[gtk/projective-transform: 1/2] gsk: Add some private transform apis

[Matthias Clasen <matthiasc src gnome org>]

commit 33c064f4f1f11596200eb9fffae37c6867a94f70
Author: Matthias Clasen <mclasen redhat com>
Date:   Tue Sep 1 08:36:45 2020 -0400

    gsk: Add some private transform apis
    
    Some of the graphene_matrix_transform apis don't work
    correctly with projective matrices, so add our own
    variants.

 gsk/gsktransform.c        | 77 +++++++++++++++++++++++++++++++++++++++++++++++
 gsk/gsktransformprivate.h | 10 ++++++
 2 files changed, 87 insertions(+)
---
diff --git a/gsk/gsktransform.c b/gsk/gsktransform.c
index a1b65ff13f..528b115865 100644
--- a/gsk/gsktransform.c
+++ b/gsk/gsktransform.c
@@ -2165,3 +2165,80 @@ gsk_transform_parse (const char    *string,
 
   return result; 
 }
+
+/* Some of the graphene_matrix_transform apis yield unexpected
+ * results with projective matrices, since they silently drop
+ * the w component, so we provide working alternatives here.
+ */
+void
+gsk_transform_point (const graphene_matrix_t *m,
+                     const graphene_point_t  *p,
+                     graphene_point_t        *res)
+{
+  graphene_vec4_t vec4;
+  float w;
+
+  graphene_vec4_init (&vec4, p->x, p->y, 0.0f, 1.0f);
+  graphene_matrix_transform_vec4 (m, &vec4, &vec4);
+
+  w = graphene_vec4_get_w (&vec4);
+  res->x = graphene_vec4_get_x (&vec4) / w;
+  res->y = graphene_vec4_get_y (&vec4) / w;
+}
+
+void
+gsk_transform_point3d (const graphene_matrix_t  *m,
+                       const graphene_point3d_t *p,
+                       graphene_point3d_t       *res)
+{
+  graphene_vec4_t vec4;
+  float w;
+
+  graphene_vec4_init (&vec4, p->x, p->y, 0.0f, 1.0f);
+  graphene_matrix_transform_vec4 (m, &vec4, &vec4);
+
+  w = graphene_vec4_get_w (&vec4);
+  res->x = graphene_vec4_get_x (&vec4) / w;
+  res->y = graphene_vec4_get_y (&vec4) / w;
+  res->z = graphene_vec4_get_z (&vec4) / w;
+}
+
+void
+gsk_transform_bounds (const graphene_matrix_t *m,
+                      const graphene_rect_t   *r,
+                      graphene_rect_t         *res)
+{
+  graphene_point_t ret[4];
+  float min_x, min_y;
+  float max_x, max_y;
+  graphene_rect_t rr;
+
+  graphene_rect_normalize_r (r, &rr);
+
+#define TRANSFORM_POINT(matrix, rect, corner, out_p)   do {\
+  graphene_vec4_t __s; \
+  graphene_point_t __p; \
+  float w; \
+  graphene_rect_get_ ## corner (rect, &__p); \
+  graphene_vec4_init (&__s, __p.x, __p.y, 0.f, 1.f); \
+  graphene_matrix_transform_vec4 (matrix, &__s, &__s); \
+  w = graphene_vec4_get_w (&__s); \
+  out_p.x = graphene_vec4_get_x (&__s) / w; \
+  out_p.y = graphene_vec4_get_y (&__s) / w;           } while (0)
+
+  TRANSFORM_POINT (m, &rr, top_left, ret[0]);
+  TRANSFORM_POINT (m, &rr, top_right, ret[1]);
+  TRANSFORM_POINT (m, &rr, bottom_right, ret[2]);
+  TRANSFORM_POINT (m, &rr, bottom_left, ret[3]);
+
+#undef TRANSFORM_POINT
+
+  /* FIXME: graphene doesn't export a fast way to do this */
+  min_x = MIN (MIN (ret[0].x, ret[1].x), MIN (ret[2].x, ret[3].x));
+  min_y = MIN (MIN (ret[0].y, ret[1].y), MIN (ret[2].y, ret[3].y));
+
+  max_x = MAX (MAX (ret[0].x, ret[1].x), MAX (ret[2].x, ret[3].x));
+  max_y = MAX (MAX (ret[0].y, ret[1].y), MAX (ret[2].y, ret[3].y));
+
+  graphene_rect_init (res, min_x, min_y, max_x - min_x, max_y - min_y);
+}
diff --git a/gsk/gsktransformprivate.h b/gsk/gsktransformprivate.h
index 79dfbf03b8..3e110d3c6f 100644
--- a/gsk/gsktransformprivate.h
+++ b/gsk/gsktransformprivate.h
@@ -32,6 +32,16 @@ G_BEGIN_DECLS
 gboolean                gsk_transform_parser_parse              (GtkCssParser           *parser,
                                                                  GskTransform          **out_transform);
 
+void gsk_transform_point   (const graphene_matrix_t  *m,
+                            const graphene_point_t   *p,
+                            graphene_point_t         *res);
+void gsk_transform_point3d (const graphene_matrix_t  *m,
+                            const graphene_point3d_t *p,
+                            graphene_point3d_t       *res);
+void gsk_transform_bounds  (const graphene_matrix_t  *m,
+                            const graphene_rect_t    *r,
+                            graphene_rect_t          *res);
+
 
 G_END_DECLS