[gnome-photos] base-item: Add photos_base_item_create_preview

[Debarshi Ray <debarshir src gnome org>]

commit f2412e09bb18a8fe5c47d7cc5e69a961bf21b631
Author: Debarshi Ray <debarshir gnome org>
Date:   Mon Nov 23 20:57:51 2015 +0100

    base-item: Add photos_base_item_create_preview
    
    The implementation is synchronous because we are not doing any I/O and
    we expect it to become really fast when mipmapping is enabled. At the
    moment, without mipmaps, it isn't as fast as it should be, but it isn't
    absolutely horrible either.

 src/photos-base-item.c |  111 ++++++++++++++++++++++++++++++++++++++++++++++++
 src/photos-base-item.h |    7 +++
 2 files changed, 118 insertions(+), 0 deletions(-)
---
diff --git a/src/photos-base-item.c b/src/photos-base-item.c
index 7ee60ad..90b4333 100644
--- a/src/photos-base-item.c
+++ b/src/photos-base-item.c
@@ -30,6 +30,7 @@
 #include <string.h>
 
 #include <gdk/gdk.h>
+#include <gegl-plugin.h>
 #include <gio/gio.h>
 #include <glib.h>
 #include <glib/gi18n.h>
@@ -1380,6 +1381,116 @@ photos_base_item_can_trash (PhotosBaseItem *self)
 }
 
 
+cairo_surface_t *
+photos_base_item_create_preview (PhotosBaseItem *self,
+                                 gint size,
+                                 gint scale,
+                                 const gchar *operation,
+                                 const gchar *first_property_name,
+                                 ...)
+{
+  PhotosBaseItemPrivate *priv = self->priv;
+  GeglBuffer *buffer_orig = NULL;
+  GeglBuffer *buffer = NULL;
+  GeglNode *buffer_source;
+  GeglNode *crop;
+  GeglNode *graph = NULL;
+  GeglNode *operation_node;
+  GeglOperation *op;
+  GeglProcessor *processor = NULL;
+  GeglRectangle bbox;
+  GeglRectangle roi;
+  cairo_surface_t *surface = NULL;
+  static const cairo_user_data_key_t key;
+  const Babl *format;
+  const gchar *name;
+  gdouble x;
+  gdouble y;
+  gdouble zoom;
+  gint min_dimension;
+  gint size_scaled;
+  gint stride;
+  gint64 end;
+  gint64 start;
+  guchar *buf = NULL;
+  va_list ap;
+
+  g_return_val_if_fail (operation != NULL && operation[0] != '\0', NULL);
+  g_return_val_if_fail (priv->buffer_source != NULL, NULL);
+  g_return_val_if_fail (priv->edit_graph != NULL, NULL);
+  g_return_val_if_fail (priv->load_graph != NULL, NULL);
+
+  op = gegl_node_get_gegl_operation (priv->buffer_source);
+  g_return_val_if_fail (op != NULL, NULL);
+
+  name = gegl_operation_get_name (op);
+  g_return_val_if_fail (g_strcmp0 (name, "gegl:buffer-source") == 0, NULL);
+
+  gegl_node_get (priv->buffer_source, "buffer", &buffer_orig, NULL);
+  buffer = gegl_buffer_dup (buffer_orig);
+
+  bbox = *gegl_buffer_get_extent (buffer);
+  min_dimension = bbox.height < bbox.width ? bbox.height : bbox.width;
+  x = (gdouble) (bbox.width - min_dimension) / 2.0;
+  y = (gdouble) (bbox.height - min_dimension) / 2.0;
+  size_scaled = size * scale;
+  zoom = (gdouble) size_scaled / (gdouble) min_dimension;
+
+  graph = gegl_node_new ();
+  buffer_source = gegl_node_new_child (graph, "operation", "gegl:buffer-source", "buffer", buffer, NULL);
+  crop = gegl_node_new_child (graph,
+                              "operation", "gegl:crop",
+                              "height", (gdouble) min_dimension,
+                              "width", (gdouble) min_dimension,
+                              "x", x,
+                              "y", y,
+                              NULL);
+
+  operation_node = gegl_node_new_child (graph, "operation", operation, NULL);
+
+  va_start (ap, first_property_name);
+  gegl_node_set_valist (operation_node, first_property_name, ap);
+  va_end (ap);
+
+  gegl_node_link_many (buffer_source, crop, operation_node, NULL);
+  processor = gegl_node_new_processor (operation_node, NULL);
+
+  start = g_get_monotonic_time ();
+
+  while (gegl_processor_work (processor, NULL));
+
+  end = g_get_monotonic_time ();
+  photos_debug (PHOTOS_DEBUG_GEGL, "Create Preview: Process: %" G_GINT64_FORMAT, end - start);
+
+  roi.height = size_scaled;
+  roi.width = size_scaled;
+  roi.x = (gint) (x * zoom + 0.5);
+  roi.y = (gint) (y * zoom + 0.5);
+
+  stride = cairo_format_stride_for_width (CAIRO_FORMAT_ARGB32, roi.width);
+  buf = g_malloc0 (stride * roi.height);
+  format = babl_format ("cairo-ARGB32");
+
+  start = g_get_monotonic_time ();
+
+  gegl_node_blit (operation_node, zoom, &roi, format, buf, GEGL_AUTO_ROWSTRIDE, GEGL_BLIT_DEFAULT);
+
+  end = g_get_monotonic_time ();
+  photos_debug (PHOTOS_DEBUG_GEGL, "Create Preview: Node Blit: %" G_GINT64_FORMAT, end - start);
+
+  surface = cairo_image_surface_create_for_data (buf, CAIRO_FORMAT_ARGB32, roi.width, roi.height, stride);
+  cairo_surface_set_device_scale (surface, (gdouble) scale, (gdouble) scale);
+  cairo_surface_set_user_data (surface, &key, buf, (cairo_destroy_func_t) g_free);
+
+  g_object_unref (buffer);
+  g_object_unref (buffer_orig);
+  g_object_unref (graph);
+  g_object_unref (processor);
+
+  return surface;
+}
+
+
 void
 photos_base_item_destroy (PhotosBaseItem *self)
 {
diff --git a/src/photos-base-item.h b/src/photos-base-item.h
index 884e925..7cf2ba8 100644
--- a/src/photos-base-item.h
+++ b/src/photos-base-item.h
@@ -91,6 +91,13 @@ GType               photos_base_item_get_type                (void) G_GNUC_CONST
 
 gboolean            photos_base_item_can_trash               (PhotosBaseItem *self);
 
+cairo_surface_t    *photos_base_item_create_preview          (PhotosBaseItem *self,
+                                                              gint size,
+                                                              gint scale,
+                                                              const gchar *operation,
+                                                              const gchar *first_property_name,
+                                                              ...) G_GNUC_NULL_TERMINATED 
G_GNUC_WARN_UNUSED_RESULT;
+
 void                photos_base_item_destroy                 (PhotosBaseItem *self);
 
 gchar              *photos_base_item_download                (PhotosBaseItem *self,