Additive Behaviors (aka control patterns, delegate protocols, behavioral mixins, etc)

[cookiecrook]

There is a shared desire for additive behaviors, taking the form of multiple proposals.

1. Microsoft UIAutomation "control patterns" InvokePattern, etc. https://msdn.microsoft.com/en-us/library/ms752362(v=vs.110).aspx
2. Cocoa Protocol examples for view delegates
   • NSTableViewDataSource e.g. tableView:objectValueForTableColumn:row: https://developer.apple.com/library/mac/documentation/Cocoa/Reference/NSTableViewDelegate_Protocol/ https://developer.apple.com/library/mac/documentation/Cocoa/Conceptual/TableView/Introduction/Introduction.html#//apple_ref/doc/uid/10000026i
   • iOS UIAccessibilityAction Protocol: e.g. accessibilityIncrement on sliders https://developer.apple.com/library/prerelease/ios/documentation/UIKit/Reference/UIAccessibilityAction_Protocol/index.html#//apple_ref/occ/instm/NSObject/accessibilityIncrement
   • OS X NSAccessibility Protocols e.g. accessibilityPerformIncrement on sliders https://developer.apple.com/library/mac/documentation/AppKit/Reference/NSAccessibilitySlider_Protocol/index.html#//apple_ref/occ/intfm/NSAccessibilitySlider/accessibilityPerformIncrement
3. General JavaScript framework behavioral mix-ins
   • Ember http://emberjs.com/api/classes/Ember.Mixin.html
   • React https://facebook.github.io/react/docs/reusable-components.html#mixins
   • Angular https://www.google.com/search?q=Angular+mixins
4. Class-less JavaScript using apply() to inherit functionality from other objects
   • http://blog.berniesumption.com/software/inheritance-is-evil-and-must-be-destroyed/
   • http://www.crockford.com/javascript/inheritance.html

The biggest challenge here is that, despite mix-ins being common in JavaScript frameworks, there is no precedent for this in DOM or another web standard, so we want to be cautious that any proposal fits well within the Web Platform.

[robdodson]

Example accessibility specific mixin from Polymer / Web Components land https://elements.polymer-project.org/elements/iron-a11y-keys-behavior

[robdodson]

This may be covered by one of the above but I'd also throw in something like https://html.spec.whatwg.org/multipage/interaction.html#run-synthetic-click-activation-steps. Very handy that defining an onclick on button gets triggered by enter or space. I'd love to have this for custom elements.