React events: add onPressMove and pressRetentionOffset to Press

This implementation differs from equivalents in React Native in the following ways:

1. A move during a press will not cancel onLongPress.
2. A move to outside the retention target will cancel the press and not
reactivate when moved back within the retention target.

packages/react-events/README.md

@@ -4,7 +4,7 @@
 events API that is not available in open source builds.*
 
 Event components do not render a host node. They listen to native browser events
-dispatched  on the host node of their child and transform those events into
+dispatched on the host node of their child and transform those events into
 high-level events for applications.
 
 
@@ -176,7 +176,8 @@ Disables all `Press` events.
 
 ### onLongPress: (e: PressEvent) => void
 
-Called once the element has been pressed for the length of `delayLongPress`.
+Called once the element has been pressed for the length of `delayLongPress`. If
+the press point moves more than 10px `onLongPress` is cancelled.
 
 ### onLongPressChange: boolean => void
 
@@ -202,17 +203,23 @@ Called when the element changes press state (i.e., after `onPressStart` and
 
 ### onPressEnd: (e: PressEvent) => void
 
-Called once the element is no longer pressed. If the press starts again before
-the `delayPressEnd` threshold is exceeded then the delay is reset to prevent
-`onPressEnd` being called during a press.
+Called once the element is no longer pressed (because it was released, or moved
+beyond the hit bounds). If the press starts again before the `delayPressEnd`
+threshold is exceeded then the delay is reset to prevent `onPressEnd` being
+called during a press.
+
+### onPressMove: (e: PressEvent) => void
+
+Called when an active press moves within the hit bounds of the element. Never
+called for keyboard-initiated press events.
 
 ### onPressStart: (e: PressEvent) => void
 
 Called once the element is pressed down. If the press is released before the
 `delayPressStart` threshold is exceeded then the delay is cut short and
 `onPressStart` is called immediately.
 
-### pressRententionOffset: PressOffset
+### pressRetentionOffset: PressOffset
 
 Defines how far the pointer (while held down) may move outside the bounds of the
 element before it is deactivated. Once deactivated, the pointer (still held

packages/react-events/src/Press.js

@@ -21,8 +21,14 @@ type PressProps = {
   onPress: (e: PressEvent) => void,
   onPressChange: boolean => void,
   onPressEnd: (e: PressEvent) => void,
+  onPressMove: (e: PressEvent) => void,
   onPressStart: (e: PressEvent) => void,
-  pressRententionOffset: Object,
+  pressRetentionOffset: {
+    top: number,
+    right: number,
+    bottom: number,
+    left: number,
+  },
 };
 
 type PressState = {
@@ -32,15 +38,23 @@ type PressState = {
   isAnchorTouched: boolean,
   isLongPressed: boolean,
   isPressed: boolean,
+  isPressWithinResponderRegion: boolean,
   longPressTimeout: null | TimeoutID,
   pressTarget: null | Element | Document,
   pressEndTimeout: null | TimeoutID,
   pressStartTimeout: null | TimeoutID,
+  responderRegion: null | $ReadOnly<{|
+    bottom: number,
+    left: number,
+    right: number,
+    top: number,
+  |}>,
   shouldSkipMouseAfterTouch: boolean,
 };
 
 type PressEventType =
   | 'press'
+  | 'pressmove'
   | 'pressstart'
   | 'pressend'
   | 'presschange'
@@ -56,6 +70,12 @@ type PressEvent = {|
 const DEFAULT_PRESS_END_DELAY_MS = 0;
 const DEFAULT_PRESS_START_DELAY_MS = 0;
 const DEFAULT_LONG_PRESS_DELAY_MS = 500;
+const DEFAULT_PRESS_RETENTION_OFFSET = {
+  bottom: 20,
+  top: 20,
+  left: 20,
+  right: 20,
+};
 
 const targetEventTypes = [
   {name: 'click', passive: false},
@@ -67,13 +87,18 @@ const targetEventTypes = [
 const rootEventTypes = [
   {name: 'keyup', passive: false},
   {name: 'pointerup', passive: false},
+  'pointermove',
   'scroll',
 ];
 
 // If PointerEvents is not supported (e.g., Safari), also listen to touch and mouse events.
 if (typeof window !== 'undefined' && window.PointerEvent === undefined) {
-  targetEventTypes.push('touchstart', 'touchend', 'mousedown', 'touchcancel');
-  rootEventTypes.push({name: 'mouseup', passive: false});
+  targetEventTypes.push('touchstart', 'touchend', 'touchcancel', 'mousedown');
+  rootEventTypes.push(
+    {name: 'mouseup', passive: false},
+    'touchmove',
+    'mousemove',
+  );
 }
 
 function createPressEvent(
@@ -229,8 +254,11 @@ function dispatchPressEndEvents(
   if (!wasActivePressStart && state.pressStartTimeout !== null) {
     clearTimeout(state.pressStartTimeout);
     state.pressStartTimeout = null;
-    // if we haven't yet activated (due to delays), activate now
-    activate(context, props, state);
+    // don't activate if a press has moved beyond the responder region
+    if (state.isPressWithinResponderRegion) {
+      // if we haven't yet activated (due to delays), activate now
+      activate(context, props, state);
+    }
   }
 
   if (state.isActivePressed) {
@@ -264,6 +292,59 @@ function calculateDelayMS(delay: ?number, min = 0, fallback = 0) {
   return Math.max(min, maybeNumber != null ? maybeNumber : fallback);
 }
 
+// TODO: account for touch hit slop
+function calculateResponderRegion(target, props) {
+  const pressRetentionOffset = {
+    ...DEFAULT_PRESS_RETENTION_OFFSET,
+    ...props.pressRetentionOffset,
+  };
+
+  const clientRect = target.getBoundingClientRect();
+
+  let bottom = clientRect.bottom;
+  let left = clientRect.left;
+  let right = clientRect.right;
+  let top = clientRect.top;
+
+  if (pressRetentionOffset) {
+    if (pressRetentionOffset.bottom != null) {
+      bottom += pressRetentionOffset.bottom;
+    }
+    if (pressRetentionOffset.left != null) {
+      left -= pressRetentionOffset.left;
+    }
+    if (pressRetentionOffset.right != null) {
+      right += pressRetentionOffset.right;
+    }
+    if (pressRetentionOffset.top != null) {
+      top -= pressRetentionOffset.top;
+    }
+  }
+
+  return {
+    bottom,
+    top,
+    left,
+    right,
+  };
+}
+
+function isPressWithinResponderRegion(
+  nativeEvent: $PropertyType<ResponderEvent, 'nativeEvent'>,
+  state: PressState,
+): boolean {
+  const {responderRegion} = state;
+  const event = (nativeEvent: any);
+
+  return (
+    responderRegion != null &&
+    (event.pageX >= responderRegion.left &&
+      event.pageX <= responderRegion.right &&
+      event.pageY >= responderRegion.top &&
+      event.pageY <= responderRegion.bottom)
+  );
+}
+
 function unmountResponder(
   context: ResponderContext,
   props: PressProps,
@@ -285,10 +366,12 @@ const PressResponder = {
       isAnchorTouched: false,
       isLongPressed: false,
       isPressed: false,
+      isPressWithinResponderRegion: true,
       longPressTimeout: null,
       pressEndTimeout: null,
       pressStartTimeout: null,
       pressTarget: null,
+      responderRegion: null,
       shouldSkipMouseAfterTouch: false,
     };
   },
@@ -330,11 +413,46 @@ const PressResponder = {
             }
           }
           state.pressTarget = target;
+          state.isPressWithinResponderRegion = true;
           dispatchPressStartEvents(context, props, state);
           context.addRootEventTypes(target.ownerDocument, rootEventTypes);
         }
         break;
       }
+      case 'pointermove':
+      case 'mousemove':
+      case 'touchmove': {
+        if (state.isPressed) {
+          if (state.shouldSkipMouseAfterTouch) {
+            return;
+          }
+
+          if (state.responderRegion == null) {
+            let currentTarget = (target: any);
+            while (
+              currentTarget.parentNode &&
+              context.isTargetWithinEventComponent(currentTarget.parentNode)
+            ) {
+              currentTarget = currentTarget.parentNode;
+            }
+            state.responderRegion = calculateResponderRegion(
+              currentTarget,
+              props,
+            );
+          }
+
+          if (isPressWithinResponderRegion(nativeEvent, state)) {
+            state.isPressWithinResponderRegion = true;
+            if (props.onPressMove) {
+              dispatchEvent(context, state, 'pressmove', props.onPressMove);
+            }
+          } else {
+            state.isPressWithinResponderRegion = false;
+            dispatchPressEndEvents(context, props, state);
+          }
+        }
+        break;
+      }
       case 'pointerup':
       case 'mouseup': {
         if (state.isPressed) {
@@ -370,6 +488,7 @@ const PressResponder = {
           context.removeRootEventTypes(rootEventTypes);
         }
         state.isAnchorTouched = false;
+        state.shouldSkipMouseAfterTouch = false;
         break;
       }
 
@@ -386,6 +505,7 @@ const PressResponder = {
             return;
           }
           state.pressTarget = target;
+          state.isPressWithinResponderRegion = true;
           dispatchPressStartEvents(context, props, state);
           context.addRootEventTypes(target.ownerDocument, rootEventTypes);
         }