SDL: Document the pixel layout of YUV format surfaces

From 08de6656fcfc9aba8cf6d78461988ad24f3a6330 Mon Sep 17 00:00:00 2001
From: Sam Lantinga <[EMAIL REDACTED]>
Date: Fri, 6 Dec 2024 16:14:05 -0800
Subject: [PATCH] Document the pixel layout of YUV format surfaces

Fixes https://github.com/libsdl-org/SDL/issues/10530
---
 include/SDL3/SDL_surface.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/include/SDL3/SDL_surface.h b/include/SDL3/SDL_surface.h
index 9114701f1ae61..ff7f0d24af105 100644
--- a/include/SDL3/SDL_surface.h
+++ b/include/SDL3/SDL_surface.h
@@ -115,6 +115,8 @@ typedef enum SDL_FlipMode
  * remaining bytes to reach the pitch are used as padding to reach a desired
  * alignment, and have undefined contents.
  *
+ * When a surface holds YUV format data, the planes are assumed to be contiguous without padding between them, e.g. a 32x32 surface in NV12 format with a pitch of 32 would consist of 32x32 bytes of Y plane followed by 32x16 bytes of UV plane.
+ *
  * \since This struct is available since SDL 3.1.3.
  *
  * \sa SDL_CreateSurface