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16 KiB
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1 line
16 KiB
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{"ast":null,"code":"/**\n * Copyright (c) 2015, Facebook, Inc.\n * All rights reserved.\n *\n * This source code is licensed under the BSD-style license found in the\n * LICENSE file in the root directory of this source tree. An additional grant\n * of patent rights can be found in the PATENTS file in the same directory.\n *\n * @providesModule normalizeWheel\n * @typechecks\n */\n'use strict';\n\nvar UserAgent_DEPRECATED = require('./UserAgent_DEPRECATED');\n\nvar isEventSupported = require('./isEventSupported'); // Reasonable defaults\n\n\nvar PIXEL_STEP = 10;\nvar LINE_HEIGHT = 40;\nvar PAGE_HEIGHT = 800;\n/**\n * Mouse wheel (and 2-finger trackpad) support on the web sucks. It is\n * complicated, thus this doc is long and (hopefully) detailed enough to answer\n * your questions.\n *\n * If you need to react to the mouse wheel in a predictable way, this code is\n * like your bestest friend. * hugs *\n *\n * As of today, there are 4 DOM event types you can listen to:\n *\n * 'wheel' -- Chrome(31+), FF(17+), IE(9+)\n * 'mousewheel' -- Chrome, IE(6+), Opera, Safari\n * 'MozMousePixelScroll' -- FF(3.5 only!) (2010-2013) -- don't bother!\n * 'DOMMouseScroll' -- FF(0.9.7+) since 2003\n *\n * So what to do? The is the best:\n *\n * normalizeWheel.getEventType();\n *\n * In your event callback, use this code to get sane interpretation of the\n * deltas. This code will return an object with properties:\n *\n * spinX -- normalized spin speed (use for zoom) - x plane\n * spinY -- \" - y plane\n * pixelX -- normalized distance (to pixels) - x plane\n * pixelY -- \" - y plane\n *\n * Wheel values are provided by the browser assuming you are using the wheel to\n * scroll a web page by a number of lines or pixels (or pages). Values can vary\n * significantly on different platforms and browsers, forgetting that you can\n * scroll at different speeds. Some devices (like trackpads) emit more events\n * at smaller increments with fine granularity, and some emit massive jumps with\n * linear speed or acceleration.\n *\n * This code does its best to normalize the deltas for you:\n *\n * - spin is trying to normalize how far the wheel was spun (or trackpad\n * dragged). This is super useful for zoom support where you want to\n * throw away the chunky scroll steps on the PC and make those equal to\n * the slow and smooth tiny steps on the Mac. Key data: This code tries to\n * resolve a single slow step on a wheel to 1.\n *\n * - pixel is normalizing the desired scroll delta in pixel units. You'll\n * get the crazy differences between browsers, but at least it'll be in\n * pixels!\n *\n * - positive value indicates scrolling DOWN/RIGHT, negative UP/LEFT. This\n * should translate to positive value zooming IN, negative zooming OUT.\n * This matches the newer 'wheel' event.\n *\n * Why are there spinX, spinY (or pixels)?\n *\n * - spinX is a 2-finger side drag on the trackpad, and a shift + wheel turn\n * with a mouse. It results in side-scrolling in the browser by default.\n *\n * - spinY is what you expect -- it's the classic axis of a mouse wheel.\n *\n * - I dropped spinZ/pixelZ. It is supported by the DOM 3 'wheel' event and\n * probably is by browsers in conjunction with fancy 3D controllers .. but\n * you know.\n *\n * Implementation info:\n *\n * Examples of 'wheel' event if you scroll slowly (down) by one step with an\n * average mouse:\n *\n * OS X + Chrome (mouse) - 4 pixel delta (wheelDelta -120)\n * OS X + Safari (mouse) - N/A pixel delta (wheelDelta -12)\n * OS X + Firefox (mouse) - 0.1 line delta (wheelDelta N/A)\n * Win8 + Chrome (mouse) - 100 pixel delta (wheelDelta -120)\n * Win8 + Firefox (mouse) - 3 line delta (wheelDelta -120)\n *\n * On the trackpad:\n *\n * OS X + Chrome (trackpad) - 2 pixel delta (wheelDelta -6)\n * OS X + Firefox (trackpad) - 1 pixel delta (wheelDelta N/A)\n *\n * On other/older browsers.. it's more
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