Godot version

4.1.1

System information

Windows 10, amd rx 480 gpu

Issue description

If you reparent a node while the mouse is moving after being pressed on it, it loses that state and never receives a release event.

This other issue is related, but is about node removal/visibility change, not reparenting: #43400 -- They might have the same underlying cause.

I ran into this while trying to make a graphical code editor where reparenting control nodes by dragging them is a basic operation.

Steps to reproduce

Create a "draggable" Control node with your own drag logic using _gui_input and mouse input events. Reparent it when the input is "pressed". It will fail to receive the release event. This causes a half-broken gui input state where other nodes can receive relative mouse motion events even though the release event has never fired.

Example:

extends PanelContainer

const do_reparent = true

var dragging = false
func _gui_input(event : InputEvent) -> void:
    if event is InputEventMouseButton:
        if event.pressed:
            print("started dragging")
            if do_reparent:
                print("reparenting")
                var parent = get_parent()
                var pos = global_position
                if parent == get_tree().current_scene:
                    reparent(parent.get_node("Panel"))
                else:
                    reparent(parent.get_parent())
                global_position = pos
            dragging = true
        else:
            print("done dragging")
            dragging = false
    
    if event is InputEventMouseMotion:
        if dragging:
            position += event.relative

func _process(delta : float) -> void:
    modulate.a = 0.5 if dragging else 1.0

Expected behavior:

Actual behavior:

Minimal reproduction project

GUIInputTest.zip