FocusEngine Framer Module

The FocusEngine module allows you to simulate the grid focus behavior seen on streaming media players like Apple TV and Roku. Use the keyboard, RemoteLayer, or another mechanism to direct focus around your prototype’s canvas.

Once initialized, any visible layer can be brought into focus, even if it’s off screen. This permits the activation of off-screen menus. Visual appearance of focused elements can be customized.

Installation

NPM Installation

$ cd /your/framer/project
$ npm i @blackpixel/framer-focusengine

Manual installation

Copy or save the FocusEngine.coffee file into your project's modules folder.

Adding It to Your Project

In your Framer project add the following:

# If you manually installed
fe = require "FocusEngine"
# else
fe = require "@blackpixel/framer-focusengine"

API

Customize focused and unfocused states

fe.focusStyle.scale = <number>
fe.focusStyle.shadowX = <number>
fe.focusStyle.shadowY = <number>
fe.focusStyle.shadowColor = <string> (hex or rgba)
fe.focusStyle.shadowBlur = <number>
fe.focusStyle.shadowSpread = <number>

fe.unfocusStyle.shadowX = <number>
fe.unfocusStyle.shadowY = <number>
fe.unfocusStyle.shadowColor = <string> (hex or rgba)
fe.unfocusStyle.shadowBlur = <number>
fe.unfocusStyle.shadowSpread = <number>

(Unfocused scale is always assumed to be the layer’s original scale. This need not be 1. You may get better visual results by drawing your layer slightly larger than needed and setting its initial scale to something less than 1.)

Customize state switch duration

fe.time = <number>

Collect layers that will participate into an array

myFocusableLayers = [layerA, layerB, layerC]

Initialize the engine with your array

fe.initialize(myFocusableLayers)

Add a layer created post-initialization

fe.addLayer(layerD)

Optionally attach changeFocus() to keyboard events

document.addEventListener "keydown", (event) ->
	keyCode = event.which
	switch keyCode
		when 13 then fe.changeFocus("select")
		when 37 then fe.changeFocus("left")
		when 38 then fe.changeFocus("up")
		when 39 then fe.changeFocus("right")
		when 40 then fe.changeFocus("down")
		else null

Place initial focus

fe.placeFocus(layerA)

focusPrevious() is available to use in conjunction with FlowComponent's showPrevious()

fe.focusPrevious()

(Note that focus cannot be placed on a layer whose visibility, or whose ancestor’s visibility, is false. You may need to delay calling focusPrevious() until the FlowComponent’s transition is ended, perhaps by using .onTransitionEnd.)

Layers can trigger behavior upon receiving or losing focus, or being selected

layerA.on "focus", ->
layerA.on "unfocus", ->
layerA.on "selected", ->

Shortcuts are also available:

layerA.onFocus ->
layerA.onUnfocus ->
layerA.onSelected ->

Integration with RemoteLayer

RemoteLayer = require "RemoteLayer"
myRemote = new RemoteLayer
	clickAction: -> fe.changeFocus("select")
	swipeUpAction: -> fe.changeFocus("up")
	swipeDownAction: -> fe.changeFocus("down")
	swipeLeftAction: -> fe.changeFocus("left")
	swipeRightAction: -> fe.changeFocus("right")

Check the currently focused layer

print fe.focus

Check whether a layer has focus

print layerA.focus

Overriding focus logic

Sometimes you will want to change focus in a way that doesn't make exact geometric sense. For example, when switching from a large header row to a smaller secondary row, you may prefer the first cell in the secondary row receive focus. Or, you may want to provide a way for focus to "loop around" at a row's end. These kinds of functions are possible through overrides.

Set a layer's overrides using the overrides object:

layerA.overrides =
	up: <layer>
	down: <layer>
	left: <layer>
	right: <layer>

It is not necessary to set all four overrides; but only for those directions which require custom behavior. Now, shifting focus from layerA will always land on the direction-specified target -- no matter what FocusEngine thinks should happen.

Obviously, you can create very counterintuitive behaviors this way. Use with care!

If a layer has custom overrides, or has been initialized with FocusEngine, you may check any of its current overrides:

print layerA.overrides?.up

The ? permits the check to fail gracefully on layers which have no overrides.

Enable debug mode to log focus changes

fe.debug = true

Example project

Download the example to try it for yourself.

Known issues

Attempting to perform a placeFocus() call as FocusEngine is changing its own focus will fail. (The call is discarded.) If you need to override FocusEngine's logic, use the overrides feature or add a slight delay to ensure the call is respected.

layerA.on "unfocus", ->
	Utils.delay 0.1, ->
		fe.placeFocus(layerB)

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