cogl/matrix: Import skew functions from Clutter

Graphene provides skewing as part of graphene_matrix_t API, and it'll
be easier for the transition to just expose similar API surfaces.

Move the matrix skew methods to CoglMatrix.

https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1439

2 files changed, 84 insertions, 0 deletions

diff --git a/cogl/cogl/cogl-matrix.c b/cogl/cogl/cogl-matrix.c
index 7bd2af0b0..17ee499dd 100644
--- a/cogl/cogl/cogl-matrix.c
+++ b/cogl/cogl/cogl-matrix.c
@@ -2246,3 +2246,42 @@ cogl_gtype_matrix_get_type (void)
 {
   return cogl_matrix_get_gtype ();
 }
+
+void
+cogl_matrix_skew_xy (CoglMatrix *matrix,
+                     float       factor)
+{
+  matrix->yx += matrix->xx * factor;
+  matrix->yy += matrix->xy * factor;
+  matrix->yz += matrix->xz * factor;
+  matrix->yw += matrix->xw * factor;
+
+  matrix->flags = (MAT_FLAG_GENERAL | MAT_DIRTY_ALL);
+  _COGL_MATRIX_DEBUG_PRINT (matrix);
+}
+
+void
+cogl_matrix_skew_xz (CoglMatrix *matrix,
+                     float       factor)
+{
+  matrix->zx += matrix->xx * factor;
+  matrix->zy += matrix->xy * factor;
+  matrix->zz += matrix->xz * factor;
+  matrix->zw += matrix->xw * factor;
+
+  matrix->flags = (MAT_FLAG_GENERAL | MAT_DIRTY_ALL);
+  _COGL_MATRIX_DEBUG_PRINT (matrix);
+}
+
+void
+cogl_matrix_skew_yz (CoglMatrix *matrix,
+                     float       factor)
+{
+  matrix->zx += matrix->yx * factor;
+  matrix->zy += matrix->yy * factor;
+  matrix->zz += matrix->yz * factor;
+  matrix->zw += matrix->yw * factor;
+
+  matrix->flags = (MAT_FLAG_GENERAL | MAT_DIRTY_ALL);
+  _COGL_MATRIX_DEBUG_PRINT (matrix);
+}
diff --git a/cogl/cogl/cogl-matrix.h b/cogl/cogl/cogl-matrix.h
index e784b094a..4b5eef699 100644
--- a/cogl/cogl/cogl-matrix.h
+++ b/cogl/cogl/cogl-matrix.h
@@ -760,6 +760,51 @@ GType cogl_matrix_get_gtype (void);
 COGL_EXPORT GType
 cogl_gtype_matrix_get_type (void);
 
+
+/**
+ * cogl_matrix_determinant:
+ * @matrix: a #CoglMatrix
+ *
+ * Computes the determinant of the @matrix.
+ *
+ * Returns: the value of the determinant
+ */
+COGL_EXPORT float
+cogl_matrix_determinant (const CoglMatrix *matrix);
+
+/**
+ * cogl_matrix_skew_xy:
+ * @matrix: a #CoglMatrix
+ * @factor: skew factor
+ *
+ * Adds a skew of factor on the X and Y axis to @matrix.
+ */
+COGL_EXPORT void
+cogl_matrix_skew_xy (CoglMatrix *matrix,
+                     float       factor);
+
+/**
+ * cogl_matrix_skew_xz:
+ * @matrix: a #CoglMatrix
+ * @factor: skew factor
+ *
+ * Adds a skew of factor on the X and Z axis to @matrix.
+ */
+COGL_EXPORT void
+cogl_matrix_skew_xz (CoglMatrix *matrix,
+                     float       factor);
+
+/**
+ * cogl_matrix_skew_yz:
+ * @matrix: a #CoglMatrix
+ * @factor: skew factor
+ *
+ * Adds a skew of factor on the Y and Z axis to @matrix.
+ */
+COGL_EXPORT void
+cogl_matrix_skew_yz (CoglMatrix *matrix,
+                     float       factor);
+
 G_END_DECLS
 
 #endif /* __COGL_MATRIX_H */