SDL: Sync SDL2 wiki -> header (66d87)

From 66d87bf0e1e29377b398d3c567e1ab3590760d8c Mon Sep 17 00:00:00 2001
From: SDL Wiki Bot <[EMAIL REDACTED]>
Date: Mon, 13 Oct 2025 06:06:49 +0000
Subject: [PATCH] Sync SDL2 wiki -> header

[ci skip]
---
 include/SDL_video.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/include/SDL_video.h b/include/SDL_video.h
index 6972af6efbb38..e1c3c278a6e38 100644
--- a/include/SDL_video.h
+++ b/include/SDL_video.h
@@ -1008,6 +1008,8 @@ extern DECLSPEC void SDLCALL SDL_GetWindowPosition(SDL_Window * window,
  * \param h the height of the window in pixels, in screen coordinates, must be
  *          > 0.
  *
+ * \threadsafety This function should only be called on the main thread.
+ *
  * \since This function is available since SDL 2.0.0.
  *
  * \sa SDL_GetWindowSize