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<link rel=“import” href=“../app-scroll-effects-behavior.html”>
<script>
/** * While scrolling down, fade in the rear background layer and fade out the front background * layer (opacity interpolated based on scroll position). */ Polymer.AppLayout.registerEffect('blend-background', { /** @this Polymer.AppLayout.ElementWithBackground */ setUp: function setUp() { var fx = {}; fx.backgroundFrontLayer = this._getDOMRef('backgroundFrontLayer'); fx.backgroundRearLayer = this._getDOMRef('backgroundRearLayer'); fx.backgroundFrontLayer.style.willChange = 'opacity'; fx.backgroundFrontLayer.style.transform = 'translateZ(0)'; fx.backgroundRearLayer.style.willChange = 'opacity'; fx.backgroundRearLayer.style.transform = 'translateZ(0)'; fx.backgroundRearLayer.style.opacity = 0; this._fxBlendBackground = fx; }, /** @this Polymer.AppLayout.ElementWithBackground */ run: function run(p, y) { var fx = this._fxBlendBackground; fx.backgroundFrontLayer.style.opacity = 1 - p; fx.backgroundRearLayer.style.opacity = p; }, /** @this Polymer.AppLayout.ElementWithBackground */ tearDown: function tearDown() { delete this._fxBlendBackground; } });
</script>