Scrolling glitch when using GraphEdit on mobile

[noidexe]

Godot version:
3.2

OS/device including version:
Description: Manjaro Linux
Release: 18.1.5
Codename: Juhraya
Kernel: Linux 5.4.15-2-MANJARO
Architecture: x86-64

Mobile targets:
Moto XT1572
Moto g(7) power

Issue description:
GraphEdit nodes scroll uncontrollably and randomly when dragging scrollbars or simple when selecting multiple GraphNodes with touch and drag.
I though it was triggered by a PanGesture being detected but it's not always the case.
Here's a video. Sorry I forgot to enable tap display. I'm touching the background and sometimes it triggers a multiple selection and sometimes it makes the scrolling jump around like crazy.
Same thing while dragging a GraphNode. Also when dragging a scrollbar.
The signal for user scrolling is emitting when the glitch occurs as you can see on the console

https://photos.app.goo.gl/CVeh18JfgECNzyce9

Steps to reproduce:

• run the attached project
• tap and drag on the GraphEdit background
  Expected:
• a multiple selection is initiated
  Actual:
• sometimes a multiple selection is initiated, sometimes the graphedit starts scrolling randomly

Minimal reproduction project:
issue36312.tar.gz

[noidexe]

Commenting the following code seems to fix the bug:

godot/scene/gui/graph_edit.cpp

Lines 1073 to 1078 in 6e64036

	Ref<InputEventPanGesture> pan_gesture = p_ev;
	if (pan_gesture.is_valid()) {
	h_scroll->set_value(h_scroll->get_value() + h_scroll->get_page() * pan_gesture->get_delta().x / 8);
	v_scroll->set_value(v_scroll->get_value() + v_scroll->get_page() * pan_gesture->get_delta().y / 8);
	}

PanGesture on android seems to be detected by a 1 finger touch and drag so it's probably conflicting with other input code. I don't know if there is any use for detecting the gesture unless it's done with more than one finger on some platform.

Also, pinch and zoom doesn't seem to trigger MagnifyGesture, at least not on Android so I'm not sure if the following lines are doing anything:

godot/scene/gui/graph_edit.cpp

Lines 1067 to 1071 in 6e64036

	Ref<InputEventMagnifyGesture> magnify_gesture = p_ev;
	if (magnify_gesture.is_valid()) {
	set_zoom_custom(zoom * magnify_gesture->get_factor(), magnify_gesture->get_position());
	}

[Calinou]

@noidexe Gestures are currently only implemented on macOS, see #13139.

[akien-mga]

Actually PanGesture was implemented in #33630.
There was then a fixup to that PR which will be in 3.2.1: #35701, but it's for the double-tap part, so likely not involved here.

[KoBeWi]

Can anyone still reproduce this bug in Godot 3.2.3 or any later release?

[noidexe]

Confirmed on 3.2.3. Exactly the same behavior.