How I can add some properties to object without touching it

[Przemysław Staniszewski <ihi marzyciel wp pl>]

Hello.

 I wonder about something like in topic. I have dia-canvas-box.c, but I
want to add one more properties like gchar *name. I want to make gobject
child of dia-canvas-box but i don't know how :( . My konwledge is poor
so i was copy first file, replace such string (like box) into another
(like box_tex) and add gchar *name into header, of course some functions
to set and get this property. But what is the correct way to make that work?

Something happy here: :)

-- 
Przemysław Staniszewski

--- /home/users/p/tmp/diacanvas2-0.14.2/diacanvas/dia-canvas-box.c	2003-11-20 21:48:36.000000000 +0100
+++ /home/users/p/Projekty/new_dyplom/src/dia-canvas-box-tex.c	2005-12-18 23:01:09.000000000 +0100
@@ -1,10 +1,10 @@
 /*
- * DiaCanvasBox
+ * DiaCanvasBoxTex
  *
  * This is LGPL'ed code.
  */
 
-#include "dia-canvas-box.h"
+#include "dia-canvas-box-tex.h"
 #include "dia-shape.h"
 #include <libart_lgpl/art_affine.h>
 #include "dia-canvas-i18n.h"
@@ -15,50 +15,51 @@
 	PROP_BORDER_WIDTH,
 	/* Depricated: */
 	PROP_BG_COLOR,
+	PROP_NAME,
 	PROP_LINE_WIDTH
 };
 
-static void dia_canvas_box_class_init (DiaCanvasBoxClass *klass);
-static void dia_canvas_box_init (DiaCanvasBox *item);
-static void dia_canvas_box_set_property (GObject *object,
+static void dia_canvas_box_tex_class_init (DiaCanvasBoxTexClass *klass);
+static void dia_canvas_box_tex_init (DiaCanvasBoxTex *item);
+static void dia_canvas_box_tex_set_property (GObject *object,
 					 guint property_id,
 					 const GValue *value,
 					 GParamSpec *pspec);
-static void dia_canvas_box_get_property (GObject *object,
+static void dia_canvas_box_tex_get_property (GObject *object,
 					 guint property_id,
 					 GValue *value,
 					 GParamSpec *pspec);
-static void dia_canvas_box_dispose	(GObject *object);
-static void dia_canvas_box_update	(DiaCanvasItem *item,
+static void dia_canvas_box_tex_dispose	(GObject *object);
+static void dia_canvas_box_tex_update	(DiaCanvasItem *item,
 					 gdouble affine[6]);
-static gboolean dia_canvas_box_get_shape_iter	(DiaCanvasItem *item,
+static gboolean dia_canvas_box_tex_get_shape_iter	(DiaCanvasItem *item,
 						 DiaCanvasIter *iter);
-static gboolean dia_canvas_box_shape_next	(DiaCanvasItem *item,
+static gboolean dia_canvas_box_tex_shape_next	(DiaCanvasItem *item,
 						 DiaCanvasIter *iter);
-static DiaShape* dia_canvas_box_shape_value	(DiaCanvasItem *item,
+static DiaShape* dia_canvas_box_tex_shape_value	(DiaCanvasItem *item,
 						 DiaCanvasIter *iter);
 static DiaCanvasElementClass *parent_class = NULL;
 
 GType
-dia_canvas_box_get_type (void)
+dia_canvas_box_tex_get_type (void)
 {
 	static GType object_type = 0;
 
 	if (!object_type) {
 		static const GTypeInfo object_info = {
-			sizeof (DiaCanvasBoxClass),
+			sizeof (DiaCanvasBoxTexClass),
 			(GBaseInitFunc) NULL,
 			(GBaseFinalizeFunc) NULL,
-			(GClassInitFunc) dia_canvas_box_class_init,
+			(GClassInitFunc) dia_canvas_box_tex_class_init,
 			(GClassFinalizeFunc) NULL,
 			(gconstpointer) NULL, /* class_data */
-			sizeof (DiaCanvasBox),
+			sizeof (DiaCanvasBoxTex),
 			(guint16) 0, /* n_preallocs */
-			(GInstanceInitFunc) dia_canvas_box_init,
+			(GInstanceInitFunc) dia_canvas_box_tex_init,
 		};
 
 		object_type = g_type_register_static (DIA_TYPE_CANVAS_ELEMENT,
-						      "DiaCanvasBox",
+						      "DiaCanvasBoxTex",
 						      &object_info, 0);
 	}
 
@@ -67,7 +68,7 @@
 
 
 static void
-dia_canvas_box_class_init (DiaCanvasBoxClass *klass)
+dia_canvas_box_tex_class_init (DiaCanvasBoxTexClass *klass)
 {
 	GObjectClass *object_class;
 	DiaCanvasItemClass *item_class;
@@ -77,15 +78,23 @@
 	
 	parent_class = g_type_class_peek_parent (klass);
 
-	object_class->get_property = dia_canvas_box_get_property;
-	object_class->set_property = dia_canvas_box_set_property;
-	object_class->dispose = dia_canvas_box_dispose;
-
-	item_class->update = dia_canvas_box_update;
-	item_class->get_shape_iter = dia_canvas_box_get_shape_iter;
-	item_class->shape_next = dia_canvas_box_shape_next;
-	item_class->shape_value = dia_canvas_box_shape_value;
+	object_class->get_property = dia_canvas_box_tex_get_property;
+	object_class->set_property = dia_canvas_box_tex_set_property;
+	object_class->dispose = dia_canvas_box_tex_dispose;
+
+	item_class->update = dia_canvas_box_tex_update;
+	item_class->get_shape_iter = dia_canvas_box_tex_get_shape_iter;
+	item_class->shape_next = dia_canvas_box_tex_shape_next;
+	item_class->shape_value = dia_canvas_box_tex_shape_value;
 
+	g_printf("Instaluje\n");
+	g_object_class_install_property (object_class,
+					 PROP_NAME,
+					 g_param_spec_string ("name",
+						_("Name"),
+						_("Name for tex box"),
+						NULL,
+					       	G_PARAM_READWRITE));
 	g_object_class_install_property (object_class,
 					 PROP_COLOR,
 					 g_param_spec_ulong ("color",
@@ -126,41 +135,49 @@
 
 
 static void
-dia_canvas_box_init (DiaCanvasBox *item)
+dia_canvas_box_tex_init (DiaCanvasBoxTex *item)
 {
 	item->color = DIA_COLOR (0, 0, 0);
 	item->fill_color = 0; /* fully transparent */
 	item->border_width = 1.0;
 	item->border = dia_shape_new (DIA_SHAPE_PATH);
+	item->name = NULL;
 }
 
 
 static void
-dia_canvas_box_set_property (GObject *object, guint property_id,
+dia_canvas_box_tex_set_property (GObject *object, guint property_id,
 			     const GValue *value, GParamSpec *pspec)
 {
-	DiaCanvasBox *box = (DiaCanvasBox*) object;
+	DiaCanvasBoxTex *box_tex = (DiaCanvasBoxTex*) object;
 
 	switch (property_id) {
 	case PROP_COLOR:
-		dia_canvas_item_preserve_property (DIA_CANVAS_ITEM (box), "color");
-		box->color = g_value_get_ulong (value);
+		dia_canvas_item_preserve_property (DIA_CANVAS_ITEM (box_tex), "color");
+		box_tex->color = g_value_get_ulong (value);
 		dia_canvas_item_request_update (DIA_CANVAS_ITEM (object));
 		break;
 	case PROP_BG_COLOR:
 		g_warning("Depricated property: bg_color, use fill_color instead");
 	case PROP_FILL_COLOR:
-		dia_canvas_item_preserve_property (DIA_CANVAS_ITEM(box), "fill_color");
-		box->fill_color = g_value_get_ulong (value);
+		dia_canvas_item_preserve_property (DIA_CANVAS_ITEM(box_tex), "fill_color");
+		box_tex->fill_color = g_value_get_ulong (value);
 		dia_canvas_item_request_update (DIA_CANVAS_ITEM (object));
 		break;
 	case PROP_LINE_WIDTH:
 		g_warning("Depricated property: line_width, use border_width instead");
 	case PROP_BORDER_WIDTH:
-		dia_canvas_item_preserve_property (DIA_CANVAS_ITEM(box), "border_width");
-		box->border_width = g_value_get_double (value);
+		dia_canvas_item_preserve_property (DIA_CANVAS_ITEM(box_tex), "border_width");
+		box_tex->border_width = g_value_get_double (value);
 		dia_canvas_item_request_update (DIA_CANVAS_ITEM (object));
 		break;
+	case PROP_NAME:
+		dia_canvas_item_preserve_property (DIA_CANVAS_ITEM(box_tex), "name");
+		if (box_tex->name) {
+			g_printf("Juz jest jakas nazwa - trzeba ja zwolnic przez free");
+		}
+		box_tex->name=g_strdup(g_value_get_string (value));
+		break;
 	default:
 		G_OBJECT_WARN_INVALID_PROPERTY_ID (object, property_id, pspec);
 		break;
@@ -168,20 +185,23 @@
 }
 
 static void
-dia_canvas_box_get_property (GObject *object, guint property_id,
+dia_canvas_box_tex_get_property (GObject *object, guint property_id,
 			     GValue *value, GParamSpec *pspec)
 {
 	switch (property_id) {
 	case PROP_COLOR:
-		g_value_set_ulong (value, DIA_CANVAS_BOX (object)->color);
+		g_value_set_ulong (value, DIA_CANVAS_BOX_TEX (object)->color);
 		break;
 	case PROP_BG_COLOR:
 	case PROP_FILL_COLOR:
-		g_value_set_ulong (value, DIA_CANVAS_BOX (object)->fill_color);
+		g_value_set_ulong (value, DIA_CANVAS_BOX_TEX (object)->fill_color);
 		break;
 	case PROP_LINE_WIDTH:
 	case PROP_BORDER_WIDTH:
-		g_value_set_double (value, DIA_CANVAS_BOX (object)->border_width);
+		g_value_set_double (value, DIA_CANVAS_BOX_TEX (object)->border_width);
+		break;
+	case PROP_NAME:
+		g_value_set_string (value, DIA_CANVAS_BOX_TEX (object)->name);
 		break;
 	default:
 		G_OBJECT_WARN_INVALID_PROPERTY_ID (object, property_id, pspec);
@@ -190,21 +210,29 @@
 }
 
 static void
-dia_canvas_box_dispose (GObject *object)
+dia_canvas_box_tex_dispose (GObject *object)
 {
-	DiaCanvasBox *box = (DiaCanvasBox*) object;
+	DiaCanvasBoxTex *box_tex = (DiaCanvasBoxTex*) object;
 
-	if (box->border) {
-		dia_shape_free (box->border);
-		box->border = NULL;
+	if (box_tex->border) {
+		dia_shape_free (box_tex->border);
+		box_tex->border = NULL;
 	}
 
+	// jesli dispose oznacza destroy
+	 if (box_tex->name)
+		      {
+			            g_free (box_tex->name);
+				          box_tex->name = NULL;
+					      }
+	  
+
 	G_OBJECT_CLASS (parent_class)->dispose (object);
 }
 
 
 static void
-dia_canvas_box_update (DiaCanvasItem *item, gdouble affine[6])
+dia_canvas_box_tex_update (DiaCanvasItem *item, gdouble affine[6])
 {
 	DiaShape *border;
 	DiaPoint p1 = { 0.0, 0.0 }, p2;
@@ -216,9 +244,9 @@
         if (DIA_CANVAS_ITEM_CLASS (parent_class)->update)
 		DIA_CANVAS_ITEM_CLASS (parent_class)->update (item, affine);
 	
-	border = DIA_CANVAS_BOX (item)->border;
+	border = DIA_CANVAS_BOX_TEX (item)->border;
 
-	half_w = DIA_CANVAS_BOX (item)->border_width / 2.0;
+	half_w = DIA_CANVAS_BOX_TEX (item)->border_width / 2.0;
 	item->bounds.top -= half_w;
 	item->bounds.left -= half_w;
 	item->bounds.bottom += half_w;
@@ -226,28 +254,28 @@
 
 	/* Create the border */
 	dia_shape_rectangle (border, &p1, &p2);
-	dia_shape_set_color (border, DIA_CANVAS_BOX (item)->color);
+	dia_shape_set_color (border, DIA_CANVAS_BOX_TEX (item)->color);
 	dia_shape_path_set_fill (border, DIA_FILL_SOLID);
-	dia_shape_path_set_fill_color (border, DIA_CANVAS_BOX (item)->fill_color);
-	dia_shape_path_set_line_width (border, DIA_CANVAS_BOX (item)->border_width);
+	dia_shape_path_set_fill_color (border, DIA_CANVAS_BOX_TEX (item)->fill_color);
+	dia_shape_path_set_line_width (border, DIA_CANVAS_BOX_TEX (item)->border_width);
 }
 
 static gboolean
-dia_canvas_box_get_shape_iter (DiaCanvasItem *item, DiaCanvasIter *iter)
+dia_canvas_box_tex_get_shape_iter (DiaCanvasItem *item, DiaCanvasIter *iter)
 {
-	iter->data[0] = DIA_CANVAS_BOX (item)->border;
+	iter->data[0] = DIA_CANVAS_BOX_TEX (item)->border;
 	return TRUE;
 }
 
 static gboolean
-dia_canvas_box_shape_next (DiaCanvasItem *item, DiaCanvasIter *iter)
+dia_canvas_box_tex_shape_next (DiaCanvasItem *item, DiaCanvasIter *iter)
 {
 	iter->data[0] = NULL;
 	return FALSE;
 }
 
 static DiaShape*
-dia_canvas_box_shape_value (DiaCanvasItem *item, DiaCanvasIter *iter)
+dia_canvas_box_tex_shape_value (DiaCanvasItem *item, DiaCanvasIter *iter)
 {
 	return iter->data[0];
 }