React events: add delay props to Press module (#15340)

* Add delay props to Press event module
* Minor naming changes to Hover events
* Add examples to react-events README

packages/react-events/README.md

@@ -3,14 +3,31 @@
 *This package is experimental. It is intended for use with the experimental React
 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
+high-level events for applications.
+
 
 ## Focus
 
 The `Focus` module responds to focus and blur events on the element it wraps.
 Focus events are dispatched for `mouse`, `pen`, `touch`, and `keyboard`
 pointer types.
 
+```js
+// Example
+const TextField = (props) => (
+  <Focus
+    onBlur={props.onBlur}
+    onFocus={props.onFocus}
+  >
+    <textarea></textarea>
+  </Focus>
+);
 ```
+
+```js
+// Types
 type FocusEvent = {}
 ```
 
@@ -38,69 +55,124 @@ The `Hover` module responds to hover events on the element it wraps. Hover
 events are only dispatched for `mouse` pointer types. Hover begins when the
 pointer enters the element's bounds and ends when the pointer leaves.
 
+```js
+// Example
+const Link = (props) => (
+  const [ hovered, setHovered ] = useState(false);
+  return (
+    <Hover onHoverChange={setHovered}>
+      <a
+        {...props}
+        href={props.href}
+        style={{
+          ...props.style,
+          textDecoration: hovered ? 'underline': 'none'
+        }}
+      />
+    </Hover>
+  );
+);
 ```
+
+```js
+// Types
 type HoverEvent = {}
 ```
 
-### disabled: boolean
+### delayHoverEnd: number
 
-Disables all `Hover` events.
+The duration of the delay between when hover ends and when `onHoverEnd` is
+called.
 
-### onHoverStart: (e: HoverEvent) => void
+### delayHoverStart: number
 
-Called once the element is hovered. It will not be called if the pointer leaves
-the element before the `delayHoverStart` threshold is exceeded. And it will not
-be called more than once before `onHoverEnd` is called.
+The duration of the delay between when hover starts and when `onHoverStart` is
+called.
 
-### onHoverEnd: (e: HoverEvent) => void
+### disabled: boolean
 
-Called once the element is no longer hovered. It will be cancelled if the
-pointer leaves the element before the `delayHoverStart` threshold is exceeded.
+Disables all `Hover` events.
 
 ### onHoverChange: boolean => void
 
 Called when the element changes hover state (i.e., after `onHoverStart` and
 `onHoverEnd`).
 
-### delayHoverStart: number
+### onHoverEnd: (e: HoverEvent) => void
 
-The duration of the delay between when hover starts and when `onHoverStart` is
-called.
+Called once the element is no longer hovered. It will be cancelled if the
+pointer leaves the element before the `delayHoverStart` threshold is exceeded.
 
-### delayHoverEnd: number
+### onHoverStart: (e: HoverEvent) => void
 
-The duration of the delay between when hover ends and when `onHoverEnd` is
-called.
+Called once the element is hovered. It will not be called if the pointer leaves
+the element before the `delayHoverStart` threshold is exceeded. And it will not
+be called more than once before `onHoverEnd` is called.
 
 
 ## Press
 
 The `Press` module responds to press events on the element it wraps. Press
 events are dispatched for `mouse`, `pen`, `touch`, and `keyboard` pointer types.
-
+Press events are only dispatched for keyboards when pressing the Enter or
+Spacebar keys. If neither `onPress` nor `onLongPress` are called, this signifies
+that the press ended outside of the element hit bounds (i.e., the user aborted
+the press).
+
+```js
+// Example
+const Button = (props) => (
+  const [ pressed, setPressed ] = useState(false);
+  return (
+    <Press
+      onPress={props.onPress}
+      onPressChange={setPressed}
+      onLongPress={props.onLongPress}
+    >
+      <div
+        {...props}
+        role="button"
+        tabIndex={0}
+        style={
+          ...buttonStyles,
+          ...(pressed && pressedStyles)
+        }}
+      />
+    </Press>
+  );
+);
 ```
+
+```js
+// Types
 type PressEvent = {}
+
+type PressOffset = {
+  top: number,
+  right: number,
+  bottom: number,
+  right: number
+};
 ```
 
-### disabled: boolean
+### delayLongPress: number = 500ms
 
-Disables all `Press` events.
+The duration of a press before `onLongPress` and `onLongPressChange` are called.
 
-### onPressStart: (e: PressEvent) => void
+### delayPressEnd: number
 
-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.
+The duration of the delay between when the press ends and when `onPressEnd` is
+called.
 
-### onPressEnd: (e: PressEvent) => void
+### delayPressStart: number
 
-Called once the element is no longer pressed. It will be cancelled if the press
-starts again before the `delayPressEnd` threshold is exceeded.
+The duration of a delay between when the press starts and when `onPressStart` is
+called. This delay is cut short (and `onPressStart` is called) if the press is
+released before the threshold is exceeded.
 
-### onPressChange: boolean => void
+### disabled: boolean
 
-Called when the element changes press state (i.e., after `onPressStart` and
-`onPressEnd`).
+Disables all `Press` events.
 
 ### onLongPress: (e: PressEvent) => void
 
@@ -117,25 +189,30 @@ Determines whether calling `onPress` should be cancelled if `onLongPress` or
 
 ### onPress: (e: PressEvent) => void
 
-Called after `onPressEnd` only if `onLongPressShouldCancelPress` returns
-`false`.
+Called immediately after a press is released, unless either 1) the press is
+released outside the hit bounds of the element (accounting for
+`pressRetentionOffset` and `TouchHitTarget`), or 2) the press was a long press,
+and `onLongPress` or `onLongPressChange` props are provided, and
+`onLongPressCancelsPress()` is `true`.
 
-### delayPressStart: number
+### onPressChange: boolean => void
 
-The duration of a delay between when the press starts and when `onPressStart` is
-called. This delay is cut short if the press ends released before the threshold
-is exceeded.
+Called when the element changes press state (i.e., after `onPressStart` and
+`onPressEnd`).
 
-### delayPressEnd: number
+### onPressEnd: (e: PressEvent) => void
 
-The duration of the delay between when the press ends and when `onPressEnd` is
-called.
+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.
 
-### delayLongPress: number = 500ms
+### onPressStart: (e: PressEvent) => void
 
-The duration of a press before `onLongPress` and `onLongPressChange` are called.
+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: { top: number, right: number, bottom: number, right: number }
+### pressRententionOffset: 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/Hover.js

@@ -36,8 +36,8 @@ type HoverEvent = {|
   type: HoverEventType,
 |};
 
-// const DEFAULT_HOVER_END_DELAY_MS = 0;
-// const DEFAULT_HOVER_START_DELAY_MS = 0;
+const DEFAULT_HOVER_END_DELAY_MS = 0;
+const DEFAULT_HOVER_START_DELAY_MS = 0;
 
 const targetEventTypes = [
   'pointerover',
@@ -98,7 +98,7 @@ function dispatchHoverStartEvents(
     state.hoverEndTimeout = null;
   }
 
-  const dispatch = () => {
+  const activate = () => {
     state.isActiveHovered = true;
 
     if (props.onHoverStart) {
@@ -115,14 +115,18 @@ function dispatchHoverStartEvents(
   };
 
   if (!state.isActiveHovered) {
-    const delay = calculateDelayMS(props.delayHoverStart, 0, 0);
-    if (delay > 0) {
+    const delayHoverStart = calculateDelayMS(
+      props.delayHoverStart,
+      0,
+      DEFAULT_HOVER_START_DELAY_MS,
+    );
+    if (delayHoverStart > 0) {
       state.hoverStartTimeout = context.setTimeout(() => {
         state.hoverStartTimeout = null;
-        dispatch();
-      }, delay);
+        activate();
+      }, delayHoverStart);
     } else {
-      dispatch();
+      activate();
     }
   }
 }
@@ -145,7 +149,7 @@ function dispatchHoverEndEvents(
     state.hoverStartTimeout = null;
   }
 
-  const dispatch = () => {
+  const deactivate = () => {
     state.isActiveHovered = false;
 
     if (props.onHoverEnd) {
@@ -162,13 +166,17 @@ function dispatchHoverEndEvents(
   };
 
   if (state.isActiveHovered) {
-    const delay = calculateDelayMS(props.delayHoverEnd, 0, 0);
-    if (delay > 0) {
+    const delayHoverEnd = calculateDelayMS(
+      props.delayHoverEnd,
+      0,
+      DEFAULT_HOVER_END_DELAY_MS,
+    );
+    if (delayHoverEnd > 0) {
       state.hoverEndTimeout = context.setTimeout(() => {
-        dispatch();
-      }, delay);
+        deactivate();
+      }, delayHoverEnd);
     } else {
-      dispatch();
+      deactivate();
     }
   }
 }