[gthumb] make code more robust

[Paolo Bacchilega <paobac src gnome org>]

commit aa4e10d4952acf2e81eb10c50e95961f7c170e4f
Author: Paolo Bacchilega <paobac src gnome org>
Date:   Mon Dec 8 23:48:17 2014 +0100

    make code more robust

 .../file_tools/gth-file-tool-adjust-colors.c       |    4 +-
 extensions/file_tools/gth-file-tool-sharpen.c      |   35 ++++++++++++--------
 2 files changed, 23 insertions(+), 16 deletions(-)
---
diff --git a/extensions/file_tools/gth-file-tool-adjust-colors.c 
b/extensions/file_tools/gth-file-tool-adjust-colors.c
index a1f6438..a93d922 100644
--- a/extensions/file_tools/gth-file-tool-adjust-colors.c
+++ b/extensions/file_tools/gth-file-tool-adjust-colors.c
@@ -416,8 +416,8 @@ gth_file_tool_adjust_colors_get_options (GthFileTool *base)
        if (viewer_page == NULL)
                return NULL;
 
-       cairo_surface_destroy (self->priv->destination);
-       cairo_surface_destroy (self->priv->preview);
+       _cairo_clear_surface (&self->priv->destination);
+       _cairo_clear_surface (&self->priv->preview);
 
        source = gth_image_viewer_page_tool_get_source (GTH_IMAGE_VIEWER_PAGE_TOOL (self));
        if (source == NULL)
diff --git a/extensions/file_tools/gth-file-tool-sharpen.c b/extensions/file_tools/gth-file-tool-sharpen.c
index 67009e7..7a304a7 100644
--- a/extensions/file_tools/gth-file-tool-sharpen.c
+++ b/extensions/file_tools/gth-file-tool-sharpen.c
@@ -42,7 +42,8 @@ struct _GthFileToolSharpenPrivate {
        GtkWidget       *preview;
        guint            apply_event;
        gboolean         show_preview;
-       gboolean         first_allocation;
+       cairo_surface_t *preview_source;
+       gboolean         image_centered;
 };
 
 
@@ -156,10 +157,9 @@ apply_cb (gpointer user_data)
                self->priv->apply_event = 0;
        }
 
-       source = gth_image_viewer_page_tool_get_source (GTH_IMAGE_VIEWER_PAGE_TOOL (self));
+       source = self->priv->preview_source;
        preview = GTH_IMAGE_VIEWER (self->priv->preview);
        if (self->priv->show_preview) {
-
                SharpenData     *sharpen_data;
                int              x, y, w ,h;
                cairo_surface_t *destination;
@@ -232,17 +232,17 @@ preview_checkbutton_toggled_cb (GtkToggleButton    *toggle_button,
 
 
 static void
-preview_size_allocate_cb (GtkWidget    *widget,
-                         GdkRectangle *allocation,
-                         gpointer      user_data)
+preview_site_allocate_cb (GtkWidget    *widget,
+                         GdkRectangle *allocation,
+                         gpointer      user_data)
 {
        GthFileToolSharpen *self = user_data;
 
-       if (! self->priv->first_allocation)
+       if (self->priv->image_centered)
                return;
-       self->priv->first_allocation = FALSE;
 
        gth_image_viewer_scroll_to_center (GTH_IMAGE_VIEWER (self->priv->preview));
+       self->priv->image_centered = TRUE;
 }
 
 
@@ -259,12 +259,15 @@ gth_file_tool_sharpen_get_options (GthFileTool *base)
 
        rtl = gtk_widget_get_direction (GTK_WIDGET (base)) == GTK_TEXT_DIR_RTL;
 
+       _cairo_clear_surface (&self->priv->preview_source);
+
        source = gth_image_viewer_page_tool_get_source (GTH_IMAGE_VIEWER_PAGE_TOOL (self));
        if (source == NULL)
                return NULL;
 
-       self->priv->first_allocation = TRUE;
+       self->priv->preview_source = cairo_surface_reference (source);
        self->priv->builder = _gtk_builder_new_from_file ("sharpen-options.ui", "file_tools");
+       self->priv->image_centered = FALSE;
        options = _gtk_builder_get_widget (self->priv->builder, "options");
        gtk_widget_show (options);
 
@@ -278,7 +281,7 @@ gth_file_tool_sharpen_get_options (GthFileTool *base)
        gth_image_viewer_set_zoom_change (GTH_IMAGE_VIEWER (self->priv->preview), GTH_ZOOM_CHANGE_KEEP_PREV);
        gth_image_viewer_set_zoom (GTH_IMAGE_VIEWER (self->priv->preview), 1.0);
        gth_image_viewer_set_zoom_enabled (GTH_IMAGE_VIEWER (self->priv->preview), FALSE);
-       gth_image_viewer_set_surface (GTH_IMAGE_VIEWER (self->priv->preview), source, -1, -1);
+       gth_image_viewer_set_surface (GTH_IMAGE_VIEWER (self->priv->preview), self->priv->preview_source, -1, 
-1);
        image_navigator = gth_image_navigator_new (GTH_IMAGE_VIEWER (self->priv->preview));
        gtk_widget_show_all (image_navigator);
        gtk_box_pack_start (GTK_BOX (GET_WIDGET ("preview_hbox")), image_navigator, TRUE, TRUE, 0);
@@ -332,10 +335,12 @@ gth_file_tool_sharpen_get_options (GthFileTool *base)
                          "clicked",
                          G_CALLBACK (preview_checkbutton_toggled_cb),
                          self);
-       g_signal_connect_after (self->priv->preview,
-                               "size-allocate",
-                               G_CALLBACK (preview_size_allocate_cb),
-                               self);
+       g_signal_connect (self->priv->preview,
+                         "size-allocate",
+                         G_CALLBACK (preview_site_allocate_cb),
+                         self);
+
+       cairo_surface_destroy (source);
 
        return options;
 }
@@ -353,6 +358,7 @@ gth_file_tool_sharpen_destroy_options (GthFileTool *base)
                self->priv->apply_event = 0;
        }
 
+       _cairo_clear_surface (&self->priv->preview_source);
        _g_clear_object (&self->priv->builder);
 }
 
@@ -414,6 +420,7 @@ gth_file_tool_sharpen_init (GthFileToolSharpen *self)
        self->priv = G_TYPE_INSTANCE_GET_PRIVATE (self, GTH_TYPE_FILE_TOOL_SHARPEN, 
GthFileToolSharpenPrivate);
        self->priv->builder = NULL;
        self->priv->show_preview = TRUE;
+       self->priv->preview_source = NULL;
 
        gth_file_tool_construct (GTH_FILE_TOOL (self),
                                 "image-sharpen-symbolic",