X11: Allow moving a fullscreen/maximized window to another screen/display

[AR-DEV-1]

• Allows X11 to move a game to another screen/display
• Tested & works as expected
• Ports Godot's PR#114820 to Redot (which was also created by me)

Note

Contributed by 2LazyDevs.

Summary by CodeRabbit

Release Notes

• Bug Fixes
  • Fixed an issue on Linux where fullscreen and maximized windows could not be properly repositioned or moved between displays. These windows are now temporarily switched to windowed mode during the operation and restored to their original state.

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[coderabbitai]

Walkthrough

Modified the window screen positioning logic in DisplayServerX11 to temporarily switch fullscreen or maximized windows to windowed mode before repositioning, then restore their original mode afterward.

Changes

Cohort / File(s)	Summary
Window Mode Transition platform/linuxbsd/x11/display_server_x11.cpp	Added temporary mode switch mechanism in window_set_current_screen: captures current window mode, transitions to windowed mode for move/resize operations, and restores original mode upon completion.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately summarizes the main change: enabling window movement to another screen/display when in fullscreen or maximized mode on X11.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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✨ Finishing touches

• 📝 Generate docstrings

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[coderabbitai]

Actionable comments posted: 1

🤖 Fix all issues with AI agents

In `@platform/linuxbsd/x11/display_server_x11.cpp`:
- Around line 2309-2315: The restore path currently calls XMoveResizeWindow to
move/resize the native window but then immediately calls
window_set_mode(current_mode, p_window) while internal state
(wd.position/wd.size) is stale; update the internal state before restoring mode
by calling the appropriate setter(s) (e.g., window_set_position and/or
window_set_size) or otherwise assign wd.position and wd.size from
screen_get_position(screen)/screen_get_size(screen) so that
window_set_mode(current_mode, p_window) sees the new position/size; locate this
logic around window_get_mode/window_set_mode, XMoveResizeWindow and wd to apply
the state sync prior to the final window_set_mode call.