cleanup manual value clamping: sdl2_to_1_2_backports.cpp (#2580)

* cleanup manual value clamping: sdl2_to_1_2_backports.cpp
* static_cast Sint16 and int in SDL_BlitScaled

Source/utils/sdl2_to_1_2_backports.cpp

@@ -1,6 +1,7 @@
 #include "./sdl2_to_1_2_backports.h"
 
 #include <cstddef>
+#include <algorithm>
 
 #include "./console.h"
 
@@ -447,26 +448,18 @@ int SDL_BlitScaled(SDL_Surface *src, SDL_Rect *srcrect,
 	dst_y0 += dst->clip_rect.y;
 	dst_y1 += dst->clip_rect.y;
 
-	final_src.x = (Sint16)SDL_floor(src_x0 + 0.5);
-	final_src.y = (Sint16)SDL_floor(src_y0 + 0.5);
-	src_w = (int)SDL_floor(src_x1 + 1 + 0.5) - (int)SDL_floor(src_x0 + 0.5);
-	src_h = (int)SDL_floor(src_y1 + 1 + 0.5) - (int)SDL_floor(src_y0 + 0.5);
-	if (src_w < 0)
-		src_w = 0;
-	if (src_h < 0)
-		src_h = 0;
+	final_src.x = static_cast<Sint16>(SDL_floor(src_x0 + 0.5));
+	final_src.y = static_cast<Sint16>(SDL_floor(src_y0 + 0.5));
+	src_w = std::max(static_cast<int>(SDL_floor(src_x1 + 1 + 0.5)) - static_cast<int>(SDL_floor(src_x0 + 0.5)), 0);
+	src_h = std::max(static_cast<int>(SDL_floor(src_y1 + 1 + 0.5)) - static_cast<int>(SDL_floor(src_y0 + 0.5)), 0);
 
 	final_src.w = static_cast<Uint16>(src_w);
 	final_src.h = static_cast<Uint16>(src_h);
 
-	final_dst.x = (Sint16)SDL_floor(dst_x0 + 0.5);
-	final_dst.y = (Sint16)SDL_floor(dst_y0 + 0.5);
-	dst_w = (int)SDL_floor(dst_x1 - dst_x0 + 1.5);
-	dst_h = (int)SDL_floor(dst_y1 - dst_y0 + 1.5);
-	if (dst_w < 0)
-		dst_w = 0;
-	if (dst_h < 0)
-		dst_h = 0;
+	final_dst.x = static_cast<Sint16>(SDL_floor(dst_x0 + 0.5));
+	final_dst.y = static_cast<Sint16>(SDL_floor(dst_y0 + 0.5));
+	dst_w = std::max(static_cast<int>(SDL_floor(dst_x1 - dst_x0 + 1.5)), 0);
+	dst_h = std::max(static_cast<int>(SDL_floor(dst_y1 - dst_y0 + 1.5)), 0);
 
 	final_dst.w = static_cast<Uint16>(dst_w);
 	final_dst.h = static_cast<Uint16>(dst_h);