[gtk+] GskRenderNode: Use C99 flexible arrays to avoid extra allocation

[Alexander Larsson <alexl src gnome org>]

commit 230d27b079c4b98b1eb5000a0e70ca95a937c9c5
Author: Alexander Larsson <alexl redhat com>
Date:   Wed Dec 21 12:20:56 2016 +0100

    GskRenderNode: Use C99 flexible arrays to avoid extra allocation
    
    Instead of a separate allocation for any arrays in the render node
    we allocate these as part of the render node itself, using C99
    flexible arrays.
    
    This leads to less allocations, which is nice, but the major reason
    for this is that it allows us to change the allocation scheme further
    in the future. For instance, we want to do stack-like allocation so
    that all the render-nodes for an entire frame are allocated in one
    (or a few) chunks.

 gsk/gskrendernode.c        |    8 +++---
 gsk/gskrendernodeimpl.c    |   54 ++++++++++++++++++-------------------------
 gsk/gskrendernodeprivate.h |    2 +-
 3 files changed, 28 insertions(+), 36 deletions(-)
---
diff --git a/gsk/gskrendernode.c b/gsk/gskrendernode.c
index 1955d74..d1fdb4f 100644
--- a/gsk/gskrendernode.c
+++ b/gsk/gskrendernode.c
@@ -72,7 +72,7 @@ gsk_render_node_finalize (GskRenderNode *self)
 
   g_clear_pointer (&self->name, g_free);
 
-  g_slice_free1 (self->node_class->struct_size, self);
+  g_free (self);
 }
 
 /*< private >
@@ -82,14 +82,14 @@ gsk_render_node_finalize (GskRenderNode *self)
  * Returns: (transfer full): the newly created #GskRenderNode
  */
 GskRenderNode *
-gsk_render_node_new (const GskRenderNodeClass *node_class)
+gsk_render_node_new (const GskRenderNodeClass *node_class, gsize extra_size)
 {
   GskRenderNode *self;
-  
+
   g_return_val_if_fail (node_class != NULL, NULL);
   g_return_val_if_fail (node_class->node_type != GSK_NOT_A_RENDER_NODE, NULL);
 
-  self = g_slice_alloc0 (node_class->struct_size);
+  self = g_malloc0 (node_class->struct_size + extra_size);
 
   self->node_class = node_class;
 
diff --git a/gsk/gskrendernodeimpl.c b/gsk/gskrendernodeimpl.c
index 0dc2c70..26ef037 100644
--- a/gsk/gskrendernodeimpl.c
+++ b/gsk/gskrendernodeimpl.c
@@ -91,7 +91,7 @@ gsk_color_node_new (const GdkRGBA         *rgba,
   g_return_val_if_fail (rgba != NULL, NULL);
   g_return_val_if_fail (bounds != NULL, NULL);
 
-  self = (GskColorNode *) gsk_render_node_new (&GSK_COLOR_NODE_CLASS);
+  self = (GskColorNode *) gsk_render_node_new (&GSK_COLOR_NODE_CLASS, 0);
 
   self->color = *rgba;
   graphene_rect_init_from_rect (&self->render_node.bounds, bounds);
@@ -110,16 +110,13 @@ struct _GskLinearGradientNode
   graphene_point_t start;
   graphene_point_t end;
 
-  GskColorStop *stops;
   gsize n_stops;
+  GskColorStop stops[];
 };
 
 static void
 gsk_linear_gradient_node_finalize (GskRenderNode *node)
 {
-  GskLinearGradientNode *self = (GskLinearGradientNode *) node;
-
-  g_free (self->stops);
 }
 
 static void
@@ -197,13 +194,13 @@ gsk_linear_gradient_node_new (const graphene_rect_t  *bounds,
   g_return_val_if_fail (end != NULL, NULL);
   g_return_val_if_fail (color_stops != NULL, NULL);
 
-  self = (GskLinearGradientNode *) gsk_render_node_new (&GSK_LINEAR_GRADIENT_NODE_CLASS);
+  self = (GskLinearGradientNode *) gsk_render_node_new (&GSK_LINEAR_GRADIENT_NODE_CLASS, sizeof 
(GskColorStop) * n_color_stops);
 
   graphene_rect_init_from_rect (&self->render_node.bounds, bounds);
   graphene_point_init_from_point (&self->start, start);
   graphene_point_init_from_point (&self->end, end);
 
-  self->stops = g_memdup (color_stops, sizeof (GskColorStop) * n_color_stops);
+  memcpy (&self->stops, color_stops, sizeof (GskColorStop) * n_color_stops);
   self->n_stops = n_color_stops;
 
   return &self->render_node;
@@ -223,13 +220,13 @@ gsk_repeating_linear_gradient_node_new (const graphene_rect_t  *bounds,
   g_return_val_if_fail (end != NULL, NULL);
   g_return_val_if_fail (color_stops != NULL, NULL);
 
-  self = (GskLinearGradientNode *) gsk_render_node_new (&GSK_REPEATING_LINEAR_GRADIENT_NODE_CLASS);
+  self = (GskLinearGradientNode *) gsk_render_node_new (&GSK_REPEATING_LINEAR_GRADIENT_NODE_CLASS, sizeof 
(GskColorStop) * n_color_stops);
 
   graphene_rect_init_from_rect (&self->render_node.bounds, bounds);
   graphene_point_init_from_point (&self->start, start);
   graphene_point_init_from_point (&self->end, end);
 
-  self->stops = g_memdup (color_stops, sizeof (GskColorStop) * n_color_stops);
+  memcpy (&self->stops, color_stops, sizeof (GskColorStop) * n_color_stops);
   self->n_stops = n_color_stops;
 
   return &self->render_node;
@@ -396,7 +393,7 @@ gsk_border_node_new (const GskRoundedRect     *outline,
   g_return_val_if_fail (border_width != NULL, NULL);
   g_return_val_if_fail (border_color != NULL, NULL);
 
-  self = (GskBorderNode *) gsk_render_node_new (&GSK_BORDER_NODE_CLASS);
+  self = (GskBorderNode *) gsk_render_node_new (&GSK_BORDER_NODE_CLASS, 0);
 
   gsk_rounded_rect_init_copy (&self->outline, outline);
   memcpy (self->border_width, border_width, sizeof (self->border_width));
@@ -489,7 +486,7 @@ gsk_texture_node_new (GskTexture            *texture,
   g_return_val_if_fail (GSK_IS_TEXTURE (texture), NULL);
   g_return_val_if_fail (bounds != NULL, NULL);
 
-  self = (GskTextureNode *) gsk_render_node_new (&GSK_TEXTURE_NODE_CLASS);
+  self = (GskTextureNode *) gsk_render_node_new (&GSK_TEXTURE_NODE_CLASS, 0);
 
   self->texture = gsk_texture_ref (texture);
   graphene_rect_init_from_rect (&self->render_node.bounds, bounds);
@@ -938,7 +935,7 @@ gsk_inset_shadow_node_new (const GskRoundedRect *outline,
   g_return_val_if_fail (outline != NULL, NULL);
   g_return_val_if_fail (color != NULL, NULL);
 
-  self = (GskInsetShadowNode *) gsk_render_node_new (&GSK_INSET_SHADOW_NODE_CLASS);
+  self = (GskInsetShadowNode *) gsk_render_node_new (&GSK_INSET_SHADOW_NODE_CLASS, 0);
 
   gsk_rounded_rect_init_copy (&self->outline, outline);
   self->color = *color;
@@ -1131,7 +1128,7 @@ gsk_outset_shadow_node_new (const GskRoundedRect *outline,
   g_return_val_if_fail (outline != NULL, NULL);
   g_return_val_if_fail (color != NULL, NULL);
 
-  self = (GskOutsetShadowNode *) gsk_render_node_new (&GSK_OUTSET_SHADOW_NODE_CLASS);
+  self = (GskOutsetShadowNode *) gsk_render_node_new (&GSK_OUTSET_SHADOW_NODE_CLASS, 0);
 
   gsk_rounded_rect_init_copy (&self->outline, outline);
   self->color = *color;
@@ -1230,7 +1227,7 @@ gsk_cairo_node_new (const graphene_rect_t *bounds)
 
   g_return_val_if_fail (bounds != NULL, NULL);
 
-  self = (GskCairoNode *) gsk_render_node_new (&GSK_CAIRO_NODE_CLASS);
+  self = (GskCairoNode *) gsk_render_node_new (&GSK_CAIRO_NODE_CLASS, 0);
 
   graphene_rect_init_from_rect (&self->render_node.bounds, bounds);
 
@@ -1329,8 +1326,8 @@ struct _GskContainerNode
 {
   GskRenderNode render_node;
 
-  GskRenderNode **children;
   guint n_children;
+  GskRenderNode *children[];
 };
 
 static void
@@ -1341,8 +1338,6 @@ gsk_container_node_finalize (GskRenderNode *node)
 
   for (i = 0; i < container->n_children; i++)
     gsk_render_node_unref (container->children[i]);
-
-  g_free (container->children);
 }
 
 static void
@@ -1402,13 +1397,12 @@ gsk_container_node_new (GskRenderNode **children,
   GskContainerNode *container;
   guint i;
 
-  container = (GskContainerNode *) gsk_render_node_new (&GSK_CONTAINER_NODE_CLASS);
+  container = (GskContainerNode *) gsk_render_node_new (&GSK_CONTAINER_NODE_CLASS, sizeof (GskRenderNode *) 
* n_children);
 
-  container->children = g_memdup (children, sizeof (GskRenderNode *) * n_children);
   container->n_children = n_children;
 
   for (i = 0; i < container->n_children; i++)
-    gsk_render_node_ref (container->children[i]);
+    container->children[i] = gsk_render_node_ref (children[i]);
 
   gsk_container_node_get_bounds (container, &container->render_node.bounds);
 
@@ -1521,7 +1515,7 @@ gsk_transform_node_new (GskRenderNode           *child,
   g_return_val_if_fail (GSK_IS_RENDER_NODE (child), NULL);
   g_return_val_if_fail (transform != NULL, NULL);
 
-  self = (GskTransformNode *) gsk_render_node_new (&GSK_TRANSFORM_NODE_CLASS);
+  self = (GskTransformNode *) gsk_render_node_new (&GSK_TRANSFORM_NODE_CLASS, 0);
 
   self->child = gsk_render_node_ref (child);
   graphene_matrix_init_from_matrix (&self->transform, transform);
@@ -1632,7 +1626,7 @@ gsk_opacity_node_new (GskRenderNode *child,
 
   g_return_val_if_fail (GSK_IS_RENDER_NODE (child), NULL);
 
-  self = (GskOpacityNode *) gsk_render_node_new (&GSK_OPACITY_NODE_CLASS);
+  self = (GskOpacityNode *) gsk_render_node_new (&GSK_OPACITY_NODE_CLASS, 0);
 
   self->child = gsk_render_node_ref (child);
   self->opacity = CLAMP (opacity, 0.0, 1.0);
@@ -1737,7 +1731,7 @@ gsk_clip_node_new (GskRenderNode         *child,
   g_return_val_if_fail (GSK_IS_RENDER_NODE (child), NULL);
   g_return_val_if_fail (clip != NULL, NULL);
 
-  self = (GskClipNode *) gsk_render_node_new (&GSK_CLIP_NODE_CLASS);
+  self = (GskClipNode *) gsk_render_node_new (&GSK_CLIP_NODE_CLASS, 0);
 
   self->child = gsk_render_node_ref (child);
   graphene_rect_normalize_r (clip, &self->clip);
@@ -1840,7 +1834,7 @@ gsk_rounded_clip_node_new (GskRenderNode         *child,
   g_return_val_if_fail (GSK_IS_RENDER_NODE (child), NULL);
   g_return_val_if_fail (clip != NULL, NULL);
 
-  self = (GskRoundedClipNode *) gsk_render_node_new (&GSK_ROUNDED_CLIP_NODE_CLASS);
+  self = (GskRoundedClipNode *) gsk_render_node_new (&GSK_ROUNDED_CLIP_NODE_CLASS, 0);
 
   self->child = gsk_render_node_ref (child);
   gsk_rounded_rect_init_copy (&self->clip, clip);
@@ -1888,8 +1882,8 @@ struct _GskShadowNode
 
   GskRenderNode *child;
 
-  GskShadow *shadows;
   gsize n_shadows;
+  GskShadow shadows[];
 };
 
 static void
@@ -1898,8 +1892,6 @@ gsk_shadow_node_finalize (GskRenderNode *node)
   GskShadowNode *self = (GskShadowNode *) node;
 
   gsk_render_node_unref (self->child);
-
-  g_free (self->shadows);
 }
 
 static void
@@ -1995,10 +1987,10 @@ gsk_shadow_node_new (GskRenderNode         *child,
   g_return_val_if_fail (shadows != NULL, NULL);
   g_return_val_if_fail (n_shadows > 0, NULL);
 
-  self = (GskShadowNode *) gsk_render_node_new (&GSK_SHADOW_NODE_CLASS);
+  self = (GskShadowNode *) gsk_render_node_new (&GSK_SHADOW_NODE_CLASS, n_shadows * sizeof (GskShadow));
 
   self->child = gsk_render_node_ref (child);
-  self->shadows = g_memdup (shadows, n_shadows * sizeof (GskShadow));
+  memcpy (&self->shadows, shadows, n_shadows * sizeof (GskShadow));
   self->n_shadows = n_shadows;
 
   gsk_shadow_node_get_bounds (self, &self->render_node.bounds);
@@ -2153,7 +2145,7 @@ gsk_blend_node_new (GskRenderNode *bottom,
   g_return_val_if_fail (GSK_IS_RENDER_NODE (bottom), NULL);
   g_return_val_if_fail (GSK_IS_RENDER_NODE (top), NULL);
 
-  self = (GskBlendNode *) gsk_render_node_new (&GSK_BLEND_NODE_CLASS);
+  self = (GskBlendNode *) gsk_render_node_new (&GSK_BLEND_NODE_CLASS, 0);
 
   self->bottom = gsk_render_node_ref (bottom);
   self->top = gsk_render_node_ref (top);
@@ -2267,7 +2259,7 @@ gsk_cross_fade_node_new (GskRenderNode *start,
   g_return_val_if_fail (GSK_IS_RENDER_NODE (start), NULL);
   g_return_val_if_fail (GSK_IS_RENDER_NODE (end), NULL);
 
-  self = (GskCrossFadeNode *) gsk_render_node_new (&GSK_CROSS_FADE_NODE_CLASS);
+  self = (GskCrossFadeNode *) gsk_render_node_new (&GSK_CROSS_FADE_NODE_CLASS, 0);
 
   self->start = gsk_render_node_ref (start);
   self->end = gsk_render_node_ref (end);
diff --git a/gsk/gskrendernodeprivate.h b/gsk/gskrendernodeprivate.h
index 2f3d37b..8eacb7a 100644
--- a/gsk/gskrendernodeprivate.h
+++ b/gsk/gskrendernodeprivate.h
@@ -36,7 +36,7 @@ struct _GskRenderNodeClass
                  cairo_t       *cr);
 };
 
-GskRenderNode *gsk_render_node_new (const GskRenderNodeClass *node_class);
+GskRenderNode *gsk_render_node_new (const GskRenderNodeClass *node_class, gsize extra_size);
 
 void gsk_render_node_get_bounds (GskRenderNode   *node,
                                  graphene_rect_t *frame);