twn_util: separate internal c-only features from public header

include/twn_types.h

@@ -0,0 +1,42 @@
+#ifndef TWN_TYPES_H
+#define TWN_TYPES_H
+
+#include <stdint.h>
+
+/* plain data aggregates that are accepted between public procedure boundaries */
+
+/* 32-bit color data */
+typedef struct Color {
+_Alignas(4)
+    uint8_t r;
+    uint8_t g;
+    uint8_t b;
+    uint8_t a;
+} Color;
+
+
+/* a rectangle with the origin at the upper left (integer) */
+typedef struct Recti {
+_Alignas(16)
+    int32_t x;
+    int32_t y;
+    int32_t w;
+    int32_t h;
+} Recti;
+
+
+/* a rectangle with the origin at the upper left (floating point) */
+typedef struct Rect {
+_Alignas(16)
+    float x;
+    float y;
+    float w;
+    float h;
+} Rect;
+
+
+typedef struct Matrix4 {
+    Vec4 row[4];
+} Matrix4;
+
+#endif