Unexpected behavior of the Exclusive property in the Popup class

[98teg]

Godot version:

3.2 Branch, commit godotengine/godot#40914

OS/device including version:

OpenGL ES 3.0 Renderer: GeForce GTX 1050 Ti/PCIe/SSE2

Issue description:

I was creating a FileDialog and I wanted to force the user to select a file. I set the Exclusive property on the Popup class to true. However, this only ensures the Popup not to hide when clicking outside the Popup window. The Popup window still closes when pressing X or the cancel button, despite the documentation stating:

If true, the popup will not be hidden when a click event occurs outside of it, or when it receives the ui_cancel action event.

So I suggest changing the documentation to better explain this behavior or to change this behavior.

Steps to reproduce:
Add a child to a Control Node that is a WindowDialog named Popup, sets its Exclusive property to activated and add a script to the parent with this code:

extends Control

func _ready():
	get_node("Popup").popup_centered()

Then, when executing the project, it is possible to close the WindowDialog when pressing X.
Minimal reproduction project:

Dialog.zip

[98teg]

I was able to work around this getting the buttons using get_close_button() and get_cancel(). Then I disabled those buttons. So I'm not sure if I should close this issue.

[Zireael07]

The documentation doesn't state that it doesn't react to X or cancel button, just not to mouse clicks outside and the input action event ui_cancel (usually the Escape key).

[98teg]

I later thought about that may be the case, but at first glance, I thought it refers to those buttons. May I suggest adding something along the lines This property does not affect the close or cancel button of the dialogs that inherits from this class?