clutter: Use graphene_matrix_inverse()

Instead of our own implementation that upscales, then downscales back,
use graphene_matrix_inverse() directly. This is possible after switching
to a z-near value that doesn't have problems with float precision.

https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1489

3 files changed, 2 insertions, 53 deletions

diff --git a/cogl/cogl/cogl-graphene.c b/cogl/cogl/cogl-graphene.c
index 90e1f5b86..d9bd3bd42 100644
--- a/cogl/cogl/cogl-graphene.c
+++ b/cogl/cogl/cogl-graphene.c
@@ -274,38 +274,3 @@ cogl_graphene_matrix_project_points (const graphene_matrix_t *matrix,
                          n_points);
     }
 }
-
-gboolean
-cogl_graphene_matrix_get_inverse (const graphene_matrix_t *matrix,
-                                  graphene_matrix_t       *inverse)
-{
-  graphene_matrix_t scaled;
-  graphene_matrix_t m;
-  gboolean invertible;
-  float pivot = G_MAXFLOAT;
-  float v[16];
-  float scale;
-
-  graphene_matrix_init_from_matrix (&m, matrix);
-  graphene_matrix_to_float (&m, v);
-
-  pivot = MIN (pivot, v[0]);
-  pivot = MIN (pivot, v[5]);
-  pivot = MIN (pivot, v[10]);
-  pivot = MIN (pivot, v[15]);
-  scale = 1.f / pivot;
-
-  graphene_matrix_init_scale (&scaled, scale, scale, scale);
-
-  /* Float precision is a limiting factor */
-  graphene_matrix_multiply (&m, &scaled, &m);
-
-  invertible = graphene_matrix_inverse (&m, inverse);
-
-  if (invertible)
-    graphene_matrix_multiply (&scaled, inverse, inverse);
-  else
-    graphene_matrix_init_identity (inverse);
-
-  return invertible;
-}
diff --git a/cogl/cogl/cogl-graphene.h b/cogl/cogl/cogl-graphene.h
index 4a561f6d8..420629710 100644
--- a/cogl/cogl/cogl-graphene.h
+++ b/cogl/cogl/cogl-graphene.h
@@ -163,22 +163,6 @@ cogl_graphene_matrix_project_points (const graphene_matrix_t *matrix,
                                      void                    *points_out,
                                      int                      n_points);
 
-/**
- * cogl_graphene_matrix_get_inverse:
- * @matrix: A 4x4 transformation matrix
- * @inverse: (out): The destination for a 4x4 inverse transformation matrix
- *
- * Gets the inverse transform of a given matrix and uses it to initialize
- * a new #graphene_matrix_t.
- *
- * Return value: %TRUE if the inverse was successfully calculated or %FALSE
- *   for degenerate transformations that can't be inverted (in this case the
- *   @inverse matrix will simply be initialized with the identity matrix)
- */
-COGL_EXPORT gboolean
-cogl_graphene_matrix_get_inverse (const graphene_matrix_t *matrix,
-                                  graphene_matrix_t       *inverse);
-
 G_END_DECLS
 
 #endif /* COGL_GRAPHENE_H */
diff --git a/cogl/cogl/cogl-matrix-stack.c b/cogl/cogl/cogl-matrix-stack.c
index 3f6883068..4e132baf5 100644
--- a/cogl/cogl/cogl-matrix-stack.c
+++ b/cogl/cogl/cogl-matrix-stack.c
@@ -358,9 +358,9 @@ cogl_matrix_stack_get_inverse (CoglMatrixStack   *stack,
   graphene_matrix_t *internal = cogl_matrix_stack_get (stack, &matrix);
 
   if (internal)
-    return cogl_graphene_matrix_get_inverse (internal, inverse);
+    return graphene_matrix_inverse (internal, inverse);
   else
-    return cogl_graphene_matrix_get_inverse (&matrix, inverse);
+    return graphene_matrix_inverse (&matrix, inverse);
 }
 
 /* In addition to writing the stack matrix into the give @matrix