From 091c475422613e77037803f076249fa506d8127d Mon Sep 17 00:00:00 2001
From: Artemii Miasoedov <artem.myasoedov@gmail.com>
Date: Sun, 16 Feb 2025 14:39:10 +0300
Subject: [PATCH] Implemented 2D affine post transformations (translate,
 rotate, scale)

---
 include/cglm/affine2d-post.h | 132 +++++++++++++++++++++++++++++++++++
 1 file changed, 132 insertions(+)
 create mode 100644 include/cglm/affine2d-post.h

diff --git a/include/cglm/affine2d-post.h b/include/cglm/affine2d-post.h
new file mode 100644
index 0000000..c6605a8
--- /dev/null
+++ b/include/cglm/affine2d-post.h
@@ -0,0 +1,132 @@
+/*
+ * Copyright (c), Recep Aslantas.
+ *
+ * MIT License (MIT), http://opensource.org/licenses/MIT
+ * Full license can be found in the LICENSE file
+ */
+
+#ifndef cglm_affine2d_post_h
+#define cglm_affine2d_post_h
+
+/*
+ Functions:
+   CGLM_INLINE void glm_translated2d(mat3 m, vec2 v);
+   CGLM_INLINE void glm_translated2d_x(mat3 m, float to);
+   CGLM_INLINE void glm_translated2d_y(mat3 m, float to);
+   CGLM_INLINE void glm_rotated2d(mat3 m, float angle);
+   CGLM_INLINE void glm_scaled2d(mat3 m, vec2 v);
+   CGLM_INLINE void glm_scaled2d_uni(mat3 m, float s);
+ */
+
+#include "vec2.h"
+
+/*!
+ * @brief translate existing transform matrix by v vector
+ *        and store result in same matrix
+ *
+ *  this is POST transform, applies to existing transform as last transform
+ *
+ * @param[in, out]  m  affine transform
+ * @param[in]       v  translate vector [x, y]
+ */
+CGLM_INLINE
+void
+glm_translated2d(mat3 m, vec2 v) {
+  glm_vec2_add(m[2], v, m[2]);
+}
+
+/*!
+ * @brief translate existing transform matrix by x factor
+ *
+ *  this is POST transform, applies to existing transform as last transform
+ *
+ * @param[in, out]  m  affine transform
+ * @param[in]       x  x factor
+ */
+CGLM_INLINE
+void
+glm_translated2d_x(mat3 m, float x) {
+  m[2][0] += x;
+}
+
+/*!
+ * @brief translate existing transform matrix by y factor
+ *
+ *  this is POST transform, applies to existing transform as last transform
+ *
+ * @param[in, out]  m  affine transform
+ * @param[in]       y  y factor
+ */
+CGLM_INLINE
+void
+glm_translated2d_y(mat3 m, float y) {
+  m[2][1] += y;
+}
+
+/*!
+ * @brief rotate existing transform matrix by angle
+ *
+ *  this is POST transform, applies to existing transform as last transform
+ *
+ * @param[in, out]   m      affine transform
+ * @param[in]   angle  angle (radians)
+ */
+CGLM_INLINE
+void
+glm_rotated2d(mat3 m, float angle) {
+  float c = cosf(angle),
+        s = sinf(angle),
+
+        m00 = m[0][0], m10 = m[1][0], m20 = m[2][0],
+        m01 = m[0][1], m11 = m[1][1], m21 = m[2][1];
+
+  m[0][0] = c * m00 - s * m01;
+  m[1][0] = c * m10 - s * m11;
+  m[2][0] = c * m20 - s * m21;
+
+  m[0][1] = s * m00 + c * m01;
+  m[1][1] = s * m10 + c * m11;
+  m[2][1] = s * m20 + c * m21;
+}
+
+/*!
+ * @brief scale existing 2d transform matrix by v vector
+ *
+ *  this is POST transform, applies to existing transform as last transform
+ *
+ * @param[in, out]   m      affine transform
+ * @param[in]   v  scale vector [x, y]
+ */
+CGLM_INLINE
+void
+glm_scaled2d(mat3 m, vec2 v) {
+  m[0][0] *= v[0];
+  m[1][0] *= v[0];
+  m[2][0] *= v[0];
+
+  m[0][1] *= v[1];
+  m[1][1] *= v[1];
+  m[2][1] *= v[1];
+}
+
+/*!
+ * @brief applies uniform scale to existing 2d transform matrix v = [s, s]
+ *
+ *  this is POST transform, applies to existing transform as last transform
+ *
+ * @param[in, out]  m  affine transform
+ * @param[in]       s  scale factor
+ */
+CGLM_INLINE
+void
+glm_scaled2d_uni(mat3 m, float s) {
+  m[0][0] *= s;
+  m[1][0] *= s;
+  m[2][0] *= s;
+
+  m[0][1] *= s;
+  m[1][1] *= s;
+  m[2][1] *= s;
+}
+
+#endif /* cglm_affine2d_post_h */