Using shortcut on Button generates `mouse_exited` signal on the selected collider

[Chaosus]

Godot version

b9375ea

System information

Windows 11

Issue description

If the user previously select a collider by using mouse (with emitted mouse_entered signal), and then pressed a shortcut connected to the button, it would generate mouse_exited signal which is incorrect:

Steps to reproduce

It is better to be tested with a provided project - run it and press B key to see that mouse_exited signal generates incorrectly.

Minimal reproduction project

test.zip

[rburing]

Bisected to 9d7d20a. The test project remade to work near that old version of Godot is attached: test_mouse_exited.zip

cc @EricEzaM

[EricEzaM]

Is it because focus is being taken by the button? Adding accept event for the button was correct I think (that commit linked above). but if the button triggering causes some signals to fire which in turn make the mouse exit event trigger, then it should be investigated if it is the desired behaviour and what code causes that to happen.

[rburing]

The mouse exit being triggered is undesired behavior IMHO.

Picking is happening in scene/main/viewport.cpp based on input events. Could you take a look?

Maybe it's something to do with is_input_handled().

[EricEzaM]

I might have time to look on the weekend. If anyone else is interested in investigating further - please go ahead.

[EricEzaM]

This is happening because of this:

godot/scene/main/viewport.cpp

Lines 3039 to 3040 in 6991e9b

	void Viewport::set_input_as_handled() {
	_drop_physics_mouseover();

As soon as input is set as accepted, mouse exit is called:

godot/scene/main/viewport.cpp

Line 2279 in 6991e9b

co->_mouse_exit();

This was added in 2019 here #29579 (cc @mrcdk (if you are still around) or @RandomShaper (who approved the logic behind the addition)), to fix #29575. Any thoughts about what we should do about this?