Fix mouse entered notifications

[Sauermann]

Make sure, that a windows initial state is mouse_in_viewport = false. This makes sure, that the mouse entered notification is sent when the mouse hovers a window for the first time. (resolve #88942)

For embedded Windows, NOTIFICATION_WM_MOUSE_ENTER is currently sent twice in a row. Remove one of the places where it is sent. Window::_update_mouse_over() is the correct one, because there it is also called for native windows. (bug detected while investigating #88942)

[akien-mga]

The rationale makes sense to me.

[akien-mga]

Thanks!

[eviltrout]

This commit broke my game, but I'm not sure if I'm doing the wrong thing or not hence me asking here rather than creating an issue.

In my game, there is a computer screen that you can interact with in a 3D world. The computer screen displays a viewport's texture, and events are proxied to it via sub_viewport.push_input(...)

Previously: my viewport was receiving InputEventMouseMotion inside it's controls via _gui_input, because the mouse_in_viewport bool was defaulting to true.

Now: InputEventMouseMotion events are not received by gui_input when push_input is used.

I found a workaround - I can call sub_viewport.notification(NOTIFICATION_VP_MOUSE_ENTER) to set the mouse_in_viewport flag from gdscript. When I do this, the mouse motion events are received as they were previously. Is this what I should be doing?

[Sauermann]

@eviltrout thanks for the report. I will look into it.
If possible, a dedicated bug-report would be appreciated.

[eviltrout]

Sure thing, here is the bug report: #89757