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diff --git a/src/services/gesture_service/gesture_service.js b/src/services/gesture_service/gesture_service.js
index 2e39003c8c..efc0ca78f7 100644
--- a/src/services/gesture_service/gesture_service.js
+++ b/src/services/gesture_service/gesture_service.js
@@ -1,71 +1,74 @@
const DIRECTION_LEFT = [-1, 0]
const DIRECTION_RIGHT = [1, 0]
const DIRECTION_UP = [0, -1]
const DIRECTION_DOWN = [0, 1]
const deltaCoord = (oldCoord, newCoord) => [newCoord[0] - oldCoord[0], newCoord[1] - oldCoord[1]]
const touchEventCoord = e => ([e.touches[0].screenX, e.touches[0].screenY])
const vectorLength = v => Math.sqrt(v[0] * v[0] + v[1] * v[1])
-const perpendicular = v => [v[1], v[0]]
+const perpendicular = v => [v[1], -v[0]]
const dotProduct = (v1, v2) => v1[0] * v2[0] + v1[1] * v2[1]
-const vectorFlatten = (v1, v2) => [v1[0] * v2[0], v1[1] * v2[1]]
+const project = (v1, v2) => {
+ const scalar = (dotProduct(v1, v2) / dotProduct(v2, v2))
+ return [scalar * v2[0], scalar * v2[1]]
+}
// direction: either use the constants above or an arbitrary 2d vector.
// threshold: how many Px to move from touch origin before checking if the
// callback should be called.
// divergentTolerance: a scalr for much of divergent direction we tolerate when
// above threshold. for example, with 1.0 we only call the callback if
// divergent component of delta is < 1.0 * direction component of delta.
const swipeGesture = (direction, onSwipe, threshold = 30, perpendicularTolerance = 1.0) => {
return {
direction,
onSwipe,
threshold,
perpendicularTolerance,
_startPos: [0, 0],
_swiping: false
}
}
const beginSwipe = (event, gesture) => {
gesture._startPos = touchEventCoord(event)
gesture._swiping = true
}
const updateSwipe = (event, gesture) => {
if (!gesture._swiping) return
// movement too small
const delta = deltaCoord(gesture._startPos, touchEventCoord(event))
if (vectorLength(delta) < gesture.threshold) return
// movement is opposite from direction
if (dotProduct(delta, gesture.direction) < 0) return
// movement perpendicular to direction is too much
- const towardsDir = vectorFlatten(gesture.direction, delta)
+ const towardsDir = project(delta, gesture.direction)
const perpendicularDir = perpendicular(gesture.direction)
- const towardsPerpendicular = vectorFlatten(perpendicularDir, delta)
+ const towardsPerpendicular = project(delta, perpendicularDir)
if (
- vectorLength(towardsDir) <
- gesture.perpendicularTolerance * vectorLength(towardsPerpendicular)
+ vectorLength(towardsDir) * gesture.perpendicularTolerance <
+ vectorLength(towardsPerpendicular)
) return
gesture.onSwipe()
gesture._swiping = false
}
const GestureService = {
DIRECTION_LEFT,
DIRECTION_RIGHT,
DIRECTION_UP,
DIRECTION_DOWN,
swipeGesture,
beginSwipe,
updateSwipe
}
export default GestureService
diff --git a/test/unit/specs/services/gesture_service/gesture_service.spec.js b/test/unit/specs/services/gesture_service/gesture_service.spec.js
new file mode 100644
index 0000000000..4a1b009a25
--- /dev/null
+++ b/test/unit/specs/services/gesture_service/gesture_service.spec.js
@@ -0,0 +1,120 @@
+import GestureService from 'src/services/gesture_service/gesture_service.js'
+
+const mockTouchEvent = (x, y) => ({
+ touches: [
+ {
+ screenX: x,
+ screenY: y
+ }
+ ]
+})
+
+describe.only('GestureService', () => {
+ describe('swipeGesture', () => {
+ it('calls the callback on a successful swipe', () => {
+ let swiped = false
+ const callback = () => { swiped = true }
+ const gesture = GestureService.swipeGesture(
+ GestureService.DIRECTION_RIGHT,
+ callback
+ )
+
+ GestureService.beginSwipe(mockTouchEvent(100, 100), gesture)
+ GestureService.updateSwipe(mockTouchEvent(200, 100), gesture)
+
+ expect(swiped).to.eql(true)
+ })
+
+ it('calls the callback only once per begin', () => {
+ let hits = 0
+ const callback = () => { hits += 1 }
+ const gesture = GestureService.swipeGesture(
+ GestureService.DIRECTION_RIGHT,
+ callback
+ )
+
+ GestureService.beginSwipe(mockTouchEvent(100, 100), gesture)
+ GestureService.updateSwipe(mockTouchEvent(150, 100), gesture)
+ GestureService.updateSwipe(mockTouchEvent(200, 100), gesture)
+
+ expect(hits).to.eql(1)
+ })
+
+ it('doesn\'t call the callback on an opposite swipe', () => {
+ let swiped = false
+ const callback = () => { swiped = true }
+ const gesture = GestureService.swipeGesture(
+ GestureService.DIRECTION_RIGHT,
+ callback
+ )
+
+ GestureService.beginSwipe(mockTouchEvent(100, 100), gesture)
+ GestureService.updateSwipe(mockTouchEvent(0, 100), gesture)
+
+ expect(swiped).to.eql(false)
+ })
+
+ it('doesn\'t call the callback on a swipe below threshold', () => {
+ let swiped = false
+ const callback = () => { swiped = true }
+ const gesture = GestureService.swipeGesture(
+ GestureService.DIRECTION_RIGHT,
+ callback,
+ 100
+ )
+
+ GestureService.beginSwipe(mockTouchEvent(100, 100), gesture)
+ GestureService.updateSwipe(mockTouchEvent(150, 100), gesture)
+
+ expect(swiped).to.eql(false)
+ })
+
+ it('doesn\'t call the callback on a perpendicular swipe', () => {
+ let swiped = false
+ const callback = () => { swiped = true }
+ const gesture = GestureService.swipeGesture(
+ GestureService.DIRECTION_RIGHT,
+ callback,
+ 30,
+ 0.5
+ )
+
+ GestureService.beginSwipe(mockTouchEvent(100, 100), gesture)
+ GestureService.updateSwipe(mockTouchEvent(150, 200), gesture)
+
+ expect(swiped).to.eql(false)
+ })
+
+ it('calls the callback on perpendicular swipe if within tolerance', () => {
+ let swiped = false
+ const callback = () => { swiped = true }
+ const gesture = GestureService.swipeGesture(
+ GestureService.DIRECTION_RIGHT,
+ callback,
+ 30,
+ 2.0
+ )
+
+ GestureService.beginSwipe(mockTouchEvent(100, 100), gesture)
+ GestureService.updateSwipe(mockTouchEvent(150, 150), gesture)
+
+ expect(swiped).to.eql(true)
+ })
+
+ it('works with any arbitrary 2d directions', () => {
+ let swiped = false
+ const callback = () => { swiped = true }
+ const gesture = GestureService.swipeGesture(
+ [-1, -1],
+ callback,
+ 30,
+ 0.1
+ )
+
+ GestureService.beginSwipe(mockTouchEvent(100, 100), gesture)
+ GestureService.updateSwipe(mockTouchEvent(60, 60), gesture)
+
+ expect(swiped).to.eql(true)
+ })
+ })
+})

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