Fix texture clipping

src/texture.cpp

@@ -30,6 +30,9 @@
 #include <png.h>
 #include <endian.h>
 #include <vector>
+#if !defined(NDEBUG)
+#	include <cmath>
+#endif
 
 #define lengthof(a) (static_cast<int32_t>(sizeof(a) / sizeof(a[0])))
 
@@ -113,6 +116,15 @@ namespace cloonel {
 		bool IsRectCompletelyInsideRect ( const RectFloat& parInner, const RectFloat& parOuter ) a_pure;
 #endif
 
+#if !defined(NDEBUG)
+		bool areEqualRel (float parA, float parB, float parEpsilon) a_pure;
+
+		//see: http://stackoverflow.com/questions/4548004/how-to-correctly-and-standardly-compare-floats
+		bool areEqualRel (float parA, float parB, float parEpsilon) {
+			return (std::fabs(parA - parB) <= parEpsilon * std::max(std::fabs(parA), std::fabs(parB)));
+		}
+#endif
+
 		///----------------------------------------------------------------------
 		///----------------------------------------------------------------------
 		SDL_Surface* SurfaceFromPng (PixelFormat parPixelFormat, ushort2 parSize, const png_structp& parPngPtr, const png_infop& parInfoPtr, std::vector<uint8_t>& parBuff) {
@@ -260,6 +272,7 @@ namespace cloonel {
 		///got set to a valid value, otherwise false.
 		///----------------------------------------------------------------------
 		bool ClipRect (RectFloat& parSrc, RectFloat& parDest, const RectFloat& parClip) {
+			assert(areEqualRel(parSrc.Width(), parDest.Width(), 0.00001f));
 			assert(parSrc.IsValid());
 			assert(parDest.IsValid());
 
@@ -268,29 +281,34 @@ namespace cloonel {
 			if (parDest.to <= parClip.from or parDest.from >= parClip.to)
 				return false;
 
-			{
+			RectFloat dst;
-				const RectFloat clip(float2(0.0f), float2(1.0f));
+			dst.from.x() = std::max(parDest.from.x(), parClip.from.x());
-				const float2 srcWidthHeight(parSrc.WidthHeight());
+			dst.from.y() = std::max(parDest.from.y(), parClip.from.y());
-				const float2 scaledOffs((parDest.from - parClip.from) / parClip.WidthHeight());
+			dst.to.x() = std::min(parDest.to.x(), parClip.to.x());
-				parSrc.from -= float2(std::min(0.0f, scaledOffs.x() * srcWidthHeight.x()), std::min(0.0f, scaledOffs.y() * srcWidthHeight.y()));
+			dst.to.y() = std::min(parDest.to.y(), parClip.to.y());
-				const float2 scaledCrop((parClip.to - parDest.to) / parClip.WidthHeight());
-				parSrc.to += float2(std::min(0.0f, scaledCrop.x() * srcWidthHeight.x()), std::min(0.0f, scaledCrop.y() * srcWidthHeight.y()));
-				assert(parSrc.IsValid());
-			}
-
-			RectFloat dst(parDest.from - parClip.from, parDest.to - parClip.from);
-			dst.from.x() = std::max(dst.from.x(), parClip.from.x());
-			dst.from.y() = std::max(dst.from.y(), parClip.from.y());
-			dst.to.x() = std::min(dst.to.x(), parClip.to.x());
-			dst.to.y() = std::min(dst.to.y(), parClip.to.y());
 
 			if (not dst.IsValid())
 				return false;
 
-			parDest.from += parClip.from;
+			assert(parDest.from <= dst.from);
-			parDest.to += parClip.from;
+			assert(parDest.to >= dst.to);
 
-			assert(parDest.IsValid());
+			RectFloat src;
+			{
+				const float2 srcWidthHeight(parSrc.WidthHeight());
+				const float2 scaledOffs((dst.from - parDest.from) / parDest.WidthHeight());
+				src.from = parSrc.from + scaledOffs * srcWidthHeight;
+				const float2 scaledCrop((parDest.to - dst.to) / parDest.WidthHeight());
+				src.to = parSrc.to - scaledCrop * srcWidthHeight;
+				assert(src.IsValid());
+
+				assert(dst.IsValid());
+				assert(dst.from >= parClip.from);
+				assert(dst.to <= parClip.to);
+				assert(areEqualRel(src.Width(), dst.Width(), 0.00001f));
+			}
+			parDest = dst;
+			parSrc = src;
 			return true;
 		}