154 lines
4.2 KiB
JavaScript
154 lines
4.2 KiB
JavaScript
/**
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* Copyright (c) Meta Platforms, Inc. and affiliates.
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*
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* This source code is licensed under the MIT license found in the
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* LICENSE file in the root directory of this source tree.
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*
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* @format
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*/
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const TouchHistoryMath = {
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/**
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* This code is optimized and not intended to look beautiful. This allows
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* computing of touch centroids that have moved after `touchesChangedAfter`
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* timeStamp. You can compute the current centroid involving all touches
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* moves after `touchesChangedAfter`, or you can compute the previous
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* centroid of all touches that were moved after `touchesChangedAfter`.
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*
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* @param {TouchHistoryMath} touchHistory Standard Responder touch track
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* data.
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* @param {number} touchesChangedAfter timeStamp after which moved touches
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* are considered "actively moving" - not just "active".
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* @param {boolean} isXAxis Consider `x` dimension vs. `y` dimension.
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* @param {boolean} ofCurrent Compute current centroid for actively moving
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* touches vs. previous centroid of now actively moving touches.
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* @return {number} value of centroid in specified dimension.
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*/
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centroidDimension: function (
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touchHistory,
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touchesChangedAfter,
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isXAxis,
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ofCurrent,
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) {
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const touchBank = touchHistory.touchBank;
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let total = 0;
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let count = 0;
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const oneTouchData =
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touchHistory.numberActiveTouches === 1
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? touchHistory.touchBank[touchHistory.indexOfSingleActiveTouch]
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: null;
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if (oneTouchData !== null) {
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if (
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oneTouchData.touchActive &&
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oneTouchData.currentTimeStamp > touchesChangedAfter
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) {
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total +=
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ofCurrent && isXAxis
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? oneTouchData.currentPageX
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: ofCurrent && !isXAxis
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? oneTouchData.currentPageY
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: !ofCurrent && isXAxis
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? oneTouchData.previousPageX
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: oneTouchData.previousPageY;
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count = 1;
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}
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} else {
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for (let i = 0; i < touchBank.length; i++) {
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const touchTrack = touchBank[i];
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if (
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touchTrack !== null &&
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touchTrack !== undefined &&
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touchTrack.touchActive &&
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touchTrack.currentTimeStamp >= touchesChangedAfter
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) {
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let toAdd; // Yuck, program temporarily in invalid state.
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if (ofCurrent && isXAxis) {
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toAdd = touchTrack.currentPageX;
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} else if (ofCurrent && !isXAxis) {
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toAdd = touchTrack.currentPageY;
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} else if (!ofCurrent && isXAxis) {
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toAdd = touchTrack.previousPageX;
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} else {
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toAdd = touchTrack.previousPageY;
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}
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total += toAdd;
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count++;
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}
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}
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}
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return count > 0 ? total / count : TouchHistoryMath.noCentroid;
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},
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currentCentroidXOfTouchesChangedAfter: function (
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touchHistory,
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touchesChangedAfter,
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) {
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return TouchHistoryMath.centroidDimension(
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touchHistory,
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touchesChangedAfter,
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true, // isXAxis
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true, // ofCurrent
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);
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},
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currentCentroidYOfTouchesChangedAfter: function (
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touchHistory,
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touchesChangedAfter,
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) {
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return TouchHistoryMath.centroidDimension(
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touchHistory,
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touchesChangedAfter,
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false, // isXAxis
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true, // ofCurrent
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);
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},
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previousCentroidXOfTouchesChangedAfter: function (
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touchHistory,
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touchesChangedAfter,
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) {
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return TouchHistoryMath.centroidDimension(
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touchHistory,
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touchesChangedAfter,
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true, // isXAxis
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false, // ofCurrent
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);
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},
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previousCentroidYOfTouchesChangedAfter: function (
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touchHistory,
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touchesChangedAfter,
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) {
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return TouchHistoryMath.centroidDimension(
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touchHistory,
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touchesChangedAfter,
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false, // isXAxis
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false, // ofCurrent
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);
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},
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currentCentroidX: function (touchHistory) {
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return TouchHistoryMath.centroidDimension(
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touchHistory,
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0, // touchesChangedAfter
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true, // isXAxis
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true, // ofCurrent
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);
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},
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currentCentroidY: function (touchHistory) {
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return TouchHistoryMath.centroidDimension(
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touchHistory,
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0, // touchesChangedAfter
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false, // isXAxis
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true, // ofCurrent
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);
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},
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noCentroid: -1,
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};
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module.exports = TouchHistoryMath;
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