snapshot: Fix wrong nodes with transformed shadows

Test included.

The test is disabled for Cairo because the Cairo blurring code can't
deal with scaling, which makes things come out wrong for the test that
checks that we do the right thing with the blur radius when scaling.

Related: !6977

gtk/gtksnapshot.c

@@ -747,8 +747,14 @@ gtk_graphene_rect_scale_affine (const graphene_rect_t *rect,
     graphene_rect_normalize (res);
 }
 
+typedef enum {
+  ENSURE_POSITIVE_SCALE = (1 << 0),
+  ENSURE_UNIFORM_SCALE = (1 << 1),
+} GtkEnsureFlags;
+
 static void
-gtk_snapshot_ensure_affine (GtkSnapshot *snapshot,
+gtk_snapshot_ensure_affine_with_flags (GtkSnapshot    *snapshot,
+                                       GtkEnsureFlags  flags,
                                        float          *scale_x,
                                        float          *scale_y,
                                        float          *dx,
@@ -765,7 +771,8 @@ gtk_snapshot_ensure_affine (GtkSnapshot *snapshot,
   else if (gsk_transform_get_category (state->transform) == GSK_TRANSFORM_CATEGORY_2D_AFFINE)
     {
       gsk_transform_to_affine (state->transform, scale_x, scale_y, dx, dy);
-      if (*scale_x < 0.0 || *scale_y < 0.0)
+      if (((flags & ENSURE_POSITIVE_SCALE) && (*scale_x < 0.0 || *scale_y < 0.0)) ||
+          ((flags & ENSURE_UNIFORM_SCALE) && (*scale_x != *scale_y)))
         {
           gtk_snapshot_autopush_transform (snapshot);
           state = gtk_snapshot_get_current_state (snapshot);
@@ -778,6 +785,19 @@ gtk_snapshot_ensure_affine (GtkSnapshot *snapshot,
     }
 }
 
+static void
+gtk_snapshot_ensure_affine (GtkSnapshot *snapshot,
+                            float       *scale_x,
+                            float       *scale_y,
+                            float       *dx,
+                            float       *dy)
+{
+  gtk_snapshot_ensure_affine_with_flags (snapshot,
+                                         ENSURE_POSITIVE_SCALE,
+                                         scale_x, scale_y,
+                                         dx, dy);
+}
+
 static void
 gtk_snapshot_ensure_translate (GtkSnapshot *snapshot,
                                float       *dx,
@@ -1377,11 +1397,19 @@ gtk_snapshot_push_shadow (GtkSnapshot     *snapshot,
                           const GskShadow *shadow,
                           gsize            n_shadows)
 {
-  const GtkSnapshotState *current_state = gtk_snapshot_get_current_state (snapshot);
   GtkSnapshotState *state;
+  GskTransform *transform;
+  float scale_x, scale_y, dx, dy;
+  gsize i;
+
+  gtk_snapshot_ensure_affine_with_flags (snapshot,
+                                         ENSURE_POSITIVE_SCALE | ENSURE_UNIFORM_SCALE,
+                                         &scale_x, &scale_y,
+                                         &dx, &dy);
+  transform = gsk_transform_scale (gsk_transform_translate (NULL, &GRAPHENE_POINT_INIT (dx, dy)), scale_x, scale_y);
 
   state = gtk_snapshot_push_state (snapshot,
-                                   current_state->transform,
+                                   transform,
                                    gtk_snapshot_collect_shadow,
                                    gtk_snapshot_clear_shadow);
 
@@ -1390,13 +1418,23 @@ gtk_snapshot_push_shadow (GtkSnapshot     *snapshot,
     {
       state->data.shadow.shadows = NULL;
       memcpy (&state->data.shadow.a_shadow, shadow, sizeof (GskShadow));
+      state->data.shadow.a_shadow.dx *= scale_x;
+      state->data.shadow.a_shadow.dy *= scale_y;
+      state->data.shadow.a_shadow.radius *= scale_x;
     }
   else
     {
       state->data.shadow.shadows = g_malloc (sizeof (GskShadow) * n_shadows);
       memcpy (state->data.shadow.shadows, shadow, sizeof (GskShadow) * n_shadows);
+      for (i = 0; i < n_shadows; i++)
+        {
+          state->data.shadow.shadows[i].dx *= scale_x;
+          state->data.shadow.shadows[i].dy *= scale_y;
+          state->data.shadow.shadows[i].radius *= scale_x;
+        }
     }
 
+  gsk_transform_unref (transform);
 }
 
 static GskRenderNode *

testsuite/gsk/compare/shadow-replay-nocairo.node

@@ -0,0 +1,63 @@
+color {
+  bounds: -10 0 70 60;
+  color: white;
+}
+
+transform {
+  transform: scale(5);
+  child: shadow {
+    shadows: black 0 1;
+    child: color {
+      bounds: 0 0 10 1;
+      color: red;
+    }
+  }
+}
+
+transform {
+  transform: rotate(90);
+  child: shadow {
+    shadows: black 5 0;
+    child: color {
+      bounds: 20 -50 5 50;
+      color: lime;
+    }
+  }
+}
+
+clip {
+  clip: 0 40 50 10;
+  child: color-matrix "larry" {
+    matrix: matrix3d(1000, 0, 0, 0,
+                     0, 1000, 0, 0,
+                     0, 0, 1000, 0,
+                     0, 0, 0, 1000);
+    child: transform {
+      transform: scale(5, 1);
+      child: shadow {
+        shadows: black 0 5 2;
+        child: color {
+          bounds: 0 40 10 5;
+          color: yellow;
+        }
+      }
+    }
+  }
+}
+
+/* This should be covered by the blur above */
+clip {
+  clip: -10 45 5 5;
+  child: "larry";
+}
+clip {
+  clip: 55 45 5 5;
+  child: "larry";
+}
+
+/* This should not */
+clip {
+  clip:  0 55 50 5;
+  child: "larry";
+}
+

testsuite/gsk/meson.build

@@ -149,6 +149,7 @@ compare_render_tests = [
   'shadow-offset-clip',
   'shadow-offset-to-outside-clip',
   'shadow-opacity',
+  'shadow-replay-nocairo',
   'shrink-rounded-border',
   'stroke',
   'stroke-clipped-nogl',