gimp/app/tools/gimpinktool.c

/* The GIMP -- an image manipulation program
 * Copyright (C) 1995 Spencer Kimball and Peter Mattis
 *
 * 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 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 "config.h"

#include <stdlib.h>
#include <string.h>

#include <gtk/gtk.h>

#include "libgimpmath/gimpmath.h"
#include "libgimpwidgets/gimpwidgets.h"

#include "tools-types.h"

#include "base/pixel-region.h"
#include "base/temp-buf.h"
#include "base/tile.h"
#include "base/tile-manager.h"

#include "paint-funcs/paint-funcs.h"

#include "core/gimp.h"
#include "core/gimpcontext.h"
#include "core/gimpdrawable.h"
#include "core/gimpimage.h"
#include "core/gimpimage-mask.h"

#include "gimpinktool.h"
#include "gimpinktool-blob.h"
#include "gimptool.h"
#include "paint_options.h"
#include "tool_manager.h"

#include "gimprc.h"
#include "undo.h"
#include "gdisplay.h"

#include "libgimp/gimpintl.h"


#define SUBSAMPLE 8

/*  the Ink structures  */

typedef Blob * (* BlobFunc) (gdouble,
			     gdouble,
			     gdouble,
			     gdouble,
			     gdouble,
			     gdouble);


typedef struct _BrushWidget BrushWidget;

struct _BrushWidget
{
  GtkWidget *widget;
  gboolean   state;
};

typedef struct _InkOptions InkOptions;

struct _InkOptions
{
  PaintOptions  paint_options;

  gdouble       size;
  gdouble       size_d;
  GtkObject    *size_w;

  gdouble       sensitivity;
  gdouble       sensitivity_d;
  GtkObject    *sensitivity_w;

  gdouble       vel_sensitivity;
  gdouble       vel_sensitivity_d;
  GtkObject    *vel_sensitivity_w;

  gdouble       tilt_sensitivity;
  gdouble       tilt_sensitivity_d;
  GtkObject    *tilt_sensitivity_w;

  gdouble       tilt_angle;
  gdouble       tilt_angle_d;
  GtkObject    *tilt_angle_w;

  BlobFunc      function;
  BlobFunc      function_d;
  GtkWidget    *function_w[3];  /* 3 radio buttons */

  gdouble       aspect;
  gdouble       aspect_d;
  gdouble       angle;
  gdouble       angle_d;
  BrushWidget  *brush_w;
};


/*  local function prototypes  */

static void        gimp_ink_tool_class_init      (GimpInkToolClass *klass);
static void        gimp_ink_tool_init            (GimpInkTool      *tool);

static void        gimp_ink_tool_finalize        (GObject          *object);

static InkOptions * ink_options_new     (void);
static void         ink_options_reset   (GimpToolOptions *tool_options);

static void        ink_button_press     (GimpTool        *tool,
					 GdkEventButton  *mevent,
					 GDisplay        *gdisp);
static void        ink_button_release   (GimpTool        *tool,
					 GdkEventButton  *bevent,
					 GDisplay        *gdisp);
static void        ink_motion           (GimpTool        *tool,
					 GdkEventMotion  *mevent,
					 GDisplay        *gdisp);
static void        ink_cursor_update    (GimpTool        *tool,
					 GdkEventMotion  *mevent,
					 GDisplay        *gdisp);
static void        ink_control          (GimpTool        *tool,
					 ToolAction       tool_action,
					 GDisplay        *gdisp);

static void        time_smoother_add    (GimpInkTool     *ink_tool,
					 guint32          value);
static gdouble     time_smoother_result (GimpInkTool     *ink_tool);
static void        time_smoother_init   (GimpInkTool     *ink_tool,
					 guint32          initval);
static void        dist_smoother_add    (GimpInkTool     *ink_tool,
					 gdouble          value);
static gdouble     dist_smoother_result (GimpInkTool     *ink_tool);
static void        dist_smoother_init   (GimpInkTool     *ink_tool,
					 gdouble          initval);

static void        ink_init             (GimpInkTool     *ink_tool, 
					 GimpDrawable    *drawable, 
					 gdouble          x, 
					 gdouble          y);
static void        ink_finish           (GimpInkTool     *ink_tool, 
					 GimpDrawable    *drawable);
static void        ink_cleanup          (void);

static void        ink_type_update      (GtkWidget       *radio_button,
					 BlobFunc         function);
static GdkPixmap * blob_pixmap          (GdkColormap     *colormap,
					 GdkVisual       *visual,
					 BlobFunc         function);
static void        paint_blob           (GdkDrawable     *drawable, 
					 GdkGC           *gc,
					 Blob            *blob);

/*  Rendering functions  */
static void        ink_set_paint_area   (GimpInkTool     *ink_tool, 
					 GimpDrawable    *drawable, 
					 Blob            *blob);
static void        ink_paste            (GimpInkTool     *ink_tool, 
					 GimpDrawable    *drawable,
					 Blob            *blob);

static void        ink_to_canvas_tiles  (GimpInkTool     *ink_tool,
					 Blob            *blob,
					 guchar          *color);

static void        ink_set_undo_tiles   (GimpDrawable    *drawable,
					 gint             x, 
					 gint             y,
					 gint             w, 
					 gint             h);
static void        ink_set_canvas_tiles (gint             x, 
					 gint             y,
					 gint             w, 
					 gint             h);

/*  Brush pseudo-widget callbacks  */
static void   brush_widget_active_rect    (BrushWidget    *brush_widget,
					   GtkWidget      *widget,
					   GdkRectangle   *rect);
static void   brush_widget_realize        (GtkWidget      *widget);
static void   brush_widget_expose         (GtkWidget      *widget,
					   GdkEventExpose *event,
					   BrushWidget    *brush_widget);
static void   brush_widget_button_press   (GtkWidget      *widget,
					   GdkEventButton *event,
					   BrushWidget    *brush_widget);
static void   brush_widget_button_release (GtkWidget      *widget,
					   GdkEventButton *event,
					   BrushWidget    *brush_widget);
static void   brush_widget_motion_notify  (GtkWidget      *widget,
					   GdkEventMotion *event,
					   BrushWidget    *brush_widget);


/* local variables */

/* the ink tool options  */
static InkOptions *ink_options = NULL;

/*  undo blocks variables  */
static TileManager *undo_tiles = NULL;

/* Tiles used to render the stroke at 1 byte/pp */
static TileManager *canvas_tiles = NULL;

/* Flat buffer that is used to used to render the dirty region
 * for composition onto the destination drawable
 */
static TempBuf *canvas_buf = NULL;

static GimpToolClass *parent_class      = NULL;


/*  functions  */

void
gimp_ink_tool_register (Gimp *gimp)
{
  tool_manager_register_tool (gimp,
			      GIMP_TYPE_INK_TOOL,
			      TRUE,
			      "gimp:ink_tool",
			      _("Ink Tool"),
			      _("Draw in ink"),
			      N_("/Tools/Paint Tools/Ink"), "K",
			      NULL, "tools/ink.html",
			      GIMP_STOCK_TOOL_INK);
}

GType
gimp_ink_tool_get_type (void)
{
  static GType tool_type = 0;

  if (! tool_type)
    {
      static const GTypeInfo tool_info =
      {
        sizeof (GimpInkToolClass),
	(GBaseInitFunc) NULL,
	(GBaseFinalizeFunc) NULL,
	(GClassInitFunc) gimp_ink_tool_class_init,
	NULL,           /* class_finalize */
	NULL,           /* class_data     */
	sizeof (GimpInkTool),
	0,              /* n_preallocs    */
	(GInstanceInitFunc) gimp_ink_tool_init,
      };

      tool_type = g_type_register_static (GIMP_TYPE_TOOL,
					  "GimpInkTool", 
                                          &tool_info, 0);
    }

  return tool_type;
}

static void
gimp_ink_tool_class_init (GimpInkToolClass *klass)
{
  GObjectClass   *object_class;
  GimpToolClass  *tool_class;

  object_class = G_OBJECT_CLASS (klass);
  tool_class   = GIMP_TOOL_CLASS (klass);

  parent_class = g_type_class_peek_parent (klass);

  object_class->finalize     = gimp_ink_tool_finalize;

  tool_class->control        = ink_control;
  tool_class->button_press   = ink_button_press;
  tool_class->button_release = ink_button_release;
  tool_class->motion         = ink_motion;
  tool_class->cursor_update  = ink_cursor_update;
}

static void
gimp_ink_tool_init (GimpInkTool *ink_tool)
{
  GimpTool *tool;

  tool = GIMP_TOOL (ink_tool);
 
  /*  The tool options  */
  if (! ink_options)
    {
      ink_options = ink_options_new ();

      tool_manager_register_tool_options (GIMP_TYPE_INK_TOOL,
					  (GimpToolOptions *) ink_options);

      ink_options_reset ((GimpToolOptions *) ink_options);
    }
}

static void
gimp_ink_tool_finalize (GObject *object)
{
  GimpInkTool *ink_tool;

  ink_tool = GIMP_INK_TOOL (object);

  if (ink_tool->last_blob)
    {
      g_free (ink_tool->last_blob);
      ink_tool->last_blob = NULL;
    }

  ink_cleanup ();

  G_OBJECT_CLASS (parent_class)->finalize (object);
}

static void 
ink_type_update (GtkWidget      *radio_button,
		 BlobFunc        function)
{
  InkOptions *options = ink_options;

  if (GTK_TOGGLE_BUTTON (radio_button)->active)
    options->function = function;

  gtk_widget_queue_draw (options->brush_w->widget);
}

static void
ink_options_reset (GimpToolOptions *tool_options)
{
  InkOptions *options;

  options = (InkOptions *) tool_options;

  paint_options_reset (tool_options);

  gtk_adjustment_set_value (GTK_ADJUSTMENT (options->size_w),
			    options->size_d);
  gtk_adjustment_set_value (GTK_ADJUSTMENT (options->sensitivity_w),
			    options->sensitivity_d);
  gtk_adjustment_set_value (GTK_ADJUSTMENT (options->tilt_sensitivity_w),
			    options->tilt_sensitivity_d);
  gtk_adjustment_set_value (GTK_ADJUSTMENT (options->vel_sensitivity_w),
			    options->vel_sensitivity_d);
  gtk_adjustment_set_value (GTK_ADJUSTMENT (options->tilt_angle_w),
			    options->tilt_angle_d);
  gtk_toggle_button_set_active (((options->function_d == blob_ellipse) ?
				 GTK_TOGGLE_BUTTON (options->function_w[0]) :
				 ((options->function_d == blob_square) ?
				  GTK_TOGGLE_BUTTON (options->function_w[1]) :
				  GTK_TOGGLE_BUTTON (options->function_w[2]))),
				TRUE);
  options->aspect = options->aspect_d;
  options->angle  = options->angle_d;
  gtk_widget_queue_draw (options->brush_w->widget);
}

static InkOptions *
ink_options_new (void)
{
  InkOptions *options;
  GtkWidget  *table;
  GtkWidget  *vbox;
  GtkWidget  *hbox;
  GtkWidget  *hbox2;
  GtkWidget  *radio_button;
  GtkWidget  *pixmap_widget;
  GtkWidget  *slider;
  GtkWidget  *frame;
  GtkWidget  *darea;
  GdkPixmap  *pixmap;

  options = g_new0 (InkOptions, 1);
  paint_options_init ((PaintOptions *) options,
		      GIMP_TYPE_INK_TOOL,
		      ink_options_reset);

  options->size             = options->size_d             = 4.4;
  options->sensitivity      = options->sensitivity_d      = 1.0;
  options->vel_sensitivity  = options->vel_sensitivity_d  = 0.8;
  options->tilt_sensitivity = options->tilt_sensitivity_d = 0.4;
  options->tilt_angle       = options->tilt_angle_d       = 0.0;
  options->function         = options->function_d         = blob_ellipse;
  options->aspect           = options->aspect_d           = 1.0;
  options->angle            = options->angle_d            = 0.0;

  /*  the main vbox  */
  vbox = gtk_vbox_new (FALSE, 2);
  gtk_box_pack_start (GTK_BOX (((GimpToolOptions *) options)->main_vbox), vbox,
		      TRUE, TRUE, 0);
  gtk_widget_show (vbox);

  /* adjust sliders */
  frame = gtk_frame_new (_("Adjustment"));
  gtk_frame_set_shadow_type (GTK_FRAME (frame), GTK_SHADOW_ETCHED_IN);
  gtk_box_pack_start (GTK_BOX (vbox), frame, FALSE, TRUE, 0);
  gtk_widget_show (frame);

  table = gtk_table_new (2, 2, FALSE);
  gtk_table_set_col_spacings (GTK_TABLE (table), 4);
  gtk_container_set_border_width (GTK_CONTAINER (table), 2);
  gtk_container_add (GTK_CONTAINER (frame), table);
  gtk_widget_show (table);

  /*  size slider  */
  options->size_w =
    gtk_adjustment_new (options->size_d, 0.0, 20.0, 1.0, 2.0, 0.0);
  slider = gtk_hscale_new (GTK_ADJUSTMENT (options->size_w));
  gtk_scale_set_value_pos (GTK_SCALE (slider), GTK_POS_TOP);
  gimp_table_attach_aligned (GTK_TABLE (table), 0, 0,
			     _("Size:"), 1.0, 1.0,
			     slider, 1, FALSE);
  gtk_range_set_update_policy (GTK_RANGE (slider), GTK_UPDATE_DELAYED);

  g_signal_connect (G_OBJECT (options->size_w), "value_changed",
		    G_CALLBACK (gimp_double_adjustment_update),
		    &options->size);

  /* angle adjust slider */
  options->tilt_angle_w =
    gtk_adjustment_new (options->tilt_angle_d, -90.0, 90.0, 1, 10.0, 0.0);
  slider = gtk_hscale_new (GTK_ADJUSTMENT (options->tilt_angle_w));
  gtk_scale_set_value_pos (GTK_SCALE (slider), GTK_POS_TOP);
  gimp_table_attach_aligned (GTK_TABLE (table), 0, 1,
			     _("Angle:"), 1.0, 1.0,
			     slider, 1, FALSE);
  gtk_range_set_update_policy (GTK_RANGE (slider), GTK_UPDATE_DELAYED);

  g_signal_connect (G_OBJECT (options->tilt_angle_w), "value_changed",
		    G_CALLBACK (gimp_double_adjustment_update),
		    &options->tilt_angle);

  /* sens sliders */
  frame = gtk_frame_new (_("Sensitivity"));
  gtk_frame_set_shadow_type (GTK_FRAME (frame), GTK_SHADOW_ETCHED_IN);
  gtk_box_pack_start (GTK_BOX (vbox), frame, FALSE, TRUE, 0);
  gtk_widget_show (frame);

  table = gtk_table_new (3, 2, FALSE);
  gtk_table_set_col_spacings (GTK_TABLE (table), 4);
  gtk_container_set_border_width (GTK_CONTAINER (table), 2);
  gtk_container_add (GTK_CONTAINER (frame), table);
  gtk_widget_show (table);

  /* size sens slider */
  options->sensitivity_w =
    gtk_adjustment_new (options->sensitivity_d, 0.0, 1.0, 0.01, 0.1, 0.0);
  slider = gtk_hscale_new (GTK_ADJUSTMENT (options->sensitivity_w));
  gtk_scale_set_value_pos (GTK_SCALE (slider), GTK_POS_TOP);
  gimp_table_attach_aligned (GTK_TABLE (table), 0, 1,
			     _("Size:"), 1.0, 1.0,
			     slider, 1, FALSE);
  gtk_range_set_update_policy (GTK_RANGE (slider), GTK_UPDATE_DELAYED);

  g_signal_connect (G_OBJECT (options->sensitivity_w), "value_changed",
		    G_CALLBACK (gimp_double_adjustment_update),
		    &options->sensitivity);
  
  /* tilt sens slider */
  options->tilt_sensitivity_w =
    gtk_adjustment_new (options->tilt_sensitivity_d, 0.0, 1.0, 0.01, 0.1, 0.0);
  slider = gtk_hscale_new (GTK_ADJUSTMENT (options->tilt_sensitivity_w));
  gtk_scale_set_value_pos (GTK_SCALE (slider), GTK_POS_TOP);
  gimp_table_attach_aligned (GTK_TABLE (table), 0, 2,
			     _("Tilt:"), 1.0, 1.0,
			     slider, 1, FALSE);
  gtk_range_set_update_policy (GTK_RANGE (slider), GTK_UPDATE_DELAYED);

  g_signal_connect (G_OBJECT (options->tilt_sensitivity_w), "value_changed",
		    G_CALLBACK (gimp_double_adjustment_update),
		    &options->tilt_sensitivity);

  /* velocity sens slider */
  options->vel_sensitivity_w =
    gtk_adjustment_new (options->vel_sensitivity_d, 0.0, 1.0, 0.01, 0.1, 0.0);
  slider = gtk_hscale_new (GTK_ADJUSTMENT (options->vel_sensitivity_w));
  gtk_scale_set_value_pos (GTK_SCALE (slider), GTK_POS_TOP);
  gimp_table_attach_aligned (GTK_TABLE (table), 0, 3,
			     _("Speed:"), 1.0, 1.0,
			     slider, 1, FALSE);
  gtk_range_set_update_policy (GTK_RANGE (slider), GTK_UPDATE_DELAYED);

  g_signal_connect (G_OBJECT (options->vel_sensitivity_w), "value_changed",
		    G_CALLBACK (gimp_double_adjustment_update),
		    &options->vel_sensitivity);

  /*  bottom hbox */
  hbox = gtk_hbox_new (FALSE, 2);
  gtk_box_pack_start (GTK_BOX (vbox), hbox, TRUE, TRUE, 0);
  gtk_widget_show (hbox);

  /* Brush type radiobuttons */
  frame = gtk_frame_new (_("Type"));
  gtk_box_pack_start (GTK_BOX (hbox), frame, TRUE, TRUE, 0);
  gtk_widget_show (frame);

  hbox2 = gtk_hbox_new (FALSE, 0);
  gtk_container_add (GTK_CONTAINER (frame), hbox2);
  
  vbox = gtk_vbox_new (FALSE, 2);
  gtk_container_set_border_width (GTK_CONTAINER (vbox), 2);
  gtk_box_pack_start (GTK_BOX (hbox2), vbox, FALSE, FALSE, 0);
  gtk_widget_show (vbox);

  pixmap = blob_pixmap (gtk_widget_get_colormap (vbox),
			gtk_widget_get_visual (vbox),
			blob_ellipse);

  pixmap_widget = gtk_pixmap_new (pixmap, NULL);
  gdk_drawable_unref (pixmap);
  gtk_misc_set_padding (GTK_MISC (pixmap_widget), 6, 0);

  radio_button = gtk_radio_button_new (NULL);
  gtk_container_add (GTK_CONTAINER (radio_button), pixmap_widget);
  gtk_box_pack_start (GTK_BOX (vbox), radio_button, FALSE, FALSE, 0);

  g_signal_connect (G_OBJECT (radio_button), "toggled",
		    G_CALLBACK (ink_type_update),
		    (gpointer) blob_ellipse);


  options->function_w[0] = radio_button;

  pixmap = blob_pixmap (gtk_widget_get_colormap (vbox),
			gtk_widget_get_visual (vbox),
			blob_square);

  pixmap_widget = gtk_pixmap_new (pixmap, NULL);
  gdk_drawable_unref (pixmap);
  gtk_misc_set_padding (GTK_MISC (pixmap_widget), 6, 0);

  radio_button =
    gtk_radio_button_new_from_widget (GTK_RADIO_BUTTON (radio_button));
  gtk_container_add (GTK_CONTAINER (radio_button), pixmap_widget);
  gtk_box_pack_start (GTK_BOX (vbox), radio_button, FALSE, FALSE, 0);

  g_signal_connect (G_OBJECT (radio_button), "toggled",
		    G_CALLBACK (ink_type_update), 
		    (gpointer) blob_square);
  

  options->function_w[1] = radio_button;

  pixmap = blob_pixmap (gtk_widget_get_colormap (vbox),
			gtk_widget_get_visual (vbox),
			blob_diamond);

  pixmap_widget = gtk_pixmap_new (pixmap, NULL);
  gdk_drawable_unref (pixmap);
  gtk_misc_set_padding (GTK_MISC (pixmap_widget), 6, 0);

  radio_button =
    gtk_radio_button_new_from_widget (GTK_RADIO_BUTTON (radio_button));
  gtk_container_add (GTK_CONTAINER (radio_button), pixmap_widget);
  gtk_box_pack_start (GTK_BOX (vbox), radio_button, FALSE, FALSE, 0);

  g_signal_connect (G_OBJECT (radio_button), "toggled",
		    G_CALLBACK (ink_type_update), 
		    (gpointer) blob_diamond);


  options->function_w[2] = radio_button;

  /* Brush shape widget */
  frame = gtk_frame_new (_("Shape"));
  gtk_box_pack_start (GTK_BOX (hbox), frame, TRUE, TRUE, 0);
  gtk_widget_show (frame);

  vbox = gtk_vbox_new (FALSE, 2);
  gtk_container_set_border_width (GTK_CONTAINER (vbox), 2);
  gtk_container_add (GTK_CONTAINER (frame), vbox);
  gtk_widget_show (vbox);

  frame = gtk_aspect_frame_new (NULL, 0.0, 0.5, 1.0, FALSE);
  gtk_frame_set_shadow_type (GTK_FRAME (frame), GTK_SHADOW_IN);
  gtk_box_pack_start (GTK_BOX (vbox), frame, TRUE, TRUE, 0);

  options->brush_w = g_new (BrushWidget, 1);
  options->brush_w->state = FALSE;

  darea = gtk_drawing_area_new();
  options->brush_w->widget = darea;

  gtk_drawing_area_size (GTK_DRAWING_AREA (darea), 60, 60);
  gtk_container_add (GTK_CONTAINER (frame), darea);

  gtk_widget_set_events (darea, 
			 GDK_BUTTON_PRESS_MASK | GDK_BUTTON_RELEASE_MASK
			 | GDK_POINTER_MOTION_MASK | GDK_EXPOSURE_MASK);

  g_signal_connect (G_OBJECT (darea), "button_press_event",
		    G_CALLBACK (brush_widget_button_press),
		    options->brush_w);
  g_signal_connect (G_OBJECT (darea), "button_release_event",
		    G_CALLBACK (brush_widget_button_release),
		    options->brush_w);
  g_signal_connect (G_OBJECT (darea), "motion_notify_event",
		    G_CALLBACK (brush_widget_motion_notify),
		    options->brush_w);
  g_signal_connect (G_OBJECT (darea), "expose_event",
		    G_CALLBACK (brush_widget_expose), 
		    options->brush_w);
  g_signal_connect (G_OBJECT (darea), "realize",
		    G_CALLBACK (brush_widget_realize),
		    options->brush_w);

  gtk_widget_show_all (hbox);

  return options;
}


/*  the brush widget functions  */

static void
brush_widget_active_rect (BrushWidget  *brush_widget,
			  GtkWidget    *widget,
			  GdkRectangle *rect)
{
  int x,y;
  int r;

  r = MIN (widget->allocation.width, widget->allocation.height) / 2;

  x = widget->allocation.width / 2 + 0.85 * r * ink_options->aspect / 10.0 *
    cos (ink_options->angle);
  y = widget->allocation.height / 2 + 0.85 * r * ink_options->aspect / 10.0 *
    sin (ink_options->angle);

  rect->x = x - 5;
  rect->y = y - 5;
  rect->width = 10;
  rect->height = 10;
}

static void
brush_widget_realize (GtkWidget *widget)
{
  gtk_style_set_background (widget->style, widget->window, GTK_STATE_ACTIVE);
}

static void
brush_widget_draw_brush (BrushWidget *brush_widget,
			 GtkWidget   *widget,
			 gdouble      xc,
			 gdouble      yc,
			 gdouble      radius)
{
  Blob *blob;

  blob = ink_options->function (xc, yc,
				radius * cos (ink_options->angle),
				radius * sin (ink_options->angle),
				(- (radius / ink_options->aspect) *
				 sin (ink_options->angle)),
				((radius / ink_options->aspect) *
				 cos (ink_options->angle)));

  paint_blob (widget->window, widget->style->fg_gc[widget->state], blob);
  g_free (blob);
}

static void
brush_widget_expose (GtkWidget      *widget,
		     GdkEventExpose *event,
		     BrushWidget    *brush_widget)
{
  GdkRectangle rect;
  int r0;

  r0 = MIN (widget->allocation.width, widget->allocation.height) / 2;

  if (r0 < 2)
    return;

  gdk_window_clear_area (widget->window, 0, 0,
			 widget->allocation.width,
			 widget->allocation.height);
  brush_widget_draw_brush (brush_widget, widget,
			   widget->allocation.width / 2,
			   widget->allocation.height / 2,
			   0.9 * r0);

  brush_widget_active_rect (brush_widget, widget, &rect);
  gdk_draw_rectangle (widget->window, widget->style->bg_gc[GTK_STATE_NORMAL],
		      TRUE,	/* filled */
		      rect.x, rect.y, 
		      rect.width, rect.height);
  gtk_draw_shadow (widget->style, widget->window, widget->state, GTK_SHADOW_OUT,
		   rect.x, rect.y,
		   rect.width, rect.height);
}

static void
brush_widget_button_press (GtkWidget      *widget,
			   GdkEventButton *event,
			   BrushWidget    *brush_widget)
{
  GdkRectangle rect;

  brush_widget_active_rect (brush_widget, widget, &rect);
  
  if ((event->x >= rect.x) && (event->x-rect.x < rect.width) &&
      (event->y >= rect.y) && (event->y-rect.y < rect.height))
    {
      brush_widget->state = TRUE;

      gtk_grab_add (brush_widget->widget);
    }
}

static void
brush_widget_button_release (GtkWidget      *widget,
			     GdkEventButton *event,
			     BrushWidget    *brush_widget)
{
  brush_widget->state = FALSE;

  gtk_grab_remove (brush_widget->widget);
}

static void
brush_widget_motion_notify (GtkWidget      *widget,
			    GdkEventMotion *event,
			    BrushWidget    *brush_widget)
{
  int x;
  int y;
  int r0;
  int rsquare;

  if (brush_widget->state)
    {
      x = event->x - widget->allocation.width / 2;
      y = event->y - widget->allocation.height / 2;
      rsquare = x*x + y*y;

      if (rsquare != 0)
	{
	  ink_options->angle = atan2 (y, x);

	  r0 = MIN (widget->allocation.width, widget->allocation.height) / 2;
	  ink_options->aspect =
	    10.0 * sqrt ((double) rsquare / (r0 * r0)) / 0.85;

	  if (ink_options->aspect < 1.0)
	    ink_options->aspect = 1.0;
	  if (ink_options->aspect > 10.0)
	    ink_options->aspect = 10.0;

	  gtk_widget_draw (widget, NULL);
	}
    }
}

/*
 * Return a black-on white pixmap in the given colormap and
 * visual that represents the BlobFunc 'function'
 */
static GdkPixmap *
blob_pixmap (GdkColormap *colormap,
	     GdkVisual   *visual,
	     BlobFunc     function)
{
  GdkPixmap *pixmap;
  GdkGC     *black_gc, *white_gc;
  GdkColor   tmp_color;
  Blob      *blob;

  pixmap = gdk_pixmap_new (NULL, 22, 21, visual->depth);

  black_gc = gdk_gc_new (pixmap);
  gdk_color_black (colormap, &tmp_color);
  gdk_gc_set_foreground (black_gc, &tmp_color);

  white_gc = gdk_gc_new (pixmap);
  gdk_color_white (colormap, &tmp_color);
  gdk_gc_set_foreground (white_gc, &tmp_color);

  gdk_draw_rectangle (pixmap, white_gc, TRUE, 0, 0, 21, 20);
  gdk_draw_rectangle (pixmap, black_gc, FALSE, 0, 0, 21, 20);
  blob = (*function) (10, 10, 8, 0, 0, 8);
  paint_blob (pixmap, black_gc, blob);
  g_free (blob);

  gdk_gc_unref (white_gc);
  gdk_gc_unref (black_gc);

  return pixmap;
}

/*
 * Draw a blob onto a drawable with the specified graphics context
 */
static void
paint_blob (GdkDrawable *drawable,
	    GdkGC       *gc,
	    Blob        *blob)
{
  int i;

  for (i=0;i<blob->height;i++)
    {
      if (blob->data[i].left <= blob->data[i].right)
	gdk_draw_line (drawable, gc,
		       blob->data[i].left,i+blob->y,
		       blob->data[i].right+1,i+blob->y);
    }
}


static Blob *
ink_pen_ellipse (gdouble x_center,
		 gdouble y_center,
		 gdouble pressure,
		 gdouble xtilt,
		 gdouble ytilt,
		 gdouble velocity)
{
  double size;
  double tsin, tcos;
  double aspect, radmin;
  double x,y;
  double tscale;
  double tscale_c;
  double tscale_s;
  
  /* Adjust the size depending on pressure. */

  size = ink_options->size * (1.0 + ink_options->sensitivity *
			      (2.0 * pressure - 1.0) );

  /* Adjust the size further depending on pointer velocity
     and velocity-sensitivity.  These 'magic constants' are
     'feels natural' tigert-approved. --ADM */

  if (velocity < 3.0)
    velocity = 3.0;

#ifdef VERBOSE
  g_print("%f (%f) -> ", (float)size, (float)velocity);
#endif  

  size = ink_options->vel_sensitivity *
    ((4.5 * size) / (1.0 + ink_options->vel_sensitivity * (2.0*(velocity))))
    + (1.0 - ink_options->vel_sensitivity) * size;

#ifdef VERBOSE
  g_print("%f\n", (float)size);
#endif

  /* Clamp resulting size to sane limits */

  if (size > ink_options->size * (1.0 + ink_options->sensitivity))
    size = ink_options->size * (1.0 + ink_options->sensitivity);

  if (size*SUBSAMPLE < 1.0) size = 1.0/SUBSAMPLE;

  /* Add brush angle/aspect to tilt vectorially */

  /* I'm not happy with the way the brush widget info is combined with
     tilt info from the brush. My personal feeling is that representing
     both as affine transforms would make the most sense. -RLL */

  tscale = ink_options->tilt_sensitivity * 10.0;
  tscale_c = tscale * cos (gimp_deg_to_rad (ink_options->tilt_angle));
  tscale_s = tscale * sin (gimp_deg_to_rad (ink_options->tilt_angle));
  x = ink_options->aspect*cos(ink_options->angle) +
    xtilt * tscale_c - ytilt * tscale_s;
  y = ink_options->aspect*sin(ink_options->angle) +
    ytilt * tscale_c + xtilt * tscale_s;
#ifdef VERBOSE
  g_print ("angle %g aspect %g; %g %g; %g %g\n",
	   ink_options->angle, ink_options->aspect, tscale_c, tscale_s, x, y);
#endif
  aspect = sqrt(x*x+y*y);

  if (aspect != 0)
    {
      tcos = x/aspect;
      tsin = y/aspect;
    }
  else
    {
      tsin = sin(ink_options->angle);
      tcos = cos(ink_options->angle);
    }

  if (aspect < 1.0) 
    aspect = 1.0;
  else if (aspect > 10.0) 
    aspect = 10.0;

  radmin = SUBSAMPLE * size/aspect;
  if (radmin < 1.0) radmin = 1.0;
  
  return ink_options->function (x_center * SUBSAMPLE, y_center * SUBSAMPLE,
				radmin*aspect*tcos, radmin*aspect*tsin,  
				-radmin*tsin, radmin*tcos);
}

static void
ink_button_press (GimpTool       *tool,
		  GdkEventButton *bevent,
		  GDisplay       *gdisp)
{
  GimpInkTool  *ink_tool;
  GimpDrawable *drawable;
  Blob         *b;
  gdouble       x, y;

  ink_tool = GIMP_INK_TOOL (tool);

  /*  Keep the coordinates of the target  */
  gdisplay_untransform_coords_f (gdisp, bevent->x, bevent->y,
				 &x, &y, TRUE);
  drawable = gimp_image_active_drawable (gdisp->gimage);

  ink_init (ink_tool, drawable, x, y);

  tool->state        = ACTIVE;
  tool->gdisp        = gdisp;
  tool->paused_count = 0;

  /*  pause the current selection and grab the pointer  */
  gdisplays_selection_visibility (gdisp->gimage, SELECTION_PAUSE);

  /* add motion memory if you press mod1 first ^ perfectmouse */
  if (((bevent->state & GDK_MOD1_MASK) != 0) != (gimprc.perfectmouse != 0))
    gdk_pointer_grab (gdisp->canvas->window, FALSE,
		      GDK_BUTTON1_MOTION_MASK | GDK_BUTTON_RELEASE_MASK,
		      NULL, NULL, bevent->time);
  else
    gdk_pointer_grab (gdisp->canvas->window, FALSE,
		      GDK_POINTER_MOTION_HINT_MASK | GDK_BUTTON1_MOTION_MASK |
		      GDK_BUTTON_RELEASE_MASK,
		      NULL, NULL, bevent->time);
  
  tool->gdisp = gdisp;
  tool->state = ACTIVE;

#warning FIXME: presure, tilt

  b = ink_pen_ellipse (x, y,
		       1.0, 0.5, 0.5,
		       /* bevent->pressure, bevent->xtilt, bevent->ytilt, */
		       10.0);

  ink_paste (ink_tool, drawable, b);
  ink_tool->last_blob = b;

  time_smoother_init (ink_tool, bevent->time);
  ink_tool->last_time = bevent->time;
  dist_smoother_init (ink_tool, 0.0);
  ink_tool->init_velocity = TRUE;
  ink_tool->lastx = x;
  ink_tool->lasty = y;

  gdisplay_flush_now (gdisp);
}

static void
ink_button_release (GimpTool       *tool,
		    GdkEventButton *bevent,
		    GDisplay       *gdisp)
{
  GimpInkTool *ink_tool;
  GimpImage   *gimage;

  ink_tool = GIMP_INK_TOOL (tool);

  gimage = gdisp->gimage;

  /*  resume the current selection and ungrab the pointer  */
  gdisplays_selection_visibility (gdisp->gimage, SELECTION_RESUME);

  gdk_pointer_ungrab (bevent->time);
  gdk_flush ();

  /*  Set tool state to inactive -- no longer painting */
  tool->state = INACTIVE;

  /*  free the last blob  */
  g_free (ink_tool->last_blob);
  ink_tool->last_blob = NULL;

  ink_finish (ink_tool, gimp_image_active_drawable (gdisp->gimage));
  gdisplays_flush ();
}


static void
dist_smoother_init (GimpInkTool *ink_tool,
		    gdouble      initval)
{
  gint i;

  ink_tool->dt_index = 0;

  for (i=0; i<DIST_SMOOTHER_BUFFER; i++)
    {
      ink_tool->dt_buffer[i] = initval;
    }
}

static gdouble
dist_smoother_result (GimpInkTool *ink_tool)
{
  gint    i;
  gdouble result = 0.0;

  for (i = 0; i < DIST_SMOOTHER_BUFFER; i++)
    {
      result += ink_tool->dt_buffer[i];
    }

  return (result / (gdouble) DIST_SMOOTHER_BUFFER);
}

static void
dist_smoother_add (GimpInkTool *ink_tool,
		   gdouble      value)
{
  ink_tool->dt_buffer[ink_tool->dt_index] = value;

  if ((++ink_tool->dt_index) == DIST_SMOOTHER_BUFFER)
    ink_tool->dt_index = 0;
}


static void
time_smoother_init (GimpInkTool *ink_tool,
		    guint32      initval)
{
  gint i;

  ink_tool->ts_index = 0;

  for (i = 0; i < TIME_SMOOTHER_BUFFER; i++)
    {
      ink_tool->ts_buffer[i] = initval;
    }
}

static gdouble
time_smoother_result (GimpInkTool *ink_tool)
{
  gint    i;
  guint64 result = 0;

  for (i = 0; i < TIME_SMOOTHER_BUFFER; i++)
    {
      result += ink_tool->ts_buffer[i];
    }

#ifdef _MSC_VER
  return (gdouble) (gint64) (result / TIME_SMOOTHER_BUFFER);
#else
  return (result / TIME_SMOOTHER_BUFFER);
#endif
}

static void
time_smoother_add (GimpInkTool *ink_tool,
		   guint32      value)
{
  ink_tool->ts_buffer[ink_tool->ts_index] = value;

  if ((++ink_tool->ts_index) == TIME_SMOOTHER_BUFFER)
    ink_tool->ts_index = 0;
}


static void
ink_motion (GimpTool       *tool,
	    GdkEventMotion *mevent,
	    GDisplay       *gdisp)
{
  GimpInkTool  *ink_tool;
  GimpDrawable *drawable;
  Blob         *b, *blob_union;

  gdouble x, y;
  gdouble pressure;
  gdouble velocity;
  gdouble dist;
  gdouble lasttime, thistime;
  
  ink_tool = GIMP_INK_TOOL (tool);

  gdisplay_untransform_coords_f (gdisp, mevent->x, mevent->y, &x, &y, TRUE);
  drawable = gimp_image_active_drawable (gdisp->gimage);

  lasttime = ink_tool->last_time;

  time_smoother_add (ink_tool, mevent->time);
  thistime = ink_tool->last_time = time_smoother_result (ink_tool);

  /* The time resolution on X-based GDK motion events is
     bloody awful, hence the use of the smoothing function.
     Sadly this also means that there is always the chance of
     having an indeterminite velocity since this event and
     the previous several may still appear to issue at the same
     instant. -ADM */

  if (thistime == lasttime)
    thistime = lasttime + 1;

  if (ink_tool->init_velocity)
    {
      dist_smoother_init (ink_tool,
			  dist = sqrt ((ink_tool->lastx-x) * (ink_tool->lastx-x) +
				       (ink_tool->lasty-y) * (ink_tool->lasty-y)));
      ink_tool->init_velocity = FALSE;
    }
  else
    {
      dist_smoother_add (ink_tool,
			 sqrt ((ink_tool->lastx-x) * (ink_tool->lastx-x) +
			       (ink_tool->lasty-y) * (ink_tool->lasty-y)));

      dist = dist_smoother_result (ink_tool);
    }

  ink_tool->lastx = x;
  ink_tool->lasty = y;

#warning FIXME: tilt, pressure

  pressure = 1.0; /* mevent->pressure; */
  velocity = 10.0 * sqrt ((dist) / (double) (thistime - lasttime));

#warning FIXME: tilt, pressure

  b = ink_pen_ellipse (x, y, pressure, 0.5, 0.5,
		       /* mevent->xtilt, mevent->ytilt, */ velocity);
  blob_union = blob_convex_union (ink_tool->last_blob, b);
  g_free (ink_tool->last_blob);
  ink_tool->last_blob = b;

  ink_paste (ink_tool, drawable, blob_union);  
  g_free (blob_union);

  gdisplay_flush_now (gdisp);
}

static void
ink_cursor_update (GimpTool       *tool,
		   GdkEventMotion *mevent,
		   GDisplay       *gdisp)
{
  GimpLayer     *layer;
  GdkCursorType  ctype = GDK_TOP_LEFT_ARROW;
  gint           x, y;

  gdisplay_untransform_coords (gdisp, mevent->x, mevent->y,
			       &x, &y, FALSE, FALSE);
  if ((layer = gimp_image_get_active_layer (gdisp->gimage))) 
    {
      int off_x, off_y;

      gimp_drawable_offsets (GIMP_DRAWABLE (layer), &off_x, &off_y);

      if (x >= off_x && y >= off_y &&
	  x < (off_x + gimp_drawable_width (GIMP_DRAWABLE (layer))) &&
	  y < (off_y + gimp_drawable_height (GIMP_DRAWABLE (layer))))
	{
	  /*  One more test--is there a selected region?
	   *  if so, is cursor inside?
	   */
	  if (gimage_mask_is_empty (gdisp->gimage))
	    ctype = GIMP_MOUSE_CURSOR;
	  else if (gimage_mask_value (gdisp->gimage, x, y))
	    ctype = GIMP_MOUSE_CURSOR;
	}
    }

  gdisplay_install_tool_cursor (gdisp,
				ctype,
				GIMP_INK_TOOL_CURSOR,
				GIMP_CURSOR_MODIFIER_NONE);
}

static void
ink_control (GimpTool   *tool,
	     ToolAction  action,
	     GDisplay   *gdisp)
{
  GimpInkTool *ink_tool;

  ink_tool = GIMP_INK_TOOL (tool);

  switch (action)
    {
    case PAUSE:
      break;

    case RESUME:
      break;

    case HALT:
      ink_cleanup ();
      break;

    default:
      break;
    }
}

static void
ink_init (GimpInkTool  *ink_tool,
	  GimpDrawable *drawable, 
	  gdouble       x,
	  gdouble       y)
{
  /*  free the block structures  */
  if (undo_tiles)
    tile_manager_destroy (undo_tiles);
  if (canvas_tiles)
    tile_manager_destroy (canvas_tiles);

  /*  Allocate the undo structure  */
  undo_tiles = tile_manager_new (gimp_drawable_width (drawable),
				 gimp_drawable_height (drawable),
				 gimp_drawable_bytes (drawable));

  /*  Allocate the canvas blocks structure  */
  canvas_tiles = tile_manager_new (gimp_drawable_width (drawable),
				   gimp_drawable_height (drawable), 1);

  /*  Get the initial undo extents  */
  ink_tool->x1 = ink_tool->x2 = x;
  ink_tool->y1 = ink_tool->y2 = y;
}

static void
ink_finish (GimpInkTool  *ink_tool,
	    GimpDrawable *drawable)
{
  /*  push an undo  */
  gimp_drawable_apply_image (drawable, ink_tool->x1, ink_tool->y1,
			     ink_tool->x2, ink_tool->y2, undo_tiles, TRUE);
  undo_tiles = NULL;

  /*  invalidate the drawable--have to do it here, because
   *  it is not done during the actual painting.
   */
  gimp_viewable_invalidate_preview (GIMP_VIEWABLE (drawable));
}

static void
ink_cleanup (void)
{
  /*  If the undo tiles exist, nuke them  */
  if (undo_tiles)
    {
      tile_manager_destroy (undo_tiles);
      undo_tiles = NULL;
    }

  /*  If the canvas blocks exist, nuke them  */
  if (canvas_tiles)
    {
      tile_manager_destroy (canvas_tiles);
      canvas_tiles = NULL;
    }

  /*  Free the temporary buffer if it exist  */
  if (canvas_buf)
    {
      temp_buf_free (canvas_buf);
      canvas_buf = NULL;
    }
}

/*********************************
 *  Rendering functions          *
 *********************************/

/* Some of this stuff should probably be combined with the 
 * code it was copied from in paint_core.c; but I wanted
 * to learn this stuff, so I've kept it simple.
 *
 * The following only supports CONSTANT mode. Incremental
 * would, I think, interact strangely with the way we
 * do things. But it wouldn't be hard to implement at all.
 */

static void
ink_set_paint_area (GimpInkTool  *ink_tool, 
		    GimpDrawable *drawable, 
		    Blob         *blob)
{
  gint x, y, width, height;
  gint x1, y1, x2, y2;
  gint bytes;

  blob_bounds (blob, &x, &y, &width, &height);

  bytes = gimp_drawable_has_alpha (drawable) ?
    gimp_drawable_bytes (drawable) : gimp_drawable_bytes (drawable) + 1;

  x1 = CLAMP (x/SUBSAMPLE - 1,            0, gimp_drawable_width (drawable));
  y1 = CLAMP (y/SUBSAMPLE - 1,            0, gimp_drawable_height (drawable));
  x2 = CLAMP ((x + width)/SUBSAMPLE + 2,  0, gimp_drawable_width (drawable));
  y2 = CLAMP ((y + height)/SUBSAMPLE + 2, 0, gimp_drawable_height (drawable));

  /*  configure the canvas buffer  */
  if ((x2 - x1) && (y2 - y1))
    canvas_buf = temp_buf_resize (canvas_buf, bytes, x1, y1,
				  (x2 - x1), (y2 - y1));
}

enum { ROW_START, ROW_STOP };

/* The insertion sort here, for SUBSAMPLE = 8, tends to beat out
 * qsort() by 4x with CFLAGS=-O2, 2x with CFLAGS=-g
 */
static void
insert_sort (gint *data,
	     gint  n)
{
  gint i, j, k;
  gint tmp1, tmp2;

  for (i=2; i<2*n; i+=2)
    {
      tmp1 = data[i];
      tmp2 = data[i+1];
      j = 0;
      while (data[j] < tmp1)
	j += 2;

      for (k=i; k>j; k-=2)
	{
	  data[k] = data[k-2];
	  data[k+1] = data[k-1];
	}

      data[j] = tmp1;
      data[j+1] = tmp2;
    }
}

static void
fill_run (guchar *dest,
	  guchar  alpha,
	  gint    w)
{
  if (alpha == 255)
    {
      memset (dest, 255, w);
    }
  else
    {
      while (w--)
	{
	  *dest = MAX(*dest, alpha);
	  dest++;
	}
    }
}

static void
render_blob_line (Blob   *blob,
		  guchar *dest,
		  gint    x,
		  gint    y,
		  gint    width)
{
  gint  buf[4 * SUBSAMPLE];
  gint *data    = buf;
  gint  n       = 0;
  gint  i, j;
  gint  current = 0;  /* number of filled rows at this point
		       * in the scan line
		       */
  gint last_x;

  /* Sort start and ends for all lines */
  
  j = y * SUBSAMPLE - blob->y;
  for (i = 0; i < SUBSAMPLE; i++)
    {
      if (j >= blob->height)
	break;

      if ((j > 0) && (blob->data[j].left <= blob->data[j].right))
	{
	  data[2 * n]                     = blob->data[j].left;
	  data[2 * n + 1]                 = ROW_START;
	  data[2 * SUBSAMPLE + 2 * n]     = blob->data[j].right;
	  data[2 * SUBSAMPLE + 2 * n + 1] = ROW_STOP;
	  n++;
	}
      j++;
    }

  /*   If we have less than SUBSAMPLE rows, compress */
  if (n < SUBSAMPLE)
    {
      for (i = 0; i < 2 * n; i++)
	data[2 * n + i] = data[2 * SUBSAMPLE + i];
    }

  /*   Now count start and end separately */
  n *= 2;

  insert_sort (data, n);

  /* Discard portions outside of tile */

  while ((n > 0) && (data[0] < SUBSAMPLE*x))
    {
      if (data[1] == ROW_START)
	current++;
      else
	current--;
      data += 2;
      n--;
    }

  while ((n > 0) && (data[2*(n-1)] >= SUBSAMPLE*(x+width)))
    n--;
  
  /* Render the row */

  last_x = 0;
  for (i = 0; i < n;)
    {
      gint cur_x = data[2 * i] / SUBSAMPLE - x;
      gint pixel;

      /* Fill in portion leading up to this pixel */
      if (current && cur_x != last_x)
	fill_run (dest + last_x, (255 * current) / SUBSAMPLE, cur_x - last_x);

      /* Compute the value for this pixel */
      pixel = current * SUBSAMPLE; 

      while (i<n)
	{
	  gint tmp_x = data[2 * i] / SUBSAMPLE;

	  if (tmp_x - x != cur_x)
	    break;

	  if (data[2 * i + 1] == ROW_START)
	    {
	      current++;
	      pixel += ((tmp_x + 1) * SUBSAMPLE) - data[2 * i];
	    }
	  else
	    {
	      current--;
	      pixel -= ((tmp_x + 1) * SUBSAMPLE) - data[2 * i];
	    }
	  
	  i++;
	}

      dest[cur_x] = MAX (dest[cur_x], (pixel * 255) / (SUBSAMPLE * SUBSAMPLE));

      last_x = cur_x + 1;
    }

  if (current != 0)
    fill_run (dest + last_x, (255 * current)/ SUBSAMPLE, width - last_x);
}

static void
render_blob (PixelRegion *dest,
	     Blob        *blob)
{
  gint      i;
  gint      h;
  guchar   *s;
  gpointer  pr;

  for (pr = pixel_regions_register (1, dest); 
       pr != NULL; 
       pr = pixel_regions_process (pr))
    {
      h = dest->h;
      s = dest->data;

      for (i=0; i<h; i++)
	{
	  render_blob_line (blob, s,
			    dest->x, dest->y + i, dest->w);
	  s += dest->rowstride;
	}
    }
}

static void
ink_paste (GimpInkTool  *ink_tool, 
	   GimpDrawable *drawable,
	   Blob         *blob)
{
  GimpImage   *gimage;
  GimpContext *context;
  PixelRegion  srcPR;
  gint         offx, offy;
  gchar        col[MAX_CHANNELS];

  if (! (gimage = gimp_drawable_gimage (drawable)))
    return;

  context = gimp_get_current_context (gimage->gimp);

  /* Get the the buffer */
  ink_set_paint_area (ink_tool, drawable, blob);
 
  /* check to make sure there is actually a canvas to draw on */
  if (!canvas_buf)
    return;

  gimp_image_get_foreground (gimage, drawable, col);

  /*  set the alpha channel  */
  col[canvas_buf->bytes - 1] = OPAQUE_OPACITY;

  /*  color the pixels  */
  color_pixels (temp_buf_data (canvas_buf), col,
		canvas_buf->width * canvas_buf->height, canvas_buf->bytes);

  /*  set undo blocks  */
  ink_set_undo_tiles (drawable,
		      canvas_buf->x, canvas_buf->y,
		      canvas_buf->width, canvas_buf->height);

  /*  initialize any invalid canvas tiles  */
  ink_set_canvas_tiles (canvas_buf->x, canvas_buf->y,
			canvas_buf->width, canvas_buf->height);

  ink_to_canvas_tiles (ink_tool, blob, col);

  /*  initialize canvas buf source pixel regions  */
  srcPR.bytes = canvas_buf->bytes;
  srcPR.x = 0; srcPR.y = 0;
  srcPR.w = canvas_buf->width;
  srcPR.h = canvas_buf->height;
  srcPR.rowstride = canvas_buf->width * canvas_buf->bytes;
  srcPR.data = temp_buf_data (canvas_buf);

  /*  apply the paint area to the gimage  */
  gimp_image_apply_image (gimage, drawable, &srcPR,
			  FALSE, 
			  (int) (gimp_context_get_opacity (context) * 255),
			  gimp_context_get_paint_mode (context),
			  undo_tiles,  /*  specify an alternative src1  */
			  canvas_buf->x, canvas_buf->y);

  /*  Update the undo extents  */
  ink_tool->x1 = MIN (ink_tool->x1, canvas_buf->x);
  ink_tool->y1 = MIN (ink_tool->y1, canvas_buf->y);
  ink_tool->x2 = MAX (ink_tool->x2, (canvas_buf->x + canvas_buf->width));
  ink_tool->y2 = MAX (ink_tool->y2, (canvas_buf->y + canvas_buf->height));

  /*  Update the gimage--it is important to call gdisplays_update_area
   *  instead of drawable_update because we don't want the drawable
   *  preview to be constantly invalidated
   */
  gimp_drawable_offsets (drawable, &offx, &offy);
  gdisplays_update_area (gimage, canvas_buf->x + offx, canvas_buf->y + offy,
			 canvas_buf->width, canvas_buf->height);
}

/* This routine a) updates the representation of the stroke
 * in the canvas tiles, then renders the dirty bit of it
 * into canvas_buf.
 */
static void
ink_to_canvas_tiles (GimpInkTool *ink_tool,
		     Blob        *blob,
		     guchar      *color)
{
  PixelRegion srcPR, maskPR;

  /*  draw the blob on the canvas tiles  */
  pixel_region_init (&srcPR, canvas_tiles,
		     canvas_buf->x, canvas_buf->y,
		     canvas_buf->width, canvas_buf->height, TRUE);

  render_blob (&srcPR, blob);

  /*  combine the canvas tiles and the canvas buf  */
  srcPR.bytes = canvas_buf->bytes;
  srcPR.x = 0; srcPR.y = 0;
  srcPR.w = canvas_buf->width;
  srcPR.h = canvas_buf->height;
  srcPR.rowstride = canvas_buf->width * canvas_buf->bytes;
  srcPR.data = temp_buf_data (canvas_buf);

  pixel_region_init (&maskPR, canvas_tiles,
		     canvas_buf->x, canvas_buf->y,
		     canvas_buf->width, canvas_buf->height, FALSE);

  /*  apply the canvas tiles to the canvas buf  */
  apply_mask_to_region (&srcPR, &maskPR, OPAQUE_OPACITY);
}

static void
ink_set_undo_tiles (GimpDrawable *drawable,
		    gint          x,
		    gint          y,
		    gint          w,
		    gint          h)
{
  gint  i, j;
  Tile *src_tile;
  Tile *dest_tile;

  for (i = y; i < (y + h); i += (TILE_HEIGHT - (i % TILE_HEIGHT)))
    {
      for (j = x; j < (x + w); j += (TILE_WIDTH - (j % TILE_WIDTH)))
	{
	  dest_tile = tile_manager_get_tile (undo_tiles, j, i, FALSE, FALSE);
	  if (tile_is_valid (dest_tile) == FALSE)
	    {
	      src_tile = tile_manager_get_tile (gimp_drawable_data (drawable),
						j, i, TRUE, FALSE);
	      tile_manager_map_tile (undo_tiles, j, i, src_tile);
	      tile_release (src_tile, FALSE);
	    }
	}
    }
}


static void
ink_set_canvas_tiles (gint x,
		      gint y,
		      gint w,
		      gint h)
{
  gint  i, j;
  Tile *tile;

  for (i = y; i < (y + h); i += (TILE_HEIGHT - (i % TILE_HEIGHT)))
    {
      for (j = x; j < (x + w); j += (TILE_WIDTH - (j % TILE_WIDTH)))
	{
	  tile = tile_manager_get_tile (canvas_tiles, j, i, FALSE, FALSE);
	  if (tile_is_valid (tile) == FALSE)
	    {
	      tile = tile_manager_get_tile (canvas_tiles, j, i, TRUE, TRUE);
	      memset (tile_data_pointer (tile, 0, 0), 
		      0, 
		      tile_size (tile));
	      tile_release (tile, TRUE);
	    }
	}
    }
}