/* TestDnD - main.c : Simple tutorial for GTK+ Drag-N-Drop
 * Copyright (C) 2005 Ryan McDougall.
 *
 *  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 2 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 Library General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 */

 #include <gtk/gtk.h>
 #include <string.h>


/******************************************************************************/
#define _BYTE   8
#define _WORD   16
#define _DWORD  32


/******************************************************************************/
/* Define a list of data types called "targets" that a destination widget will
 * accept. The string type is arbitrary, and negotiated between DnD widgets by
 * the developer. An enum or GQuark can serve as the integer target id. */
enum {
        TARGET_INT32,
        TARGET_STRING,
        TARGET_ROOTWIN
};

/* datatype (string), restrictions on DnD (GtkTargetFlags), datatype (int) */
static GtkTargetEntry target_list[] = {
        { "INTEGER",    0, TARGET_INT32 },
        { "STRING",     0, TARGET_STRING },
        { "text/plain", 0, TARGET_STRING },
        { "application/x-rootwindow-drop", 0, TARGET_ROOTWIN }
};

static guint n_targets = G_N_ELEMENTS (target_list);


/******************************************************************************/
/* Signal receivable by destination */

/* Emitted when the data has been received from the source. It should check
 * the GtkSelectionData sent by the source, and do something with it. Finally
 * it needs to finish the operation by calling gtk_drag_finish, which will emit
 * the "data-delete" signal if told to. */
static void
drag_data_received_handl
(GtkWidget *widget, GdkDragContext *context, gint x, gint y,
        GtkSelectionData *selection_data, guint target_type, guint time,
        gpointer data)
{
        glong   *_idata;
        gchar   *_sdata;

        gboolean dnd_success = FALSE;
        gboolean delete_selection_data = FALSE;

        const gchar *name = gtk_widget_get_name (widget);
        g_print ("%s: drag_data_received_handl\n", name);


        /* Deal with what we are given from source */
        if((selection_data != NULL) && (selection_data-> length >= 0))
        {
                if (context-> action == GDK_ACTION_ASK)
                {
                /* Ask the user to move or copy, then set the context action. */
                }

                if (context-> action == GDK_ACTION_MOVE)
                        delete_selection_data = TRUE;

                /* Check that we got the format we can use */
                g_print (" Receiving ");
                switch (target_type)
                {
                        case TARGET_INT32:
                                _idata = (glong*)selection_data-> data;
                                g_print ("integer: %ld", *_idata);
                                dnd_success = TRUE;
                                break;

                        case TARGET_STRING:
                                _sdata = (gchar*)selection_data-> data;
                                g_print ("string: %s", _sdata);
                                dnd_success = TRUE;
                                break;

                        default:
                                g_print ("nothing good");
                }

                g_print (".\n");
        }

        if (dnd_success == FALSE)
        {
                g_print ("DnD data transfer failed!\n");
        }

        gtk_drag_finish (context, dnd_success, delete_selection_data, time);
}

/* Emitted when a drag is over the destination */
static gboolean
drag_motion_handl
(GtkWidget *widget, GdkDragContext *context, gint x, gint y, guint t,
        gpointer user_data)
{
        // Fancy stuff here. This signal spams the console something horrible.
        //const gchar *name = gtk_widget_get_name (widget);
        //g_print ("%s: drag_motion_handl\n", name);
        return  FALSE;
}

/* Emitted when a drag leaves the destination */
static void
drag_leave_handl
(GtkWidget *widget, GdkDragContext *context, guint time, gpointer user_data)
{
        const gchar *name = gtk_widget_get_name (widget);
        g_print ("%s: drag_leave_handl\n", name);
}

/* Emitted when the user releases (drops) the selection. It should check that
 * the drop is over a valid part of the widget (if its a complex widget), and
 * itself to return true if the operation should continue. Next choose the
 * target type it wishes to ask the source for. Finally call gtk_drag_get_data
 * which will emit "drag-data-get" on the source. */
static gboolean
drag_drop_handl
(GtkWidget *widget, GdkDragContext *context, gint x, gint y, guint time,
        gpointer user_data)
{
        gboolean        is_valid_drop_site;
        GdkAtom         target_type;

        const gchar *name = gtk_widget_get_name (widget);
        g_print ("%s: drag_drop_handl\n", name);

        /* Check to see if (x,y) is a valid drop site within widget */
        is_valid_drop_site = TRUE;

        /* If the source offers a target */
        if (context-> targets)
        {
                /* Choose the best target type */
                target_type = GDK_POINTER_TO_ATOM
                        (g_list_nth_data (context-> targets, TARGET_INT32));

                /* Request the data from the source. */
                gtk_drag_get_data
                (
                        widget,         /* will receive 'drag-data-received' signal */
                        context,        /* represents the current state of the DnD */
                        target_type,    /* the target type we want */
                        time            /* time stamp */
                );
        }
        /* No target offered by source => error */
        else
        {
                is_valid_drop_site = FALSE;
        }

        return  is_valid_drop_site;
}


/******************************************************************************/
/* Signals receivable by source */

/* Emitted after "drag-data-received" is handled, and gtk_drag_finish is called
 * with the "delete" parameter set to TRUE (when DnD is GDK_ACTION_MOVE). */
static void
drag_data_delete_handl
(GtkWidget *widget, GdkDragContext *context, gpointer user_data)
{
        // We aren't moving or deleting anything here
        const gchar *name = gtk_widget_get_name (widget);
        g_print ("%s: drag_data_delete_handl\n", name);
}

/* Emitted when the destination requests data from the source via
 * gtk_drag_get_data. It should attempt to provide its data in the form
 * requested in the target_type passed to it from the destination. If it cannot,
 * it should default to a "safe" type such as a string or text, even if only to
 * print an error. Then use gtk_selection_data_set to put the source data into
 * the allocated selection_data object, which will then be passed to the
 * destination. This will cause "drag-data-received" to be emitted on the
 * destination. GdkSelectionData is based on X's selection mechanism which,
 * via X properties, is only capable of storing data in blocks of 8, 16, or
 * 32 bit units. */
static void
drag_data_get_handl
(GtkWidget *widget, GdkDragContext *context, GtkSelectionData *selection_data,
        guint target_type, guint time, gpointer user_data)
{
        const gchar *name = gtk_widget_get_name (widget);
        const gchar *string_data = "This is data from the source.";
        const glong integer_data = 42;

        g_print ("%s: drag_data_get_handl\n", name);
        g_assert (selection_data != NULL);

        g_print (" Sending ");
        switch (target_type)
        {
                /* case TARGET_SOME_OBJECT:
                 * Serialize the object and send as a string of bytes.
                 * Pixbufs, (UTF-8) text, and URIs have their own convenience
                 * setter functions */

        case TARGET_INT32:
                g_print ("integer: %ld", integer_data);
                gtk_selection_data_set
                (
                        selection_data,         /* Allocated GdkSelectionData object */
                        selection_data-> target,/* target type */
                        _DWORD,                 /* number of bits per 'unit' */
                        (guchar*) &integer_data,/* pointer to data to be sent */
                        sizeof (integer_data)   /* length of data in units */
                );
                break;

        case TARGET_STRING:
                g_print ("string: %s", string_data);
                gtk_selection_data_set
                (
                        selection_data,
                        selection_data-> target,
                        _BYTE,
                        (guchar*) string_data,
                        strlen (string_data)
                );
                break;

        case TARGET_ROOTWIN:
                g_print ("Dropped on the root window!\n");
                break;

        default:
                /* Default to some a safe target instead of fail. */
                g_assert_not_reached ();
        }

        g_print (".\n");
}

/* Emitted when DnD begins. This is often used to present custom graphics. */
static void
drag_begin_handl
(GtkWidget *widget, GdkDragContext *context, gpointer user_data)
{
        const gchar *name = gtk_widget_get_name (widget);
        g_print ("%s: drag_begin_handl\n", name);

        /* FIXME: offending lines of code */

        /* This is ok */
        /* gtk_drag_set_icon_stock (context, "gtk-ok", 0, 0); */

        /* This is not */
        gtk_drag_set_icon_stock (context, "gtk-ok", 10, 10);
}

/* Emitted when DnD ends. This is used to clean up any leftover data. */
static void
drag_end_handl
(GtkWidget *widget, GdkDragContext *context, gpointer user_data)
{
        const gchar *name = gtk_widget_get_name (widget);
        g_print ("%s: drag_end_handl\n", name);
}


/******************************************************************************/
int
main (int argc, char **argv)
{
        GtkWidget       *window;
        GtkWidget       *hbox;
        GtkWidget       *coin_source;
        GtkWidget       *well_dest;
        GtkWidget       *directions_label;
        guint           win_xsize       = 450;
        guint           win_ysize       = 50;
        guint           spacing         = 5;


        /* Always start GTK+ first! */
        gtk_init (&argc, &argv);


        /* Create the widgets */
        window  = gtk_window_new (GTK_WINDOW_TOPLEVEL);
        hbox    = gtk_hbox_new (FALSE, spacing);

        coin_source     = gtk_button_new_with_label ("[coins]");
        well_dest       = gtk_label_new ("[a well]");

        directions_label = gtk_label_new ("drag a coin and drop it in the well");


        /* Pack the widgets */
        gtk_container_add (GTK_CONTAINER (window), hbox);

        gtk_container_add (GTK_CONTAINER (hbox), coin_source);
        gtk_container_add (GTK_CONTAINER (hbox), directions_label);
        gtk_container_add (GTK_CONTAINER (hbox), well_dest);


        /* Make the window big enough for some DnD action */
        gtk_window_set_default_size (GTK_WINDOW(window), win_xsize, win_ysize);


        /* Make the "well label" a DnD destination. */
        gtk_drag_dest_set
        (
                well_dest,              /* widget that will accept a drop */
                (GtkDestDefaults)(GTK_DEST_DEFAULT_MOTION /* default actions for dest on DnD */
                | GTK_DEST_DEFAULT_HIGHLIGHT),
                target_list,            /* lists of target to support */
                n_targets,              /* size of list */
                GDK_ACTION_COPY         /* what to do with data after dropped */
        );

        /* Make the "coin button" a DnD source. */
        /* Why doesn't GtkLabel work here?
         * See Caveat Window above
         */
        gtk_drag_source_set
        (
                coin_source,            /* widget will be drag-able */
                GDK_BUTTON1_MASK,       /* modifier that will start a drag */
                target_list,            /* lists of target to support */
                n_targets,              /* size of list */
                GDK_ACTION_COPY         /* what to do with data after dropped */
        );


        /* Connect the signals */
        g_signal_connect (window, "destroy", G_CALLBACK (gtk_main_quit), NULL);

        /* All possible destination signals */
        g_signal_connect (well_dest, "drag-data-received",
                G_CALLBACK(drag_data_received_handl), NULL);

        g_signal_connect (well_dest, "drag-leave",
                G_CALLBACK (drag_leave_handl), NULL);

        g_signal_connect (well_dest, "drag-motion",
                G_CALLBACK (drag_motion_handl), NULL);

        g_signal_connect (well_dest, "drag-drop",
                G_CALLBACK (drag_drop_handl), NULL);

        /* All possible source signals */
        g_signal_connect (coin_source, "drag-data-get",
                G_CALLBACK (drag_data_get_handl), NULL);

        g_signal_connect (coin_source, "drag-data-delete",
                G_CALLBACK (drag_data_delete_handl), NULL);

        g_signal_connect (coin_source, "drag-begin",
                G_CALLBACK (drag_begin_handl), NULL);

        g_signal_connect (coin_source, "drag-end",
                G_CALLBACK (drag_end_handl), NULL);


        /* Show the widgets */
        gtk_widget_show_all (window);

        /* Start the even loop */
        gtk_main ();

        return 0;
}

