read and enhance markup <a href="/foo" class="popup">Click me</a> $('a.popup').click(function() { displayInPopup('/foo'); displayInPopup($(this).attr('href')); return false; });
- 12. Form enhancements and dialogs EXAMPLE
- 13. The X-Ray Perspective 1. Map design components to basic HTML 2. Build markup with simple styles & no JS 3. Layer visual & interaction enhancements using JS & CSS
- 15. How can Grails help? request.xhr • different response for AJAX requests • render template / view • disable SiteMesh • forward rather than redirect withFormat • respond with different data types WebUtils.isIncludeRequest • tailor response for full page or content section
- 16. Varying output for AJAX def show = { def model = // … whatever if (request.xhr) { render template: "basket", model: model } else { return model } }
- 17. Disabling SiteMesh for AJAX <!doctype html> <html> <head> <g:if test="${!request.xhr}"> <meta name="layout" content="main"> </g:if>
- 18. Pagination -> infinite scroll EXAMPLE
- 19. Test-driven progressive enhancement Use browser capability detection to… • activate script-driven behaviour • activate 'polyfills' on less capable browsers • selectively load JavaScript and CSS files • apply advanced CSS rules to capable browsers
- 20. Modernizr <html class="js flexbox canvas canvastext webgl no-touch geolocation postmessage no-websqldatabase indexeddb hashchange .dialog { if (Modernizr.geolocation) { rgba history draganddrop no-websockets background-color: #ccc; hsla multiplebgs backgroundsize // use native geolocation borderimage borderradius boxshadow } } else { textshadow opacity no-cssanimations .rgba .dialog cssgradients no-cssreflections csscolumns { // activate JavaScript polyfill csstransforms no-csstransforms3d0, 0.3); background-color: rgba(0, 0, } csstransitions fontface video audio } localstorage sessionstorage webworkers applicationcache svg inlinesvg smil svgclippaths">
- 22. Yepnope.js yepnope({ test : Modernizr.geolocation, yep : 'normal.js', nope : ['polyfill.js', 'wrapper.js’] });
- 24. Mobile-first progressive enhancement body { background: url(low-res-image.png); } • Build for mobile devices first @media screen and (min-width: 480px) { • Layer up to desktop using media queries body { background: url(hi-res-image.png); • }Prevent large images & supplementary max-width: 1140px; content sections loading #main, #sidebar { float: left; } #main { width: 65%; } #sidebar { width: 35%; } }
- 25. What to avoid in Grails AJAX tags: • g:formRemote • g:remoteField • g:remoteFunction • g:remoteLink
- 26. Resources plugin & templates <r:use module="div-enhance-script"/> • Useful for highly modular apps • Script included at end of page • Can be used multiple times & script is only included once
- 27. Resources plugin & yepnope.js <r:script disposition="head"> yepnope({ test : Modernizr.geolocation, yep : "${r.resource(uri: 'normal.js')}", nope : [ "${r.resource(uri: 'polyfill.js')}", "${r.resource(uri: 'wrapper.js')}" ] }); </r:script>