Bundled react-native-scroller and react-native-gesture-responder

Author: msageryd

src/Gallery.js

@@ -1,7 +1,7 @@
 import React, { PureComponent } from 'react';
 import { View, ViewPropTypes } from 'react-native';
 import PropTypes from 'prop-types';
-import { createResponder } from 'react-native-gesture-responder';
+import { createResponder } from './libraries/GestureResponder';
 import TransformableImage from './libraries/TransformableImage';
 import ViewPager from './libraries/ViewPager';
 

src/libraries/GestureResponder/TouchDistanceMath.js

@@ -0,0 +1,40 @@
+'use strict';
+
+export function distance(touchTrackA, touchTrackB, ofCurrent) {
+  let xa, ya, xb, yb;
+  if(ofCurrent) {
+    xa = touchTrackA.currentPageX;
+    ya = touchTrackA.currentPageY;
+    xb = touchTrackB.currentPageX;
+    yb = touchTrackB.currentPageY;
+  } else {
+    xa = touchTrackA.previousPageX;
+    ya = touchTrackA.previousPageY;
+    xb = touchTrackB.previousPageX;
+    yb = touchTrackB.previousPageY;
+  }
+  return Math.sqrt(Math.pow(xa - xb, 2) + Math.pow(ya - yb, 2));
+}
+
+export function maxDistance(touchBank, ofCurrent) {
+  let max = 0;
+  for(let i = 0; i < touchBank.length - 1; i++) {
+    for(let j = i+1; j < touchBank.length; j++) {
+      let d = distance(touchBank[i], touchBank[j], ofCurrent);
+      if(d > max) {
+        max = d;
+      }
+    }
+  }
+  return max;
+}
+
+export function pinchDistance(touchHistory, touchesChangedAfter, ofCurrent) {
+  let touchBank = touchHistory.touchBank;
+  if(touchHistory.numberActiveTouches > 1) {
+    let filteredTouchBank = touchBank.filter((touchTrack) => {
+      return touchTrack && touchTrack.currentTimeStamp >= touchesChangedAfter;
+    });
+    return maxDistance(filteredTouchBank, ofCurrent);
+  }
+}

src/libraries/GestureResponder/TouchHistoryMath.js

@@ -0,0 +1,99 @@
+/**
+ * @providesModule TouchHistoryMath
+ */
+
+'use strict';
+
+var TouchHistoryMath = {
+  /**
+   * This code is optimized and not intended to look beautiful. This allows
+   * computing of touch centroids that have moved after `touchesChangedAfter`
+   * timeStamp. You can compute the current centroid involving all touches
+   * moves after `touchesChangedAfter`, or you can compute the previous
+   * centroid of all touches that were moved after `touchesChangedAfter`.
+   *
+   * @param {TouchHistoryMath} touchHistory Standard Responder touch track
+   * data.
+   * @param {number} touchesChangedAfter timeStamp after which moved touches
+   * are considered "actively moving" - not just "active".
+   * @param {boolean} isXAxis Consider `x` dimension vs. `y` dimension.
+   * @param {boolean} ofCurrent Compute current centroid for actively moving
+   * touches vs. previous centroid of now actively moving touches.
+   * @return {number} value of centroid in specified dimension.
+   */
+  centroidDimension: function (touchHistory, touchesChangedAfter, isXAxis, ofCurrent) {
+    var touchBank = touchHistory.touchBank;
+    var total = 0;
+    var count = 0;
+
+    var oneTouchData = touchHistory.numberActiveTouches === 1 ? touchHistory.touchBank[touchHistory.indexOfSingleActiveTouch] : null;
+
+    if (oneTouchData !== null) {
+      if (oneTouchData.touchActive && oneTouchData.currentTimeStamp > touchesChangedAfter) {
+        total += ofCurrent && isXAxis ? oneTouchData.currentPageX : ofCurrent && !isXAxis ? oneTouchData.currentPageY : !ofCurrent && isXAxis ? oneTouchData.previousPageX : oneTouchData.previousPageY;
+        count = 1;
+      }
+    } else {
+      for (var i = 0; i < touchBank.length; i++) {
+        var touchTrack = touchBank[i];
+        if (touchTrack !== null && touchTrack !== undefined && touchTrack.touchActive && touchTrack.currentTimeStamp >= touchesChangedAfter) {
+          var toAdd; // Yuck, program temporarily in invalid state.
+          if (ofCurrent && isXAxis) {
+            toAdd = touchTrack.currentPageX;
+          } else if (ofCurrent && !isXAxis) {
+            toAdd = touchTrack.currentPageY;
+          } else if (!ofCurrent && isXAxis) {
+            toAdd = touchTrack.previousPageX;
+          } else {
+            toAdd = touchTrack.previousPageY;
+          }
+          total += toAdd;
+          count++;
+        }
+      }
+    }
+    return count > 0 ? total / count : TouchHistoryMath.noCentroid;
+  },
+
+  currentCentroidXOfTouchesChangedAfter: function (touchHistory, touchesChangedAfter) {
+    return TouchHistoryMath.centroidDimension(touchHistory, touchesChangedAfter, true, // isXAxis
+    true // ofCurrent
+    );
+  },
+
+  currentCentroidYOfTouchesChangedAfter: function (touchHistory, touchesChangedAfter) {
+    return TouchHistoryMath.centroidDimension(touchHistory, touchesChangedAfter, false, // isXAxis
+    true // ofCurrent
+    );
+  },
+
+  previousCentroidXOfTouchesChangedAfter: function (touchHistory, touchesChangedAfter) {
+    return TouchHistoryMath.centroidDimension(touchHistory, touchesChangedAfter, true, // isXAxis
+    false // ofCurrent
+    );
+  },
+
+  previousCentroidYOfTouchesChangedAfter: function (touchHistory, touchesChangedAfter) {
+    return TouchHistoryMath.centroidDimension(touchHistory, touchesChangedAfter, false, // isXAxis
+    false // ofCurrent
+    );
+  },
+
+  currentCentroidX: function (touchHistory) {
+    return TouchHistoryMath.centroidDimension(touchHistory, 0, // touchesChangedAfter
+    true, // isXAxis
+    true // ofCurrent
+    );
+  },
+
+  currentCentroidY: function (touchHistory) {
+    return TouchHistoryMath.centroidDimension(touchHistory, 0, // touchesChangedAfter
+    false, // isXAxis
+    true // ofCurrent
+    );
+  },
+
+  noCentroid: -1
+};
+
+module.exports = TouchHistoryMath;