add plutovg_matrix_rotate_translate

aleyn · Jan 15, 2021 · 91ebcfc · 91ebcfc
1 parent e779c12
commit 91ebcfc
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diff --git a/include/plutovg.h b/include/plutovg.h
@@ -45,10 +45,12 @@ void plutovg_matrix_init_translate(plutovg_matrix_t* matrix, double x, double y)
 void plutovg_matrix_init_scale(plutovg_matrix_t* matrix, double x, double y);
 void plutovg_matrix_init_shear(plutovg_matrix_t* matrix, double x, double y);
 void plutovg_matrix_init_rotate(plutovg_matrix_t* matrix, double radians);
+void plutovg_matrix_init_rotate_translate(plutovg_matrix_t* matrix, double radians, double x, double y);
 void plutovg_matrix_translate(plutovg_matrix_t* matrix, double x, double y);
 void plutovg_matrix_scale(plutovg_matrix_t* matrix, double x, double y);
 void plutovg_matrix_shear(plutovg_matrix_t* matrix, double x, double y);
 void plutovg_matrix_rotate(plutovg_matrix_t* matrix, double radians);
+void plutovg_matrix_rotate_translate(plutovg_matrix_t* matrix, double radians, double x, double y);
 void plutovg_matrix_multiply(plutovg_matrix_t* matrix, const plutovg_matrix_t* a, const plutovg_matrix_t* b);
 int plutovg_matrix_invert(plutovg_matrix_t* matrix);
 void plutovg_matrix_map(const plutovg_matrix_t* matrix, double x, double y, double* _x, double* _y);

diff --git a/source/plutovg-geometry.c b/source/plutovg-geometry.c
@@ -39,6 +39,17 @@ void plutovg_matrix_init_rotate(plutovg_matrix_t* matrix, double radians)
     plutovg_matrix_init(matrix, c, s, -s, c, 0.0, 0.0);
 }
 
+void plutovg_matrix_init_rotate_translate(plutovg_matrix_t* matrix, double radians, double x, double y)
+{
+    double c = cos(radians);
+    double s = sin(radians);
+
+    double cx = x * (1 - c) + y * s;
+    double cy = y * (1 - c) - x * s;
+
+    plutovg_matrix_init(matrix, c, s, -s, c, cx, cy);
+}
+
 void plutovg_matrix_translate(plutovg_matrix_t* matrix, double x, double y)
 {
     plutovg_matrix_t m;
@@ -67,6 +78,13 @@ void plutovg_matrix_rotate(plutovg_matrix_t* matrix, double radians)
     plutovg_matrix_multiply(matrix, &m, matrix);
 }
 
+void plutovg_matrix_rotate_translate(plutovg_matrix_t* matrix, double radians, double x, double y)
+{
+    plutovg_matrix_t m;
+    plutovg_matrix_init_rotate_translate(&m, radians, x, y);
+    plutovg_matrix_multiply(matrix, &m, matrix);
+}
+
 void plutovg_matrix_multiply(plutovg_matrix_t* matrix, const plutovg_matrix_t* a, const plutovg_matrix_t* b)
 {
     double m00 = a->m00 * b->m00 + a->m10 * b->m01;