Tree Node doesn't support touch controls

[Pingar5]

Godot version

3.4.4.stable.official

System information

Built on Windows 10, running on Android 10

Issue description

The Tree node doesn't respond to touch events and emulating mouse with touch doesn't act the same as just using a mouse. The most prevalent issue in my case is that the item_activated signal never fires on mobile, even if I double tap an item.

Steps to reproduce

1. Add a tree component to a scene
2. Add a script to add sample items to the tree
3. Connect it's item_activated signal to something
4. Run the project on android
5. Double tap an item in the tree, no signal will be produced

Minimal reproduction project

tree-mobile-input-minimal-project.zip
I had to delete the android build template for this to upload, so you'll need to install that once you open the project, then if you run the game and activate an item, the screen should go green.

[Calinou]

IIRC, double-clicking emulation was never properly implemented on mobile (or if it does, it requires a very high level of precision).

[madmiraal]

Supporting touch events on BaseButton, which is required to get touch support working on all GUI controls that depend on it is captured in godotengine/godot-proposals#3976. Implementing multi-touch support in GUI controls, a prerequisite for godotengine/godot-proposals#3976 is fixed with #49215 and its 3.x version #34383.

Double-tap being broken is what causes #8151, and is fixed with #59760 and its 3.x version #59761.