Bug 215979 – Rewrite main thread scroll latching logic

• Component: Scrolling
• Status: RESOLVED FIXED

[Simon Fraser (smfr)]

The main thread scroll event handling and latching logic has evolved over time and lacks a real design; see issues noted in bug 215741.

[Simon Fraser (smfr)]

Created attachment 407545 [details]
Patch

[Simon Fraser (smfr)]

Created attachment 407551 [details]
Patch

[Simon Fraser (smfr)]

Created attachment 407553 [details]
Patch

[Simon Fraser (smfr)]

Created attachment 407554 [details]
Patch

[Tim Horton]

Comment on attachment 407554 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=407554&action=review

> Source/WebCore/page/scrolling/ScrollLatchingController.cpp:55
> +// FIXME: This logic is different frmo ScrollingTreeLatchingController, which simply lets the latching state elapse after 100ms.

frmo

> Source/WebCore/page/scrolling/ScrollLatchingController.cpp:186
> +    // We always allow the main frame receive wheel events to permit rubber-banding.

Some grammar

> Source/WebCore/page/scrolling/ScrollLatchingController.h:75
> +        Frame* frame { nullptr }; // Icky raw pointer. Use FrameIdentifier?

Did you want to fix this before landing?

> Source/WebCore/page/scrolling/ScrollingTreeLatchingController.cpp:40
>  static const Seconds resetLatchedStateTimeout { 100_ms };

Should we plop this in one place and use it from both?

> Source/WebCore/platform/PlatformWheelEvent.h:155
> +    bool isGestureContinuation() const; // The fingers-down part of the gesture.

But not momentum?

> LayoutTests/ChangeLog:14
> [phone]  Simon Fraser  <[e-mail]>

Double changelog

[Simon Fraser (smfr)]

https://trac.webkit.org/r266333

[Radar WebKit Bug Importer]

<rdar://problem/68034254>

[Fujii Hironori]

The mouse wheel doesn't scroll page in trunk@266333 for WinCairo WK1 and WK2.
This change seems the culprit.

[Simon Fraser (smfr)]

Fixed in bug 215990.