commit 96fa1d20a5862580bab03c8c3bf12a95fef5a77d
author Antonio Gomes <tonikitoo@igalia.com> Tue May 30 14:02:46 2023
committer Chromium LUCI CQ <chromium-scoped@luci-project-accounts.iam.gserviceaccount.com> Tue May 30 14:02:46 2023
tree 7c553070b98b8f237f2c44405df140c165b4ac4a
parent e26eb46a542f638f30d844bd39050eb0f5f70dfa

Decrease WaylandWindowDragController::kHorizontalRailExitThreshold

It was observed that under certain multi-monitor setups, detaching a
tab upwards with touch was making the newly created window disappear
upon drop.

One broken set up is:

- DUT w/ builtin monitor + extended monitor connected
- the user virtually places the extended monitor above the builtin
  monitor (in settings > device > displays > arrangement)

Test steps:

- create a browser (eg lacros) window with at least two tabs on the
  builtin display (the one placed virtually below in the disposition
  setup)
- start dragging a tab upwards to detach it.

The newly created window gets created translucent, which indicates that
Ash understands it as belonging to a different display (in this case,
the monitor virtually above).
Once the user let go the drop operation, the newly created tab simply
disappears.

The problem:

Today, when ozone/wayland receives a wl_date_device::leave event, it
emits a pointer/touch event with a negative Y coordinative to emulate
a drag upwards. In case of pointer, -1 is used, whereas in case of touch,
-1000 is used.
The high value used for touch is intentional, and aims at force an
exit on the horizontal rail mode set in SnapScrollController
(//ui/events/gesture_detection/snap_scroll_controller.cc).

In case there is a monitor virtually placed above, the generated
touch event upon wl_data_device::leave might match the coordinates of that
monitor, and cause the newly created window to be wrong placed into that
display.

This CL adjusts the threshold to be minimally higher than
`GestureDetector::Config::touch_slop`, which controls the horizontal
scroll rails in [1].

[1] //ui/events/gesture_detection/gesture_detector.h

BUG=1430664
R=nickdiego@igalia.com

Change-Id: I89eded1199fe280292472bb3042a15d9409fe32f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4573506
Reviewed-by: Nick Yamane <nickdiego@igalia.com>
Commit-Queue: Antonio Gomes <tonikitoo@igalia.com>
Cr-Commit-Position: refs/heads/main@{#1150525}