Merge remote-tracking branch 'upstream/develop' into minimal-scopes-mode

* upstream/develop: (173 commits)
  Fix: Change condition
  fix typo
  update store according to retweeted status
  #433 - update sort by for conversation
  display replies_count right after reply icon
  expose replies_count from mastodon api
  Apparently, MastoAPI gives status in ancestors if you try opening a repeat...
  make side drawer use gesture service and fix its animations
  review/remove error hiding
  errata
  review
  #433 - sort conversation for retweets and clean up
  Revert "Merge branch 'revert-987b5162' into 'develop'"
  Revert "Merge branch 'mastoapi/friends-tl' into 'develop'"
  Add await to login action'
  Remove console log
  Fix warnings in user profile routing
  Add tests for gesture service, fix bug with perpendicular directions
  #255 - clean up autocomplete form
  #255 - clean up user settings page with self-closing html tags
  ...

1 files changed, 74 insertions, 0 deletions

diff --git a/src/services/gesture_service/gesture_service.js b/src/services/gesture_service/gesture_service.js
new file mode 100644
index 00000000..88a328f3
--- /dev/null
+++ b/src/services/gesture_service/gesture_service.js
@@ -0,0 +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 dotProduct = (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 scalar 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 = project(delta, gesture.direction)
+  const perpendicularDir = perpendicular(gesture.direction)
+  const towardsPerpendicular = project(delta, perpendicularDir)
+  if (
+    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