[c][cpp] Clipping fix, see #1219

spine-c/spine-c/src/spine/SkeletonClipping.c

@@ -161,21 +161,33 @@ int /*boolean*/ _clip(spSkeletonClipping* self, float x1, float y1, float x2, fl
 			int side2 = deltaX * (inputY2 - edgeY2) - deltaY * (inputX2 - edgeX2) > 0;
 			if (deltaX * (inputY - edgeY2) - deltaY * (inputX - edgeX2) > 0) {
 				float c0, c2;
-				float ua;
+				float s, ua;
 				if (side2) {
 					spFloatArray_add(output, inputX2);
 					spFloatArray_add(output, inputY2);
 					continue;
 				}
 				c0 = inputY2 - inputY, c2 = inputX2 - inputX;
-				ua = (c2 * (edgeY - inputY) - c0 * (edgeX - inputX)) / (c0 * (edgeX2 - edgeX) - c2 * (edgeY2 - edgeY));
-				spFloatArray_add(output, edgeX + (edgeX2 - edgeX) * ua);
-				spFloatArray_add(output, edgeY + (edgeY2 - edgeY) * ua);
+				s = c0 * (edgeX2 - edgeX) - c2 * (edgeY2 - edgeY);
+				if (ABS(s) > 0.000001f) {
+					ua = (c2 * (edgeY - inputY) - c0 * (edgeX - inputX)) / s;
+					spFloatArray_add(output, edgeX + (edgeX2 - edgeX) * ua);
+					spFloatArray_add(output, edgeY + (edgeY2 - edgeY) * ua);
+				} else {
+					spFloatArray_add(output, edgeX);
+					spFloatArray_add(output, edgeY);
+				}
 			} else if (side2) {
 				float c0 = inputY2 - inputY, c2 = inputX2 - inputX;
-				float ua = (c2 * (edgeY - inputY) - c0 * (edgeX - inputX)) / (c0 * (edgeX2 - edgeX) - c2 * (edgeY2 - edgeY));
-				spFloatArray_add(output, edgeX + (edgeX2 - edgeX) * ua);
-				spFloatArray_add(output, edgeY + (edgeY2 - edgeY) * ua);
+				float s = c0 * (edgeX2 - edgeX) - c2 * (edgeY2 - edgeY);
+				if (ABS(s) > 0.000001f) {
+					float ua = (c2 * (edgeY - inputY) - c0 * (edgeX - inputX)) / s;
+					spFloatArray_add(output, edgeX + (edgeX2 - edgeX) * ua);
+					spFloatArray_add(output, edgeY + (edgeY2 - edgeY) * ua);
+				} else {
+					spFloatArray_add(output, edgeX);
+					spFloatArray_add(output, edgeY);
+				}
 				spFloatArray_add(output, inputX2);
 				spFloatArray_add(output, inputY2);
 			}

spine-cpp/spine-cpp/src/spine/SkeletonClipping.cpp

@@ -250,17 +250,27 @@ bool SkeletonClipping::clip(float x1, float y1, float x2, float y2, float x3, fl
 				}
 				// v1 inside, v2 outside
 				float c0 = inputY2 - inputY, c2 = inputX2 - inputX;
-				float ua = (c2 * (edgeY - inputY) - c0 * (edgeX - inputX)) /
-						   (c0 * (edgeX2 - edgeX) - c2 * (edgeY2 - edgeY));
-				output->add(edgeX + (edgeX2 - edgeX) * ua);
-				output->add(edgeY + (edgeY2 - edgeY) * ua);
+				float s = c0 * (edgeX2 - edgeX) - c2 * (edgeY2 - edgeY);
+				if (MathUtil::abs(s) > 0.000001f) {
+					float ua = (c2 * (edgeY - inputY) - c0 * (edgeX - inputX)) / s;
+					output->add(edgeX + (edgeX2 - edgeX) * ua);
+					output->add(edgeY + (edgeY2 - edgeY) * ua);
+				} else {
+					output->add(edgeX);
+					output->add(edgeY);
+				}
 			} else if (side2) {
 				// v1 outside, v2 inside
 				float c0 = inputY2 - inputY, c2 = inputX2 - inputX;
-				float ua = (c2 * (edgeY - inputY) - c0 * (edgeX - inputX)) /
-						   (c0 * (edgeX2 - edgeX) - c2 * (edgeY2 - edgeY));
-				output->add(edgeX + (edgeX2 - edgeX) * ua);
-				output->add(edgeY + (edgeY2 - edgeY) * ua);
+				float s = c0 * (edgeX2 - edgeX) - c2 * (edgeY2 - edgeY);
+				if (MathUtil::abs(s) > 0.000001f) {
+					float ua = (c2 * (edgeY - inputY) - c0 * (edgeX - inputX)) / s;
+					output->add(edgeX + (edgeX2 - edgeX) * ua);
+					output->add(edgeY + (edgeY2 - edgeY) * ua);
+				} else {
+					output->add(edgeX);
+					output->add(edgeY);
+				}
 				output->add(inputX2);
 				output->add(inputY2);
 			}