/**
 * center.c
 *   A very basic GIMP plugin, attached to images, that finds and
 *   returns the center of the image.
 *
 *   Copyright (c) 2013 Samuel A. Rebelsky.  All rights reserved.
 *
 *   This file is part of The Glimmer Guide to GIMP Plugins (aka GGGP).
 *
 *   GGGP 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.
 *
 *   GGGP 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 GGGP.  If not, see <http://www.gnu.org/licenses/>.
 */


// +---------+---------------------------------------------------------
// | Headers |
// +---------+

#include <libgimp/gimp.h>

#include <stdio.h>


// +--------+----------------------------------------------------------
// | Macros |
// +--------+

/**
 * Print a string (somewhere).  Right now, this prints to stderr, which
 * means it only works when the program is run from the terminal.
 */
#define REPORT(str) fprintf (stderr, "*** %s ***\n", str)

/**
 * Print an integer.
 */
#define REPORT_INT(i) fprintf (stderr, "*** %s: %d ***\n", #i, i)


// +--------------------------+----------------------------------------
// | Function Predeclarations |
// +--------------------------+

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


// +-------------+-----------------------------------------------------
// | Boilerplate |
// +-------------+

/**
 * The four key functions.  This structure *must* be called PLUG_IN_INFO.
 */
GimpPlugInInfo PLUG_IN_INFO =
  {
    NULL,
    NULL,
    query,
    run
  };

/**
 * Indicate that we're ready to begin the main part of the code.
 */
MAIN ()


// +-------------------------+-----------------------------------------
// | Standard GIMP Functions |
// +-------------------------+

static void
init (void)
{
} // init

static void
quit (void)
{
} // quit

static void 
query (void)
{
  REPORT ("Installing center");
  // Build the description of the parameters that the function expects.  
  // Each parameter has a type, a name, and a description
  // All plug-ins must take a run-mode.   Plug-ins associated with an
  // image
  static GimpParamDef args[] =
    {
      { GIMP_PDB_INT32, "run-mode", "Run mode" },
      { GIMP_PDB_IMAGE, "image", "Input image" },
      { GIMP_PDB_DRAWABLE, "drawable", "Input layer or other drawable" }
    }; // args

  static GimpParamDef returns[] =
    {
      { GIMP_PDB_INT32, "x", "x value of center" },
      { GIMP_PDB_INT32, "y", "y value of center" },
    }; // returns


  // Tell the GIMP about our plugin.
  gimp_install_procedure (
    "gggp-image-center",                                // Name
    "Get the center of an image",                       // Blurb
    "Get the center of an image",                       // Help
    "Samuel A. Rebelsky",                               // Author
    "Copyright (c) Samuel A. Rebelsky.  All rights reserved.",
                                                        // Copyright
    "2013",                                             // Year
    "<Image>/GGGP/GetCenter",                           // Path
    NULL,                                               // Image types
    GIMP_PLUGIN,                                        // Type
    3,                                                  // Number of params
    2,                                                  // Number of return vals
    args,                                               // Param descriptions
    returns                                             // Return descriptions
    );

} // query

static void
run (const gchar      *name,
           gint              nparams,
           const GimpParam  *params,
           gint             *nreturn_vals,
           GimpParam       **return_vals)
{
  // We make the array of results static so that it lives beyond
  // this procedure.
  static GimpParam results[3];

  // Get the width and the heigth of the image
  int image = params[1].data.d_image;

  // Set up return types
  results[0].type = GIMP_PDB_STATUS;
  results[1].type = GIMP_PDB_INT32;
  results[2].type = GIMP_PDB_INT32;

  // Set up return values
  if (image > 0)
    {
      results[0].data.d_status = GIMP_PDB_SUCCESS;
      results[1].data.d_int32 = gimp_image_width (image) / 2;
      results[2].data.d_int32 = gimp_image_width (image) / 2;
    }
  else
    {
      results[0].data.d_status = GIMP_PDB_CALLING_ERROR;
      results[1].data.d_int32 = 0;
      results[2].data.d_int32 = 0;
    }

  // And we're done
  *nreturn_vals = 3;
  *return_vals = results;
} // run