cogl-matrix: Add a public cogl_matrix_transpose()

This function takes a single matrix argument and replaces the matrix
with its transpose.

Reviewed-by: Robert Bragg <robert@linux.intel.com>

cogl/cogl-matrix.c

@@ -1689,7 +1689,6 @@ cogl_matrix_init_from_quaternion (CoglMatrix *matrix,
   _cogl_matrix_init_from_quaternion (matrix, quaternion);
 }
 
-#if 0
 /*
  * Transpose a float matrix.
  */
@@ -1713,7 +1712,6 @@ _cogl_matrix_util_transposef (float to[16], const float from[16])
   to[14] = from[11];
   to[15] = from[15];
 }
-#endif
 
 void
 cogl_matrix_view_2d_in_frustum (CoglMatrix *matrix,
@@ -2122,3 +2120,18 @@ cogl_matrix_look_at (CoglMatrix *matrix,
 
   cogl_matrix_multiply (matrix, matrix, &tmp);
 }
+
+void
+cogl_matrix_transpose (CoglMatrix *matrix)
+{
+  float new_values[16];
+
+  /* We don't need to do anything if the matrix is the identity matrix */
+  if (!(matrix->flags & MAT_DIRTY_TYPE) &&
+      matrix->type == COGL_MATRIX_TYPE_IDENTITY)
+    return;
+
+  _cogl_matrix_util_transposef (new_values, cogl_matrix_get_array (matrix));
+
+  cogl_matrix_init_from_array (matrix, new_values);
+}

cogl/cogl-matrix.h

@@ -653,6 +653,18 @@ cogl_matrix_project_points (const CoglMatrix *matrix,
 gboolean
 cogl_matrix_is_identity (const CoglMatrix *matrix);
 
+/**
+ * cogl_matrix_transpose:
+ * @matrix: A #CoglMatrix
+ *
+ * Replaces @matrix with its transpose. Ie, every element (i,j) in the
+ * new matrix is taken from element (j,i) in the old matrix.
+ *
+ * Since: 1.10
+ */
+void
+cogl_matrix_transpose (CoglMatrix *matrix);
+
 #ifdef _COGL_SUPPORTS_GTYPE_INTEGRATION
 
 #define COGL_GTYPE_TYPE_MATRIX (cogl_gtype_matrix_get_type ())

doc/reference/cogl-2.0-experimental/cogl-2.0-experimental-sections.txt

@@ -486,6 +486,7 @@ cogl_matrix_multiply
 cogl_matrix_rotate
 cogl_matrix_translate
 cogl_matrix_scale
+cogl_matrix_transpose
 cogl_matrix_get_array
 cogl_matrix_get_inverse
 cogl_matrix_transform_point

doc/reference/cogl/cogl-sections.txt

@@ -463,6 +463,7 @@ cogl_matrix_multiply
 cogl_matrix_rotate
 cogl_matrix_translate
 cogl_matrix_scale
+cogl_matrix_transpose
 cogl_matrix_init_from_array
 cogl_matrix_get_array
 cogl_matrix_get_inverse