gtk2/gtk/gtksnapshot.c

/* GTK - The GIMP Toolkit
 * Copyright (C) 2016 Benjamin Otte <otte@gnome.org>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library. If not, see <http://www.gnu.org/licenses/>.
 */

#include "config.h"

#include "gtksnapshot.h"
#include "gtksnapshotprivate.h"

#include "gtkcsscolorvalueprivate.h"
#include "gtkcssshadowvalueprivate.h"
#include "gtkdebug.h"
#include "gtkrenderbackgroundprivate.h"
#include "gtkrenderborderprivate.h"
#include "gtkrendericonprivate.h"
#include "gtkrendernodepaintableprivate.h"
#include "gtkstylecontextprivate.h"
#include "gsktransformprivate.h"

#include "gsk/gskrendernodeprivate.h"

#include "gtk/gskpango.h"

#define GDK_ARRAY_NAME gtk_snapshot_nodes
#define GDK_ARRAY_TYPE_NAME GtkSnapshotNodes
#define GDK_ARRAY_ELEMENT_TYPE GskRenderNode *
#define GDK_ARRAY_FREE_FUNC gsk_render_node_unref
#include "gdk/gdkarrayimpl.c"

/**
 * SECTION:gtksnapshot
 * @Short_description: Auxiliary object for snapshots
 * @Title: GtkSnapshot
 *
 * GtkSnapshot is an auxiliary object that assists in creating #GskRenderNodes
 * in the #GdkPaintableInterface.snapshot() vfunc. It functions in a similar way to
 * a cairo context, and maintains a stack of render nodes and their associated
 * transformations.
 *
 * The node at the top of the stack is the the one that gtk_snapshot_append_…
 * functions operate on. Use the gtk_snapshot_push_… functions and gtk_snapshot_pop()
 * to change the current node.
 *
 * The typical way to obtain a GtkSnapshot object is as an argument to
 * the #GtkWidgetClass.snapshot() vfunc. If you need to create your own GtkSnapshot,
 * use gtk_snapshot_new().
 */

typedef struct _GtkSnapshotState GtkSnapshotState;

typedef GskRenderNode * (* GtkSnapshotCollectFunc) (GtkSnapshot      *snapshot,
                                                    GtkSnapshotState *state,
                                                    GskRenderNode   **nodes,
                                                    guint             n_nodes);

struct _GtkSnapshotState {
  guint                  start_node_index;
  guint                  n_nodes;

  GskTransform *         transform;

  GtkSnapshotCollectFunc collect_func;
  union {
    struct {
      double             opacity;
    } opacity;
    struct {
      double             radius;
    } blur;
    struct {
      graphene_matrix_t matrix;
      graphene_vec4_t offset;
    } color_matrix;
    struct {
      graphene_rect_t bounds;
      graphene_rect_t child_bounds;
    } repeat;
    struct {
      graphene_rect_t bounds;
    } clip;
    struct {
      GskRoundedRect bounds;
    } rounded_clip;
    struct {
      gsize n_shadows;
      GskShadow *shadows;
      GskShadow a_shadow; /* Used if n_shadows == 1 */
    } shadow;
    struct {
      GskBlendMode blend_mode;
      GskRenderNode *bottom_node;
    } blend;
    struct {
      double progress;
      GskRenderNode *start_node;
    } cross_fade;
    struct {
      char *message;
    } debug;
  } data;
};

static void gtk_snapshot_state_clear (GtkSnapshotState *state);

#define GDK_ARRAY_NAME gtk_snapshot_states
#define GDK_ARRAY_TYPE_NAME GtkSnapshotStates
#define GDK_ARRAY_ELEMENT_TYPE GtkSnapshotState
#define GDK_ARRAY_FREE_FUNC gtk_snapshot_state_clear
#define GDK_ARRAY_BY_VALUE 1
#include "gdk/gdkarrayimpl.c"

/* This is a nasty little hack. We typedef GtkSnapshot to the fake object GdkSnapshot
 * so that we don't need to typecast between them.
 * After all, the GdkSnapshot only exist so poor language bindings don't trip. Hardcore
 * C code can just blatantly ignore such layering violations with a typedef.
 */
struct _GdkSnapshot {
  GObject                parent_instance; /* it's really GdkSnapshot, but don't tell anyone! */

  GtkSnapshotStates      state_stack;
  GtkSnapshotNodes       nodes;
};

struct _GtkSnapshotClass {
  GObjectClass           parent_class; /* it's really GdkSnapshotClass, but don't tell anyone! */
};

G_DEFINE_TYPE (GtkSnapshot, gtk_snapshot, GDK_TYPE_SNAPSHOT)

static void
gtk_snapshot_dispose (GObject *object)
{
  GtkSnapshot *snapshot = GTK_SNAPSHOT (object);

  if (!gtk_snapshot_states_is_empty (&snapshot->state_stack))
    gsk_render_node_unref (gtk_snapshot_to_node (snapshot));

  g_assert (gtk_snapshot_states_is_empty (&snapshot->state_stack));
  g_assert (gtk_snapshot_nodes_is_empty (&snapshot->nodes));

  G_OBJECT_CLASS (gtk_snapshot_parent_class)->dispose (object);
}

static void
gtk_snapshot_class_init (GtkSnapshotClass *klass)
{
  GObjectClass *gobject_class = G_OBJECT_CLASS (klass);

  gobject_class->dispose = gtk_snapshot_dispose;
}

static void
gtk_snapshot_init (GtkSnapshot *self)
{
}

static GskRenderNode *
gtk_snapshot_collect_default (GtkSnapshot       *snapshot,
                              GtkSnapshotState  *state,
                              GskRenderNode    **nodes,
                              guint              n_nodes)
{
  GskRenderNode *node;

  if (n_nodes == 0)
    {
      node = NULL;
    }
  else if (n_nodes == 1)
    {
      node = gsk_render_node_ref (nodes[0]);
    }
  else
    {
      node = gsk_container_node_new (nodes, n_nodes);
    }

  return node;
}

static GtkSnapshotState *
gtk_snapshot_push_state (GtkSnapshot            *snapshot,
                         GskTransform           *transform,
                         GtkSnapshotCollectFunc  collect_func)
{
  const gsize n_states = gtk_snapshot_states_get_size (&snapshot->state_stack);
  GtkSnapshotState *state;

  gtk_snapshot_states_set_size (&snapshot->state_stack, n_states + 1);
  state = gtk_snapshot_states_get (&snapshot->state_stack, n_states);

  state->transform = gsk_transform_ref (transform);
  state->collect_func = collect_func;
  state->start_node_index = gtk_snapshot_nodes_get_size (&snapshot->nodes);
  state->n_nodes = 0;

  return state;
}

static GtkSnapshotState *
gtk_snapshot_get_current_state (const GtkSnapshot *snapshot)
{
  gsize size = gtk_snapshot_states_get_size (&snapshot->state_stack);

  g_assert (size > 0);

  return gtk_snapshot_states_get (&snapshot->state_stack, size - 1);
}

static GtkSnapshotState *
gtk_snapshot_get_previous_state (const GtkSnapshot *snapshot)
{
  gsize size = gtk_snapshot_states_get_size (&snapshot->state_stack);

  g_assert (size > 1);

  return gtk_snapshot_states_get (&snapshot->state_stack, size - 2);
}

static void
gtk_snapshot_state_clear (GtkSnapshotState *state)
{
  gsk_transform_unref (state->transform);
}

/**
 * gtk_snapshot_new:
 *
 * Creates a new #GtkSnapshot.
 *
 * Returns: a newly-allocated #GtkSnapshot
 */
GtkSnapshot *
gtk_snapshot_new (void)
{
  GtkSnapshot *snapshot;

  snapshot = g_object_new (GTK_TYPE_SNAPSHOT, NULL);

  gtk_snapshot_states_init (&snapshot->state_stack);
  gtk_snapshot_nodes_init (&snapshot->nodes);

  gtk_snapshot_push_state (snapshot,
                           NULL,
                           gtk_snapshot_collect_default);

  return snapshot;
}

/**
 * gtk_snapshot_free_to_node: (skip)
 * @snapshot: (transfer full): a #GtkSnapshot
 *
 * Returns the node that was constructed by @snapshot
 * and frees @snapshot.
 *
 * Returns: (transfer full): a newly-created #GskRenderNode
 */
GskRenderNode *
gtk_snapshot_free_to_node (GtkSnapshot *snapshot)
{
  GskRenderNode *result;

  result = gtk_snapshot_to_node (snapshot);
  g_object_unref (snapshot);

  return result;
}

/**
 * gtk_snapshot_free_to_paintable: (skip)
 * @snapshot: (transfer full): a #GtkSnapshot
 * @size: (allow-none): The size of the resulting paintable
 *     or %NULL to use the bounds of the snapshot
 *
 * Returns a paintable for the node that was
 * constructed by @snapshot and frees @snapshot.
 *
 * Returns: (transfer full): a newly-created #GdkPaintable
 */
GdkPaintable *
gtk_snapshot_free_to_paintable (GtkSnapshot           *snapshot,
                                const graphene_size_t *size)
{
  GdkPaintable *result;

  result = gtk_snapshot_to_paintable (snapshot, size);
  g_object_unref (snapshot);

  return result;
}

static GskRenderNode *
gtk_snapshot_collect_autopush_transform (GtkSnapshot      *snapshot,
                                         GtkSnapshotState *state,
                                         GskRenderNode   **nodes,
                                         guint             n_nodes)
{
  GskRenderNode *node, *transform_node;
  GtkSnapshotState *previous_state;

  previous_state = gtk_snapshot_get_previous_state (snapshot);

  node = gtk_snapshot_collect_default (snapshot, state, nodes, n_nodes);
  if (node == NULL)
    return NULL;

  transform_node = gsk_transform_node_new (node, previous_state->transform);

  gsk_render_node_unref (node);

  return transform_node;
}

static void
gtk_snapshot_autopush_transform (GtkSnapshot *snapshot)
{
  gtk_snapshot_push_state (snapshot,
                           NULL,
                           gtk_snapshot_collect_autopush_transform);
}

static gboolean
gtk_snapshot_state_should_autopop (const GtkSnapshotState *state)
{
  return state->collect_func == gtk_snapshot_collect_autopush_transform;
}

static GskRenderNode *
gtk_snapshot_collect_debug (GtkSnapshot      *snapshot,
                            GtkSnapshotState *state,
                            GskRenderNode   **nodes,
                            guint             n_nodes)
{
  GskRenderNode *node, *debug_node;

  node = gtk_snapshot_collect_default (snapshot, state, nodes, n_nodes);
  if (node == NULL)
    return NULL;

  debug_node = gsk_debug_node_new (node, state->data.debug.message);

  gsk_render_node_unref (node);

  return debug_node;
}

/**
 * gtk_snapshot_push_debug:
 * @snapshot: a #GtkSnapshot
 * @message: a printf-style format string
 * @...: arguments for @message
 *
 * Inserts a debug node with a message. Debug nodes don't affect
 * the rendering at all, but can be helpful in identifying parts
 * of a render node tree dump, for example in the GTK inspector.
 */
void
gtk_snapshot_push_debug (GtkSnapshot *snapshot,
                         const char  *message,
                         ...)
{
  GtkSnapshotState *current_state = gtk_snapshot_get_current_state (snapshot);

  if (GTK_DEBUG_CHECK (SNAPSHOT))
    {
      va_list args;
      GtkSnapshotState *state;

      state = gtk_snapshot_push_state (snapshot,
                                       current_state->transform,
                                       gtk_snapshot_collect_debug);



      va_start (args, message);
      state->data.debug.message = g_strdup_vprintf (message, args);
      va_end (args);
    }
  else
    {
      gtk_snapshot_push_state (snapshot,
                               current_state->transform,
                               gtk_snapshot_collect_default);
    }
}

static GskRenderNode *
gtk_snapshot_collect_opacity (GtkSnapshot      *snapshot,
                              GtkSnapshotState *state,
                              GskRenderNode   **nodes,
                              guint             n_nodes)
{
  GskRenderNode *node, *opacity_node;

  node = gtk_snapshot_collect_default (snapshot, state, nodes, n_nodes);
  if (node == NULL)
    return NULL;

  if (state->data.opacity.opacity == 1.0)
    {
      opacity_node = node;
    }
  else if (state->data.opacity.opacity == 0.0)
    {
      gsk_render_node_unref (node);
      opacity_node = NULL;
    }
  else
    {
      opacity_node = gsk_opacity_node_new (node, state->data.opacity.opacity);
      gsk_render_node_unref (node);
    }

  return opacity_node;
}

/**
 * gtk_snapshot_push_opacity:
 * @snapshot: a #GtkSnapshot
 * @opacity: the opacity to use
 *
 * Modifies the opacity of an image.
 *
 * The image is recorded until the next call to gtk_snapshot_pop().
 */
void
gtk_snapshot_push_opacity (GtkSnapshot *snapshot,
                           double       opacity)
{
  GtkSnapshotState *current_state = gtk_snapshot_get_current_state (snapshot);
  GtkSnapshotState *state;

  state = gtk_snapshot_push_state (snapshot,
                                   current_state->transform,
                                   gtk_snapshot_collect_opacity);
  state->data.opacity.opacity = CLAMP (opacity, 0.0, 1.0);
}

static GskRenderNode *
gtk_snapshot_collect_blur (GtkSnapshot      *snapshot,
                           GtkSnapshotState *state,
                           GskRenderNode   **nodes,
                           guint             n_nodes)
{
  GskRenderNode *node, *blur_node;
  double radius;

  node = gtk_snapshot_collect_default (snapshot, state, nodes, n_nodes);
  if (node == NULL)
    return NULL;

  radius = state->data.blur.radius;

  if (radius == 0.0)
    return node;

  blur_node = gsk_blur_node_new (node, radius);

  gsk_render_node_unref (node);

  return blur_node;
}

/**
 * gtk_snapshot_push_blur:
 * @snapshot: a #GtkSnapshot
 * @radius: the blur radius to use
 *
 * Blurs an image.
 *
 * The image is recorded until the next call to gtk_snapshot_pop().
 */
void
gtk_snapshot_push_blur (GtkSnapshot *snapshot,
                        double       radius)
{
  const GtkSnapshotState *current_state = gtk_snapshot_get_current_state (snapshot);
  GtkSnapshotState *state;

  state = gtk_snapshot_push_state (snapshot,
                                   current_state->transform,
                                   gtk_snapshot_collect_blur);
  state->data.blur.radius = radius;
}

static GskRenderNode *
merge_color_matrix_nodes (const graphene_matrix_t *matrix2,
                          const graphene_vec4_t   *offset2,
                          GskRenderNode           *child)
{
  const graphene_matrix_t *mat1 = gsk_color_matrix_node_peek_color_matrix (child);
  const graphene_vec4_t *offset1 = gsk_color_matrix_node_peek_color_offset (child);
  graphene_matrix_t mat2 = *matrix2;
  graphene_vec4_t off2 = *offset2;
  GskRenderNode *result;

  g_assert (gsk_render_node_get_node_type (child) == GSK_COLOR_MATRIX_NODE);

  /* color matrix node: color = mat * p + offset; for a pixel p.
   * color =  mat1 * (mat2 * p + offset2) + offset1;
   *       =  mat1 * mat2  * p + offset2 * mat1 + offset1
   *       = (mat1 * mat2) * p + (offset2 * mat1 + offset1)
   * Which this code does.
   * mat1 and offset1 come from @child.
   */

  graphene_matrix_transform_vec4 (mat1, offset2, &off2);
  graphene_vec4_add (&off2, offset1, &off2);

  graphene_matrix_multiply (mat1, &mat2, &mat2);

  result = gsk_color_matrix_node_new (gsk_color_matrix_node_get_child (child),
                                      &mat2, &off2);

  return result;
}

static GskRenderNode *
gtk_snapshot_collect_color_matrix (GtkSnapshot      *snapshot,
                                   GtkSnapshotState *state,
                                   GskRenderNode   **nodes,
                                   guint             n_nodes)
{
  GskRenderNode *node, *result;

  node = gtk_snapshot_collect_default (snapshot, state, nodes, n_nodes);
  if (node == NULL)
    return NULL;

  if (gsk_render_node_get_node_type (node) == GSK_COLOR_MATRIX_NODE)
    {
      result = merge_color_matrix_nodes (&state->data.color_matrix.matrix,
                                         &state->data.color_matrix.offset,
                                         node);
      gsk_render_node_unref (node);
    }
  else if (gsk_render_node_get_node_type (node) == GSK_TRANSFORM_NODE)
    {
      GskRenderNode *transform_child = gsk_transform_node_get_child (node);
      GskRenderNode *color_matrix;

      if (gsk_render_node_get_node_type (transform_child) == GSK_COLOR_MATRIX_NODE)
        {
          color_matrix = merge_color_matrix_nodes (&state->data.color_matrix.matrix,
                                                   &state->data.color_matrix.offset,
                                                   transform_child);
        }
      else
        {
          color_matrix = gsk_color_matrix_node_new (transform_child,
                                                    &state->data.color_matrix.matrix,
                                                    &state->data.color_matrix.offset);
        }
      result = gsk_transform_node_new (color_matrix,
                                       gsk_transform_node_get_transform (node));
      gsk_render_node_unref (color_matrix);
      gsk_render_node_unref (node);
      node = NULL;
    }
  else
    {
      result = gsk_color_matrix_node_new (node,
                                          &state->data.color_matrix.matrix,
                                          &state->data.color_matrix.offset);
      gsk_render_node_unref (node);
    }

  return result;
}

/**
 * gtk_snapshot_push_color_matrix:
 * @snapshot: a #GtkSnapshot
 * @color_matrix: the color matrix to use
 * @color_offset: the color offset to use
 *
 * Modifies the colors of an image by applying an affine transformation
 * in RGB space.
 *
 * The image is recorded until the next call to gtk_snapshot_pop().
 */
void
gtk_snapshot_push_color_matrix (GtkSnapshot             *snapshot,
                                const graphene_matrix_t *color_matrix,
                                const graphene_vec4_t   *color_offset)
{
  const GtkSnapshotState *current_state = gtk_snapshot_get_current_state (snapshot);
  GtkSnapshotState *state;

  state = gtk_snapshot_push_state (snapshot,
                                   current_state->transform,
                                   gtk_snapshot_collect_color_matrix);

  graphene_matrix_init_from_matrix (&state->data.color_matrix.matrix, color_matrix);
  graphene_vec4_init_from_vec4 (&state->data.color_matrix.offset, color_offset);
}

static GskRenderNode *
gtk_snapshot_collect_repeat (GtkSnapshot      *snapshot,
                             GtkSnapshotState *state,
                             GskRenderNode   **nodes,
                             guint             n_nodes)
{
  GskRenderNode *node, *repeat_node;
  const graphene_rect_t *bounds = &state->data.repeat.bounds;
  const graphene_rect_t *child_bounds = &state->data.repeat.child_bounds;

  node = gtk_snapshot_collect_default (snapshot, state, nodes, n_nodes);
  if (node == NULL)
    return NULL;

  if (gsk_render_node_get_node_type (node) == GSK_COLOR_NODE &&
      graphene_rect_equal (child_bounds, &node->bounds))
    {
      /* Repeating a color node entirely is pretty easy by just increasing
       * the size of the color node. */
      GskRenderNode *color_node = gsk_color_node_new (gsk_color_node_peek_color (node), bounds);

      gsk_render_node_unref (node);

      return color_node;
    }

  repeat_node = gsk_repeat_node_new (bounds,
                                     node,
                                     child_bounds->size.width > 0 ? child_bounds : NULL);

  gsk_render_node_unref (node);

  return repeat_node;
}

static void
gtk_graphene_rect_scale_affine (const graphene_rect_t *rect,
                                float                  scale_x,
                                float                  scale_y,
                                float                  dx,
                                float                  dy,
                                graphene_rect_t       *res)
{
  res->origin.x = scale_x * rect->origin.x + dx;
  res->origin.y = scale_y * rect->origin.y + dy;
  res->size.width = scale_x * rect->size.width;
  res->size.height = scale_y * rect->size.height;

  if (scale_x < 0 || scale_y < 0)
    graphene_rect_normalize (res);
}

static void
gtk_rounded_rect_scale_affine (GskRoundedRect       *dest,
                               const GskRoundedRect *src,
                               float                 scale_x,
                               float                 scale_y,
                               float                 dx,
                               float                 dy)
{
  guint flip;
  guint i;

  g_assert (dest != src);

  gtk_graphene_rect_scale_affine (&src->bounds, scale_x, scale_y, dx, dy, &dest->bounds);
  flip = ((scale_x < 0) ? 1 : 0) + (scale_y < 0 ? 2 : 0);

  for (i = 0; i < 4; i++)
    {
      dest->corner[i].width = src->corner[i ^ flip].width * fabsf (scale_x);
      dest->corner[i].height = src->corner[i ^ flip].height * fabsf (scale_y);
    }
}

static void
gtk_snapshot_ensure_affine (GtkSnapshot *snapshot,
                            float       *scale_x,
                            float       *scale_y,
                            float       *dx,
                            float       *dy)
{
  const GtkSnapshotState *state = gtk_snapshot_get_current_state (snapshot);

  if (gsk_transform_get_category (state->transform) < GSK_TRANSFORM_CATEGORY_2D_AFFINE)
    {
      gtk_snapshot_autopush_transform (snapshot);
      state = gtk_snapshot_get_current_state (snapshot);
    }
  
  gsk_transform_to_affine (state->transform, scale_x, scale_y, dx, dy);
}

static void
gtk_snapshot_ensure_translate (GtkSnapshot *snapshot,
                               float       *dx,
                               float       *dy)
{
  const GtkSnapshotState *state = gtk_snapshot_get_current_state (snapshot);

  if (gsk_transform_get_category (state->transform) < GSK_TRANSFORM_CATEGORY_2D_TRANSLATE)
    {
      gtk_snapshot_autopush_transform (snapshot);
      state = gtk_snapshot_get_current_state (snapshot);
    }
  
  gsk_transform_to_translate (state->transform, dx, dy);
}

static void
gtk_snapshot_ensure_identity (GtkSnapshot *snapshot)
{
  const GtkSnapshotState *state = gtk_snapshot_get_current_state (snapshot);

  if (gsk_transform_get_category (state->transform) < GSK_TRANSFORM_CATEGORY_IDENTITY)
    gtk_snapshot_autopush_transform (snapshot);
}

/**
 * gtk_snapshot_push_repeat:
 * @snapshot: a #GtkSnapshot
 * @bounds: the bounds within which to repeat
 * @child_bounds: (nullable): the bounds of the child or %NULL
 *   to use the full size of the collected child node
 *
 * Creates a node that repeats the child node.
 *
 * The child is recorded until the next call to gtk_snapshot_pop().
 */
void
gtk_snapshot_push_repeat (GtkSnapshot           *snapshot,
                          const graphene_rect_t *bounds,
                          const graphene_rect_t *child_bounds)
{
  GtkSnapshotState *state;
  graphene_rect_t real_child_bounds = { { 0 } };
  float scale_x, scale_y, dx, dy;

  gtk_snapshot_ensure_affine (snapshot, &scale_x, &scale_y, &dx, &dy);

  if (child_bounds)
    gtk_graphene_rect_scale_affine (child_bounds, scale_x, scale_y, dx, dy, &real_child_bounds);

  state = gtk_snapshot_push_state (snapshot,
                                   gtk_snapshot_get_current_state (snapshot)->transform,
                                   gtk_snapshot_collect_repeat);

  gtk_graphene_rect_scale_affine (bounds, scale_x, scale_y, dx, dy, &state->data.repeat.bounds);
  state->data.repeat.child_bounds = real_child_bounds;
}

static GskRenderNode *
gtk_snapshot_collect_clip (GtkSnapshot      *snapshot,
                           GtkSnapshotState *state,
                           GskRenderNode   **nodes,
                           guint             n_nodes)
{
  GskRenderNode *node, *clip_node;

  node = gtk_snapshot_collect_default (snapshot, state, nodes, n_nodes);
  if (node == NULL)
    return NULL;

  /* Check if the child node will even be clipped */
  if (graphene_rect_contains_rect (&state->data.clip.bounds, &node->bounds))
    return node;

  if (state->data.clip.bounds.size.width == 0 ||
      state->data.clip.bounds.size.height == 0)
    return NULL;

  clip_node = gsk_clip_node_new (node, &state->data.clip.bounds);

  gsk_render_node_unref (node);

  return clip_node;
}

/**
 * gtk_snapshot_push_clip:
 * @snapshot: a #GtkSnapshot
 * @bounds: the rectangle to clip to
 *
 * Clips an image to a rectangle.
 *
 * The image is recorded until the next call to gtk_snapshot_pop().
 */
void
gtk_snapshot_push_clip (GtkSnapshot           *snapshot,
                        const graphene_rect_t *bounds)
{
  GtkSnapshotState *state;
  float scale_x, scale_y, dx, dy;
 
  gtk_snapshot_ensure_affine (snapshot, &scale_x, &scale_y, &dx, &dy);

  state = gtk_snapshot_push_state (snapshot,
                                   gtk_snapshot_get_current_state (snapshot)->transform,
                                   gtk_snapshot_collect_clip);

  gtk_graphene_rect_scale_affine (bounds, scale_x, scale_y, dx, dy, &state->data.clip.bounds);
}

static GskRenderNode *
gtk_snapshot_collect_rounded_clip (GtkSnapshot      *snapshot,
                                   GtkSnapshotState *state,
                                   GskRenderNode   **nodes,
                                   guint             n_nodes)
{
  GskRenderNode *node, *clip_node;

  node = gtk_snapshot_collect_default (snapshot, state, nodes, n_nodes);
  if (node == NULL)
    return NULL;

  /* If the given radius is 0 in all corners, we can just create a normal clip node */
  if (gsk_rounded_rect_is_rectilinear (&state->data.rounded_clip.bounds))
    {
      /* ... and do the same optimization */
      if (graphene_rect_contains_rect (&state->data.rounded_clip.bounds.bounds, &node->bounds))
        return node;

      clip_node = gsk_clip_node_new (node, &state->data.rounded_clip.bounds.bounds);
    }
  else
    {
      if (gsk_rounded_rect_contains_rect (&state->data.rounded_clip.bounds, &node->bounds))
        return node;

      clip_node = gsk_rounded_clip_node_new (node, &state->data.rounded_clip.bounds);
    }

  if (clip_node->bounds.size.width == 0 ||
      clip_node->bounds.size.height == 0)
    {
      gsk_render_node_unref (node);
      gsk_render_node_unref (clip_node);
      return NULL;
    }

  gsk_render_node_unref (node);

  return clip_node;
}

/**
 * gtk_snapshot_push_rounded_clip:
 * @snapshot: a #GtkSnapshot
 * @bounds: the rounded rectangle to clip to
 *
 * Clips an image to a rounded rectangle.
 *
 * The image is recorded until the next call to gtk_snapshot_pop().
 */
void
gtk_snapshot_push_rounded_clip (GtkSnapshot          *snapshot,
                                const GskRoundedRect *bounds)
{
  GtkSnapshotState *state;
  float scale_x, scale_y, dx, dy;

  gtk_snapshot_ensure_affine (snapshot, &scale_x, &scale_y, &dx, &dy);

  state = gtk_snapshot_push_state (snapshot,
                                   gtk_snapshot_get_current_state (snapshot)->transform,
                                   gtk_snapshot_collect_rounded_clip);

  gtk_rounded_rect_scale_affine (&state->data.rounded_clip.bounds, bounds, scale_x, scale_y, dx, dy);
}

static GskRenderNode *
gtk_snapshot_collect_shadow (GtkSnapshot      *snapshot,
                             GtkSnapshotState *state,
                             GskRenderNode   **nodes,
                             guint             n_nodes)
{
  GskRenderNode *node, *shadow_node;

  node = gtk_snapshot_collect_default (snapshot, state, nodes, n_nodes);
  if (node == NULL)
    return NULL;

  shadow_node = gsk_shadow_node_new (node,
                                     state->data.shadow.shadows != NULL ?
                                     state->data.shadow.shadows :
                                     &state->data.shadow.a_shadow,
                                     state->data.shadow.n_shadows);

  gsk_render_node_unref (node);
  g_free (state->data.shadow.shadows);

  return shadow_node;
}

/**
 * gtk_snapshot_push_shadow:
 * @snapshot: a #GtkSnapshot
 * @shadow: the first shadow specification
 * @n_shadows: number of shadow specifications
 *
 * Applies a shadow to an image.
 *
 * The image is recorded until the next call to gtk_snapshot_pop().
 */
void
gtk_snapshot_push_shadow (GtkSnapshot     *snapshot,
                          const GskShadow *shadow,
                          gsize            n_shadows)
{
  const GtkSnapshotState *current_state = gtk_snapshot_get_current_state (snapshot);
  GtkSnapshotState *state;

  state = gtk_snapshot_push_state (snapshot,
                                   current_state->transform,
                                   gtk_snapshot_collect_shadow);

  state->data.shadow.n_shadows = n_shadows;
  if (n_shadows == 1)
    {
      state->data.shadow.shadows = NULL;
      memcpy (&state->data.shadow.a_shadow, shadow, sizeof (GskShadow));
    }
  else
    {
      state->data.shadow.shadows = g_malloc (sizeof (GskShadow) * n_shadows);
      memcpy (state->data.shadow.shadows, shadow, sizeof (GskShadow) * n_shadows);
    }

}

static GskRenderNode *
gtk_snapshot_collect_blend_top (GtkSnapshot      *snapshot,
                                GtkSnapshotState *state,
                                GskRenderNode   **nodes,
                                guint             n_nodes)
{
  GskRenderNode *bottom_node, *top_node, *blend_node;
  GdkRGBA transparent = { 0, 0, 0, 0 };

  top_node = gtk_snapshot_collect_default (snapshot, state, nodes, n_nodes);
  bottom_node = state->data.blend.bottom_node;

  g_assert (top_node != NULL || bottom_node != NULL);

  /* XXX: Is this necessary? Do we need a NULL node? */
  if (top_node == NULL)
    top_node = gsk_color_node_new (&transparent, &bottom_node->bounds);
  if (bottom_node == NULL)
    bottom_node = gsk_color_node_new (&transparent, &top_node->bounds);

  blend_node = gsk_blend_node_new (bottom_node, top_node, state->data.blend.blend_mode);

  gsk_render_node_unref (top_node);
  gsk_render_node_unref (bottom_node);

  return blend_node;
}

static GskRenderNode *
gtk_snapshot_collect_blend_bottom (GtkSnapshot      *snapshot,
                                   GtkSnapshotState *state,
                                   GskRenderNode   **nodes,
                                   guint             n_nodes)
{
  GtkSnapshotState *prev_state = gtk_snapshot_get_previous_state (snapshot);

  g_assert (prev_state->collect_func == gtk_snapshot_collect_blend_top);

  prev_state->data.blend.bottom_node = gtk_snapshot_collect_default (snapshot, state, nodes, n_nodes);

  return NULL;
}

/**
 * gtk_snapshot_push_blend:
 * @snapshot: a #GtkSnapshot
 * @blend_mode: blend mode to use
 *
 * Blends together 2 images with the given blend mode.
 *
 * Until the first call to gtk_snapshot_pop(), the bottom image for the
 * blend operation will be recorded. After that call, the top image to
 * be blended will be recorded until the second call to gtk_snapshot_pop().
 *
 * Calling this function requires 2 subsequent calls to gtk_snapshot_pop().
 **/
void
gtk_snapshot_push_blend (GtkSnapshot  *snapshot,
                         GskBlendMode  blend_mode)
{
  GtkSnapshotState *current_state = gtk_snapshot_get_current_state (snapshot);
  GtkSnapshotState *top_state;

  top_state = gtk_snapshot_push_state (snapshot,
                                       current_state->transform,
                                       gtk_snapshot_collect_blend_top);
  top_state->data.blend.blend_mode = blend_mode;

  gtk_snapshot_push_state (snapshot,
                           top_state->transform,
                           gtk_snapshot_collect_blend_bottom);
}

static GskRenderNode *
gtk_snapshot_collect_cross_fade_end (GtkSnapshot      *snapshot,
                                     GtkSnapshotState *state,
                                     GskRenderNode   **nodes,
                                     guint             n_nodes)
{
  GskRenderNode *start_node, *end_node, *node;

  end_node = gtk_snapshot_collect_default (snapshot, state, nodes, n_nodes);
  start_node = state->data.cross_fade.start_node;

  if (state->data.cross_fade.progress <= 0.0)
    {
      node = start_node;

      if (end_node)
        gsk_render_node_unref (end_node);
    }
  else if (state->data.cross_fade.progress >= 1.0)
    {
      node = end_node;

      if (start_node)
        gsk_render_node_unref (start_node);
    }
  else if (start_node && end_node)
    {
      node = gsk_cross_fade_node_new (start_node, end_node, state->data.cross_fade.progress);

      gsk_render_node_unref (start_node);
      gsk_render_node_unref (end_node);
    }
  else if (start_node)
    {
      node = gsk_opacity_node_new (start_node, 1.0 - state->data.cross_fade.progress);

      gsk_render_node_unref (start_node);
    }
  else if (end_node)
    {
      node = gsk_opacity_node_new (end_node, state->data.cross_fade.progress);

      gsk_render_node_unref (end_node);
    }
  else
    {
      node = NULL;
    }

  return node;
}

static GskRenderNode *
gtk_snapshot_collect_cross_fade_start (GtkSnapshot      *snapshot,
                                       GtkSnapshotState *state,
                                       GskRenderNode   **nodes,
                                       guint             n_nodes)
{
  GtkSnapshotState *prev_state = gtk_snapshot_get_previous_state (snapshot);

  g_assert (prev_state->collect_func == gtk_snapshot_collect_cross_fade_end);

  prev_state->data.cross_fade.start_node = gtk_snapshot_collect_default (snapshot, state, nodes, n_nodes);

  return NULL;
}

/**
 * gtk_snapshot_push_cross_fade:
 * @snapshot: a #GtkSnapshot
 * @progress: progress between 0.0 and 1.0
 *
 * Snapshots a cross-fade operation between two images with the
 * given @progress.
 *
 * Until the first call to gtk_snapshot_pop(), the start image
 * will be snapshot. After that call, the end image will be recorded
 * until the second call to gtk_snapshot_pop().
 *
 * Calling this function requires 2 calls to gtk_snapshot_pop().
 **/
void
gtk_snapshot_push_cross_fade (GtkSnapshot *snapshot,
                              double       progress)
{
  const GtkSnapshotState *current_state = gtk_snapshot_get_current_state (snapshot);
  GtkSnapshotState *end_state;

  end_state = gtk_snapshot_push_state (snapshot,
                                       current_state->transform,
                                       gtk_snapshot_collect_cross_fade_end);
  end_state->data.cross_fade.progress = progress;

  gtk_snapshot_push_state (snapshot,
                           end_state->transform,
                           gtk_snapshot_collect_cross_fade_start);
}

static GskRenderNode *
gtk_snapshot_pop_one (GtkSnapshot *snapshot)
{
  GtkSnapshotState *state;
  guint state_index;
  GskRenderNode *node;

  if (gtk_snapshot_states_is_empty (&snapshot->state_stack))
    {
      g_warning ("Too many gtk_snapshot_pop() calls.");
      return NULL;
    }

  state = gtk_snapshot_get_current_state (snapshot);
  state_index = gtk_snapshot_states_get_size (&snapshot->state_stack) - 1;

  if (state->collect_func)
    {
      node = state->collect_func (snapshot,
                                  state,
                                  (GskRenderNode **) gtk_snapshot_nodes_index (&snapshot->nodes, state->start_node_index),
                                  state->n_nodes);

      /* The collect func may not modify the state stack... */
      g_assert (state_index == gtk_snapshot_states_get_size (&snapshot->state_stack) - 1);

      /* Remove all the state's nodes from the list of nodes */
      g_assert (state->start_node_index + state->n_nodes == gtk_snapshot_nodes_get_size (&snapshot->nodes));
      gtk_snapshot_nodes_splice (&snapshot->nodes, state->start_node_index, state->n_nodes, NULL, 0);
    }
  else
    {
      GtkSnapshotState *previous_state;

      node = NULL;

      /* move the nodes to the parent */
      previous_state = gtk_snapshot_get_previous_state (snapshot);
      previous_state->n_nodes += state->n_nodes;
      g_assert (previous_state->start_node_index + previous_state->n_nodes == gtk_snapshot_nodes_get_size (&snapshot->nodes));
    }

  gtk_snapshot_states_splice (&snapshot->state_stack, state_index, 1, NULL, 0);

  return node;
}

static void
gtk_snapshot_append_node_internal (GtkSnapshot   *snapshot,
                                   GskRenderNode *node)
{
  GtkSnapshotState *current_state;

  current_state = gtk_snapshot_get_current_state (snapshot);

  if (current_state)
    {
      gtk_snapshot_nodes_append (&snapshot->nodes, node);
      current_state->n_nodes ++;
    }
  else
    {
      g_critical ("Tried appending a node to an already finished snapshot.");
    }
}

static GskRenderNode *
gtk_snapshot_pop_internal (GtkSnapshot *snapshot)
{
  GtkSnapshotState *state;
  GskRenderNode *node;
  guint forgotten_restores = 0;

  for (state = gtk_snapshot_get_current_state (snapshot);
       gtk_snapshot_state_should_autopop (state) ||
       state->collect_func == NULL;
       state = gtk_snapshot_get_current_state (snapshot))
    {
      if (state->collect_func == NULL)
        forgotten_restores++;

      node = gtk_snapshot_pop_one (snapshot);
      if (node)
        gtk_snapshot_append_node_internal (snapshot, node);
    }

  if (forgotten_restores)
    {
      g_warning ("Too many gtk_snapshot_save() calls. %u saves remaining.", forgotten_restores);
    }

  return gtk_snapshot_pop_one (snapshot);
}

/**
 * gtk_snapshot_push_collect:
 *
 * PRIVATE.
 *
 * Puhses state so a later pop_collect call can collect all nodes
 * appended until that point.
 */
void
gtk_snapshot_push_collect (GtkSnapshot *snapshot)
{
  gtk_snapshot_push_state (snapshot,
                           NULL,
                           gtk_snapshot_collect_default);
}

GskRenderNode *
gtk_snapshot_pop_collect (GtkSnapshot *snapshot)
{
  GskRenderNode *result = gtk_snapshot_pop_internal (snapshot);

  return result;
}

/**
 * gtk_snapshot_to_node:
 * @snapshot: a #GtkSnapshot
 *
 * Returns the render node that was constructed
 * by @snapshot. After calling this function, it
 * is no longer possible to add more nodes to
 * @snapshot. The only function that should be
 * called after this is g_object_unref().
 *
 * Returns: (transfer full): the constructed #GskRenderNode
 */
GskRenderNode *
gtk_snapshot_to_node (GtkSnapshot *snapshot)
{
  GskRenderNode *result;

  result = gtk_snapshot_pop_internal (snapshot);

  /* We should have exactly our initial state */
  if (!gtk_snapshot_states_is_empty (&snapshot->state_stack))
    {
      g_warning ("Too many gtk_snapshot_push() calls. %zu states remaining.",
                 gtk_snapshot_states_get_size (&snapshot->state_stack));
    }

  gtk_snapshot_states_clear (&snapshot->state_stack);
  gtk_snapshot_nodes_clear (&snapshot->nodes);

  return result;
}

/**
 * gtk_snapshot_to_paintable:
 * @snapshot: a #GtkSnapshot
 * @size: (allow-none): The size of the resulting paintable
 *     or %NULL to use the bounds of the snapshot
 *
 * Returns a paintable encapsulating the render node
 * that was constructed by @snapshot. After calling
 * this function, it is no longer possible to add more
 * nodes to @snapshot. The only function that should be
 * called after this is g_object_unref().
 *
 * Returns: (transfer full): a new #GdkPaintable
 */
GdkPaintable *
gtk_snapshot_to_paintable (GtkSnapshot           *snapshot,
                           const graphene_size_t *size)
{
  GskRenderNode *node;
  GdkPaintable *paintable;
  graphene_rect_t bounds;

  node = gtk_snapshot_to_node (snapshot);
  if (size)
    {
      graphene_size_init_from_size (&bounds.size, size);
    }
  else
    {
      gsk_render_node_get_bounds (node, &bounds);
      bounds.size.width += bounds.origin.x;
      bounds.size.height += bounds.origin.y;
    }
  bounds.origin.x = 0;
  bounds.origin.y = 0;

  paintable = gtk_render_node_paintable_new (node, &bounds);
  gsk_render_node_unref (node);

  return paintable;
}

/**
 * gtk_snapshot_pop:
 * @snapshot: a #GtkSnapshot
 *
 * Removes the top element from the stack of render nodes,
 * and appends it to the node underneath it.
 */
void
gtk_snapshot_pop (GtkSnapshot *snapshot)
{
  GskRenderNode *node;

  node = gtk_snapshot_pop_internal (snapshot);

  if (node)
    gtk_snapshot_append_node_internal (snapshot, node);
}

/**
 * gtk_snapshot_save:
 * @snapshot: a #GtkSnapshot
 *
 * Makes a copy of the current state of @snapshot and saves it
 * on an internal stack of saved states for @snapshot. When
 * gtk_snapshot_restore() is called, @snapshot will be restored to
 * the saved state. Multiple calls to gtk_snapshot_save() and
 * gtk_snapshot_restore() can be nested; each call to
 * gtk_snapshot_restore() restores the state from the matching paired
 * gtk_snapshot_save().
 *
 * It is necessary to clear all saved states with corresponding calls
 * to gtk_snapshot_restore().
 **/
void
gtk_snapshot_save (GtkSnapshot *snapshot)
{
  g_return_if_fail (GTK_IS_SNAPSHOT (snapshot));

  gtk_snapshot_push_state (snapshot,
                           gtk_snapshot_get_current_state (snapshot)->transform,
                           NULL);
}

/**
 * gtk_snapshot_restore:
 * @snapshot: a #GtkSnapshot
 *
 * Restores @snapshot to the state saved by a preceding call to
 * gtk_snapshot_save() and removes that state from the stack of
 * saved states.
 **/
void
gtk_snapshot_restore (GtkSnapshot *snapshot)
{
  GtkSnapshotState *state;
  GskRenderNode *node;

  for (state = gtk_snapshot_get_current_state (snapshot);
       gtk_snapshot_state_should_autopop (state);
       state = gtk_snapshot_get_current_state (snapshot))
    {
      node = gtk_snapshot_pop_one (snapshot);
      if (node)
        gtk_snapshot_append_node_internal (snapshot, node);
    }

  if (state->collect_func != NULL)
    {
      g_warning ("Too many gtk_snapshot_restore() calls.");
      return;
    }

  node = gtk_snapshot_pop_one (snapshot);
  g_assert (node == NULL);
}

/**
 * gtk_snapshot_transform:
 * @snapshot: a #GtkSnapshot
 * @transform: (allow-none): the transform to apply
 *
 * Transforms @snapshot's coordinate system with the given @transform.
 **/
void
gtk_snapshot_transform (GtkSnapshot  *snapshot,
                        GskTransform *transform)
{
  GtkSnapshotState *state;

  g_return_if_fail (GTK_IS_SNAPSHOT (snapshot));

  state = gtk_snapshot_get_current_state (snapshot);
  state->transform = gsk_transform_transform (state->transform, transform);
}

/**
 * gtk_snapshot_transform_matrix:
 * @snapshot: a #GtkSnapshot
 * @matrix: the matrix to multiply the transform with
 *
 * Transforms @snapshot's coordinate system with the given @matrix.
 **/
void
gtk_snapshot_transform_matrix (GtkSnapshot             *snapshot,
                               const graphene_matrix_t *matrix)
{
  GtkSnapshotState *state;

  g_return_if_fail (GTK_IS_SNAPSHOT (snapshot));
  g_return_if_fail (matrix != NULL);

  state = gtk_snapshot_get_current_state (snapshot);
  state->transform = gsk_transform_matrix (state->transform, matrix);
}

/**
 * gtk_snapshot_translate:
 * @snapshot: a #GtkSnapshot
 * @point: the point to translate the snapshot by
 *
 * Translates @snapshot's coordinate system by @point in 2-dimensional space.
 */
void
gtk_snapshot_translate (GtkSnapshot            *snapshot,
                        const graphene_point_t *point)
{
  GtkSnapshotState *state;

  g_return_if_fail (GTK_IS_SNAPSHOT (snapshot));
  g_return_if_fail (point != NULL);

  state = gtk_snapshot_get_current_state (snapshot);
  state->transform = gsk_transform_translate (state->transform, point);
}

/**
 * gtk_snapshot_translate_3d:
 * @snapshot: a #GtkSnapshot
 * @point: the point to translate the snapshot by
 *
 * Translates @snapshot's coordinate system by @point.
 */
void
gtk_snapshot_translate_3d (GtkSnapshot              *snapshot,
                           const graphene_point3d_t *point)
{
  GtkSnapshotState *state;

  g_return_if_fail (GTK_IS_SNAPSHOT (snapshot));
  g_return_if_fail (point != NULL);

  state = gtk_snapshot_get_current_state (snapshot);
  state->transform = gsk_transform_translate_3d (state->transform, point);
}

/**
 * gtk_snapshot_rotate:
 * @snapshot: a #GtkSnapshot
 * @angle: the rotation angle, in degrees (clockwise)
 *
 * Rotates @@snapshot's coordinate system by @angle degrees in 2D space -
 * or in 3D speak, rotates around the z axis.
 */
void
gtk_snapshot_rotate (GtkSnapshot *snapshot,
                     float        angle)
{
  GtkSnapshotState *state;

  g_return_if_fail (GTK_IS_SNAPSHOT (snapshot));

  state = gtk_snapshot_get_current_state (snapshot);
  state->transform = gsk_transform_rotate (state->transform, angle);
}

/**
 * gtk_snapshot_rotate_3d:
 * @snapshot: a #GtkSnapshot
 * @angle: the rotation angle, in degrees (clockwise)
 * @axis: The rotation axis
 *
 * Rotates @snapshot's coordinate system by @angle degrees around @axis.
 *
 * For a rotation in 2D space, use gsk_transform_rotate().
 */
void
gtk_snapshot_rotate_3d (GtkSnapshot           *snapshot,
                        float                  angle,
                        const graphene_vec3_t *axis)
{
  GtkSnapshotState *state;

  g_return_if_fail (GTK_IS_SNAPSHOT (snapshot));
  g_return_if_fail (axis != NULL);

  state = gtk_snapshot_get_current_state (snapshot);
  state->transform = gsk_transform_rotate_3d (state->transform, angle, axis);
}

/**
 * gtk_snapshot_scale:
 * @snapshot: a #GtkSnapshot
 * @factor_x: scaling factor on the X axis
 * @factor_y: scaling factor on the Y axis
 *
 * Scales @snapshot's coordinate system in 2-dimensional space by
 * the given factors.
 *
 * Use gtk_snapshot_scale_3d() to scale in all 3 dimensions.
 **/
void
gtk_snapshot_scale (GtkSnapshot *snapshot,
                    float        factor_x,
                    float        factor_y)
{
  GtkSnapshotState *state;

  g_return_if_fail (GTK_IS_SNAPSHOT (snapshot));

  state = gtk_snapshot_get_current_state (snapshot);
  state->transform = gsk_transform_scale (state->transform, factor_x, factor_y);
}

/**
 * gtk_snapshot_scale_3d:
 * @snapshot: a #GtkSnapshot
 * @factor_x: scaling factor on the X axis
 * @factor_y: scaling factor on the Y axis
 * @factor_z: scaling factor on the Z axis
 *
 * Scales @snapshot's coordinate system by the given factors.
 */
void
gtk_snapshot_scale_3d (GtkSnapshot *snapshot,
                       float        factor_x,
                       float        factor_y,
                       float        factor_z)
{
  GtkSnapshotState *state;

  g_return_if_fail (GTK_IS_SNAPSHOT (snapshot));

  state = gtk_snapshot_get_current_state (snapshot);
  state->transform = gsk_transform_scale_3d (state->transform, factor_x, factor_y, factor_z);
}

/**
 * gtk_snapshot_perspective:
 * @snapshot: a #GtkSnapshot
 * @depth: distance of the z=0 plane
 *
 * Applies a perspective projection transform.
 *
 * See gsk_transform_perspective() for a discussion on the details.
 */
void
gtk_snapshot_perspective (GtkSnapshot *snapshot,
                          float        depth)
{
  GtkSnapshotState *state;

  g_return_if_fail (GTK_IS_SNAPSHOT (snapshot));

  state = gtk_snapshot_get_current_state (snapshot);
  state->transform = gsk_transform_perspective (state->transform, depth);
}

/**
 * gtk_snapshot_append_node:
 * @snapshot: a #GtkSnapshot
 * @node: a #GskRenderNode
 *
 * Appends @node to the current render node of @snapshot,
 * without changing the current node. If @snapshot does
 * not have a current node yet, @node will become the
 * initial node.
 */
void
gtk_snapshot_append_node (GtkSnapshot   *snapshot,
                          GskRenderNode *node)
{
  g_return_if_fail (snapshot != NULL);
  g_return_if_fail (GSK_IS_RENDER_NODE (node));

  gtk_snapshot_ensure_identity (snapshot);

  gtk_snapshot_append_node_internal (snapshot, gsk_render_node_ref (node));
}

/**
 * gtk_snapshot_append_cairo:
 * @snapshot: a #GtkSnapshot
 * @bounds: the bounds for the new node
 *
 * Creates a new render node and appends it to the current render
 * node of @snapshot, without changing the current node.
 *
 * Returns: a cairo_t suitable for drawing the contents of the newly
 *     created render node
 */
cairo_t *
gtk_snapshot_append_cairo (GtkSnapshot           *snapshot,
                           const graphene_rect_t *bounds)
{
  GskRenderNode *node;
  graphene_rect_t real_bounds;
  float scale_x, scale_y, dx, dy;
  cairo_t *cr;

  g_return_val_if_fail (snapshot != NULL, NULL);
  g_return_val_if_fail (bounds != NULL, NULL);

  gtk_snapshot_ensure_affine (snapshot, &scale_x, &scale_y, &dx, &dy);
  gtk_graphene_rect_scale_affine (bounds, scale_x, scale_y, dx, dy, &real_bounds);

  node = gsk_cairo_node_new (&real_bounds);

  gtk_snapshot_append_node_internal (snapshot, node);

  cr = gsk_cairo_node_get_draw_context (node);

  cairo_scale (cr, scale_x, scale_y);
  cairo_translate (cr, dx, dy);

  return cr;
}

/**
 * gtk_snapshot_append_texture:
 * @snapshot: a #GtkSnapshot
 * @texture: the #GdkTexture to render
 * @bounds: the bounds for the new node
 *
 * Creates a new render node drawing the @texture into the given @bounds and appends it
 * to the current render node of @snapshot.
 **/
void
gtk_snapshot_append_texture (GtkSnapshot           *snapshot,
                             GdkTexture            *texture,
                             const graphene_rect_t *bounds)
{
  GskRenderNode *node;
  graphene_rect_t real_bounds;
  float scale_x, scale_y, dx, dy;

  g_return_if_fail (snapshot != NULL);
  g_return_if_fail (GDK_IS_TEXTURE (texture));
  g_return_if_fail (bounds != NULL);

  gtk_snapshot_ensure_affine (snapshot, &scale_x, &scale_y, &dx, &dy);
  gtk_graphene_rect_scale_affine (bounds, scale_x, scale_y, dx, dy, &real_bounds);
  node = gsk_texture_node_new (texture, &real_bounds);

  gtk_snapshot_append_node_internal (snapshot, node);
}

/**
 * gtk_snapshot_append_color:
 * @snapshot: a #GtkSnapshot
 * @color: the #GdkRGBA to draw
 * @bounds: the bounds for the new node
 *
 * Creates a new render node drawing the @color into the given @bounds and appends it
 * to the current render node of @snapshot.
 *
 * You should try to avoid calling this function if @color is transparent.
 **/
void
gtk_snapshot_append_color (GtkSnapshot           *snapshot,
                           const GdkRGBA         *color,
                           const graphene_rect_t *bounds)
{
  GskRenderNode *node;
  graphene_rect_t real_bounds;
  float scale_x, scale_y, dx, dy;

  g_return_if_fail (snapshot != NULL);
  g_return_if_fail (color != NULL);
  g_return_if_fail (bounds != NULL);

  gtk_snapshot_ensure_affine (snapshot, &scale_x, &scale_y, &dx, &dy);
  gtk_graphene_rect_scale_affine (bounds, scale_x, scale_y, dx, dy, &real_bounds);

  node = gsk_color_node_new (color, &real_bounds);

  gtk_snapshot_append_node_internal (snapshot, node);
}

/**
 * gtk_snapshot_render_background:
 * @snapshot: a #GtkSnapshot
 * @context: the #GtkStyleContext to use
 * @x: X origin of the rectangle
 * @y: Y origin of the rectangle
 * @width: rectangle width
 * @height: rectangle height
 *
 * Creates a render node for the CSS background according to @context,
 * and appends it to the current node of @snapshot, without changing
 * the current node.
 */
void
gtk_snapshot_render_background (GtkSnapshot     *snapshot,
                                GtkStyleContext *context,
                                double           x,
                                double           y,
                                double           width,
                                double           height)
{
  GtkCssBoxes boxes;

  g_return_if_fail (snapshot != NULL);
  g_return_if_fail (GTK_IS_STYLE_CONTEXT (context));

  gtk_css_boxes_init_border_box (&boxes,
                                 gtk_style_context_lookup_style (context),
                                 x, y, width, height);
  gtk_css_style_snapshot_background (&boxes, snapshot);
}

/**
 * gtk_snapshot_render_frame:
 * @snapshot: a #GtkSnapshot
 * @context: the #GtkStyleContext to use
 * @x: X origin of the rectangle
 * @y: Y origin of the rectangle
 * @width: rectangle width
 * @height: rectangle height
 *
 * Creates a render node for the CSS border according to @context,
 * and appends it to the current node of @snapshot, without changing
 * the current node.
 */
void
gtk_snapshot_render_frame (GtkSnapshot     *snapshot,
                           GtkStyleContext *context,
                           double           x,
                           double           y,
                           double           width,
                           double           height)
{
  GtkCssBoxes boxes;

  g_return_if_fail (snapshot != NULL);
  g_return_if_fail (GTK_IS_STYLE_CONTEXT (context));

  gtk_css_boxes_init_border_box (&boxes,
                                 gtk_style_context_lookup_style (context),
                                 x, y, width, height);
  gtk_css_style_snapshot_border (&boxes, snapshot);
}

/**
 * gtk_snapshot_render_focus:
 * @snapshot: a #GtkSnapshot
 * @context: the #GtkStyleContext to use
 * @x: X origin of the rectangle
 * @y: Y origin of the rectangle
 * @width: rectangle width
 * @height: rectangle height
 *
 * Creates a render node for the focus outline according to @context,
 * and appends it to the current node of @snapshot, without changing
 * the current node.
 */
void
gtk_snapshot_render_focus (GtkSnapshot     *snapshot,
                           GtkStyleContext *context,
                           double           x,
                           double           y,
                           double           width,
                           double           height)
{
  GtkCssBoxes boxes;

  g_return_if_fail (snapshot != NULL);
  g_return_if_fail (GTK_IS_STYLE_CONTEXT (context));

  gtk_css_boxes_init_border_box (&boxes,
                                 gtk_style_context_lookup_style (context),
                                 x, y, width, height);
  gtk_css_style_snapshot_outline (&boxes, snapshot);
}

/**
 * gtk_snapshot_render_layout:
 * @snapshot: a #GtkSnapshot
 * @context: the #GtkStyleContext to use
 * @x: X origin of the rectangle
 * @y: Y origin of the rectangle
 * @layout: the #PangoLayout to render
 *
 * Creates a render node for rendering @layout according to the style
 * information in @context, and appends it to the current node of @snapshot,
 * without changing the current node.
 */
void
gtk_snapshot_render_layout (GtkSnapshot     *snapshot,
                            GtkStyleContext *context,
                            double           x,
                            double           y,
                            PangoLayout     *layout)
{
  const bool needs_translate = (x != 0 || y != 0);
  const GdkRGBA *fg_color;
  GtkCssValue *shadows_value;
  gboolean has_shadow;

  g_return_if_fail (snapshot != NULL);
  g_return_if_fail (GTK_IS_STYLE_CONTEXT (context));
  g_return_if_fail (PANGO_IS_LAYOUT (layout));

  if (needs_translate)
    {
      gtk_snapshot_save (snapshot);
      gtk_snapshot_translate (snapshot, &GRAPHENE_POINT_INIT (x, y));
    }

  fg_color = gtk_css_color_value_get_rgba (_gtk_style_context_peek_property (context, GTK_CSS_PROPERTY_COLOR));

  shadows_value = _gtk_style_context_peek_property (context, GTK_CSS_PROPERTY_TEXT_SHADOW);
  has_shadow = gtk_css_shadow_value_push_snapshot (shadows_value, snapshot);

  gtk_snapshot_append_layout (snapshot, layout, fg_color);

  if (has_shadow)
    gtk_snapshot_pop (snapshot);

  if (needs_translate)
    gtk_snapshot_restore (snapshot);
}

void
gtk_snapshot_append_text (GtkSnapshot           *snapshot,
                          PangoFont             *font,
                          PangoGlyphString      *glyphs,
                          const GdkRGBA         *color,
                          float                  x,
                          float                  y)
{
  GskRenderNode *node;
  float dx, dy;

  gtk_snapshot_ensure_translate (snapshot, &dx, &dy);

  node = gsk_text_node_new (font,
                            glyphs,
                            color,
                            &GRAPHENE_POINT_INIT (x + dx, y + dy));
  if (node == NULL)
    return;

  gtk_snapshot_append_node_internal (snapshot, node);
}

/**
 * gtk_snapshot_append_linear_gradient:
 * @snapshot: a #GtkSnapshot
 * @bounds: the rectangle to render the linear gradient into
 * @start_point: the point at which the linear gradient will begin
 * @end_point: the point at which the linear gradient will finish
 * @stops: (array length=n_stops): a pointer to an array of #GskColorStop defining the gradient
 * @n_stops: the number of elements in @stops
 *
 * Appends a linear gradient node with the given stops to @snapshot.
 */
void
gtk_snapshot_append_linear_gradient (GtkSnapshot            *snapshot,
                                     const graphene_rect_t  *bounds,
                                     const graphene_point_t *start_point,
                                     const graphene_point_t *end_point,
                                     const GskColorStop     *stops,
                                     gsize                   n_stops)
{
  GskRenderNode *node;
  graphene_rect_t real_bounds;
  graphene_point_t real_start_point;
  graphene_point_t real_end_point;
  float scale_x, scale_y, dx, dy;
  const GdkRGBA *first_color;
  gboolean need_gradient = FALSE;
  int i;

  g_return_if_fail (snapshot != NULL);
  g_return_if_fail (start_point != NULL);
  g_return_if_fail (end_point != NULL);
  g_return_if_fail (stops != NULL);
  g_return_if_fail (n_stops > 1);

  gtk_snapshot_ensure_affine (snapshot, &scale_x, &scale_y, &dx, &dy);
  gtk_graphene_rect_scale_affine (bounds, scale_x, scale_y, dx, dy, &real_bounds);
  real_start_point.x = scale_x * start_point->x + dx;
  real_start_point.y = scale_y * start_point->y + dy;
  real_end_point.x = scale_x * end_point->x + dx;
  real_end_point.y = scale_y * end_point->y + dy;

  first_color = &stops[0].color;
  for (i = 0; i < n_stops; i ++)
    {
      if (!gdk_rgba_equal (first_color, &stops[i].color))
        {
          need_gradient = TRUE;
          break;
        }
    }

  if (need_gradient)
    node = gsk_linear_gradient_node_new (&real_bounds,
                                         &real_start_point,
                                         &real_end_point,
                                         stops,
                                         n_stops);
  else
    node = gsk_color_node_new (first_color, &real_bounds);

  gtk_snapshot_append_node_internal (snapshot, node);
}

/**
 * gtk_snapshot_append_repeating_linear_gradient:
 * @snapshot: a #GtkSnapshot
 * @bounds: the rectangle to render the linear gradient into
 * @start_point: the point at which the linear gradient will begin
 * @end_point: the point at which the linear gradient will finish
 * @stops: (array length=n_stops): a pointer to an array of #GskColorStop defining the gradient
 * @n_stops: the number of elements in @stops
 *
 * Appends a repeating linear gradient node with the given stops to @snapshot.
 */
void
gtk_snapshot_append_repeating_linear_gradient (GtkSnapshot            *snapshot,
                                               const graphene_rect_t  *bounds,
                                               const graphene_point_t *start_point,
                                               const graphene_point_t *end_point,
                                               const GskColorStop     *stops,
                                               gsize                   n_stops)
{
  GskRenderNode *node;
  graphene_rect_t real_bounds;
  graphene_point_t real_start_point;
  graphene_point_t real_end_point;
  float scale_x, scale_y, dx, dy;

  g_return_if_fail (snapshot != NULL);
  g_return_if_fail (start_point != NULL);
  g_return_if_fail (end_point != NULL);
  g_return_if_fail (stops != NULL);
  g_return_if_fail (n_stops > 1);

  gtk_snapshot_ensure_affine (snapshot, &scale_x, &scale_y, &dx, &dy);
  gtk_graphene_rect_scale_affine (bounds, scale_x, scale_y, dx, dy, &real_bounds);
  real_start_point.x = scale_x * start_point->x + dx;
  real_start_point.y = scale_y * start_point->y + dy;
  real_end_point.x = scale_x * end_point->x + dx;
  real_end_point.y = scale_y * end_point->y + dy;

  node = gsk_repeating_linear_gradient_node_new (&real_bounds,
                                                 &real_start_point,
                                                 &real_end_point,
                                                 stops,
                                                 n_stops);

  gtk_snapshot_append_node_internal (snapshot, node);
}

/**
 * gtk_snapshot_append_border:
 * @snapshot: a #GtkSnapshot
 * @outline: a #GskRoundedRect describing the outline of the border
 * @border_width: (array fixed-size=4): the stroke width of the border on
 *     the top, right, bottom and left side respectively.
 * @border_color: (array fixed-size=4): the color used on the top, right,
 *     bottom and left side.
 *
 * Appends a stroked border rectangle inside the given @outline. The
 * 4 sides of the border can have different widths and colors.
 **/
void
gtk_snapshot_append_border (GtkSnapshot          *snapshot,
                            const GskRoundedRect *outline,
                            const float           border_width[4],
                            const GdkRGBA         border_color[4])
{
  GskRenderNode *node;
  GskRoundedRect real_outline;
  float scale_x, scale_y, dx, dy;

  g_return_if_fail (snapshot != NULL);
  g_return_if_fail (outline != NULL);
  g_return_if_fail (border_width != NULL);
  g_return_if_fail (border_color != NULL);

  gtk_snapshot_ensure_affine (snapshot, &scale_x, &scale_y, &dx, &dy);
  gtk_rounded_rect_scale_affine (&real_outline, outline, scale_x, scale_y, dx, dy);

  node = gsk_border_node_new (&real_outline, border_width, border_color);

  gtk_snapshot_append_node_internal (snapshot, node);
}

/**
 * gtk_snapshot_append_inset_shadow:
 * @snapshot: a #GtkSnapshot
 * @outline: outline of the region surrounded by shadow
 * @color: color of the shadow
 * @dx: horizontal offset of shadow
 * @dy: vertical offset of shadow
 * @spread: how far the shadow spreads towards the inside
 * @blur_radius: how much blur to apply to the shadow
 *
 * Appends an inset shadow into the box given by @outline.
 */
void
gtk_snapshot_append_inset_shadow (GtkSnapshot          *snapshot,
                                  const GskRoundedRect *outline,
                                  const GdkRGBA        *color,
                                  float                 dx,
                                  float                 dy,
                                  float                 spread,
                                  float                 blur_radius)
{
  GskRenderNode *node;
  GskRoundedRect real_outline;
  float scale_x, scale_y, x, y;

  g_return_if_fail (snapshot != NULL);
  g_return_if_fail (outline != NULL);
  g_return_if_fail (color != NULL);

  gtk_snapshot_ensure_affine (snapshot, &scale_x, &scale_y, &x, &y);
  gtk_rounded_rect_scale_affine (&real_outline, outline, scale_x, scale_y, x, y);

  node = gsk_inset_shadow_node_new (&real_outline,
                                    color,
                                    scale_x * dx,
                                    scale_y * dy,
                                    spread,
                                    blur_radius);

  gtk_snapshot_append_node_internal (snapshot, node);
}

/**
 * gtk_snapshot_append_outset_shadow:
 * @snapshot: a #GtkSnapshot
 * @outline: outline of the region surrounded by shadow
 * @color: color of the shadow
 * @dx: horizontal offset of shadow
 * @dy: vertical offset of shadow
 * @spread: how far the shadow spreads towards the outside
 * @blur_radius: how much blur to apply to the shadow
 *
 * Appends an outset shadow node around the box given by @outline.
 */
void
gtk_snapshot_append_outset_shadow (GtkSnapshot          *snapshot,
                                   const GskRoundedRect *outline,
                                   const GdkRGBA        *color,
                                   float                 dx,
                                   float                 dy,
                                   float                 spread,
                                   float                 blur_radius)
{
  GskRenderNode *node;
  GskRoundedRect real_outline;
  float scale_x, scale_y, x, y;

  g_return_if_fail (snapshot != NULL);
  g_return_if_fail (outline != NULL);
  g_return_if_fail (color != NULL);

  gtk_snapshot_ensure_affine (snapshot, &scale_x, &scale_y, &x, &y);
  gtk_rounded_rect_scale_affine (&real_outline, outline, scale_x, scale_y, x, y);

  node = gsk_outset_shadow_node_new (&real_outline,
                                     color,
                                     scale_x * dx,
                                     scale_y * dy,
                                     spread,
                                     blur_radius);


  gtk_snapshot_append_node_internal (snapshot, node);
}