[w3c/uievents] Expose wheel event scrolling state to DOM events (#170)

Current DOM 'wheel' events only expose bare-minimum data that don't fully capture how modern scrollwheels and trackpads behave.

Scrolling on trackpads can give additional information about the state of scrolling that determines the first wheel event of a scrolling sequence (from the time that user starts scrolling till when they lift their fingers). This information helps with optimizations like async wheel events which lets preventDefault call only on the first wheel event of a scroll sequence to cancel the event and the rest of the wheel events in the sequence are non-cancellable.

```
interface WheelEvent : MouseEvent {
...
+    readonly    attribute boolean       isFirstEvent;
};
```

or when only the first wheel event in a scroll sequence is cancellable:

```
interface WheelEvent : MouseEvent {
...
+    readonly    attribute boolean       isCancellable;
};
```

-- 
You are receiving this because you are subscribed to this thread.
Reply to this email directly or view it on GitHub:
https://github.com/w3c/uievents/issues/170