123 lines
3.9 KiB
JavaScript
123 lines
3.9 KiB
JavaScript
/**
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* @providesModule TouchHistoryMath
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*/
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"use strict";
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var 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(touchHistory, touchesChangedAfter, isXAxis, ofCurrent) {
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var touchBank = touchHistory.touchBank;
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var total = 0;
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var count = 0;
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var oneTouchData = touchHistory.numberActiveTouches === 1 ?
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touchHistory.touchBank[touchHistory.indexOfSingleActiveTouch] : null;
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if (oneTouchData !== null) {
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if (oneTouchData.touchActive && oneTouchData.currentTimeStamp > touchesChangedAfter) {
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total += ofCurrent && isXAxis ? oneTouchData.currentPageX :
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ofCurrent && !isXAxis ? oneTouchData.currentPageY :
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!ofCurrent && isXAxis ? 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 (var i = 0; i < touchBank.length; i++) {
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var touchTrack = touchBank[i];
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if (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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var 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(touchHistory, touchesChangedAfter) {
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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(touchHistory, touchesChangedAfter) {
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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(touchHistory, touchesChangedAfter) {
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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(touchHistory, touchesChangedAfter) {
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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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