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/*global Slider: false, rAF: false, quadLimit: false */
// -------------------------- demo -------------------------- //
var canvas, ctx;
var canvasW, canvasH;
var slider;
var cells = [];
var leftBound, rightBound;
var cellWidths = [ 0.2, 0.2, 0.4, 0.2, 0.3 ];
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 cellX = 0;
var gutter = 40;
for ( var i=0, len = cellWidths.length; i < len; i++ ) {
var cellWidth = cellWidths[i];
var cell = {
width: canvasW * cellWidth,
height: canvasH - 40,
x: cellX,
index: i
};
cellX += cell.width + gutter;
cells.push( cell );
}
leftBound = 100;
rightBound = canvasW - 100;
canvas.addEventListener( 'mousedown', onMousedown, false );
slider = new Slider( leftBound, 0 );
slider.width = cellX - gutter;
animate();
}
// -------------------------- animate -------------------------- //
function animate() {
if ( !isDragging ) {
applyLeftBoundForce();
applyRightBoundForce();
}
slider.update();
render();
rAF( animate );
}
function applyLeftBoundForce() {
var sliderX = slider.x;
var distance = leftBound - sliderX;
var force = distance * 0.05;
force = Math.min( force, 0 );
// prevent slider from bounds too far back
// don't apply force if slider is returning from outside bounds
if ( force && slider.velocity < 0 ) {
// resting position
var restPosition = slider.getRestingPosition();
if ( restPosition.x < leftBound ) {
force = ( leftBound - slider.x ) / restPosition.frictionSum - slider.velocity;
}
}
slider.applyForce( force );
}
function applyRightBoundForce() {
var sliderX = slider.x + slider.width;
var distance = rightBound - sliderX;
var force = distance * 0.05;
force = Math.max( force, 0 );
// prevent slider from bounds too far back
// don't apply force if slider is returning from outside bounds
if ( force && slider.velocity > 0 ) {
// resting position
var restPosition = slider.getRestingPosition();
if ( restPosition.x + slider.width > rightBound ) {
force = ( rightBound - sliderX ) / restPosition.frictionSum - slider.velocity;
}
}
slider.applyForce( force );
}
// -------------------------- render -------------------------- //
function render() {
ctx.clearRect( 0, 0, canvasW, canvasH );
// bounds
ctx.lineWidth = 1;
ctx.strokeStyle = 'hsla(300, 100%, 40%, 1)';
line( leftBound, 0, leftBound, canvasH );
line( rightBound, 0, rightBound, canvasH );
// cells
ctx.save();
ctx.translate( slider.x, 0 );
for ( var i=0, len = cells.length; i < len; i++ ) {
var cell = cells[i];
var hue = i * 70;
ctx.fillStyle = 'hsla(' + hue + ', 100%, 40%, 0.5)';
ctx.fillRect( cell.x, 20, cell.width, cell.height );
// target line
ctx.strokeStyle = 'yellow';
line( cell.target, 40, cell.target, cell.height );
}
ctx.restore();
}
function line( x1, y1, x2, y2 ) {
ctx.beginPath();
ctx.moveTo( x1, y1 );
ctx.lineTo( x2, y2 );
ctx.stroke();
ctx.closePath();
}
function circle( x, y, radius ) {
ctx.beginPath();
ctx.arc( x, y, radius, 0, Math.PI * 2 );
ctx.fill();
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;
var dragX = slider.dragStartX + moveX;
// limit dragging beyond left bound
dragX = quadLimit( dragX, leftBound, canvasW / 2, canvasW );
// limit dragging beyond right bound
var rightDragBound = rightBound - slider.width;
dragX = quadLimit( dragX, rightDragBound, rightDragBound - canvasW / 2, rightDragBound - canvasW );
slider.x = dragX;
currentTime = new Date();
}
function onMouseup( event ) {
dragEnd();
window.removeEventListener( 'mousemove', onMousemove, false );
window.removeEventListener( 'mousemove', onMouseup, false );
}
function dragEnd() {
if ( previousX ) {
// set slider velocity
slider.velocity = ( slider.x - previousX ) / ( currentTime - previousTime );
slider.velocity *= 1000 / 60;
// reset previousX
previousX = null;
}
isDragging = false;
}
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