From: Holger Schemel <info@artsoft.org>
Date: Tue, 19 May 2020 16:03:12 +0000 (+0200)
Subject: added workaround for a bug in SDL 2.0.12 which prevents transparency
X-Git-Tag: 4.2.0.0~203
X-Git-Url: https://git.artsoft.org/?a=commitdiff_plain;h=6b6c9eb24c469d8b1fea8d76172b549b45f7cd77;p=rocksndiamonds.git

added workaround for a bug in SDL 2.0.12 which prevents transparency

Unfortunately, the current stable release version 2.0.12 of the SDL
library used by R'n'D has a critical bug that causes all transparent
images in R'n'D to be opaque, which hurts the game graphics at various
places.

The cause of this bug is in SDL_ConvertSurface(), which does not copy
the color key anymore.

The bug is documented in the SDL bug tracking system as follows:
https://bugzilla.libsdl.org/show_bug.cgi?id=2979

The bug will be fixed in the next stable release of the SDL library.

This workaround checks if a converted surface should have a color key,
and explicitly sets it if it is missing in the newly created surface.
---

diff --git a/src/libgame/sdl.c b/src/libgame/sdl.c
index 7fb650f1..457f567a 100644
--- a/src/libgame/sdl.c
+++ b/src/libgame/sdl.c
@@ -353,6 +353,11 @@ SDL_Surface *SDLGetNativeSurface(SDL_Surface *surface)
   if (new_surface == NULL)
     Error(ERR_EXIT, "SDL_ConvertSurface() failed: %s", SDL_GetError());
 
+  // workaround for a bug in SDL 2.0.12 (which does not convert the color key)
+  if (SDLHasColorKey(surface) && !SDLHasColorKey(new_surface))
+    SDL_SetColorKey(new_surface, SET_TRANSPARENT_PIXEL,
+		    SDLGetColorKey(surface));
+
   return new_surface;
 }