[gnome-directory-thumbnailer] core: Add a --show-overlay option to show a ‘folder’ overlay on thumbnails

[Philip Withnall <pwithnall src gnome org>]

commit 33f9297e4fe6922c9d13e345ac78b290f37bb087
Author: Philip Withnall <philip withnall collabora co uk>
Date:   Mon Oct 21 16:05:03 2013 +0100

    core: Add a --show-overlay option to show a ‘folder’ overlay on thumbnails
    
    This overlays the standard GNOME folder icon on the generated thumbnails,
    which can help differentiate folder thumbnails from other files in the same
    parent folder.

 configure.ac |    3 +-
 src/main.c   |   92 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 93 insertions(+), 2 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 0f8b9d5..06a8c23 100644
--- a/configure.ac
+++ b/configure.ac
@@ -26,6 +26,7 @@ GLIB_REQS=2.35.0
 GIO_REQS=2.22.0
 GDK_PIXBUF_REQS=2.6.0
 GNOME_DESKTOP_REQS=2.2.0
+GTK_REQS=3.0
 
 # gnome-directory-thumbnailer versioning
 GDT_VERSION_MAJOR=gdt_version_major
@@ -36,7 +37,7 @@ AC_SUBST([GDT_VERSION_MINOR])
 AC_SUBST([GDT_VERSION_MICRO])
 
 # gnome-directory-thumbnailer dependencies
-PKG_CHECK_MODULES(GDT, [gobject-2.0 glib-2.0 >= $GLIB_REQS gio-2.0 >= $GIO_REQS gdk-pixbuf-2.0 >= 
$GDK_PIXBUF_REQS gnome-desktop-3.0 >= $GNOME_DESKTOP_REQS])
+PKG_CHECK_MODULES(GDT, [gobject-2.0 glib-2.0 >= $GLIB_REQS gio-2.0 >= $GIO_REQS gdk-pixbuf-2.0 >= 
$GDK_PIXBUF_REQS gtk+-3.0 >= $GTK_REQS gnome-desktop-3.0 >= $GNOME_DESKTOP_REQS])
 
 # Internationalisation
 GETTEXT_PACKAGE=AC_PACKAGE_NAME
diff --git a/src/main.c b/src/main.c
index 6ca7ee8..1e99b31 100644
--- a/src/main.c
+++ b/src/main.c
@@ -26,6 +26,7 @@
 #include <glib.h>
 #include <glib/gi18n.h>
 #include <gio/gio.h>
+#include <gtk/gtk.h>
 #include <locale.h>
 #include <math.h>
 
@@ -53,6 +54,7 @@
 
 /* Command line options. */
 static gint output_size = -1; /* pixels */
+static gboolean show_overlay = FALSE;
 static gchar **filenames = NULL; /* needs to be freed with g_strfreev() */
 
 /* Maximum possible interestingness a file could have. See calculate_file_interestingness(). */
@@ -61,6 +63,21 @@ static gchar **filenames = NULL; /* needs to be freed with g_strfreev() */
 /* Default limit on the depth of directory trees which can be recursively thumbnailed. */
 #define DEFAULT_RECURSION_LIMIT 5
 
+/* Width and height of the folder icon overlay on generated thumbnails (in pixels).
+ * The *_NORMAL size is for normal-sized thumbnails (up to 128px), and the *_LARGE size is for up to 256px.
+ * These sizes are used if the generated thumbnail is exactly 128px or 256px wide or tall. If it’s smaller,
+ * the overlay will be scaled down proportionally. */
+#define OVERLAY_SIZE_NORMAL 32 /* pixels */
+#define OVERLAY_SIZE_LARGE 64 /* pixels */
+
+/* X and Y offset of the folder icon overlay from the top-left corner of generated thumbnails (in pixels).
+ * As above, the *_NORMAL and *_LARGE variants are for thumbnails up to 128px and 256px, respectively.
+ * As with OVERLAY_SIZE_*, these offsets will be scaled down for non-maximally-sized thumbnails */
+#define OVERLAY_X_NORMAL 4 /* pixels */
+#define OVERLAY_Y_NORMAL 4 /* pixels */
+#define OVERLAY_X_LARGE 8 /* pixels */
+#define OVERLAY_Y_LARGE 8 /* pixels */
+
 /**
  * calculate_file_interestingness:
  * @file_info: information about the file
@@ -428,6 +445,7 @@ save_pixbuf (GdkPixbuf *pixbuf, GFile *output_file, GError **error)
 /* Command line options. */
 static const GOptionEntry entries[] = {
        { "size", 's', 0, G_OPTION_ARG_INT, &output_size, N_("Maximum size of the thumbnail in pixels 
(maximum width or height)"), NULL },
+       { "show-overlay", 'o', 0, G_OPTION_ARG_NONE, &show_overlay, N_("Show the normal folder icon as an 
overlay on the thumbnail"), NULL },
        { G_OPTION_REMAINING, '\0', 0, G_OPTION_ARG_FILENAME_ARRAY, &filenames, NULL, N_("[INPUT FILE] 
[OUTPUT FILE]") },
        { NULL },
 };
@@ -439,6 +457,7 @@ enum {
        STATUS_ERROR_GENERATING_THUMBNAIL = 2,
        STATUS_ERROR_GENERATING_THUMBNAIL_EMPTY_DIRECTORY = 3,
        STATUS_ERROR_SAVING_THUMBNAIL = 4,
+       STATUS_ERROR_LOADING_OVERLAY = 5,
 };
 
 int
@@ -451,6 +470,7 @@ main (int argc, char *argv[])
        GdkPixbuf *pixbuf = NULL;
        GnomeDesktopThumbnailFactory *factory = NULL;
        GnomeDesktopThumbnailSize thumbnail_size;
+       gint scaled_width, scaled_height;  /* dimensions of the thumbnail after scaling for the --size option 
*/
 
        /* Localisation */
        setlocale (LC_ALL, "");
@@ -514,7 +534,7 @@ main (int argc, char *argv[])
 
        /* Scale the pixbuf down if necessary. */
        if (output_size != -1) {
-               gint original_width, original_height, scaled_width, scaled_height;
+               gint original_width, original_height;
                gdouble scale;
 
                original_width = gdk_pixbuf_get_width (pixbuf);
@@ -541,6 +561,76 @@ main (int argc, char *argv[])
                }
        }
 
+       /* Add the normal folder icon as an overlay if necessary. */
+       if (show_overlay == TRUE) {
+               GtkIconTheme *icon_theme;
+               GdkPixbuf *folder_pixbuf;
+               gint overlay_size, overlay_x, overlay_y;
+               gint scaled_overlay_size, scaled_overlay_x, scaled_overlay_y;
+               gdouble scale;
+
+               /* Re-query the dimensions since we don’t know which dimensions 
gnome_desktop_thumbnail_scale_down_pixbuf() chose. */
+               scaled_width = gdk_pixbuf_get_width (pixbuf);
+               scaled_height = gdk_pixbuf_get_height (pixbuf);
+
+               g_debug ("Scaled width: %i, height: %i.", scaled_width, scaled_height);
+
+               g_debug ("Adding overlay image.");
+
+               /* Initialise GTK+ just to load the icon. This seems a little wasteful, but there’s no other 
option. */
+               gtk_init (&argc, &argv);
+
+               switch (thumbnail_size) {
+                       case GNOME_DESKTOP_THUMBNAIL_SIZE_NORMAL:
+                               overlay_size = OVERLAY_SIZE_NORMAL;
+                               overlay_x = OVERLAY_X_NORMAL;
+                               overlay_y = OVERLAY_Y_NORMAL;
+                               scale = (gdouble) MAX (scaled_width, scaled_height) / 128.0;
+                               break;
+                       case GNOME_DESKTOP_THUMBNAIL_SIZE_LARGE:
+                               overlay_size = OVERLAY_SIZE_LARGE;
+                               overlay_x = OVERLAY_X_LARGE;
+                               overlay_y = OVERLAY_Y_LARGE;
+                               scale = (gdouble) MAX (scaled_width, scaled_height) / 256.0;
+                               break;
+                       default:
+                               g_assert_not_reached ();
+               }
+
+               g_debug ("Overlay size: %i, position: (%i, %i), scale: %f.", overlay_size, overlay_x, 
overlay_y, scale);
+
+               scaled_overlay_size = overlay_size * scale;
+               scaled_overlay_x = overlay_x * scale;
+               scaled_overlay_y = overlay_y * scale;
+
+               g_debug ("Scaled overlay size: %i, position: (%i, %i).", scaled_overlay_size, 
scaled_overlay_x, scaled_overlay_y);
+
+               /* Load the theme’s folder icon. */
+               icon_theme = gtk_icon_theme_get_default ();
+               folder_pixbuf = gtk_icon_theme_load_icon (icon_theme, "folder", scaled_overlay_size, 0 /* no 
flags */, &child_error);
+               g_object_unref (icon_theme);
+
+               if (child_error != NULL) {
+                       /* Failed to load the icon. Shame. */
+                       g_printerr (_("Couldn’t load folder overlay icon: %s\n"), child_error->message);
+                       g_error_free (child_error);
+
+                       status = STATUS_ERROR_LOADING_OVERLAY;
+                       goto done;
+               }
+
+               /* Overlay it on the thumbnail. */
+               gdk_pixbuf_composite (folder_pixbuf, pixbuf,
+                                     scaled_overlay_x, scaled_overlay_y,  /* destination X, Y */
+                                     scaled_overlay_size, scaled_overlay_size,  /* destination width, height 
*/
+                                     0.0, 0.0,  /* source offset X, Y */
+                                     1.0, 1.0,  /* source scale X, Y */
+                                     GDK_INTERP_BILINEAR,
+                                     255);  /* overall alpha */
+
+               g_object_unref (folder_pixbuf);
+       }
+
        /* Save it. */
        save_pixbuf (pixbuf, output_file, &child_error);
        if (child_error != NULL) {