SDL-1.2: atari:video:xbios: mark shadow buffer as software surface

From 963bc45fc355423fed48c93df6b01b3b9ebfa15f Mon Sep 17 00:00:00 2001
From: Miro Kropacek <[EMAIL REDACTED]>
Date: Sun, 30 Jun 2024 00:48:33 +0200
Subject: [PATCH] atari:video:xbios: mark shadow buffer as software surface

This caused problems before commit 064e24a but perhaps there are other
hidden issues so better fix the root cause.
---
 src/video/xbios/SDL_xbios.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/video/xbios/SDL_xbios.c b/src/video/xbios/SDL_xbios.c
index 5752197e..4fcde0f3 100644
--- a/src/video/xbios/SDL_xbios.c
+++ b/src/video/xbios/SDL_xbios.c
@@ -458,6 +458,8 @@ static SDL_Surface *XBIOS_SetVideoMode(_THIS, SDL_Surface *current,
 		SDL_memset(XBIOS_shadowscreenmem, 0, new_screen_size);
 
 		XBIOS_shadowscreen=(void *) (( (long) XBIOS_shadowscreenmem+255) & 0xFFFFFF00UL);
+
+		modeflags &= ~SDL_HWSURFACE;
 	}
 
 	/* Output buffer needs to be twice in size for the software double-line mode */