An option to RLE-compress masked art

Saves about 200 KiB RAM in dungeon at a large performance cost.
Almost never a good idea, except for severely RAM-constrained devices (e.g. RG99).

CMake/Definitions.cmake

@@ -15,6 +15,7 @@ foreach(
   GPERF_HEAP_FIRST_GAME_ITERATION
   STREAM_ALL_AUDIO
   PACKET_ENCRYPTION
+  DEVILUTIONX_MASKED_ART_RLE
 )
   if(${def_name})
     list(APPEND DEVILUTIONX_DEFINITIONS ${def_name})

CMakeLists.txt

@@ -59,6 +59,8 @@ mark_as_advanced(DISABLE_STREAMING_SOUNDS)
 option(STREAM_ALL_AUDIO "Stream all the audio. For extremely RAM-constrained platforms.")
 mark_as_advanced(STREAM_ALL_AUDIO)
 
+option(DEVILUTIONX_MASKED_ART_RLE "RLE-compress masked art in memory (e.g. fonts). Slightly lower RAM usage at a significant performance cost." OFF)
+
 if(TSAN)
   set(ASAN OFF)
 endif()

Source/DiabloUI/art.cpp

@@ -148,8 +148,21 @@ void LoadArt(const char *pszFile, Art *art, int frames, SDL_Color *pPalette, con
 void LoadMaskedArt(const char *pszFile, Art *art, int frames, int mask, const std::array<uint8_t, 256> *colorMapping)
 {
 	LoadArt(pszFile, art, frames, nullptr, colorMapping);
-	if (art->surface != nullptr)
-		SDLC_SetColorKey(art->surface.get(), mask);
+	if (art->surface == nullptr)
+		return;
+	SDL_Surface *surface = art->surface.get();
+#if SDL_VERSION_ATLEAST(2, 0, 0)
+#ifdef DEVILUTIONX_MASKED_ART_RLE
+	SDL_SetSurfaceRLE(surface, 1);
+#endif
+	SDL_SetColorKey(surface, SDL_TRUE, mask);
+#else
+	int flags = SDL_SRCCOLORKEY;
+#ifdef DEVILUTIONX_MASKED_ART_RLE
+	flags |= SDL_RLEACCEL;
+#endif
+	SDL_SetColorKey(surface, flags, mask);
+#endif
 }
 
 void LoadArt(Art *art, const std::uint8_t *artData, int w, int h, int frames)

Source/utils/sdl_compat.h

@@ -35,15 +35,6 @@ inline const Uint8 *SDLC_GetKeyState()
 #endif
 }
 
-inline int SDLC_SetColorKey(SDL_Surface *surface, Uint32 key)
-{
-#ifdef USE_SDL1
-	return SDL_SetColorKey(surface, SDL_SRCCOLORKEY, key);
-#else
-	return SDL_SetColorKey(surface, SDL_TRUE, key);
-#endif
-}
-
 // Copies the colors into the surface's palette.
 inline int SDLC_SetSurfaceColors(SDL_Surface *surface, SDL_Color *colors, int firstcolor, int ncolors)
 {