1 files changed, 43 insertions, 0 deletions
diff --git a/src/rotrect.c b/src/rotrect.c
new file mode 100644
index 0000000..5abae13
--- /dev/null
+++ b/src/rotrect.c
@@ -0,0 +1,43 @@
+#include "rotrect.h"
+#include "cfg.h"
+#include "lzy.h"
+#include <math.h>
+
+static void
+rotate(double *x, double *y, double angle)
+{
+	const double s = sin(angle);
+	const double c = cos(angle);
+	const double ox = *x;
+	const double oy = *y;
+
+	*x = ox * c - oy * s;
+	*y = ox * s + oy * c;
+}
+
+void
+rotrect(double x, double y, double width, double height, double angle)
+{
+	double xs[4] = {
+		width / 2.0,
+		width / 2.0,
+		-width / 2.0,
+		-width / 2.0,
+	};
+	double ys[4] = {
+		-height / 2.0,
+		height / 2.0,
+		height / 2.0,
+		-height / 2.0,
+	};
+	for (int i = 0; i < 4; i++) {
+		rotate(&xs[i], &ys[i], angle);
+		xs[i] = round(xs[i] + x);
+		ys[i] = round(ys[i] + y);
+	}
+	LZY_DrawLine(xs[0], ys[0], xs[1], ys[1]);
+	LZY_DrawLine(xs[1], ys[1], xs[2], ys[2]);
+	LZY_DrawLine(xs[2], ys[2], xs[3], ys[3]);
+	LZY_DrawLine(xs[3], ys[3], xs[0], ys[0]);
+}
+