| Summary: | Touchpad based kinetic scrolling in gtk applications does not work | ||
|---|---|---|---|
| Product: | [Plasma] kwin | Reporter: | Marcus Gursch <marcus.gursch> |
| Component: | input | Assignee: | KWin default assignee <kwin-bugs-null> |
| Status: | RESOLVED FIXED | ||
| Severity: | normal | CC: | bugseforuns, emilio, hujq, nate, postix |
| Priority: | NOR | Keywords: | wayland |
| Version: | 5.24.5 | ||
| Target Milestone: | --- | ||
| Platform: | Manjaro | ||
| OS: | Linux | ||
| Latest Commit: | https://invent.kde.org/plasma/kwin/commit/e6b5cf283e619c712fe5f5f99e1c00bce06a7846 | Version Fixed In: | 6.0 |
| Sentry Crash Report: | |||
A possibly relevant merge request was started @ https://invent.kde.org/plasma/kwin/-/merge_requests/4057 Git commit e6b5cf283e619c712fe5f5f99e1c00bce06a7846 by Vlad Zahorodnii. Committed on 05/05/2023 at 10:27. Pushed by vladz into branch 'master'. core: Batch pointer input device events This change introduces InputDevice::pointerFrame(). The main motivation behind it is to allow batching multiple pointer events within a single event frame. M +6 -0 autotests/integration/test_helpers.cpp M +5 -0 src/backends/fakeinput/fakeinputdevice.cpp M +6 -0 src/backends/libinput/connection.cpp M +4 -0 src/backends/wayland/wayland_backend.cpp M +3 -0 src/backends/x11/windowed/x11_windowed_backend.cpp M +1 -0 src/core/inputdevice.h M +38 -10 src/input.cpp M +1 -0 src/input.h M +9 -0 src/pointer_input.cpp M +4 -0 src/pointer_input.h https://invent.kde.org/plasma/kwin/commit/e6b5cf283e619c712fe5f5f99e1c00bce06a7846 *** Bug 469965 has been marked as a duplicate of this bug. *** |
SUMMARY Touchpad based kinetic scrolling in gtk applications does not work when using kwin (wayland). After doing some digging and testing I found that the reason is the way wl_pointer.axis_stop events are sent to application windows. kwin (actually kwayland-server before it was merged in kwin) currently sends the stop event for each axis in its own frame: ``` [13: wl_pointer] frame [13: wl_pointer] axis_source: 1 (finger) [13: wl_pointer] axis_stop: time: 1054759; axis: 0 (vertical) [13: wl_pointer] frame [13: wl_pointer] axis_source: 1 (finger) [13: wl_pointer] axis_stop: time: 1054759; axis: 1 (horizontal) [13: wl_pointer] frame ``` In other compositors (weston, wlroots based like sway, mutter) the stop events for both axes are bundled in a single frame: ``` [13: wl_pointer] frame [13: wl_pointer] axis_source: 1 (finger) [13: wl_pointer] axis_stop: time: 1054759; axis: 0 (vertical) [13: wl_pointer] axis_stop: time: 1054759; axis: 1 (horizontal) [13: wl_pointer] frame ``` After patching kwayland-server to behave like sway etc kinetic scrolling works. The patch needs more work obviously and is only intended to show the bare minimum of changes to "make it work": ``` diff --git a/src/server/pointer_interface.cpp b/src/server/pointer_interface.cpp index b552ac4..128c6d9 100644 --- a/src/server/pointer_interface.cpp +++ b/src/server/pointer_interface.cpp @@ -236,7 +236,11 @@ void PointerInterface::sendAxis(Qt::Orientation orientation, qreal delta, qint32 } d->send_axis(resource->handle, d->seat->timestamp(), wlOrientation, wl_fixed_from_double(delta)); } else if (version >= WL_POINTER_AXIS_STOP_SINCE_VERSION) { - d->send_axis_stop(resource->handle, d->seat->timestamp(), wlOrientation); + if (wlOrientation == 0) + { + d->send_axis_stop(resource->handle, d->seat->timestamp(), 0); + d->send_axis_stop(resource->handle, d->seat->timestamp(), 1); + } } } } ``` STEPS TO REPRODUCE 1. Open some gtk application, e.g. use gedit to display a large text file. 2. Scroll using touchpad and lift fingers while they are moving. OBSERVED RESULT The scrolling stops immediately after lifting the fingers. EXPECTED RESULT The scrolling goes on after lifting the fingers up. SOFTWARE/OS VERSIONS OS: Manjaro 21.2.6 uname -a: Linux marcus-surface 5.17.9-arch1-2-surface #1 SMP PREEMPT Wed, 25 May 2022 15:31:19 +0000 x86_64 GNU/Linux KDE Plasma Version: KDE Plasma 5.24.5 KDE Frameworks Version: 5.94.0 Qt Version: 5.15.4