Changeset 287593 in webkit

Timestamp:

Jan 4, 2022, 3:48:08 PM (5 years ago)

Author:

Simon Fraser

Message:

"canceled" wheel events to non-zero deltas cause scrolling jumps in PDFs and CodeMirror
​https://bugs.webkit.org/show_bug.cgi?id=234825

Reviewed by Tim Horton.

Source/WebKit:

On some macOS versions, interrupting a momentum scroll via a two-finger tap on the trackpad can
result in the following sequence of wheel events: momentumPhase:end -> phase:mayBegin -> phase:cancelled,
and that last canceled event can have non-zero deltas (rdar://86653042).

Protect against this by zeroing out the deltas for cancelled wheel events when constructing WebEvents
from NSEvents. Code in Element::dispatchWheelEvent() ensures that we don't dispatch wheel events with
zero deltas to script, fixing CodeMirror.

Jumps only affected PDFs (and scrollable selects) because those are the code paths that don't go via
ScrollingEffectsController, which already ignores Cancelled events.

Test: fast/scrolling/mac/canceled-event-with-non-zero-deltas.html

• Shared/mac/WebEventFactory.mm:

(WebKit::WebEventFactory::createWebWheelEvent):

LayoutTests:

• fast/scrolling/mac/canceled-event-with-non-zero-deltas-expected.txt: Added.
• fast/scrolling/mac/canceled-event-with-non-zero-deltas.html: Added.

Location:

trunk

Files:

• LayoutTests/ChangeLog (modified) (1 diff)
• LayoutTests/fast/scrolling/mac/canceled-event-with-non-zero-deltas-expected.txt (added)
• LayoutTests/fast/scrolling/mac/canceled-event-with-non-zero-deltas.html (added)
• Source/WebKit/ChangeLog (modified) (1 diff)
• Source/WebKit/Shared/mac/WebEventFactory.mm (modified) (1 diff)

trunk/LayoutTests/ChangeLog

@@ +1 @@
+2022-01-04  Simon Fraser  <simon.fraser@apple.com>
+
+        "canceled" wheel events to non-zero deltas cause scrolling jumps in PDFs and CodeMirror
+        https://bugs.webkit.org/show_bug.cgi?id=234825
+
+        Reviewed by Tim Horton.
+
+        * fast/scrolling/mac/canceled-event-with-non-zero-deltas-expected.txt: Added.
+        * fast/scrolling/mac/canceled-event-with-non-zero-deltas.html: Added.
+
 2022-01-04  Devin Rousso  <drousso@apple.com>
 

trunk/Source/WebKit/ChangeLog

@@ +1 @@
+2022-01-04  Simon Fraser  <simon.fraser@apple.com>
+
+        "canceled" wheel events to non-zero deltas cause scrolling jumps in PDFs and CodeMirror
+        https://bugs.webkit.org/show_bug.cgi?id=234825
+
+        Reviewed by Tim Horton.
+
+        On some macOS versions, interrupting a momentum scroll via a two-finger tap on the trackpad can
+        result in the following sequence of wheel events: momentumPhase:end -> phase:mayBegin -> phase:cancelled,
+        and that last canceled event can have non-zero deltas (rdar://86653042).
+
+        Protect against this by zeroing out the deltas for cancelled wheel events when constructing WebEvents
+        from NSEvents. Code in Element::dispatchWheelEvent() ensures that we don't dispatch wheel events with
+        zero deltas to script, fixing CodeMirror.
+
+        Jumps only affected PDFs (and scrollable selects) because those are the code paths that don't go via
+        ScrollingEffectsController, which already ignores Cancelled events.
+
+        Test: fast/scrolling/mac/canceled-event-with-non-zero-deltas.html
+
+        * Shared/mac/WebEventFactory.mm:
+        (WebKit::WebEventFactory::createWebWheelEvent):
+
 2022-01-04  Wenson Hsieh  <wenson_hsieh@apple.com>
 

trunk/Source/WebKit/Shared/mac/WebEventFactory.mm

@@ -439 +439 @@
     auto ioHIDEventWallTime = WebCore::eventTimeStampSince1970(ioHIDEventTimestamp);
 
+    if (phase == WebWheelEvent::PhaseCancelled) {
+        deltaX = 0;
+        deltaY = 0;
+        wheelTicksX = 0;
+        wheelTicksY = 0;
+        unacceleratedScrollingDelta = { };
+        rawPlatformDelta = std::nullopt;
+    }
+
     return WebWheelEvent(WebEvent::Wheel, WebCore::IntPoint(position), WebCore::IntPoint(globalPosition), WebCore::FloatSize(deltaX, deltaY), WebCore::FloatSize(wheelTicksX, wheelTicksY),
         granularity, directionInvertedFromDevice, phase, momentumPhase, hasPreciseScrollingDeltas,