Update gestures.md to reflect current state of gesture recognition algorithm

gestures.md

@@ -1,51 +1,35 @@
-# Per-device
 ```mermaid
 sequenceDiagram
-    participant cg as ClientGestureLibrary
-    participant ci as Interactor
     participant cc as ClientController
     participant sc as ServerController
-    participant mh as MessageHandler
     participant sv as ServerView
-    participant svg as ServerViewGroup
-    participant item
-
-    cg ->> ci : recognize gesture
-    ci ->> cc : call handler received from controller
-    cc ->> sc : emit message with gesture data
-    sc ->> mh : handle the gesture
-    mh ->> sv : transform x,y from view coordinates to workspace coordinates
-    sv ->> mh : (x, y) point
-    mh ->> item : emit gesture event
-
-    note over sc, item: item is selected using the Track gesture,<br>first point down finds an item to lock, or the view
-```
-
-# Multi-device:
-```mermaid
-sequenceDiagram
-    participant cc as ClientController
-    participant sc as ServerController
     participant dv as Device
     participant gc as GestureController
-    participant sg as ServerGestureLibrary
     participant mh as MessageHandler
-    participant sv as ServerView
-    participant svg as ServerViewGroup
-    participant item
+    participant ws as WorkSpace
+    actor user
 
-    cc ->> sc : emit pointer event
-    sc ->> dv : transform x,y from view coordinates to device coordinates
-    dv ->> sc : (x, y) point
-    sc ->> gc : process pointer event
-    gc ->> sg : process pointer event
-    sg ->> mh : recognize gesture
-    mh ->> svg : transform x,y point from device coordinates to workspace coordinates
+    cc ->> sc : transmit pointer event with (clientX, clientY)
+    sc ->> sv : transform (clientX, clientY) to view coordinates
+    sv ->> sc : (viewX, viewY)
 
-    svg ->> mh : (x, y) point
-    mh ->> item : emit gesture event
+    alt if event is pointerdown and the view has no locked item
+        sc ->> ws : obtain item lock, possibly on the view group
+        ws ->> sv : set locked item
+    end
 
-    note over sc, item: item is selected using the Track gesture,<br>first point down finds an item to lock, or the view
-```
+    sc ->> user : emit pointer event with (viewX, viewY)
+    sc ->> dv : transform (clientX, clientY) to device coordinates
+    dv ->> sc : (deviceX, deviceY)
+    sc ->> gc : process pointer event
+    gc ->> mh : recognize gesture with (deviceCentroidX, deviceCentroidY)
+    mh ->> dv : transform (deviceCentroidX, deviceCentroidY) back to client coordinates
+    dv ->> mh : (clientCentroidX, clientCentroidY)
+    mh ->> sv : transform (clientCentroidX, clientCentroidY) to workspace coordinates
+    sv ->> mh : (viewCentroidX, viewCentroidY)
+    mh ->> user : emit gesture event with (viewCentroidX, viewCentroidY)
 
-This double transformation is actually correct. The device transformation moves the pointer event to where the device is located physically relative to other devices, that is: where in the server view group the event takes place. Further transforming from where in the view group the event takes place to where in the workspace it takes place is therefore logical. However, if we are to use this same process for single-device gestures we need to provide a unique ServerViewGroup for each ServerView when in single-device mode.
+    alt if event is pointerup and there are no inputs remaining in the device group
+        sc ->> sv : release locked item
+    end
+```