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/*global Cell: false, Slider: false, rAF: false */
// -------------------------- demo -------------------------- //
var canvas, ctx;
var canvasW, canvasH;
var slider;
var cells = [];
var estimateX = 0;
var selectedIndex = 0;
var activeAttractor;
var activeAttractorIndex = 1;
document.addEventListener( 'DOMContentLoaded', init, false );
function init() {
canvas = document.querySelector('canvas');
ctx = canvas.getContext('2d');
// set size
canvasW = canvas.width = window.innerWidth - 20;
canvasH = canvas.height = 300;
// create cells
var cellWidth = canvasW / 3;
for ( var i=0; i < 5; i++ ) {
var cell = new Cell({
width: cellWidth,
height: canvasH - 40,
x: ( cellWidth + 40 ) * i,
index: i
});
cells.push( cell );
}
canvas.addEventListener( 'mousedown', onMousedown, false );
slider = new Slider();
animate();
}
// -------------------------- animate -------------------------- //
function animate() {
if ( !isDragging ) {
slider.applyForce( getAttraction() );
}
slider.update();
render();
rAF( animate );
}
function getAttraction() {
var cell = cells[ selectedIndex ];
var attractorX = cell.x + cell.width / 2;
var distance = -attractorX - slider.x;
var force = distance * 0.03;
return force;
}
// -------------------------- render -------------------------- //
function render() {
ctx.clearRect( 0, 0, canvasW, canvasH );
// cursor
var cursorX = canvasW / 2;
ctx.lineWidth = 1;
ctx.strokeStyle = 'hsla(300, 100%, 40%, 1)';
ctx.beginPath();
ctx.moveTo( cursorX, 0 );
ctx.lineTo( cursorX , canvasH );
ctx.stroke();
ctx.closePath();
// cells
ctx.save();
ctx.translate( slider.x + cursorX, 0 );
for ( var i=0, len = cells.length; i < len; i++ ) {
var cell = cells[i];
ctx.fillStyle = 'hsla(0, 100%, 50%, 0.5)';
ctx.fillRect( cell.x, 20, cell.width, cell.height );
// target line
var cellTargetX = cell.x + cell.width / 2;
ctx.strokeStyle = 'yellow';
line( cellTargetX, 40, cellTargetX, cell.height );
}
ctx.restore();
}
function line( x1, y1, x2, y2 ) {
ctx.beginPath();
ctx.moveTo( x1, y1 );
ctx.lineTo( x2, y2 );
ctx.stroke();
ctx.closePath();
}
// -------------------------- mouse -------------------------- //
var isDragging = false;
var dragStartX;
function onMousedown( event ) {
event.preventDefault();
isDragging = true;
window.addEventListener( 'mousemove', onMousemove, false );
window.addEventListener( 'mouseup', onMouseup, false );
dragStartX = event.pageX;
slider.dragStartX = slider.x;
slider.velocity = 0;
}
var previousX;
var previousTime;
var currentTime;
function onMousemove( event ) {
// previous
previousX = slider.x;
previousTime = currentTime;
// current
var moveX = event.pageX - dragStartX;
slider.x = slider.dragStartX + moveX;
currentTime = new Date();
}
function onMouseup( event ) {
dragEnd();
// console.log( particle.velocity );
window.removeEventListener( 'mousemove', onMousemove, false );
window.removeEventListener( 'mousemove', onMouseup, false );
}
function dragEnd() {
if ( previousX ) {
// set particle velocity
slider.velocity = ( slider.x - previousX ) / ( currentTime - previousTime );
slider.velocity *= 1000 / 60;
estimateX = slider.getRestingPosition();
// reset previousX
previousX = null;
} else {
estimateX = slider.x;
}
// remember this for checking later
var prevIndex = selectedIndex;
// get closest attractor to end position
var minDistance = Infinity;
var targetX, distance;
for ( var i=0, len = cells.length; i < len; i++ ) {
var cell = cells[i];
targetX = cell.x + cell.width / 2;
distance = Math.abs( -estimateX - targetX );
if ( distance < minDistance ) {
selectedIndex = i;
minDistance = distance;
}
}
// if not enough velocity to escape current attractor
// boost it
if ( selectedIndex === prevIndex ) {
var selectedCell = cells[ selectedIndex ];
targetX = selectedCell.x + selectedCell.width / 2;
distance = -slider.x - targetX;
// console.log( ~~distance, ~~slider.velocity );
if ( distance > 0 && slider.velocity < -1 && cells[ selectedIndex + 1 ] ) {
// if moving towards the right, and positive velocity, and the next attractor
selectedIndex++;
} else if ( distance < 0 && slider.velocity > 1 && cells[ selectedIndex - 1 ] ) {
// if moving towards the left, and negative velocity, and previous attractor
selectedIndex--;
}
}
isDragging = false;
}
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