[gthumb/gthumb-3-4] image overview: scale the image asynchronously

[Paolo Bacchilega <paobac src gnome org>]

commit d30168f5526cf802268166ccae35174c65bc9080
Author: Paolo Bacchilega <paobac src gnome org>
Date:   Sun Apr 2 18:29:20 2017 +0200

    image overview: scale the image asynchronously

 gthumb/gth-image-overview.c |  100 ++++++++++++++++++++++++++++++++++++++-----
 1 files changed, 89 insertions(+), 11 deletions(-)
---
diff --git a/gthumb/gth-image-overview.c b/gthumb/gth-image-overview.c
index 18a15d8..5803002 100644
--- a/gthumb/gth-image-overview.c
+++ b/gthumb/gth-image-overview.c
@@ -61,6 +61,7 @@ struct _GthImageOverviewPrivate {
        gboolean                 update_preview;
        GdkDevice               *grab_pointer;
        GdkDevice               *grab_keyboard;
+       GthTask                 *scale_task;
 };
 
 
@@ -119,7 +120,9 @@ gth_image_overview_finalize (GObject *object)
        self = GTH_IMAGE_OVERVIEW (object);
 
        _gth_image_overviewer_disconnect_from_viewer (self);
-       cairo_surface_destroy (self->priv->preview);
+       _cairo_clear_surface (&self->priv->preview);
+       if (self->priv->scale_task != NULL)
+               gth_task_cancel (self->priv->scale_task);
 
        G_OBJECT_CLASS (gth_image_overview_parent_class)->finalize (object);
 }
@@ -160,11 +163,76 @@ _gth_image_overview_update_zoom_info (GthImageOverview *self)
 }
 
 
+/* -- _gth_image_overview_update_preview -- */
+
+
+typedef struct {
+       GthImageOverview *overview;
+       cairo_surface_t  *scaled;
+} ScaleData;
+
+
 static void
-_gth_image_overview_update_preview (GthImageOverview *self)
+scale_data_free (ScaleData *scale_data)
 {
+       if (scale_data == NULL)
+               return;
+       cairo_surface_destroy (scale_data->scaled);
+       g_object_unref (scale_data->overview);
+       g_free (scale_data);
+}
+
+
+static gpointer
+_gth_image_overview_scale_exec (GthAsyncTask *task,
+                               gpointer      user_data)
+{
+       ScaleData        *scale_data = user_data;
+       GthImageOverview *overview = scale_data->overview;
        cairo_surface_t  *image;
 
+       _gth_image_overview_update_zoom_info (overview);
+       image = gth_image_viewer_get_current_image (scale_data->overview->priv->viewer);
+       if (image != NULL)
+               scale_data->scaled = _cairo_image_surface_scale (image,
+                                                                overview->priv->preview_area.width,
+                                                                overview->priv->preview_area.height,
+                                                                SCALE_FILTER_GOOD,
+                                                                task);
+
+       return NULL;
+}
+
+
+static void
+_gth_image_overview_scale_after (GthAsyncTask *task,
+                                GError       *error,
+                                gpointer      user_data)
+{
+       ScaleData *scale_data = user_data;
+
+       if (error == NULL) {
+               GthImageOverview *overview = scale_data->overview;
+
+               _cairo_clear_surface (&overview->priv->preview);
+               if (scale_data->scaled != NULL)
+                       overview->priv->preview = cairo_surface_reference (scale_data->scaled);
+               gtk_widget_queue_resize (GTK_WIDGET (overview));
+
+               if (GTH_TASK (task) == overview->priv->scale_task)
+                       overview->priv->scale_task = NULL;
+       }
+
+       g_object_unref (task);
+}
+
+
+static void
+_gth_image_overview_update_preview (GthImageOverview *self)
+{
+       cairo_surface_t *image;
+       ScaleData       *scale_data;
+
        if (self->priv->viewer == NULL)
                return;
 
@@ -175,22 +243,31 @@ _gth_image_overview_update_preview (GthImageOverview *self)
 
        cairo_surface_destroy (self->priv->preview);
        self->priv->preview = NULL;
+       self->priv->preview_width = 50;
+       self->priv->preview_height = 50;
+       self->priv->visible_area.width = 0;
+       self->priv->visible_area.height = 0;
 
        image = gth_image_viewer_get_current_image (self->priv->viewer);
        if (image == NULL) {
-               self->priv->preview_width = 0;
-               self->priv->preview_height = 0;
-               self->priv->visible_area.width = 0;
-               self->priv->visible_area.height = 0;
                gtk_widget_queue_draw (GTK_WIDGET (self));
-
                return;
        }
 
-       _gth_image_overview_update_zoom_info (self);
-       self->priv->preview = _cairo_image_surface_scale_fast (image,
-                                                              self->priv->preview_area.width,
-                                                              self->priv->preview_area.height);
+       /* queue scale task */
+
+       if (self->priv->scale_task != NULL)
+               gth_task_cancel (self->priv->scale_task);
+
+       scale_data = g_new0 (ScaleData, 1);
+       scale_data->overview = g_object_ref (self);
+
+       self->priv->scale_task = gth_async_task_new (NULL,
+                                                    _gth_image_overview_scale_exec,
+                                                    _gth_image_overview_scale_after,
+                                                    scale_data,
+                                                    (GDestroyNotify) scale_data_free);
+       gth_task_exec (self->priv->scale_task, NULL);
 }
 
 
@@ -699,6 +776,7 @@ gth_image_overview_init (GthImageOverview *self)
        self->priv->update_preview = TRUE;
        self->priv->grab_pointer = NULL;
        self->priv->grab_keyboard = NULL;
+       self->priv->scale_task = NULL;
 
        gtk_widget_set_has_window (GTK_WIDGET (self), TRUE);
        gtk_widget_set_can_focus (GTK_WIDGET (self), FALSE);