/* GIMP - The GNU Image Manipulation Program
 *
 * file-pdf-save.c - PDF file exporter, based on the cairo PDF surface
 *
 * Copyright (C) 2010 Barak Itkin <lightningismyname@gmail.com>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

/* The PDF export plugin has 3 main procedures:
 * 1. file-pdf-save
 *    This is the main procedure. It has 3 options for optimizations of
 *    the pdf file, and it can show a gui. This procedure works on a single
 *    image.
 * 2. file-pdf-save-defaults
 *    This procedures is the one that will be invoked by gimp's file-save,
 *    when the pdf extension is chosen. If it's in RUN_INTERACTIVE, it will
 *    pop a user interface with more options, like file-pdf-save. If it's in
 *    RUN_NONINTERACTIVE, it will simply use the default values. Note that on
 *    RUN_WITH_LAST_VALS there will be no gui, however the values will be the
 *    ones that were used in the last interactive run (or the defaults if none
 *    are available.
 * 3. file-pdf-save-multi
 *    This procedures is more advanced, and it allows the creation of multiple
 *    paged pdf files. It will be located in File/Create/Multiple page PDF...
 *
 * It was suggested that file-pdf-save-multi will be removed from the UI as it
 * does not match the product vision (GIMP isn't a program for editing multiple
 * paged documents).
 */

/* Known Issues (except for the coding style issues):
 * 1. Grayscale layers are inverted (although layer masks which are not grayscale,
 * are not inverted)
 * 2. Exporting some fonts doesn't work since gimp_text_layer_get_font Returns a
 * font which is sometimes incompatiable with pango_font_description_from_string
 * (gimp_text_layer_get_font sometimes returns suffixes such as "semi-expanded" to
 * the font's name although the GIMP's font selection dialog shows the don'ts name
 * normally - This should be checked again in GIMP 2.7)
 * 3. Indexed layers can't be optimized yet (Since gimp_histogram won't work on
 * indexed layers)
 * 4. Rendering the pango layout requires multiplying the size in PANGO_SCALE. This
 * means I'll need to do some hacking on the markup returned from GIMP.
 * 5. When accessing the contents of layer groups is supported, we should do use it
 * (since this plugin should preserve layers).
 *
 * Also, there are 2 things which we should warn the user about:
 * 1. Cairo does not support bitmap masks for text.
 * 2. Currently layer modes are ignored. We do support layers, including
 * transparency and opacity, but layer modes are not supported.
 */

/* Changelog
 *
 * April 29, 2009 | Barak Itkin <lightningismyname@gmail.com>
 *   First version of the plugin. This is only a proof of concept and not a full
 *   working plugin.
 *
 * May 6, 2009 Barak | Itkin <lightningismyname@gmail.com>
 *   Added new features and several bugfixes:
 *   - Added handling for image resolutions
 *   - fixed the behaviour of getting font sizes
 *   - Added various optimizations (solid rectangles instead of bitmaps, ignoring
 *     invisible layers, etc.) as a macro flag.
 *   - Added handling for layer masks, use CAIRO_FORMAT_A8 for grayscale drawables.
 *   - Indexed layers are now supported
 *
 * August 17, 2009 | Barak Itkin <lightningismyname@gmail.com>
 *   Most of the plugin was rewritten from scratch and it now has several new
 *   features:
 *   - Got rid of the optimization macros in the code. The gui now supports
 *     selecting which optimizations to apply.
 *   - Added a procedure to allow the creation of multiple paged PDF's
 *   - Registered the plugin on "<Image>/File/Create/PDF"
 *
 * August 21, 2009 | Barak Itkin <lightningismyname@gmail.com>
 *   Fixed a typo that prevented the plugin from compiling...
 *   A migration to the new GIMP 2.8 api, which includes:
 *   - Now using gimp_export_dialog_new
 *   - Using gimp_text_layer_get_hint_style (2.8) instead of the depreceated
 *     gimp_text_layer_get_hinting (2.6).
 *
 * August 24, 2010 | Barak Itkin <lightningismyname@gmail.com>
 *   More migrations to the new GIMP 2.8 api:
 *   - Now using the GimpItem api
 *   - Using gimp_text_layer_get_markup where possible
 *   - Fixed some compiler warnings
 *   Also merged the header and c file into one file, Updated some of the comments
 *   and documentation, and moved this into the main source repository.
 */

#include "config.h"

#include <errno.h>

#include <glib/gstdio.h>
#include <cairo-pdf.h>
#include <pango/pangocairo.h>

#include <libgimp/gimp.h>
#include <libgimp/gimpui.h>

#include "libgimp/stdplugins-intl.h"


#define SAVE_PROC               "file-pdf-save"
#define SAVE2_PROC              "file-pdf-save2"
#define SAVE_MULTI_PROC         "file-pdf-save-multi"
#define PLUG_IN_BINARY          "file-pdf-save"
#define PLUG_IN_ROLE            "gimp-file-pdf-save"

#define DATA_OPTIMIZE           "file-pdf-data-optimize"
#define DATA_IMAGE_LIST         "file-pdf-data-multi-page"

/* Gimp will crash before you reach this limitation :D */
#define MAX_PAGE_COUNT           350
#define MAX_FILE_NAME_LENGTH     350

#define THUMB_WIDTH              90
#define THUMB_HEIGHT             120

#define GIMP_PLUGIN_PDF_SAVE_ERROR gimp_plugin_pdf_save_error_quark ()

typedef enum
{
  GIMP_PLUGIN_PDF_SAVE_ERROR_FAILED
} GimpPluginPDFError;

GQuark gimp_plugin_pdf_save_error_quark (void);

typedef enum
{
  SA_RUN_MODE,
  SA_IMAGE,
  SA_DRAWABLE,
  SA_FILENAME,
  SA_RAW_FILENAME,
  SA_VECTORIZE,
  SA_IGNORE_HIDDEN,
  SA_APPLY_MASKS,
  SA_LAYERS_AS_PAGES,
  SA_REVERSE_ORDER,
  SA_ARG_COUNT
} SaveArgs;

typedef enum
{
  SMA_RUN_MODE,
  SMA_COUNT,
  SMA_IMAGES,
  SMA_VECTORIZE,
  SMA_IGNORE_HIDDEN,
  SMA_APPLY_MASKS,
  SMA_FILENAME,
  SMA_RAWFILENAME,
  SMA_ARG_COUNT
} SaveMultiArgs;

typedef struct
{
  gboolean vectorize;
  gboolean ignore_hidden;
  gboolean apply_masks;
  gboolean layers_as_pages;
  gboolean reverse_order;
} PdfOptimize;

typedef struct
{
  gint32  images[MAX_PAGE_COUNT];
  guint32 image_count;
  gchar   file_name[MAX_FILE_NAME_LENGTH];
} PdfMultiPage;

typedef struct
{
  PdfOptimize  optimize;
  GArray      *images;
} PdfMultiVals;

enum
{
  THUMB,
  PAGE_NUMBER,
  IMAGE_NAME,
  IMAGE_ID
};

typedef struct
{
  GdkPixbuf *thumb;
  gint32     page_number;
  gchar     *image_name;
} Page;


static void              query                      (void);

static void              run                        (const gchar     *name,
                                                     gint             nparams,
                                                     const GimpParam *param,
                                                     gint            *nreturn_vals,
                                                     GimpParam      **return_vals);

static gboolean          init_vals                  (const gchar     *name,
                                                     gint             nparams,
                                                     const GimpParam *param,
                                                     gboolean        *single,
                                                     gboolean        *defaults,
                                                     GimpRunMode     *run_mode);

static void              init_image_list_defaults   (gint32           image);

static void              validate_image_list        (void);

static gboolean          gui_single                 (void);

static gboolean          gui_multi                  (void);

static void              choose_file_call           (GtkWidget       *browse_button,
                                                     gpointer         file_entry);

static gboolean          get_image_list             (void);

static GtkTreeModel    * create_model               (void);

static void              add_image_call             (GtkWidget       *widget,
                                                     gpointer         img_combo);
static void              del_image_call             (GtkWidget       *widget,
                                                     gpointer         icon_view);
static void              remove_call                (GtkTreeModel    *tree_model,
                                                     GtkTreePath     *path,
                                                     gpointer         user_data);
static void              recount_pages              (void);

static cairo_surface_t * get_cairo_surface          (gint32           drawable_ID,
                                                     gboolean         as_mask,
                                                     GError         **error);

static GimpRGB           get_layer_color            (gint32           layer_ID,
                                                     gboolean        *single);

static void              drawText                   (gint32           text_id,
                                                     gdouble          opacity,
                                                     cairo_t         *cr,
                                                     gdouble          x_res,
                                                     gdouble          y_res);

static gboolean     dnd_remove = TRUE;
static PdfMultiPage multi_page;

static PdfOptimize optimize =
{
  TRUE,  /* vectorize */
  TRUE,  /* ignore_hidden */
  TRUE,  /* apply_masks */
  FALSE, /* layers_as_pages */
  FALSE  /* reverse_order */
};

static GtkTreeModel *model;
static GtkWidget    *file_choose;
static gchar        *file_name;

GimpPlugInInfo PLUG_IN_INFO =
{
  NULL,
  NULL,
  query,
  run
};

G_DEFINE_QUARK (gimp-plugin-pdf-save-error-quark, gimp_plugin_pdf_save_error)

MAIN()

static void
query (void)
{
  static GimpParamDef save_args[] =
  {
    { GIMP_PDB_INT32,    "run-mode",      "Run mode" },
    { GIMP_PDB_IMAGE,    "image",         "Input image" },
    { GIMP_PDB_DRAWABLE, "drawable",      "Input drawable" },
    { GIMP_PDB_STRING,   "filename",      "The name of the file to save the image in" },
    { GIMP_PDB_STRING,   "raw-filename",  "The name of the file to save the image in" },
    { GIMP_PDB_INT32,    "vectorize",     "Convert bitmaps to vector graphics where possible. TRUE or FALSE" },
    { GIMP_PDB_INT32,    "ignore-hidden", "Omit hidden layers and layers with zero opacity. TRUE or FALSE" },
    { GIMP_PDB_INT32,    "apply-masks",   "Apply layer masks before saving. TRUE or FALSE (Keeping them will not change the output)" }
  };

  static GimpParamDef save2_args[] =
  {
    { GIMP_PDB_INT32,    "run-mode",        "Run mode" },
    { GIMP_PDB_IMAGE,    "image",           "Input image" },
    { GIMP_PDB_DRAWABLE, "drawable",        "Input drawable" },
    { GIMP_PDB_STRING,   "filename",        "The name of the file to save the image in" },
    { GIMP_PDB_STRING,   "raw-filename",    "The name of the file to save the image in" },
    { GIMP_PDB_INT32,    "vectorize",       "Convert bitmaps to vector graphics where possible. TRUE or FALSE" },
    { GIMP_PDB_INT32,    "ignore-hidden",   "Omit hidden layers and layers with zero opacity. TRUE or FALSE" },
    { GIMP_PDB_INT32,    "apply-masks",     "Apply layer masks before saving. TRUE or FALSE (Keeping them will not change the output)" },
    { GIMP_PDB_INT32,    "layers-as-pages", "Layers as pages. TRUE or FALSE" },
    { GIMP_PDB_INT32,    "reverse-order",   "Reverse the pages order. TRUE or FALSE" }
  };

  static GimpParamDef save_multi_args[] =
  {
    { GIMP_PDB_INT32,      "run-mode",        "Run mode" },
    { GIMP_PDB_INT32,      "count",           "The amount of images entered (This will be the amount of pages). 1 <= count <= MAX_PAGE_COUNT" },
    { GIMP_PDB_INT32ARRAY, "images",          "Input image for each page (An image can appear more than once)" },
    { GIMP_PDB_INT32,      "vectorize",       "Convert bitmaps to vector graphics where possible. TRUE or FALSE" },
    { GIMP_PDB_INT32,      "ignore-hidden",   "Omit hidden layers and layers with zero opacity. TRUE or FALSE" },
    { GIMP_PDB_INT32,      "apply-masks",     "Apply layer masks before saving. TRUE or FALSE (Keeping them will not change the output)" },
    { GIMP_PDB_STRING,     "filename",        "The name of the file to save the image in" },
    { GIMP_PDB_STRING,     "raw-filename",    "The name of the file to save the image in" }
  };

  gimp_install_procedure (SAVE_PROC,
                          "Save files in PDF format",
                          "Saves files in Adobe's Portable Document Format. "
                          "PDF is designed to be easily processed by a variety "
                          "of different platforms, and is a distant cousin of "
                          "PostScript.",
                          "Barak Itkin",
                          "Copyright Barak Itkin",
                          "August 2009",
                          N_("Portable Document Format"),
                          "RGB*, GRAY*, INDEXED*",
                          GIMP_PLUGIN,
                          G_N_ELEMENTS (save_args), 0,
                          save_args, NULL);

  gimp_install_procedure (SAVE2_PROC,
                          "Save files in PDF format",
                          "Saves files in Adobe's Portable Document Format. "
                          "PDF is designed to be easily processed by a variety "
                          "of different platforms, and is a distant cousin of "
                          "PostScript.\n"
                          "This procedure adds an extra parameter to "
                          "file-pdf-save to save layers as pages.",
                          "Barak Itkin, Lionel N., Jehan",
                          "Copyright Barak Itkin, Lionel N., Jehan",
                          "August 2009, 2017",
                          N_("Portable Document Format"),
                          "RGB*, GRAY*, INDEXED*",
                          GIMP_PLUGIN,
                          G_N_ELEMENTS (save2_args), 0,
                          save2_args, NULL);

  gimp_install_procedure (SAVE_MULTI_PROC,
                          "Save files in PDF format",
                          "Saves files in Adobe's Portable Document Format. "
                          "PDF is designed to be easily processed by a variety "
                          "of different platforms, and is a distant cousin of "
                          "PostScript.",
                          "Barak Itkin",
                          "Copyright Barak Itkin",
                          "August 2009",
                          N_("_Create multipage PDF..."),
                          "RGB*, GRAY*, INDEXED*",
                          GIMP_PLUGIN,
                          G_N_ELEMENTS (save_multi_args), 0,
                          save_multi_args, NULL);

#if 0
  gimp_plugin_menu_register (SAVE_MULTI_PROC,
                             "<Image>/File/Create/PDF");
#endif

  gimp_register_file_handler_mime (SAVE2_PROC, "application/pdf");
  gimp_register_save_handler (SAVE2_PROC, "pdf", "");
}

static cairo_status_t
write_func (void                *fp,
            const unsigned char *data,
            unsigned int         size)
{
  return fwrite (data, 1, size, fp) == size ? CAIRO_STATUS_SUCCESS
                                            : CAIRO_STATUS_WRITE_ERROR;
}

static void
run (const gchar      *name,
     gint              nparams,
     const GimpParam  *param,
     gint             *nreturn_vals,
     GimpParam       **return_vals)
{
  static GimpParam        values[2];
  GimpPDBStatusType       status = GIMP_PDB_SUCCESS;
  GimpRunMode             run_mode;
  gboolean                single_image;
  gboolean                defaults_proc;
  cairo_surface_t        *pdf_file;
  cairo_t                *cr;
  GimpExportCapabilities  capabilities;
  FILE                   *fp;
  gint                    i;
  GError                 *error = NULL;

  INIT_I18N ();
  gegl_init (NULL, NULL);

  /* Setting mandatory output values */
  *nreturn_vals = 1;
  *return_vals  = values;

  values[0].type          = GIMP_PDB_STATUS;
  values[0].data.d_status = status;

  /* Initializing all the settings */
  multi_page.image_count = 0;

  if (! init_vals (name, nparams, param, &single_image,
                   &defaults_proc, &run_mode))
    {
      values[0].data.d_status = GIMP_PDB_CALLING_ERROR;
      return;
    }

  /* Starting the executions */
  if (run_mode == GIMP_RUN_INTERACTIVE)
    {
      if (single_image)
        {
          if (! gui_single ())
            {
              values[0].data.d_status = GIMP_PDB_CANCEL;
              return;
            }
        }
      else if (! gui_multi ())
        {
          values[0].data.d_status = GIMP_PDB_CANCEL;
          return;
        }

      if (file_name == NULL)
        {
          values[0].data.d_status = GIMP_PDB_CALLING_ERROR;
          gimp_message (_("You must select a file to save!"));
          return;
        }
    }

  fp = g_fopen (file_name, "wb");
  if (fp == NULL)
    {
      *nreturn_vals = 2;

      values[0].data.d_status = GIMP_PDB_EXECUTION_ERROR;
      values[1].type          = GIMP_PDB_STRING;
      if (error == NULL)
        {
          g_set_error (&error, G_FILE_ERROR, g_file_error_from_errno (errno),
                       _("Could not open '%s' for writing: %s"),
                       gimp_filename_to_utf8 (file_name), g_strerror (errno));
        }
      values[1].data.d_string = error->message;
      return;
    }

  pdf_file = cairo_pdf_surface_create_for_stream (write_func, fp, 1, 1);

  if (cairo_surface_status (pdf_file) != CAIRO_STATUS_SUCCESS)
    {
      g_message (_("An error occurred while creating the PDF file:\n"
                   "%s\n"
                   "Make sure you entered a valid filename and that the "
                   "selected location isn't read only!"),
                 cairo_status_to_string (cairo_surface_status (pdf_file)));

      values[0].data.d_status = GIMP_PDB_EXECUTION_ERROR;
      return;
    }

  cr = cairo_create (pdf_file);

  capabilities = (GIMP_EXPORT_CAN_HANDLE_RGB    |
                  GIMP_EXPORT_CAN_HANDLE_ALPHA  |
                  GIMP_EXPORT_CAN_HANDLE_GRAY   |
                  GIMP_EXPORT_CAN_HANDLE_LAYERS |
                  GIMP_EXPORT_CAN_HANDLE_INDEXED);
  /* This seems counter-intuitive, but not setting the mask capability
   * will apply any layer mask upon gimp_export_image().
   */
  if (! optimize.apply_masks)
    capabilities |= GIMP_EXPORT_CAN_HANDLE_LAYER_MASKS;

  for (i = 0; i < multi_page.image_count; i++)
    {
      gint32    image_ID = multi_page.images[i];
      gboolean  exported;
      gint32   *layers;
      gint32    n_layers;
      gdouble   x_res, y_res;
      gdouble   x_scale, y_scale;
      gint32    temp;
      gint      j;

      temp = gimp_image_get_active_drawable (image_ID);
      if (temp < 1)
        continue;

      /* Save the state of the surface before any changes, so that
       * settings from one page won't affect all the others
       */
      cairo_save (cr);

      if (gimp_export_image (&image_ID, &temp, NULL,
                             capabilities) == GIMP_EXPORT_EXPORT)
        {
          exported = TRUE;
        }
      else
        {
          exported = FALSE;
        }

      gimp_image_get_resolution (image_ID, &x_res, &y_res);
      x_scale = 72.0 / x_res;
      y_scale = 72.0 / y_res;

      cairo_pdf_surface_set_size (pdf_file,
                                  gimp_image_width (image_ID) * x_scale,
                                  gimp_image_height (image_ID) * y_scale);

      /* This way we set how many pixels are there in every inch.
       * It's very important for PangoCairo
       */
      cairo_surface_set_fallback_resolution (pdf_file, x_res, y_res);

      /* Cairo has a concept of user-space vs device-space units.
       * From what I understand, by default the user-space unit is the
       * typographical "point". Since we work mostly with pixels, not
       * points, the following call simply scales the transformation
       * matrix from points to pixels, relatively to the image
       * resolution, knowing that 1 typographical point == 1/72 inch.
       */
      cairo_scale (cr, x_scale, y_scale);

      layers = gimp_image_get_layers (image_ID, &n_layers);

      /* Fill image with background color -
       * otherwise the output PDF will always show white for background,
       * and may display artifacts at transparency boundaries
       */
      if (gimp_drawable_has_alpha (layers[n_layers - 1]))
        {
          GimpRGB color;

          cairo_rectangle (cr, 0.0, 0.0,
                           gimp_image_width (image_ID),
                           gimp_image_height (image_ID));
          gimp_context_get_background (&color);
          cairo_set_source_rgb (cr,
                                color.r,
                                color.g,
                                color.b);
          cairo_fill (cr);
        }

      /* Now, we should loop over the layers of each image */
      for (j = 0; j < n_layers; j++)
        {
          gint32           layer_ID;
          gint32           mask_ID    = -1;
          cairo_surface_t *mask_image = NULL;
          gdouble          opacity;
          gboolean         single_color;
          gint             x, y;

          if (optimize.reverse_order && optimize.layers_as_pages)
            layer_ID = layers [j];
          else
            layer_ID = layers [n_layers - j - 1];

          opacity = gimp_layer_get_opacity (layer_ID) / 100.0;

          if ((gimp_item_get_visible (layer_ID) && opacity > 0.0) ||
              ! optimize.ignore_hidden)
            {
              mask_ID = gimp_layer_get_mask (layer_ID);
              if (mask_ID != -1)
                {
                  mask_image = get_cairo_surface (mask_ID, TRUE,
                                                  &error);
                  if (error != NULL)
                    {
                      *nreturn_vals = 2;

                      /* free the resources */
                      cairo_surface_destroy (pdf_file);
                      cairo_destroy (cr);
                      fclose (fp);

                      values[0].data.d_status = GIMP_PDB_EXECUTION_ERROR;

                      values[1].type          = GIMP_PDB_STRING;
                      values[1].data.d_string = error->message;
                      return;
                    }
                }
              gimp_drawable_offsets (layer_ID, &x, &y);

              if (! gimp_item_is_text_layer (layer_ID))
                {
                  /* For raster layers */

                  GimpRGB layer_color;

                  layer_color = get_layer_color (layer_ID, &single_color);

                  cairo_rectangle (cr, x, y,
                                   gimp_drawable_width (layer_ID),
                                   gimp_drawable_height (layer_ID));

                  if (optimize.vectorize && single_color)
                    {
                      cairo_set_source_rgba (cr,
                                             layer_color.r,
                                             layer_color.g,
                                             layer_color.b,
                                             layer_color.a * opacity);
                      if (mask_ID != -1)
                        cairo_mask_surface (cr, mask_image, x, y);
                      else
                        cairo_fill (cr);
                    }
                  else
                    {
                      cairo_surface_t *layer_image;

                      layer_image = get_cairo_surface (layer_ID, FALSE,
                                                       &error);
                      if (error != NULL)
                        {
                          *nreturn_vals = 2;

                          /* free the resources */
                          cairo_surface_destroy (pdf_file);
                          cairo_destroy (cr);
                          fclose (fp);

                          values[0].data.d_status = GIMP_PDB_EXECUTION_ERROR;

                          values[1].type          = GIMP_PDB_STRING;
                          values[1].data.d_string = error->message;
                          return;
                        }

                      cairo_clip (cr);

                      cairo_set_source_surface (cr, layer_image, x, y);
                      cairo_push_group (cr);
                      cairo_paint_with_alpha (cr, opacity);
                      cairo_pop_group_to_source (cr);

                      if (mask_ID != -1)
                        cairo_mask_surface (cr, mask_image, x, y);
                      else
                        cairo_paint (cr);

                      cairo_reset_clip (cr);

                      cairo_surface_destroy (layer_image);
                    }
                }
              else
                {
                  /* For text layers */
                  drawText (layer_ID, opacity, cr, x_res, y_res);
                }
              /* draw new page if "layers as pages" option is checked */
              if (optimize.layers_as_pages &&
                  g_strcmp0 (name, SAVE2_PROC) == 0)
                cairo_show_page (cr);
            }
          /* We are done with the layer - time to free some resources */
          if (mask_ID != -1)
            cairo_surface_destroy (mask_image);
        }

      /* We are done with this image - Show it!
       * Unless that's a multi-page to avoid blank page at the end
       */
      if (g_strcmp0 (name, SAVE2_PROC) != 0 ||
          ! optimize.layers_as_pages)
        cairo_show_page (cr);
      cairo_restore (cr);

      if (exported)
        gimp_image_delete (image_ID);
    }

  /* We are done with all the images - time to free the resources */
  cairo_surface_destroy (pdf_file);
  cairo_destroy (cr);

  fclose (fp);

  /* Finally done, let's save the parameters */
  gimp_set_data (DATA_OPTIMIZE, &optimize, sizeof (optimize));

  if (! single_image)
    {
      g_strlcpy (multi_page.file_name, file_name, MAX_FILE_NAME_LENGTH);
      gimp_set_data (DATA_IMAGE_LIST, &multi_page, sizeof (multi_page));
    }
}

/******************************************************/
/* Beginning of parameter handling functions          */
/******************************************************/

/* A function that takes care of loading the basic parameters
 */
static gboolean
init_vals (const gchar      *name,
           gint              nparams,
           const GimpParam  *param,
           gboolean         *single_image,
           gboolean         *defaults_proc,
           GimpRunMode      *run_mode)
{
  gboolean had_saved_list = FALSE;
  gboolean single;
  gboolean defaults = FALSE;
  gint32   i;
  gint32   image;

  if ((g_str_equal (name, SAVE_PROC) && nparams == SA_ARG_COUNT - 2) ||
      (g_str_equal (name, SAVE2_PROC) && nparams == SA_ARG_COUNT))
    {
      single = TRUE;
      *run_mode = param[SA_RUN_MODE].data.d_int32;
      image = param[SA_IMAGE].data.d_int32;
      file_name = param[SA_FILENAME].data.d_string;

      if (*run_mode == GIMP_RUN_NONINTERACTIVE)
        {
          optimize.apply_masks = param[SA_APPLY_MASKS].data.d_int32;
          optimize.vectorize = param[SA_VECTORIZE].data.d_int32;
          optimize.ignore_hidden = param[SA_IGNORE_HIDDEN].data.d_int32;
          if (nparams == SA_ARG_COUNT)
          {
            optimize.layers_as_pages = param[SA_LAYERS_AS_PAGES].data.d_int32;
            optimize.reverse_order = param[SA_REVERSE_ORDER].data.d_int32;
          }
        }
      else
        defaults = TRUE;
    }
  else if (g_str_equal (name, SAVE_MULTI_PROC))
    {
      single = FALSE;
      if (nparams != SMA_ARG_COUNT)
        return FALSE;

      *run_mode = param[SMA_RUN_MODE].data.d_int32;
      image = -1;
      file_name = param[SMA_FILENAME].data.d_string;

      optimize.apply_masks = param[SMA_APPLY_MASKS].data.d_int32;
      optimize.vectorize = param[SMA_VECTORIZE].data.d_int32;
      optimize.ignore_hidden = param[SMA_IGNORE_HIDDEN].data.d_int32;
    }
  else
    {
      return FALSE;
    }

  switch (*run_mode)
    {
    case GIMP_RUN_NONINTERACTIVE:
      if (single)
        {
          init_image_list_defaults (image);
        }
      else
        {
          multi_page.image_count = param[SMA_COUNT].data.d_int32;
          if (param[SMA_IMAGES].data.d_int32array != NULL)
            for (i = 0; i < param[SMA_COUNT].data.d_int32; i++)
              multi_page.images[i] = param[SMA_IMAGES].data.d_int32array[i];
        }
      break;

    case GIMP_RUN_INTERACTIVE:
      /* Possibly retrieve data */
      gimp_get_data (DATA_OPTIMIZE, &optimize);
      had_saved_list = gimp_get_data (DATA_IMAGE_LIST, &multi_page);

      if (had_saved_list && (file_name == NULL || strlen (file_name) == 0))
        {
          file_name = multi_page.file_name;
        }

      if (single || ! had_saved_list )
        init_image_list_defaults (image);
      break;

    case GIMP_RUN_WITH_LAST_VALS:
      /* Possibly retrieve data */
      if (! single)
        {
          had_saved_list = gimp_get_data (DATA_IMAGE_LIST, &multi_page);
          if (had_saved_list)
            {
              file_name = multi_page.file_name;
            }
        }
      else
        {
          init_image_list_defaults (image);
        }
      gimp_get_data (DATA_OPTIMIZE, &optimize);
      break;
    }

  *defaults_proc = defaults;
  *single_image = single;

  validate_image_list ();

  return TRUE;
}

/* A function that initializes the image list to default values */
static void
init_image_list_defaults (gint32 image)
{
  if (image != -1)
    {
      multi_page.images[0]   = image;
      multi_page.image_count = 1;
    }
  else
    {
      multi_page.image_count = 0;
    }
}

/* A function that removes images that are no longer valid from the
 * image list
 */
static void
validate_image_list (void)
{
  gint32  valid = 0;
  guint32 i     = 0;

  for (i = 0 ; i < MAX_PAGE_COUNT && i < multi_page.image_count ; i++)
    {
      if (gimp_image_is_valid (multi_page.images[i]))
        {
          multi_page.images[valid] = multi_page.images[i];
          valid++;
        }
    }

  multi_page.image_count = valid;
}


/******************************************************/
/* Beginning of GUI functions                         */
/******************************************************/

/* The main GUI function for saving single-paged PDFs */

static gboolean
gui_single (void)
{
  GtkWidget *window;
  GtkWidget *vbox;
  GtkWidget *vectorize_c;
  GtkWidget *ignore_hidden_c;
  GtkWidget *apply_c;
  GtkWidget *layers_as_pages_c;
  GtkWidget *reverse_order_c;
  gboolean   run;
  gint32     n_layers;

  gimp_ui_init (PLUG_IN_BINARY, FALSE);

  window = gimp_export_dialog_new ("PDF", PLUG_IN_ROLE, SAVE_PROC);

  vbox = gtk_box_new (GTK_ORIENTATION_VERTICAL, 12);
  gtk_box_pack_start (GTK_BOX (gimp_export_dialog_get_content_area (window)),
                      vbox, TRUE, TRUE, 0);

  gtk_container_set_border_width (GTK_CONTAINER (window), 12);

  ignore_hidden_c = gtk_check_button_new_with_label (_("Omit hidden layers and layers with zero opacity"));
  gtk_toggle_button_set_active (GTK_TOGGLE_BUTTON (ignore_hidden_c),
                                optimize.ignore_hidden);
  gtk_box_pack_end (GTK_BOX (vbox), ignore_hidden_c, TRUE, TRUE, 0);

  vectorize_c = gtk_check_button_new_with_label (_("Convert bitmaps to vector graphics where possible"));
  gtk_toggle_button_set_active (GTK_TOGGLE_BUTTON (vectorize_c),
                                optimize.vectorize);
  gtk_box_pack_end (GTK_BOX (vbox), vectorize_c, TRUE, TRUE, 0);

  apply_c = gtk_check_button_new_with_label (_("Apply layer masks before saving"));
  gtk_toggle_button_set_active (GTK_TOGGLE_BUTTON (apply_c),
                                optimize.apply_masks);
  gtk_box_pack_end (GTK_BOX (vbox), apply_c, TRUE, TRUE, 0);
  gimp_help_set_help_data (apply_c, _("Keeping the masks will not change the output"), NULL);

  reverse_order_c = gtk_check_button_new_with_label (_("Reverse the pages order"));
  gtk_toggle_button_set_active (GTK_TOGGLE_BUTTON (reverse_order_c),
                                optimize.reverse_order);
  gtk_box_pack_end (GTK_BOX (vbox), reverse_order_c, TRUE, TRUE, 0);

  layers_as_pages_c = gtk_check_button_new_with_label (_("Layers as pages"));
  gtk_toggle_button_set_active (GTK_TOGGLE_BUTTON (layers_as_pages_c),
                                optimize.layers_as_pages);
  gimp_image_get_layers (multi_page.images[0], &n_layers);
  gtk_box_pack_end (GTK_BOX (vbox), layers_as_pages_c, TRUE, TRUE, 0);

  if (n_layers <= 1)
  {
    gtk_widget_set_sensitive(layers_as_pages_c, FALSE);
    gtk_toggle_button_set_active (GTK_TOGGLE_BUTTON (layers_as_pages_c),
                                  FALSE);
  }

  g_object_bind_property (layers_as_pages_c, "active",
                          reverse_order_c,  "sensitive",
                          G_BINDING_SYNC_CREATE);

  gtk_widget_show_all (window);

  run = gtk_dialog_run (GTK_DIALOG (window)) == GTK_RESPONSE_OK;

  optimize.ignore_hidden =
    gtk_toggle_button_get_active (GTK_TOGGLE_BUTTON (ignore_hidden_c));
  optimize.vectorize =
    gtk_toggle_button_get_active (GTK_TOGGLE_BUTTON (vectorize_c));
  optimize.apply_masks =
    gtk_toggle_button_get_active (GTK_TOGGLE_BUTTON (apply_c));
  optimize.layers_as_pages =
    gtk_toggle_button_get_active (GTK_TOGGLE_BUTTON (layers_as_pages_c));
  optimize.reverse_order =
    gtk_toggle_button_get_active (GTK_TOGGLE_BUTTON (reverse_order_c));

  gtk_widget_destroy (window);

  return run;
}

/* The main GUI function for saving multi-paged PDFs */

static gboolean
gui_multi (void)
{
  GtkWidget   *window;
  GtkWidget   *vbox;
  GtkWidget   *file_label;
  GtkWidget   *file_entry;
  GtkWidget   *file_browse;
  GtkWidget   *file_hbox;
  GtkWidget   *vectorize_c;
  GtkWidget   *ignore_hidden_c;
  GtkWidget   *apply_c;
  GtkWidget   *scroll;
  GtkWidget   *page_view;
  GtkWidget   *h_but_box;
  GtkWidget   *del;
  GtkWidget   *h_box;
  GtkWidget   *img_combo;
  GtkWidget   *add_image;
  gboolean     run;
  const gchar *temp;

  gimp_ui_init (PLUG_IN_BINARY, FALSE);

  window = gimp_export_dialog_new ("PDF", PLUG_IN_ROLE, SAVE_MULTI_PROC);

  vbox = gtk_box_new (GTK_ORIENTATION_VERTICAL, 10);
  gtk_box_pack_start (GTK_BOX (gimp_export_dialog_get_content_area (window)),
                      vbox, TRUE, TRUE, 0);

  gtk_container_set_border_width (GTK_CONTAINER (window), 12);

  file_hbox = gtk_box_new (GTK_ORIENTATION_HORIZONTAL, 5);
  file_label = gtk_label_new (_("Save to:"));
  file_entry = gtk_entry_new ();
  if (file_name != NULL)
    gtk_entry_set_text (GTK_ENTRY (file_entry), file_name);
  file_browse = gtk_button_new_with_label (_("Browse..."));
  file_choose = gtk_file_chooser_dialog_new (_("Multipage PDF export"),
                                             GTK_WINDOW (window),
                                             GTK_FILE_CHOOSER_ACTION_SAVE,
                                             _("_Save"),   GTK_RESPONSE_OK,
                                             _("_Cancel"), GTK_RESPONSE_CANCEL,
                                             NULL);

  gtk_box_pack_start (GTK_BOX (file_hbox), file_label, FALSE, FALSE, 0);
  gtk_box_pack_start (GTK_BOX (file_hbox), file_entry, TRUE, TRUE, 0);
  gtk_box_pack_start (GTK_BOX (file_hbox), file_browse, FALSE, FALSE, 0);

  gtk_box_pack_start (GTK_BOX (vbox), file_hbox, TRUE, TRUE, 0);

  page_view = gtk_icon_view_new ();
  model = create_model ();
  gtk_icon_view_set_model (GTK_ICON_VIEW (page_view), model);
  gtk_icon_view_set_reorderable (GTK_ICON_VIEW (page_view), TRUE);
  gtk_icon_view_set_selection_mode (GTK_ICON_VIEW (page_view),
                                    GTK_SELECTION_MULTIPLE);

  gtk_icon_view_set_pixbuf_column (GTK_ICON_VIEW (page_view), THUMB);
  gtk_icon_view_set_text_column (GTK_ICON_VIEW (page_view), PAGE_NUMBER);
  gtk_icon_view_set_tooltip_column (GTK_ICON_VIEW (page_view), IMAGE_NAME);

  scroll = gtk_scrolled_window_new (NULL, NULL);
  gtk_widget_set_size_request (scroll, -1, 300);

  gtk_scrolled_window_set_policy (GTK_SCROLLED_WINDOW (scroll),
                                  GTK_POLICY_AUTOMATIC, GTK_POLICY_ALWAYS);
  gtk_container_add (GTK_CONTAINER (scroll), page_view);

  gtk_box_pack_start (GTK_BOX (vbox), scroll, TRUE, TRUE, 0);

  h_but_box = gtk_button_box_new (GTK_ORIENTATION_HORIZONTAL);
  gtk_button_box_set_layout (GTK_BUTTON_BOX (h_but_box), GTK_BUTTONBOX_START);

  del = gtk_button_new_with_label (_("Remove the selected pages"));
  gtk_box_pack_start (GTK_BOX (h_but_box), del, TRUE, TRUE, 0);

  gtk_box_pack_start (GTK_BOX (vbox), h_but_box, FALSE, FALSE, 0);

  h_box = gtk_box_new (GTK_ORIENTATION_HORIZONTAL, 5);

  img_combo = gimp_image_combo_box_new (NULL, NULL);
  gtk_box_pack_start (GTK_BOX (h_box), img_combo, FALSE, FALSE, 0);

  add_image = gtk_button_new_with_label (_("Add this image"));
  gtk_box_pack_start (GTK_BOX (h_box), add_image, FALSE, FALSE, 0);

  gtk_box_pack_start (GTK_BOX (vbox), h_box, FALSE, FALSE, 0);

  ignore_hidden_c = gtk_check_button_new_with_label (_("Omit hidden layers and layers with zero opacity"));
  gtk_toggle_button_set_active (GTK_TOGGLE_BUTTON (ignore_hidden_c),
                                optimize.ignore_hidden);
  gtk_box_pack_end (GTK_BOX (vbox), ignore_hidden_c, FALSE, FALSE, 0);

  vectorize_c = gtk_check_button_new_with_label (_("Convert bitmaps to vector graphics where possible"));
  gtk_toggle_button_set_active (GTK_TOGGLE_BUTTON (vectorize_c),
                                optimize.vectorize);
  gtk_box_pack_end (GTK_BOX (vbox), vectorize_c, FALSE, FALSE, 0);

  apply_c = gtk_check_button_new_with_label (_("Apply layer masks before saving"));
  gtk_toggle_button_set_active (GTK_TOGGLE_BUTTON (apply_c),
                                optimize.apply_masks);
  gtk_box_pack_end (GTK_BOX (vbox), apply_c, FALSE, FALSE, 0);
  gimp_help_set_help_data (apply_c, _("Keeping the masks will not change the output"), NULL);

  gtk_widget_show_all (window);

  g_signal_connect (G_OBJECT (file_browse), "clicked",
                    G_CALLBACK (choose_file_call),
                    file_entry);

  g_signal_connect (G_OBJECT (add_image), "clicked",
                    G_CALLBACK (add_image_call),
                    img_combo);

  g_signal_connect (G_OBJECT (del), "clicked",
                    G_CALLBACK (del_image_call),
                    page_view);

  g_signal_connect (G_OBJECT (model), "row-deleted",
                    G_CALLBACK (remove_call),
                    NULL);

  run = gtk_dialog_run (GTK_DIALOG (window)) == GTK_RESPONSE_OK;

  run &= get_image_list ();

  temp = gtk_entry_get_text (GTK_ENTRY (file_entry));
  g_stpcpy (file_name, temp);

  optimize.ignore_hidden =
    gtk_toggle_button_get_active (GTK_TOGGLE_BUTTON (ignore_hidden_c));
  optimize.vectorize =
    gtk_toggle_button_get_active (GTK_TOGGLE_BUTTON (vectorize_c));
  optimize.apply_masks =
    gtk_toggle_button_get_active (GTK_TOGGLE_BUTTON (apply_c));

  gtk_widget_destroy (window);

  return run;
}

/* A function that is called when the button for browsing for file
 * locations was clicked
 */
static void
choose_file_call (GtkWidget *browse_button,
                  gpointer   file_entry)
{
  GFile *file = g_file_new_for_path (gtk_entry_get_text (GTK_ENTRY (file_entry)));

  gtk_file_chooser_set_uri (GTK_FILE_CHOOSER (file_choose),
                            g_file_get_uri (file));

  if (gtk_dialog_run (GTK_DIALOG (file_choose)) == GTK_RESPONSE_OK)
    {
      file = gtk_file_chooser_get_file (GTK_FILE_CHOOSER (file_choose));
      gtk_entry_set_text (GTK_ENTRY (file_entry), g_file_get_path (file));
    }

  file_name = g_file_get_path (file);
  gtk_widget_hide (file_choose);
}

/* A function to create the basic GtkTreeModel for the icon view */
static GtkTreeModel*
create_model (void)
{
  GtkListStore *model;
  guint32       i;

  /* validate_image_list was called earlier, so all the images
   * up to multi_page.image_count are valid
   */
  model = gtk_list_store_new (4,
                              GDK_TYPE_PIXBUF, /* THUMB */
                              G_TYPE_STRING,   /* PAGE_NUMBER */
                              G_TYPE_STRING,   /* IMAGE_NAME */
                              G_TYPE_INT);     /* IMAGE_ID */

  for (i = 0 ; i < multi_page.image_count && i < MAX_PAGE_COUNT ; i++)
    {
      GtkTreeIter iter;
      gint32      image = multi_page.images[i];
      GdkPixbuf  *pixbuf;

      pixbuf = gimp_image_get_thumbnail (image, THUMB_WIDTH, THUMB_HEIGHT,
                                         GIMP_PIXBUF_SMALL_CHECKS);

      gtk_list_store_append (model, &iter);
      gtk_list_store_set (model, &iter,
                          THUMB,       pixbuf,
                          PAGE_NUMBER, g_strdup_printf (_("Page %d"), i + 1),
                          IMAGE_NAME,  gimp_image_get_name (image),
                          IMAGE_ID,    image,
                          -1);

      g_object_unref (pixbuf);
    }

  return GTK_TREE_MODEL (model);
}

/* A function that puts the images from the model inside the images
 * (pages) array
 */
static gboolean
get_image_list (void)
{
  GtkTreeIter iter;
  gboolean    valid;

  multi_page.image_count = 0;

  for (valid = gtk_tree_model_get_iter_first (model, &iter);
       valid;
       valid = gtk_tree_model_iter_next (model, &iter))
    {
      gint32 image;

      gtk_tree_model_get (model, &iter,
                          IMAGE_ID, &image,
                          -1);
      multi_page.images[multi_page.image_count] = image;
      multi_page.image_count++;
    }

  if (multi_page.image_count == 0)
    {
      g_message (_("Error! In order to save the file, at least one image "
                   "should be added!"));
      return FALSE;
    }

  return TRUE;
}

/* A function that is called when the button for adding an image was
 * clicked
 */
static void
add_image_call (GtkWidget *widget,
                gpointer   img_combo)
{
  GtkListStore *store;
  GtkTreeIter   iter;
  gint32        image;
  GdkPixbuf    *pixbuf;

  dnd_remove = FALSE;

  gimp_int_combo_box_get_active (img_combo, &image);

  store = GTK_LIST_STORE (model);

  pixbuf = gimp_image_get_thumbnail (image, THUMB_WIDTH, THUMB_HEIGHT,
                                     GIMP_PIXBUF_SMALL_CHECKS);

  gtk_list_store_append (store, &iter);
  gtk_list_store_set (store, &iter,
                      PAGE_NUMBER, g_strdup_printf (_("Page %d"),
                                                    multi_page.image_count+1),
                      THUMB,       pixbuf,
                      IMAGE_NAME,  gimp_image_get_name (image),
                      IMAGE_ID,    image,
                      -1);

  g_object_unref (pixbuf);

  multi_page.image_count++;

  dnd_remove = TRUE;
}

/* A function that is called when the button for deleting the selected
 * images was clicked
 */
static void
del_image_call (GtkWidget *widget,
                gpointer   icon_view)
{
  GList                *list;
  GtkTreeRowReference **items;
  GtkTreePath          *item_path;
  GtkTreeIter           item;
  gpointer              temp;
  guint32               len;

  dnd_remove = FALSE;

  list = gtk_icon_view_get_selected_items (GTK_ICON_VIEW (icon_view));

  len = g_list_length (list);
  if (len > 0)
    {
      gint i;

      items = g_newa (GtkTreeRowReference*, len);

      for (i = 0; i < len; i++)
        {
          temp = g_list_nth_data (list, i);
          items[i] = gtk_tree_row_reference_new (model, temp);
          gtk_tree_path_free (temp);
        }
      g_list_free (list);

      for (i = 0; i < len; i++)
        {
          item_path = gtk_tree_row_reference_get_path (items[i]);

          gtk_tree_model_get_iter (model, &item, item_path);
          gtk_list_store_remove (GTK_LIST_STORE (model), &item);

          gtk_tree_path_free (item_path);

          gtk_tree_row_reference_free (items[i]);
          multi_page.image_count--;
        }
    }

  dnd_remove = TRUE;

  recount_pages ();
}

/* A function that is called on rows-deleted signal. It will call the
 * function to relabel the pages
 */
static void
remove_call (GtkTreeModel *tree_model,
             GtkTreePath  *path,
             gpointer      user_data)
{

  if (dnd_remove)
    /* The gtk documentation says that we should not free the indices array */
    recount_pages ();
}

/* A function to relabel the pages in the icon view, when their order
 * was changed
 */
static void
recount_pages (void)
{
  GtkListStore *store;
  GtkTreeIter   iter;
  gboolean      valid;
  gint32        i = 0;

  store = GTK_LIST_STORE (model);

  for (valid = gtk_tree_model_get_iter_first (model, &iter);
       valid;
       valid = gtk_tree_model_iter_next (model, &iter))
    {
      gtk_list_store_set (store, &iter,
                          PAGE_NUMBER, g_strdup_printf (_("Page %d"), i + 1),
                          -1);
      i++;
    }
}


/******************************************************/
/* Beginning of the actual PDF functions              */
/******************************************************/

static cairo_surface_t *
get_cairo_surface (gint32     drawable_ID,
                   gboolean   as_mask,
                   GError   **error)
{
  GeglBuffer      *src_buffer;
  GeglBuffer      *dest_buffer;
  cairo_surface_t *surface;
  cairo_status_t   status;
  cairo_format_t   format;
  gint             width;
  gint             height;

  src_buffer = gimp_drawable_get_buffer (drawable_ID);

  width  = gegl_buffer_get_width  (src_buffer);
  height = gegl_buffer_get_height (src_buffer);

  if (as_mask)
    format = CAIRO_FORMAT_A8;
  else if (gimp_drawable_has_alpha (drawable_ID))
    format = CAIRO_FORMAT_ARGB32;
  else
    format = CAIRO_FORMAT_RGB24;

  surface = cairo_image_surface_create (format, width, height);

  status = cairo_surface_status (surface);
  if (status != CAIRO_STATUS_SUCCESS)
    {
      switch (status)
        {
        case CAIRO_STATUS_INVALID_SIZE:
          g_set_error_literal (error,
                               GIMP_PLUGIN_PDF_SAVE_ERROR,
                               GIMP_PLUGIN_PDF_SAVE_ERROR_FAILED,
                               _("Cannot handle the size (either width or height) of the image."));
          break;
        default:
          g_set_error (error,
                       GIMP_PLUGIN_PDF_SAVE_ERROR,
                       GIMP_PLUGIN_PDF_SAVE_ERROR_FAILED,
                       "Cairo error: %s",
                       cairo_status_to_string (status));
          break;
        }

      return NULL;
    }

  dest_buffer = gimp_cairo_surface_create_buffer (surface);
  if (as_mask)
    {
      /* src_buffer represents a mask in "Y u8", "Y u16", etc. formats.
       * Yet cairo_mask*() functions only care about the alpha channel of
       * the surface. Hence I change the format of dest_buffer so that the
       * Y channel of src_buffer actually refers to the A channel of
       * dest_buffer/surface in Cairo.
       */
      gegl_buffer_set_format (dest_buffer, babl_format ("Y u8"));
    }

  gegl_buffer_copy (src_buffer, NULL, GEGL_ABYSS_NONE, dest_buffer, NULL);

  cairo_surface_mark_dirty (surface);

  g_object_unref (src_buffer);
  g_object_unref (dest_buffer);

  return surface;
}

/* A function to check if a drawable is single colored This allows to
 * convert bitmaps to vector where possible
 */
static GimpRGB
get_layer_color (gint32    layer_ID,
                 gboolean *single)
{
  GimpRGB col;
  gdouble red, green, blue, alpha;
  gdouble dev, devSum;
  gdouble median, pixels, count, precentile;

  devSum = 0;
  red = 0;
  green = 0;
  blue = 0;
  alpha = 0;
  dev = 0;

  if (gimp_drawable_is_indexed (layer_ID))
    {
      /* FIXME: We can't do a proper histogram on indexed layers! */
      *single = FALSE;
      col. r = col.g = col.b = col.a = 0;
      return col;
    }

  if (gimp_drawable_bpp (layer_ID) >= 3)
    {
      /* Are we in RGB mode? */

      gimp_drawable_histogram (layer_ID, GIMP_HISTOGRAM_RED, 0.0, 1.0,
                               &red, &dev, &median, &pixels, &count, &precentile);
      devSum += dev;
      gimp_drawable_histogram (layer_ID, GIMP_HISTOGRAM_GREEN, 0.0, 1.0,
                               &green, &dev, &median, &pixels, &count, &precentile);
      devSum += dev;
      gimp_drawable_histogram (layer_ID, GIMP_HISTOGRAM_BLUE, 0.0, 1.0,
                               &blue, &dev, &median, &pixels, &count, &precentile);
      devSum += dev;
    }
  else
    {
      /* We are in Grayscale mode (or Indexed) */

      gimp_drawable_histogram (layer_ID, GIMP_HISTOGRAM_VALUE, 0.0, 1.0,
                               &red, &dev, &median, &pixels, &count, &precentile);
      devSum += dev;
      green = red;
      blue = red;
    }

  if (gimp_drawable_has_alpha (layer_ID))
    gimp_drawable_histogram (layer_ID, GIMP_HISTOGRAM_ALPHA, 0.0, 1.0,
                             &alpha, &dev, &median, &pixels, &count, &precentile);
  else
    alpha = 255;

  devSum += dev;
  *single = devSum == 0;

  col.r = red/255;
  col.g = green/255;
  col.b = blue/255;
  col.a = alpha/255;

  return col;
}

/* A function that uses Pango to render the text to our cairo surface,
 * in the same way it was the user saw it inside gimp.
 * Needs some work on choosing the font name better, and on hinting
 * (freetype and pango differences)
 */
static void
drawText (gint32    text_id,
          gdouble   opacity,
          cairo_t  *cr,
          gdouble   x_res,
          gdouble   y_res)
{
  GimpImageType         type   = gimp_drawable_type (text_id);
  gchar                *text   = gimp_text_layer_get_text (text_id);
  gchar                *markup = gimp_text_layer_get_markup (text_id);
  gchar                *font_family;
  cairo_font_options_t *options;
  gint                  x;
  gint                  y;
  GimpRGB               color;
  GimpUnit              unit;
  gdouble               size;
  GimpTextHintStyle     hinting;
  GimpTextJustification j;
  gboolean              justify;
  PangoAlignment        align;
  GimpTextDirection     dir;
  PangoDirection        pango_dir;
  PangoLayout          *layout;
  PangoContext         *context;
  PangoFontDescription *font_description;
  gdouble               indent;
  gdouble               line_spacing;
  gdouble               letter_spacing;
  PangoAttribute       *letter_spacing_at;
  PangoAttrList        *attr_list = pango_attr_list_new ();
  PangoFontMap         *fontmap;

  cairo_save (cr);

  options = cairo_font_options_create ();
  attr_list = pango_attr_list_new ();
  cairo_get_font_options (cr, options);

  /* Position */
  gimp_drawable_offsets (text_id, &x, &y);
  cairo_move_to (cr, x, y);

  /* Color */
  /* When dealing with a gray/indexed image, the viewed color of the text layer
   * can be different than the one kept in the memory */
  if (type == GIMP_RGBA_IMAGE)
    gimp_text_layer_get_color (text_id, &color);
  else
    gimp_image_pick_color (gimp_item_get_image (text_id),
                           text_id, x, y, FALSE, FALSE, 0, &color);

  cairo_set_source_rgba (cr, color.r, color.g, color.b, opacity);

  /* Hinting */
  hinting = gimp_text_layer_get_hint_style (text_id);
  switch (hinting)
    {
    case GIMP_TEXT_HINT_STYLE_NONE:
      cairo_font_options_set_hint_style (options, CAIRO_HINT_STYLE_NONE);
      break;

    case GIMP_TEXT_HINT_STYLE_SLIGHT:
      cairo_font_options_set_hint_style (options, CAIRO_HINT_STYLE_SLIGHT);
      break;

    case GIMP_TEXT_HINT_STYLE_MEDIUM:
      cairo_font_options_set_hint_style (options, CAIRO_HINT_STYLE_MEDIUM);
      break;

    case GIMP_TEXT_HINT_STYLE_FULL:
      cairo_font_options_set_hint_style (options, CAIRO_HINT_STYLE_FULL);
      break;
    }

  /* Antialiasing */
  if (gimp_text_layer_get_antialias (text_id))
    cairo_font_options_set_antialias (options, CAIRO_ANTIALIAS_DEFAULT);
  else
    cairo_font_options_set_antialias (options, CAIRO_ANTIALIAS_NONE);

  /* We are done with cairo's settings. It's time to create the
   * context
   */
  fontmap = pango_cairo_font_map_new_for_font_type (CAIRO_FONT_TYPE_FT);

  pango_cairo_font_map_set_resolution (PANGO_CAIRO_FONT_MAP (fontmap), y_res);

  context = pango_font_map_create_context (fontmap);
  g_object_unref (fontmap);

  pango_cairo_context_set_font_options (context, options);

  /* Text Direction */
  dir = gimp_text_layer_get_base_direction (text_id);

  if (dir == GIMP_TEXT_DIRECTION_RTL)
    pango_dir = PANGO_DIRECTION_RTL;
  else
    pango_dir = PANGO_DIRECTION_LTR;

  pango_context_set_base_dir (context, pango_dir);

  /* We are done with the context's settings. It's time to create the
   * layout
   */
  layout = pango_layout_new (context);
  pango_layout_set_wrap (layout, PANGO_WRAP_WORD_CHAR);

  /* Font */
  font_family = gimp_text_layer_get_font (text_id);

  /* We need to find a way to convert GIMP's returned font name to a
   * normal Pango name... Hopefully GIMP 2.8 with Pango will fix it.
   */
  font_description = pango_font_description_from_string (font_family);

  /* Font Size */
  size = gimp_text_layer_get_font_size (text_id, &unit);
  size = gimp_units_to_pixels (size, unit, y_res);
  pango_font_description_set_absolute_size (font_description, size * PANGO_SCALE);

  pango_layout_set_font_description (layout, font_description);

  /* Width */
  pango_layout_set_width (layout, gimp_drawable_width (text_id) * PANGO_SCALE);

  /* Justification, and Alignment */
  justify = FALSE;
  j = gimp_text_layer_get_justification (text_id);

  if (j == GIMP_TEXT_JUSTIFY_CENTER)
    align = PANGO_ALIGN_CENTER;
  else if (j == GIMP_TEXT_JUSTIFY_LEFT)
    align = PANGO_ALIGN_LEFT;
  else if (j == GIMP_TEXT_JUSTIFY_RIGHT)
    align = PANGO_ALIGN_RIGHT;
  else /* We have GIMP_TEXT_JUSTIFY_FILL */
    {
      if (dir == GIMP_TEXT_DIRECTION_LTR)
        align = PANGO_ALIGN_LEFT;
      else
        align = PANGO_ALIGN_RIGHT;
      justify = TRUE;
    }

  /* Indentation */
  indent = gimp_text_layer_get_indent (text_id);
  pango_layout_set_indent (layout, (int)(PANGO_SCALE * indent));

  /* Line Spacing */
  line_spacing = gimp_text_layer_get_line_spacing (text_id);
  pango_layout_set_spacing (layout, (int)(PANGO_SCALE * line_spacing));

  /* Letter Spacing */
  letter_spacing = gimp_text_layer_get_letter_spacing (text_id);
  letter_spacing_at = pango_attr_letter_spacing_new ((int)(PANGO_SCALE * letter_spacing));
  pango_attr_list_insert (attr_list, letter_spacing_at);

  pango_layout_set_justify (layout, justify);
  pango_layout_set_alignment (layout, align);

  pango_layout_set_attributes (layout, attr_list);

  /* Use the pango markup of the text layer */

  if (markup != NULL && markup[0] != '\0')
    pango_layout_set_markup (layout, markup, -1);
  else /* If we can't find a markup, then it has just text */
    pango_layout_set_text (layout, text, -1);

  pango_cairo_show_layout (cr, layout);

  g_free (text);
  g_free (font_family);

  g_object_unref (layout);
  pango_font_description_free (font_description);
  g_object_unref (context);
  pango_attr_list_unref (attr_list);

  cairo_font_options_destroy (options);

  cairo_restore (cr);
}
