diff --git a/sc2/src/libs/graphics/sdl/primitives.c b/sc2/src/libs/graphics/sdl/primitives.c
index c83521334..6dd539a1b 100644
--- a/sc2/src/libs/graphics/sdl/primitives.c
+++ b/sc2/src/libs/graphics/sdl/primitives.c
@@ -533,18 +533,10 @@ blt_prim(SDL_Surface *src, SDL_Rect src_r, RenderPixelFn plot, int factor,
 		mask = srcfmt->Amask;
 		key = 0;
 	}
-#if SDL_MAJOR_VERSION == 1
-	else if (src->flags & SDL_SRCCOLORKEY)
-	{	// colorkey transparency
-		mask = ~srcfmt->Amask;
-		key = srcfmt->colorkey & mask;
-	}
-#else
-	else if (SDL_GetColorKey (src, &key) == 0)
+	else if (TFB_GetColorKey (src, &key) == 0)
 	{
 		mask = ~0;
 	}
-#endif
 	// TODO: calculate the source and destination pointers directly
 	//   instead of using the plot(x,y) version
 	for (y = 0; y < src_r.h; ++y)
diff --git a/sc2/src/libs/graphics/sdl/sdl1_common.c b/sc2/src/libs/graphics/sdl/sdl1_common.c
index 651931342..f1ace3351 100644
--- a/sc2/src/libs/graphics/sdl/sdl1_common.c
+++ b/sc2/src/libs/graphics/sdl/sdl1_common.c
@@ -110,283 +110,6 @@ TFB_ReInitGraphics (int driver, int flags, int width, int height)
 	return result;
 }
 
-/* Probably ought to clean this away at some point. */
-SDL_Surface *
-TFB_DisplayFormatAlpha (SDL_Surface *surface)
-{
-	SDL_Surface* newsurf;
-	SDL_PixelFormat* dstfmt;
-	const SDL_PixelFormat* srcfmt = surface->format;
-	
-	// figure out what format to use (alpha/no alpha)
-	if (surface->format->Amask)
-		dstfmt = format_conv_surf->format;
-	else
-		dstfmt = SDL_Screen->format;
-
-	if (srcfmt->BytesPerPixel == dstfmt->BytesPerPixel &&
-			srcfmt->Rmask == dstfmt->Rmask &&
-			srcfmt->Gmask == dstfmt->Gmask &&
-			srcfmt->Bmask == dstfmt->Bmask &&
-			srcfmt->Amask == dstfmt->Amask)
-		return surface; // no conversion needed
-
-	newsurf = SDL_ConvertSurface (surface, dstfmt, surface->flags);
-	// SDL_SRCCOLORKEY and SDL_SRCALPHA cannot work at the same time,
-	// so we need to disable one of them
-	if ((surface->flags & SDL_SRCCOLORKEY) && newsurf
-			&& (newsurf->flags & SDL_SRCCOLORKEY)
-			&& (newsurf->flags & SDL_SRCALPHA))
-		SDL_SetAlpha (newsurf, 0, 255);
-
-	return newsurf;
-}
-
-void
-TFB_BlitSurface (SDL_Surface *src, SDL_Rect *srcrect, SDL_Surface *dst,
-		SDL_Rect *dstrect, int blend_numer, int blend_denom)
-{
-	BOOLEAN has_colorkey;
-	int x, y, x1, y1, x2, y2, dst_x2, dst_y2, nr, ng, nb;
-	int srcx, srcy, w, h;
-	Uint8 sr, sg, sb, dr, dg, db;
-	Uint32 src_pixval, dst_pixval, colorkey;
-	GetPixelFn src_getpix, dst_getpix;
-	PutPixelFn putpix;
-	SDL_Rect fulldst;
-
-	if (blend_numer == blend_denom)
-	{
-		// normal blit: dst = src
-		
-		// log_add (log_Debug, "normal blit\n");
-		SDL_BlitSurface (src, srcrect, dst, dstrect);
-		return;
-	}
-		
-	// NOTE: following clipping code is copied from SDL-1.2.4 sources
-
-	// If the destination rectangle is NULL, use the entire dest surface
-	if (dstrect == NULL)
-	{
-		fulldst.x = fulldst.y = 0;
-		dstrect = &fulldst;
-	}
-
-	// clip the source rectangle to the source surface
-	if (srcrect)
-	{
-		int maxw, maxh;
-
-		srcx = srcrect->x;
-		w = srcrect->w;
-		if (srcx < 0) 
-		{
-			w += srcx;
-			dstrect->x -= srcx;
-			srcx = 0;
-		}
-		maxw = src->w - srcx;
-		if (maxw < w)
-			w = maxw;
-
-		srcy = srcrect->y;
-		h = srcrect->h;
-		if (srcy < 0) 
-		{
-			h += srcy;
-			dstrect->y -= srcy;
-			srcy = 0;
-		}
-		maxh = src->h - srcy;
-		if (maxh < h)
-			h = maxh;
-	}
-	else
-	{
-		srcx = 0;
-		srcy = 0;
-		w = src->w;
-		h = src->h;
-	}
-
-	// clip the destination rectangle against the clip rectangle
-	{
-		SDL_Rect *clip = &dst->clip_rect;
-		int dx, dy;
-
-		dx = clip->x - dstrect->x;
-		if (dx > 0)
-		{
-			w -= dx;
-			dstrect->x += dx;
-			srcx += dx;
-		}
-		dx = dstrect->x + w - clip->x - clip->w;
-		if (dx > 0)
-			w -= dx;
-
-		dy = clip->y - dstrect->y;
-		if (dy > 0)
-		{
-			h -= dy;
-			dstrect->y += dy;
-			srcy += dy;
-		}
-		dy = dstrect->y + h - clip->y - clip->h;
-		if (dy > 0)
-			h -= dy;
-	}
-
-	dstrect->w = w;
-	dstrect->h = h;
-
-	if (w <= 0 || h <= 0)
-		return;
-
-	x1 = srcx;
-	y1 = srcy;
-	x2 = srcx + w;
-	y2 = srcy + h;
-
-	if (src->flags & SDL_SRCCOLORKEY)
-	{
-		has_colorkey = TRUE;
-		colorkey = src->format->colorkey;
-	}
-	else
-	{
-		has_colorkey = FALSE;
-		colorkey = 0;  /* Satisfying compiler */
-	}
-
-	src_getpix = getpixel_for (src);
-	dst_getpix = getpixel_for (dst);
-	putpix = putpixel_for (dst);
-
-	if (blend_denom < 0)
-	{
-		// additive blit: dst = src + dst
-#if 0
-		log_add (log_Debug, "additive blit %d %d, src %d %d %d %d dst %d %d,"
-				" srcbpp %d", blend_numer, blend_denom, x1, y1, x2, y2,
-				dstrect->x, dstrect->y, src->format->BitsPerPixel);
-#endif		
-		for (y = y1; y < y2; ++y)
-		{
-			dst_y2 = dstrect->y + (y - y1);
-			for (x = x1; x < x2; ++x)
-			{
-				dst_x2 = dstrect->x + (x - x1);
-				src_pixval = src_getpix (src, x, y);
-
-				if (has_colorkey && src_pixval == colorkey)
-					continue;
-
-				dst_pixval = dst_getpix (dst, dst_x2, dst_y2);
-				
-				SDL_GetRGB (src_pixval, src->format, &sr, &sg, &sb);
-				SDL_GetRGB (dst_pixval, dst->format, &dr, &dg, &db);
-
-				nr = sr + dr;
-				ng = sg + dg;
-				nb = sb + db;
-
-				if (nr > 255)
-					nr = 255;
-				if (ng > 255)
-					ng = 255;
-				if (nb > 255)
-					nb = 255;
-
-				putpix (dst, dst_x2, dst_y2,
-						SDL_MapRGB (dst->format, nr, ng, nb));
-			}
-		}
-	}
-	else if (blend_numer < 0)
-	{
-		// subtractive blit: dst = src - dst
-#if 0
-		log_add (log_Debug, "subtractive blit %d %d, src %d %d %d %d"
-				" dst %d %d, srcbpp %d", blend_numer, blend_denom,
-					x1, y1, x2, y2, dstrect->x, dstrect->y,
-					src->format->BitsPerPixel);
-#endif		
-		for (y = y1; y < y2; ++y)
-		{
-			dst_y2 = dstrect->y + (y - y1);
-			for (x = x1; x < x2; ++x)
-			{
-				dst_x2 = dstrect->x + (x - x1);
-				src_pixval = src_getpix (src, x, y);
-
-				if (has_colorkey && src_pixval == colorkey)
-					continue;
-
-				dst_pixval = dst_getpix (dst, dst_x2, dst_y2);
-
-				SDL_GetRGB (src_pixval, src->format, &sr, &sg, &sb);
-				SDL_GetRGB (dst_pixval, dst->format, &dr, &dg, &db);
-
-				nr = sr - dr;
-				ng = sg - dg;
-				nb = sb - db;
-
-				if (nr < 0)
-					nr = 0;
-				if (ng < 0)
-					ng = 0;
-				if (nb < 0)
-					nb = 0;
-
-				putpix (dst, dst_x2, dst_y2,
-						SDL_MapRGB (dst->format, nr, ng, nb));
-			}
-		}
-	}
-	else 
-	{
-		// modulated blit: dst = src * (blend_numer / blend_denom) 
-
-		float f = blend_numer / (float)blend_denom;
-#if 0
-		log_add (log_Debug, "modulated blit %d %d, f %f, src %d %d %d %d"
-				" dst %d %d, srcbpp %d\n", blend_numer, blend_denom, f,
-				x1, y1, x2, y2, dstrect->x, dstrect->y,
-				src->format->BitsPerPixel);
-#endif		
-		for (y = y1; y < y2; ++y)
-		{
-			dst_y2 = dstrect->y + (y - y1);
-			for (x = x1; x < x2; ++x)
-			{
-				dst_x2 = dstrect->x + (x - x1);
-				src_pixval = src_getpix (src, x, y);
-
-				if (has_colorkey && src_pixval == colorkey)
-					continue;
-				
-				SDL_GetRGB (src_pixval, src->format, &sr, &sg, &sb);
-
-				nr = (int)(sr * f);
-				ng = (int)(sg * f);
-				nb = (int)(sb * f);
-
-				if (nr > 255)
-					nr = 255;
-				if (ng > 255)
-					ng = 255;
-				if (nb > 255)
-					nb = 255;
-
-				putpix (dst, dst_x2, dst_y2,
-						SDL_MapRGB (dst->format, nr, ng, nb));
-			}
-		}
-	}
-}
-
 void
 TFB_SetGamma (float gamma)
 {
diff --git a/sc2/src/libs/graphics/sdl/sdl2_common.c b/sc2/src/libs/graphics/sdl/sdl2_common.c
index 272cdc2e9..f1998ccc3 100644
--- a/sc2/src/libs/graphics/sdl/sdl2_common.c
+++ b/sc2/src/libs/graphics/sdl/sdl2_common.c
@@ -79,7 +79,7 @@ TFB_ReInitGraphics (int driver, int flags, int width, int height)
 
 	GfxFlags = flags;
 
-	result = TFB_Pure_ConfigureVideo (TFB_GFXDRIVER_SDL_PURE, flags, 
+	result = TFB_Pure_ConfigureVideo (TFB_GFXDRIVER_SDL_PURE, flags,
 			width, height, togglefullscreen);
 
 	if (flags & TFB_GFXFLAGS_FULLSCREEN)
@@ -90,276 +90,6 @@ TFB_ReInitGraphics (int driver, int flags, int width, int height)
 	return result;
 }
 
-/* Probably ought to clean this away at some point. */
-SDL_Surface *
-TFB_DisplayFormatAlpha (SDL_Surface *surface)
-{
-	SDL_Surface* newsurf;
-	SDL_PixelFormat* dstfmt;
-	const SDL_PixelFormat* srcfmt = surface->format;
-	
-	// figure out what format to use (alpha/no alpha)
-	if (surface->format->Amask)
-		dstfmt = format_conv_surf->format;
-	else
-		dstfmt = SDL_Screen->format;
-
-	if (srcfmt->BytesPerPixel == dstfmt->BytesPerPixel &&
-			srcfmt->Rmask == dstfmt->Rmask &&
-			srcfmt->Gmask == dstfmt->Gmask &&
-			srcfmt->Bmask == dstfmt->Bmask &&
-			srcfmt->Amask == dstfmt->Amask)
-		return surface; // no conversion needed
-
-	newsurf = SDL_ConvertSurface (surface, dstfmt, 0);
-
-	return newsurf;
-}
-
-void
-TFB_BlitSurface (SDL_Surface *src, SDL_Rect *srcrect, SDL_Surface *dst,
-		SDL_Rect *dstrect, int blend_numer, int blend_denom)
-{
-	BOOLEAN has_colorkey;
-	int x, y, x1, y1, x2, y2, dst_x2, dst_y2, nr, ng, nb;
-	int srcx, srcy, w, h;
-	Uint8 sr, sg, sb, dr, dg, db;
-	Uint32 src_pixval, dst_pixval, colorkey;
-	GetPixelFn src_getpix, dst_getpix;
-	PutPixelFn putpix;
-	SDL_Rect fulldst;
-
-	if (blend_numer == blend_denom)
-	{
-		// normal blit: dst = src
-		
-		// log_add (log_Debug, "normal blit\n");
-		SDL_BlitSurface (src, srcrect, dst, dstrect);
-		return;
-	}
-		
-	// NOTE: following clipping code is copied from SDL-1.2.4 sources
-
-	// If the destination rectangle is NULL, use the entire dest surface
-	if (dstrect == NULL)
-	{
-		fulldst.x = fulldst.y = 0;
-		dstrect = &fulldst;
-	}
-
-	// clip the source rectangle to the source surface
-	if (srcrect)
-	{
-		int maxw, maxh;
-
-		srcx = srcrect->x;
-		w = srcrect->w;
-		if (srcx < 0) 
-		{
-			w += srcx;
-			dstrect->x -= srcx;
-			srcx = 0;
-		}
-		maxw = src->w - srcx;
-		if (maxw < w)
-			w = maxw;
-
-		srcy = srcrect->y;
-		h = srcrect->h;
-		if (srcy < 0) 
-		{
-			h += srcy;
-			dstrect->y -= srcy;
-			srcy = 0;
-		}
-		maxh = src->h - srcy;
-		if (maxh < h)
-			h = maxh;
-	}
-	else
-	{
-		srcx = 0;
-		srcy = 0;
-		w = src->w;
-		h = src->h;
-	}
-
-	// clip the destination rectangle against the clip rectangle
-	{
-		SDL_Rect *clip = &dst->clip_rect;
-		int dx, dy;
-
-		dx = clip->x - dstrect->x;
-		if (dx > 0)
-		{
-			w -= dx;
-			dstrect->x += dx;
-			srcx += dx;
-		}
-		dx = dstrect->x + w - clip->x - clip->w;
-		if (dx > 0)
-			w -= dx;
-
-		dy = clip->y - dstrect->y;
-		if (dy > 0)
-		{
-			h -= dy;
-			dstrect->y += dy;
-			srcy += dy;
-		}
-		dy = dstrect->y + h - clip->y - clip->h;
-		if (dy > 0)
-			h -= dy;
-	}
-
-	dstrect->w = w;
-	dstrect->h = h;
-
-	if (w <= 0 || h <= 0)
-		return;
-
-	x1 = srcx;
-	y1 = srcy;
-	x2 = srcx + w;
-	y2 = srcy + h;
-
-	if (SDL_GetColorKey (src, &colorkey) < 0)
-	{
-		has_colorkey = FALSE;
-		colorkey = 0;  /* Satisfying compiler */
-	}
-	else
-	{
-		has_colorkey = TRUE;
-	}
-
-	src_getpix = getpixel_for (src);
-	dst_getpix = getpixel_for (dst);
-	putpix = putpixel_for (dst);
-
-	if (blend_denom < 0)
-	{
-		// additive blit: dst = src + dst
-#if 0
-		log_add (log_Debug, "additive blit %d %d, src %d %d %d %d dst %d %d,"
-				" srcbpp %d", blend_numer, blend_denom, x1, y1, x2, y2,
-				dstrect->x, dstrect->y, src->format->BitsPerPixel);
-#endif		
-		for (y = y1; y < y2; ++y)
-		{
-			dst_y2 = dstrect->y + (y - y1);
-			for (x = x1; x < x2; ++x)
-			{
-				dst_x2 = dstrect->x + (x - x1);
-				src_pixval = src_getpix (src, x, y);
-
-				if (has_colorkey && src_pixval == colorkey)
-					continue;
-
-				dst_pixval = dst_getpix (dst, dst_x2, dst_y2);
-				
-				SDL_GetRGB (src_pixval, src->format, &sr, &sg, &sb);
-				SDL_GetRGB (dst_pixval, dst->format, &dr, &dg, &db);
-
-				nr = sr + dr;
-				ng = sg + dg;
-				nb = sb + db;
-
-				if (nr > 255)
-					nr = 255;
-				if (ng > 255)
-					ng = 255;
-				if (nb > 255)
-					nb = 255;
-
-				putpix (dst, dst_x2, dst_y2,
-						SDL_MapRGB (dst->format, nr, ng, nb));
-			}
-		}
-	}
-	else if (blend_numer < 0)
-	{
-		// subtractive blit: dst = src - dst
-#if 0
-		log_add (log_Debug, "subtractive blit %d %d, src %d %d %d %d"
-				" dst %d %d, srcbpp %d", blend_numer, blend_denom,
-					x1, y1, x2, y2, dstrect->x, dstrect->y,
-					src->format->BitsPerPixel);
-#endif		
-		for (y = y1; y < y2; ++y)
-		{
-			dst_y2 = dstrect->y + (y - y1);
-			for (x = x1; x < x2; ++x)
-			{
-				dst_x2 = dstrect->x + (x - x1);
-				src_pixval = src_getpix (src, x, y);
-
-				if (has_colorkey && src_pixval == colorkey)
-					continue;
-
-				dst_pixval = dst_getpix (dst, dst_x2, dst_y2);
-
-				SDL_GetRGB (src_pixval, src->format, &sr, &sg, &sb);
-				SDL_GetRGB (dst_pixval, dst->format, &dr, &dg, &db);
-
-				nr = sr - dr;
-				ng = sg - dg;
-				nb = sb - db;
-
-				if (nr < 0)
-					nr = 0;
-				if (ng < 0)
-					ng = 0;
-				if (nb < 0)
-					nb = 0;
-
-				putpix (dst, dst_x2, dst_y2,
-						SDL_MapRGB (dst->format, nr, ng, nb));
-			}
-		}
-	}
-	else 
-	{
-		// modulated blit: dst = src * (blend_numer / blend_denom) 
-
-		float f = blend_numer / (float)blend_denom;
-#if 0
-		log_add (log_Debug, "modulated blit %d %d, f %f, src %d %d %d %d"
-				" dst %d %d, srcbpp %d\n", blend_numer, blend_denom, f,
-				x1, y1, x2, y2, dstrect->x, dstrect->y,
-				src->format->BitsPerPixel);
-#endif		
-		for (y = y1; y < y2; ++y)
-		{
-			dst_y2 = dstrect->y + (y - y1);
-			for (x = x1; x < x2; ++x)
-			{
-				dst_x2 = dstrect->x + (x - x1);
-				src_pixval = src_getpix (src, x, y);
-
-				if (has_colorkey && src_pixval == colorkey)
-					continue;
-				
-				SDL_GetRGB (src_pixval, src->format, &sr, &sg, &sb);
-
-				nr = (int)(sr * f);
-				ng = (int)(sg * f);
-				nb = (int)(sb * f);
-
-				if (nr > 255)
-					nr = 255;
-				if (ng > 255)
-					ng = 255;
-				if (nb > 255)
-					nb = 255;
-
-				putpix (dst, dst_x2, dst_y2,
-						SDL_MapRGB (dst->format, nr, ng, nb));
-			}
-		}
-	}
-}
-
 void
 TFB_SetGamma (float gamma)
 {
diff --git a/sc2/src/libs/graphics/sdl/sdl_common.c b/sc2/src/libs/graphics/sdl/sdl_common.c
index 5b6976e29..b2fe9d4fd 100644
--- a/sc2/src/libs/graphics/sdl/sdl_common.c
+++ b/sc2/src/libs/graphics/sdl/sdl_common.c
@@ -80,8 +80,8 @@ TFB_InitGraphics (int driver, int flags, int width, int height)
 		result = TFB_Pure_InitGraphics (driver, flags, width, height);
 	}
 
-	sprintf (caption, "The Ur-Quan Masters v%d.%d.%d%s", 
-			UQM_MAJOR_VERSION, UQM_MINOR_VERSION, 
+	sprintf (caption, "The Ur-Quan Masters v%d.%d.%d%s",
+			UQM_MAJOR_VERSION, UQM_MINOR_VERSION,
 			UQM_PATCH_VERSION, UQM_EXTRA_VERSION);
 	SDL_WM_SetCaption (caption, NULL);
 
@@ -121,7 +121,7 @@ TFB_ProcessEvents ()
 				/* Up to three different state changes can occur in one event. */
 				/* Here, disregard least significant change (mouse focus). */
 				// This controls the automatic sleep/pause when minimized.
-				// On small displays (e.g. mobile devices), APPINPUTFOCUS would 
+				// On small displays (e.g. mobile devices), APPINPUTFOCUS would
 				//  be an appropriate substitution for APPACTIVE:
 				// if (Event.active.state & SDL_APPINPUTFOCUS)
 				if (Event.active.state & SDL_APPACTIVE)
@@ -192,7 +192,7 @@ TFB_SwapBuffers (int force_full_redraw)
 		force_full_redraw = TFB_REDRAW_FADING;
 
 	last_fade_amount = fade_amount;
-	last_transition_amount = transition_amount;	
+	last_transition_amount = transition_amount;
 
 	graphics_backend->preprocess (force_full_redraw, transition_amount,
 			fade_amount);
@@ -217,7 +217,7 @@ TFB_SwapBuffers (int force_full_redraw)
 		}
 		else
 		{
-			graphics_backend->color (255, 255, 255, 
+			graphics_backend->color (255, 255, 255,
 					fade_amount - 255, NULL);
 		}
 	}
@@ -230,6 +230,40 @@ TFB_SwapBuffers (int force_full_redraw)
 	graphics_backend->postprocess ();
 }
 
+/* Probably ought to clean this away at some point. */
+SDL_Surface *
+TFB_DisplayFormatAlpha (SDL_Surface *surface)
+{
+	SDL_Surface* newsurf;
+	SDL_PixelFormat* dstfmt;
+	const SDL_PixelFormat* srcfmt = surface->format;
+
+	// figure out what format to use (alpha/no alpha)
+	if (surface->format->Amask)
+		dstfmt = format_conv_surf->format;
+	else
+		dstfmt = SDL_Screen->format;
+
+	if (srcfmt->BytesPerPixel == dstfmt->BytesPerPixel &&
+			srcfmt->Rmask == dstfmt->Rmask &&
+			srcfmt->Gmask == dstfmt->Gmask &&
+			srcfmt->Bmask == dstfmt->Bmask &&
+			srcfmt->Amask == dstfmt->Amask)
+		return surface; // no conversion needed
+
+	newsurf = SDL_ConvertSurface (surface, dstfmt, surface->flags);
+	// Colorkeys and surface-level alphas cannot work at the same time,
+	// so we need to disable one of them
+	if (TFB_HasColorKey (surface) && newsurf &&
+			TFB_HasColorKey (newsurf) &&
+			TFB_HasSurfaceAlphaMod (newsurf))
+	{
+		TFB_DisableSurfaceAlphaMod (newsurf);
+	}
+
+	return newsurf;
+}
+
 // This function should only be called from the graphics thread,
 // like from a TFB_DrawCommand_Callback command.
 TFB_Canvas
@@ -238,6 +272,250 @@ TFB_GetScreenCanvas (SCREEN screen)
 	return SDL_Screens[screen];
 }
 
+void
+TFB_BlitSurface (SDL_Surface *src, SDL_Rect *srcrect, SDL_Surface *dst,
+		SDL_Rect *dstrect, int blend_numer, int blend_denom)
+{
+	BOOLEAN has_colorkey;
+	int x, y, x1, y1, x2, y2, dst_x2, dst_y2, nr, ng, nb;
+	int srcx, srcy, w, h;
+	Uint8 sr, sg, sb, dr, dg, db;
+	Uint32 src_pixval, dst_pixval, colorkey;
+	GetPixelFn src_getpix, dst_getpix;
+	PutPixelFn putpix;
+	SDL_Rect fulldst;
+
+	if (blend_numer == blend_denom)
+	{
+		// normal blit: dst = src
+
+		// log_add (log_Debug, "normal blit\n");
+		SDL_BlitSurface (src, srcrect, dst, dstrect);
+		return;
+	}
+
+	// NOTE: following clipping code is copied from SDL-1.2.4 sources
+
+	// If the destination rectangle is NULL, use the entire dest surface
+	if (dstrect == NULL)
+	{
+		fulldst.x = fulldst.y = 0;
+		dstrect = &fulldst;
+	}
+
+	// clip the source rectangle to the source surface
+	if (srcrect)
+	{
+		int maxw, maxh;
+
+		srcx = srcrect->x;
+		w = srcrect->w;
+		if (srcx < 0)
+		{
+			w += srcx;
+			dstrect->x -= srcx;
+			srcx = 0;
+		}
+		maxw = src->w - srcx;
+		if (maxw < w)
+			w = maxw;
+
+		srcy = srcrect->y;
+		h = srcrect->h;
+		if (srcy < 0)
+		{
+			h += srcy;
+			dstrect->y -= srcy;
+			srcy = 0;
+		}
+		maxh = src->h - srcy;
+		if (maxh < h)
+			h = maxh;
+	}
+	else
+	{
+		srcx = 0;
+		srcy = 0;
+		w = src->w;
+		h = src->h;
+	}
+
+	// clip the destination rectangle against the clip rectangle
+	{
+		SDL_Rect *clip = &dst->clip_rect;
+		int dx, dy;
+
+		dx = clip->x - dstrect->x;
+		if (dx > 0)
+		{
+			w -= dx;
+			dstrect->x += dx;
+			srcx += dx;
+		}
+		dx = dstrect->x + w - clip->x - clip->w;
+		if (dx > 0)
+			w -= dx;
+
+		dy = clip->y - dstrect->y;
+		if (dy > 0)
+		{
+			h -= dy;
+			dstrect->y += dy;
+			srcy += dy;
+		}
+		dy = dstrect->y + h - clip->y - clip->h;
+		if (dy > 0)
+			h -= dy;
+	}
+
+	dstrect->w = w;
+	dstrect->h = h;
+
+	if (w <= 0 || h <= 0)
+		return;
+
+	x1 = srcx;
+	y1 = srcy;
+	x2 = srcx + w;
+	y2 = srcy + h;
+
+	if (TFB_GetColorKey (src, &colorkey) < 0)
+	{
+		has_colorkey = FALSE;
+		colorkey = 0;  /* Satisfying compiler */
+	}
+	else
+	{
+		has_colorkey = TRUE;
+	}
+
+	src_getpix = getpixel_for (src);
+	dst_getpix = getpixel_for (dst);
+	putpix = putpixel_for (dst);
+
+	if (blend_denom < 0)
+	{
+		// additive blit: dst = src + dst
+#if 0
+		log_add (log_Debug, "additive blit %d %d, src %d %d %d %d dst %d %d,"
+				" srcbpp %d", blend_numer, blend_denom, x1, y1, x2, y2,
+				dstrect->x, dstrect->y, src->format->BitsPerPixel);
+#endif
+		for (y = y1; y < y2; ++y)
+		{
+			dst_y2 = dstrect->y + (y - y1);
+			for (x = x1; x < x2; ++x)
+			{
+				dst_x2 = dstrect->x + (x - x1);
+				src_pixval = src_getpix (src, x, y);
+
+				if (has_colorkey && src_pixval == colorkey)
+					continue;
+
+				dst_pixval = dst_getpix (dst, dst_x2, dst_y2);
+
+				SDL_GetRGB (src_pixval, src->format, &sr, &sg, &sb);
+				SDL_GetRGB (dst_pixval, dst->format, &dr, &dg, &db);
+
+				nr = sr + dr;
+				ng = sg + dg;
+				nb = sb + db;
+
+				if (nr > 255)
+					nr = 255;
+				if (ng > 255)
+					ng = 255;
+				if (nb > 255)
+					nb = 255;
+
+				putpix (dst, dst_x2, dst_y2,
+						SDL_MapRGB (dst->format, nr, ng, nb));
+			}
+		}
+	}
+	else if (blend_numer < 0)
+	{
+		// subtractive blit: dst = src - dst
+#if 0
+		log_add (log_Debug, "subtractive blit %d %d, src %d %d %d %d"
+				" dst %d %d, srcbpp %d", blend_numer, blend_denom,
+					x1, y1, x2, y2, dstrect->x, dstrect->y,
+					src->format->BitsPerPixel);
+#endif
+		for (y = y1; y < y2; ++y)
+		{
+			dst_y2 = dstrect->y + (y - y1);
+			for (x = x1; x < x2; ++x)
+			{
+				dst_x2 = dstrect->x + (x - x1);
+				src_pixval = src_getpix (src, x, y);
+
+				if (has_colorkey && src_pixval == colorkey)
+					continue;
+
+				dst_pixval = dst_getpix (dst, dst_x2, dst_y2);
+
+				SDL_GetRGB (src_pixval, src->format, &sr, &sg, &sb);
+				SDL_GetRGB (dst_pixval, dst->format, &dr, &dg, &db);
+
+				nr = sr - dr;
+				ng = sg - dg;
+				nb = sb - db;
+
+				if (nr < 0)
+					nr = 0;
+				if (ng < 0)
+					ng = 0;
+				if (nb < 0)
+					nb = 0;
+
+				putpix (dst, dst_x2, dst_y2,
+						SDL_MapRGB (dst->format, nr, ng, nb));
+			}
+		}
+	}
+	else
+	{
+		// modulated blit: dst = src * (blend_numer / blend_denom)
+
+		float f = blend_numer / (float)blend_denom;
+#if 0
+		log_add (log_Debug, "modulated blit %d %d, f %f, src %d %d %d %d"
+				" dst %d %d, srcbpp %d\n", blend_numer, blend_denom, f,
+				x1, y1, x2, y2, dstrect->x, dstrect->y,
+				src->format->BitsPerPixel);
+#endif
+		for (y = y1; y < y2; ++y)
+		{
+			dst_y2 = dstrect->y + (y - y1);
+			for (x = x1; x < x2; ++x)
+			{
+				dst_x2 = dstrect->x + (x - x1);
+				src_pixval = src_getpix (src, x, y);
+
+				if (has_colorkey && src_pixval == colorkey)
+					continue;
+
+				SDL_GetRGB (src_pixval, src->format, &sr, &sg, &sb);
+
+				nr = (int)(sr * f);
+				ng = (int)(sg * f);
+				nb = (int)(sb * f);
+
+				if (nr > 255)
+					nr = 255;
+				if (ng > 255)
+					ng = 255;
+				if (nb > 255)
+					nb = 255;
+
+				putpix (dst, dst_x2, dst_y2,
+						SDL_MapRGB (dst->format, nr, ng, nb));
+			}
+		}
+	}
+}
+
 void
 TFB_UploadTransitionScreen (void)
 {