In Godot 3.0, if I create a scene with a CenterContainer, and I set as a child of it ANY type of button, the button will be visible, but putting a Rect under it such as TextureRect or ColorRect will result in it setting the
rect_size value to
Vector2(0, 0), ergo, it becomes invisible.
I mean, I can create a ToolButton, set its icon to the image I want and set its
enabled_focus_mode value to "None", and that'll work for me, but what I want to know WHY this is happening.