Created
December 12, 2011 18:06
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Add easing functions to jQuery based on the CSS spec for transition timing functions.
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// jQuery.addEasing(string) | |
// | |
// Interprets and adds easing functions to jQuery.easing | |
// according to the CSS spec for transition timing functions. | |
// | |
// e.g. | |
// jQuery.addEasing('cubic-bezier(0.4, 0.2, 0.66, 1)'); | |
(function(jQuery, undefined){ | |
// Timing function definitions from the CSS specification | |
var easing = { | |
'linear': [0, 0, 1, 1], | |
'ease': [0.25, 0.1, 0.25, 1], | |
'ease-in': [0.42, 0, 1, 1], | |
'ease-out': [0, 0, 0.58, 1], | |
'ease-in-out': [0.42, 0, 0.58, 1] | |
}; | |
// Cubic bezier function purloined from | |
// blogs.msdn.com/b/eternalcoding/archive/2011/12/06/css3-transitions.aspx | |
function makeBezier(x1, y1, x2, y2) { | |
return function (t) { | |
// Extract X (which is equal to time here) | |
var f0 = 1 - 3 * x2 + 3 * x1, | |
f1 = 3 * x2 - 6 * x1, | |
f2 = 3 * x1, | |
refinedT = t, | |
i, refinedT2, refinedT3, x, slope; | |
for (i = 0; i < 5; i++) { | |
refinedT2 = refinedT * refinedT; | |
refinedT3 = refinedT2 * refinedT; | |
x = f0 * refinedT3 + f1 * refinedT2 + f2 * refinedT; | |
slope = 1.0 / (3.0 * f0 * refinedT2 + 2.0 * f1 * refinedT + f2); | |
refinedT -= (x - t) * slope; | |
refinedT = Math.min(1, Math.max(0, refinedT)); | |
} | |
return 3 * Math.pow(1 - refinedT, 2) * refinedT * y1 + | |
3 * (1 - refinedT) * Math.pow(refinedT, 2) * y2 + | |
Math.pow(refinedT, 3); | |
}; | |
} | |
function addEasing(str) { | |
var fn = jQuery.easing[str], | |
name, coords, l; | |
// Return the cached function if it exists. | |
if (fn) { return fn; } | |
// Get the standard easing function if it's defined. | |
if (easing[str]) { | |
name = str; | |
coords = easing[str]; | |
str = 'cubic-bezier(' + coords.join(', ') + ')'; | |
} | |
// Else assume this is a cubic-bezier. It must be. | |
else { | |
coords = str.match(/\d*\.?\d+/g); | |
l = coords.length; // Should be 4 | |
while (l--) { | |
coords[l] = parseFloat(coords[l]); | |
} | |
} | |
fn = makeBezier.apply(this, coords); | |
jQuery.easing[str] = fn; | |
if (name) { jQuery.easing[name] = fn }; | |
return fn; | |
} | |
jQuery.addEasing = addEasing; | |
})(jQuery); |
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