[Webkit-unassigned] [Bug 235436] New: [GTK] REGRESSION: Touch scrolling is broken

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=235436

            Bug ID: 235436
           Summary: [GTK] REGRESSION: Touch scrolling is broken
           Product: WebKit
           Version: WebKit Nightly Build
          Hardware: Unspecified
                OS: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: WebKitGTK
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: alexm at gnome.org
                CC: bugs-noreply at webkitgtk.org

There are 2 issues, I'm not sure whether they are symptoms of the same thing or not.

1. Scrolling is very very slow and delayed - I've investigated this and it's caused by unwanted smooth scroll animations
2. Kinetic scrolling is too fast

With a quick hack:

```diff
diff --git a/Source/WebKit/UIProcess/API/gtk/WebKitWebViewBase.cpp b/Source/WebKit/UIProcess/API/gtk/WebKitWebViewBase.cpp
index 559a89bfc027..c940e565bea8 100644
--- a/Source/WebKit/UIProcess/API/gtk/WebKitWebViewBase.cpp
+++ b/Source/WebKit/UIProcess/API/gtk/WebKitWebViewBase.cpp
@@ -3017,7 +3017,7 @@ void webkitWebViewBaseSynthesizeWheelEvent(WebKitWebViewBase* webViewBase, const
         delta.scale(static_cast<float>(Scrollbar::pixelsPerLineStep()));

     priv->pageProxy->handleWheelEvent(NativeWebWheelEvent(const_cast<GdkEvent*>(event), { x, y }, widgetRootCoords(GTK_WIDGET(webViewBase), x, y),
-        delta, wheelTicks, toWebKitWheelEventPhase(phase), toWebKitWheelEventPhase(momentumPhase), priv->wheelHasPreciseDeltas));
+        delta, wheelTicks, toWebKitWheelEventPhase(phase), toWebKitWheelEventPhase(momentumPhase), priv->wheelHasPreciseDeltas || TRUE));
 }

 void webkitWebViewBaseSetWheelHasPreciseDeltas(WebKitWebViewBase* webViewBase, bool hasPreciseDeltas)
```

the lag indeed goes away, but kinetic scrolling just stops working altogether. Without that hack and with smooth scrolling disabled, kinetic scrolling seems like it immediately jumps at the position where it would end up if it was animating. With it enabled I can't tell if it's smooth or kinetic scrolling animating.

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