Fix Embedded Game over expanded bottom panel

[Hilderin]

• Fixes Embedded game draws over expanded bottom panel #102901

The issue came from the fact that when the bottom panel is expanded, the embedded game must be started hidden. That was not supported by Godot and the DisplayServer. I had to add a new HIDDEN flag and a new --hidden command line argument to start the game hidden. The new --hidden argument is passed to the game on startup when the embedded control is hidden (aka the bottom panel is fully expanded).

[giokhmaladze]

Gave it a try, don't know about code but original issue is resolved and everything else looks good 🎉🚀

There is one thing I noticed while I was testing it, not sure if this is concern of this PR but became noticeable now:

• If mouse is captured in the game, Input.mouse_mode = Input.MOUSE_MODE_CAPTURED you can't move mouse in the editor, even when game is hidden (see the video)

mouse_captured.mp4

• Also this case seems like separate issue (could reproduce it on master as well), but since we are here if you start project, and switch to different window before it starts, cursor teleports in the center of embedded game window, and you can't move it outside it's bounds (even though it's actually not visible), notice, mouse interactions are not blocked on new window it just seems to be position bound

mouse_cant_go_beyond_game_c.mp4

MRP:
mouse-capture-mrp.zip

[Hilderin]

Thanks for testing. It seems that the capture mouse is enable even if the game window is hidden and not focused. This should probably not happen, I'll the see what I can do about it.

[Hilderin]

I fixed the mouse captured which was still active when the game window did not have the focus or was hidden. Turns out that it could happen without in the embedded mode with the right timing if the Input.mouse_mode = Input.MOUSE_MODE_CAPTURED was called when the game did not have the focus.

There was an issue with the new --hidden because the game process was still focused/activated even if it was hidden.

[bruvzg]

For the reference, #91262 (macOS changes can be salvaged for WINDOW_FLAG_HIDDEN support).

Also, some extra changes from aforementioned PR that probaly should be included (irrelevnat for embedding, but can cause issues since new flag is exposed):

• Suppress IME activation for hiddeen windows and window_move_to_foreground on X11.
• ShowWindow is called in other places, and these should check for flag as well.

I was not able to reproduce the issue, so have not tested it.

[giokhmaladze]

gave it another try, mouse pointer isn't locked in editor anymore (when bottom panel is expanded) 🎉

• mouse pointer is still moved in the center of where game view would be
• mouse pointer is still bound to game view borders when you switch outside godot before starting scene
  • this is more apparent when project is big and takes several seconds to load and if you use external code editor
    • you click start button
    • switch to external text editor
    • game is started in godot
      • mouse pointer is teleported in the center of game view
      • you cant move it outside of it unless you focus on godot and switch back