Added initialize_value and value_is_empty callbacks.

2000-05-19  Christopher James Lahey  <clahey@helixcode.com>

	* e-table-example-1.c, e-table-example-2.c, e-table-simple.c,
	e-table-simple.h, e-table-size-test.c, test-check.c, test-cols.c,
	test-table.c: Added initialize_value and value_is_empty callbacks.

	* e-table-model.c, e-table-model.h: Added initialize_value and
	value_is_callback virtual functions to the ETableModel class.

	* e-table-subset.c: Perpetuate the initialize_value and
	value_is_empty methods.

svn path=/trunk/; revision=3138

23 files changed, 656 insertions, 168 deletions

diff --git a/widgets/e-table/ChangeLog b/widgets/e-table/ChangeLog
index 8d26a03b34..c824ddd142 100644
--- a/widgets/e-table/ChangeLog
+++ b/widgets/e-table/ChangeLog
@@ -1,5 +1,15 @@
 2000-05-19  Christopher James Lahey  <clahey@helixcode.com>
 
+	* e-table-example-1.c, e-table-example-2.c, e-table-simple.c,
+	e-table-simple.h, e-table-size-test.c, test-check.c, test-cols.c,
+	test-table.c: Added initialize_value and value_is_empty callbacks.
+
+	* e-table-model.c, e-table-model.h: Added initialize_value and
+	value_is_callback virtual functions to the ETableModel class.
+
+	* e-table-subset.c: Perpetuate the initialize_value and
+	value_is_empty methods.
+
 From a patch by Iain Holmes <ih@csd.abdn.ac.uk>
 	
 	* e-table-config.c, e-table.c: Fixed getting text content from a
diff --git a/widgets/e-table/e-table-example-1.c b/widgets/e-table/e-table-example-1.c
index 70689c2953..fbaa3389a2 100644
--- a/widgets/e-table/e-table-example-1.c
+++ b/widgets/e-table/e-table-example-1.c
@@ -157,6 +157,20 @@ my_free_value (ETableModel *etc, int col, void *value, void *data)
 	g_free (value);
 }
 
+/* This function creates an empty value. */
+static void *
+my_initialize_value (ETableModel *etc, int col, void *data)
+{
+	return g_strdup ("");
+}
+
+/* This function reports if a value is empty. */
+static gboolean
+my_value_is_empty (ETableModel *etc, int col, const void *value, void *data)
+{
+	return !(value && *(char *)value);
+}
+
 /* This function is for when the model is unfrozen.  This can mostly
    be ignored for simple models.  */
 static void
@@ -184,7 +198,9 @@ create_table (void)
 	e_table_model = e_table_simple_new (
 					    my_col_count, my_row_count, my_value_at,
 					    my_set_value_at, my_is_cell_editable,
-					    my_duplicate_value, my_free_value, my_thaw, NULL);
+					    my_duplicate_value, my_free_value, 
+					    my_initialize_value, my_value_is_empty,
+					    my_thaw, NULL);
 	/*
 	 * Next we create a header.  The ETableHeader is used in two
 	 * different way.  The first is the full_header.  This is the
diff --git a/widgets/e-table/e-table-example-2.c b/widgets/e-table/e-table-example-2.c
index 5bc6910437..c318507ea4 100644
--- a/widgets/e-table/e-table-example-2.c
+++ b/widgets/e-table/e-table-example-2.c
@@ -121,66 +121,90 @@ my_col_count (ETableModel *etc, void *data)
 static int
 my_row_count (ETableModel *etc, void *data)
 {
-  return ROWS;
+	return ROWS;
 }
 
 static void *
 my_value_at (ETableModel *etc, int col, int row, void *data)
 {
-  if (col == COLOR_COLUMN){
-    if (importance_data[row]){
-      return color1;
-    } else {
-      return color2;
-    }
-  } else if (col == IMPORTANCE_COLUMN){
-    return (gpointer) importance_data[row];
-  } else {
-	return (void *) table_data [row][col];
-  }
+	if (col == COLOR_COLUMN){
+		if (importance_data[row]){
+			return color1;
+		} else {
+			return color2;
+		}
+	} else if (col == IMPORTANCE_COLUMN){
+		return (gpointer) importance_data[row];
+	} else {
+		return (void *) table_data [row][col];
+	}
 }
 
 static void
 my_set_value_at (ETableModel *etc, int col, int row, const void *val, void *data)
 {
-  if (col == COLOR_COLUMN){ 
-  } else if (col == IMPORTANCE_COLUMN){
-    importance_data[row] = (gboolean) val;
-  } else {
-	g_free (table_data [row][col]);
-	table_data [row][col] = g_strdup (val);
-  }
+	if (col == COLOR_COLUMN){ 
+	} else if (col == IMPORTANCE_COLUMN){
+		importance_data[row] = (gboolean) val;
+	} else {
+		g_free (table_data [row][col]);
+		table_data [row][col] = g_strdup (val);
+	}
 }
 
 static gboolean
 my_is_cell_editable (ETableModel *etc, int col, int row, void *data)
 {
-  if (col == IMPORTANCE_COLUMN)
-    return FALSE;
-  else
-    return TRUE;
+	if (col == IMPORTANCE_COLUMN)
+		return FALSE;
+	else
+		return TRUE;
 }
 
 static void *
 my_duplicate_value (ETableModel *etc, int col, const void *value, void *data)
 {
-  if (col == COLOR_COLUMN){
-    return (void *) value;
-  } else if (col == IMPORTANCE_COLUMN){
-    return (void *) value;
-  } else {
-    return g_strdup (value);
-  }
+	if (col == COLOR_COLUMN){
+		return (void *) value;
+	} else if (col == IMPORTANCE_COLUMN){
+		return (void *) value;
+	} else {
+		return g_strdup (value);
+	}
 }
 
 static void
 my_free_value (ETableModel *etc, int col, void *value, void *data)
 {
-  if (col == COLOR_COLUMN){
-  } else if (col == IMPORTANCE_COLUMN){
-  } else {
-    g_free (value);
-  }
+	if (col == COLOR_COLUMN){
+	} else if (col == IMPORTANCE_COLUMN){
+	} else {
+		g_free (value);
+	}
+}
+
+static void *
+my_initialize_value (ETableModel *etc, int col, void *data)
+{
+	if (col == COLOR_COLUMN){
+		return NULL;
+	} else if (col == IMPORTANCE_COLUMN){
+		return NULL;
+	} else {
+		return g_strdup ("");
+	}
+}
+
+static gboolean
+my_value_is_empty (ETableModel *etc, int col, const void *value, void *data)
+{
+	if (col == COLOR_COLUMN){
+		return value == NULL;
+	} else if (col == IMPORTANCE_COLUMN){
+		return value == NULL;
+	} else {
+		return !(value && *(char *)value);
+	}
 }
 
 static void
@@ -213,7 +237,9 @@ create_table ()
 	e_table_model = e_table_simple_new (
 					    my_col_count, my_row_count, my_value_at,
 					    my_set_value_at, my_is_cell_editable,
-					    my_duplicate_value, my_free_value, my_thaw, NULL);
+					    my_duplicate_value, my_free_value,
+					    my_initialize_value, my_value_is_empty,
+					    my_thaw, NULL);
 	/*
 	  Next we create a header.  The ETableHeader is used in two
 	  different way.  The first is the full_header.  This is the
diff --git a/widgets/e-table/e-table-model.c b/widgets/e-table/e-table-model.c
index 3ea01c05e1..7ed8a9ba5f 100644
--- a/widgets/e-table/e-table-model.c
+++ b/widgets/e-table/e-table-model.c
@@ -107,6 +107,30 @@ e_table_model_free_value (ETableModel *e_table_model, int col, void *value)
 		ETM_CLASS (e_table_model)->free_value (e_table_model, col, value);
 }
 
+void *
+e_table_model_initialize_value (ETableModel *e_table_model, int col)
+{
+	g_return_val_if_fail (e_table_model != NULL, NULL);
+	g_return_val_if_fail (E_IS_TABLE_MODEL (e_table_model), NULL);
+
+	if (ETM_CLASS (e_table_model)->initialize_value)
+		return ETM_CLASS (e_table_model)->initialize_value (e_table_model, col);
+	else
+		return NULL;
+}
+
+gboolean
+e_table_model_value_is_empty (ETableModel *e_table_model, int col, const void *value)
+{
+	g_return_val_if_fail (e_table_model != NULL, FALSE);
+	g_return_val_if_fail (E_IS_TABLE_MODEL (e_table_model), FALSE);
+
+	if (ETM_CLASS (e_table_model)->value_is_empty)
+		return ETM_CLASS (e_table_model)->value_is_empty (e_table_model, col, value);
+	else
+		return FALSE;
+}
+
 static void
 e_table_model_destroy (GtkObject *object)
 {
@@ -117,6 +141,7 @@ e_table_model_destroy (GtkObject *object)
 static void
 e_table_model_class_init (GtkObjectClass *object_class)
 {
+	ETableModelClass *klass = E_TABLE_MODEL_CLASS(object_class);
 	e_table_model_parent_class = gtk_type_class (gtk_object_get_type ());
 	
 	object_class->destroy = e_table_model_destroy;
@@ -162,6 +187,22 @@ e_table_model_class_init (GtkObjectClass *object_class)
 				GTK_TYPE_NONE, 1, GTK_TYPE_INT);
 
 	gtk_object_class_add_signals (object_class, e_table_model_signals, LAST_SIGNAL);
+
+	klass->column_count = NULL;     
+	klass->row_count = NULL;        
+	klass->value_at = NULL;         
+	klass->set_value_at = NULL;     
+	klass->is_cell_editable = NULL; 
+	klass->duplicate_value = NULL;  
+	klass->free_value = NULL;       
+	klass->initialize_value = NULL; 
+	klass->value_is_empty = NULL;   
+	klass->thaw = NULL;             
+	klass->model_changed = NULL;    
+	klass->model_row_changed = NULL;
+	klass->model_cell_changed = NULL;
+	klass->model_row_inserted = NULL;
+	klass->model_row_deleted = NULL;
 }
 
 
diff --git a/widgets/e-table/e-table-model.h b/widgets/e-table/e-table-model.h
index e542754f22..0c8d51b882 100644
--- a/widgets/e-table/e-table-model.h
+++ b/widgets/e-table/e-table-model.h
@@ -28,8 +28,14 @@ typedef struct {
 	void        (*set_value_at)     (ETableModel *etm, int col, int row, const void *value);
 	gboolean    (*is_cell_editable) (ETableModel *etm, int col, int row);
 
-	void       *(*duplicate_value)   (ETableModel *etm, int col, const void *value);
-	void        (*free_value)        (ETableModel *etm, int col, void *value);
+	/* Allocate a copy of the given value. */
+	void       *(*duplicate_value)  (ETableModel *etm, int col, const void *value);
+	/* Free an allocated value. */
+	void        (*free_value)       (ETableModel *etm, int col, void *value);
+	/* Return an allocated empty value. */
+	void	   *(*initialize_value) (ETableModel *etm, int col);
+	/* Return TRUE if value is equivalent to an empty cell. */
+	gboolean    (*value_is_empty)   (ETableModel *etm, int col, const void *value);
 	
 	void        (*thaw)             (ETableModel *etm);
 	/*
@@ -62,6 +68,8 @@ gboolean    e_table_model_is_cell_editable (ETableModel *e_table_model, int col,
 
 void       *e_table_model_duplicate_value  (ETableModel *e_table_model, int col, const void *value);
 void        e_table_model_free_value       (ETableModel *e_table_model, int col, void *value);
+void       *e_table_model_initialize_value (ETableModel *e_table_model, int col);
+gboolean    e_table_model_value_is_empty   (ETableModel *e_table_model, int col, const void *value);
 
 void        e_table_model_freeze           (ETableModel *e_table_model);
 void        e_table_model_thaw             (ETableModel *e_table_model);
diff --git a/widgets/e-table/e-table-simple.c b/widgets/e-table/e-table-simple.c
index e8c4d1debb..7e0135b21e 100644
--- a/widgets/e-table/e-table-simple.c
+++ b/widgets/e-table/e-table-simple.c
@@ -18,63 +18,103 @@
 static int
 simple_column_count (ETableModel *etm)
 {
-	ETableSimple *simple = (ETableSimple *)etm;
+	ETableSimple *simple = E_TABLE_SIMPLE(etm);
 
-	return simple->col_count (etm, simple->data);
+	if (simple->col_count)
+		return simple->col_count (etm, simple->data);
+	else
+		return 0;
 }
 
 static int
 simple_row_count (ETableModel *etm)
 {
-	ETableSimple *simple = (ETableSimple *)etm;
+	ETableSimple *simple = E_TABLE_SIMPLE(etm);
 
-	return simple->row_count (etm, simple->data);
+	if (simple->row_count)
+		return simple->row_count (etm, simple->data);
+	else
+		return 0;
 }
 
 static void *
 simple_value_at (ETableModel *etm, int col, int row)
 {
-	ETableSimple *simple = (ETableSimple *)etm;
+	ETableSimple *simple = E_TABLE_SIMPLE(etm);
 
-	return simple->value_at (etm, col, row, simple->data);
+	if (simple->value_at)
+		return simple->value_at (etm, col, row, simple->data);
+	else
+		return NULL;
 }
 
 static void
 simple_set_value_at (ETableModel *etm, int col, int row, const void *val)
 {
-	ETableSimple *simple = (ETableSimple *)etm;
+	ETableSimple *simple = E_TABLE_SIMPLE(etm);
 
-	simple->set_value_at (etm, col, row, val, simple->data);
+	if (simple->set_value_at)
+		simple->set_value_at (etm, col, row, val, simple->data);
 }
 
 static gboolean
 simple_is_cell_editable (ETableModel *etm, int col, int row)
 {
-	ETableSimple *simple = (ETableSimple *)etm;
+	ETableSimple *simple = E_TABLE_SIMPLE(etm);
 
-	return simple->is_cell_editable (etm, col, row, simple->data);
+	if (simple->is_cell_editable)
+		return simple->is_cell_editable (etm, col, row, simple->data);
+	else
+		return FALSE;
 }
 
+/* The default for simple_duplicate_value is to return the raw value. */
 static void *
 simple_duplicate_value (ETableModel *etm, int col, const void *value)
 {
-	ETableSimple *simple = (ETableSimple *)etm;
+	ETableSimple *simple = E_TABLE_SIMPLE(etm);
 
-	return simple->duplicate_value (etm, col, value, simple->data);
+	if (simple->duplicate_value)
+		return simple->duplicate_value (etm, col, value, simple->data);
+	else
+		return (void *)value;
 }
 
 static void
 simple_free_value (ETableModel *etm, int col, void *value)
 {
-	ETableSimple *simple = (ETableSimple *)etm;
+	ETableSimple *simple = E_TABLE_SIMPLE(etm);
 
-	simple->free_value (etm, col, value, simple->data);
+	if (simple->free_value)
+		simple->free_value (etm, col, value, simple->data);
+}
+
+static void *
+simple_initialize_value (ETableModel *etm, int col)
+{
+	ETableSimple *simple = E_TABLE_SIMPLE(etm);
+	
+	if (simple->initialize_value)
+		return simple->initialize_value (etm, col, simple->data);
+	else
+		return NULL;
+}
+
+static gboolean
+simple_value_is_empty (ETableModel *etm, int col, const void *value)
+{
+	ETableSimple *simple = E_TABLE_SIMPLE(etm);
+	
+	if (simple->value_is_empty)
+		return simple->value_is_empty (etm, col, value, simple->data);
+	else
+		return FALSE;
 }
 
 static void
 simple_thaw (ETableModel *etm)
 {
-	ETableSimple *simple = (ETableSimple *)etm;
+	ETableSimple *simple = E_TABLE_SIMPLE(etm);
 
 	simple->thaw (etm, simple->data);
 }
@@ -91,6 +131,8 @@ e_table_simple_class_init (GtkObjectClass *object_class)
 	model_class->is_cell_editable = simple_is_cell_editable;
 	model_class->duplicate_value = simple_duplicate_value;
 	model_class->free_value = simple_free_value;
+	model_class->initialize_value = simple_initialize_value;
+	model_class->value_is_empty = simple_value_is_empty;
 	model_class->thaw = simple_thaw;
 }
 
@@ -125,6 +167,8 @@ e_table_simple_new (ETableSimpleColumnCountFn col_count,
 		    ETableSimpleIsCellEditableFn is_cell_editable,
 		    ETableSimpleDuplicateValueFn duplicate_value,
 		    ETableSimpleFreeValueFn free_value,
+		    ETableSimpleInitializeValueFn initialize_value,
+		    ETableSimpleValueIsEmptyFn value_is_empty,
 		    ETableSimpleThawFn thaw,
 		    void *data)
 {
@@ -137,9 +181,11 @@ e_table_simple_new (ETableSimpleColumnCountFn col_count,
 	et->value_at = value_at;
 	et->set_value_at = set_value_at;
 	et->is_cell_editable = is_cell_editable;
-	et->thaw = thaw;
 	et->duplicate_value = duplicate_value;
 	et->free_value = free_value;
+	et->initialize_value = initialize_value;
+	et->value_is_empty = value_is_empty;
+	et->thaw = thaw;
 	et->data = data;
 	
 	return (ETableModel *) et;
diff --git a/widgets/e-table/e-table-simple.h b/widgets/e-table/e-table-simple.h
index 51134f45aa..ab97452f10 100644
--- a/widgets/e-table/e-table-simple.h
+++ b/widgets/e-table/e-table-simple.h
@@ -4,14 +4,22 @@
 
 #include "e-table-model.h"
 
-typedef int         (*ETableSimpleColumnCountFn)    (ETableModel *etm, void *data);
-typedef	int         (*ETableSimpleRowCountFn)       (ETableModel *etm, void *data);
-typedef	void       *(*ETableSimpleValueAtFn)        (ETableModel *etm, int col, int row, void *data);
-typedef	void        (*ETableSimpleSetValueAtFn)     (ETableModel *etm, int col, int row, const void *val, void *data);
-typedef	gboolean    (*ETableSimpleIsCellEditableFn) (ETableModel *etm, int col, int row, void *data);
-typedef	void       *(*ETableSimpleDuplicateValueFn) (ETableModel *etm, int col, const void *val, void *data);
-typedef	void        (*ETableSimpleFreeValueFn)      (ETableModel *etm, int col, void *val, void *data);
-typedef void        (*ETableSimpleThawFn)           (ETableModel *etm, void *data);
+#define E_TABLE_SIMPLE_TYPE        (e_table_simple_get_type ())
+#define E_TABLE_SIMPLE(o)          (GTK_CHECK_CAST ((o), E_TABLE_SIMPLE_TYPE, ETableSimple))
+#define E_TABLE_SIMPLE_CLASS(k)    (GTK_CHECK_CLASS_CAST((k), E_TABLE_SIMPLE_TYPE, ETableSimpleClass))
+#define E_IS_TABLE_SIMPLE(o)       (GTK_CHECK_TYPE ((o), E_TABLE_SIMPLE_TYPE))
+#define E_IS_TABLE_SIMPLE_CLASS(k) (GTK_CHECK_CLASS_TYPE ((k), E_TABLE_SIMPLE_TYPE))
+
+typedef int         (*ETableSimpleColumnCountFn)     (ETableModel *etm, void *data);
+typedef	int         (*ETableSimpleRowCountFn)        (ETableModel *etm, void *data);
+typedef	void       *(*ETableSimpleValueAtFn)         (ETableModel *etm, int col, int row, void *data);
+typedef	void        (*ETableSimpleSetValueAtFn)      (ETableModel *etm, int col, int row, const void *val, void *data);
+typedef	gboolean    (*ETableSimpleIsCellEditableFn)  (ETableModel *etm, int col, int row, void *data);
+typedef	void       *(*ETableSimpleDuplicateValueFn)  (ETableModel *etm, int col, const void *val, void *data);
+typedef	void        (*ETableSimpleFreeValueFn)       (ETableModel *etm, int col, void *val, void *data);
+typedef void       *(*ETableSimpleInitializeValueFn) (ETableModel *etm, int col, void *data);
+typedef gboolean    (*ETableSimpleValueIsEmptyFn)    (ETableModel *etm, int col, const void *val, void *data);
+typedef void        (*ETableSimpleThawFn)            (ETableModel *etm, void *data);
 
 typedef struct {
 	ETableModel parent;
@@ -23,6 +31,8 @@ typedef struct {
 	ETableSimpleIsCellEditableFn is_cell_editable;
 	ETableSimpleDuplicateValueFn duplicate_value;
 	ETableSimpleFreeValueFn      free_value;
+	ETableSimpleInitializeValueFn initialize_value;
+	ETableSimpleValueIsEmptyFn value_is_empty;
 	ETableSimpleThawFn           thaw;
 	void *data;
 } ETableSimple;
@@ -40,6 +50,8 @@ ETableModel *e_table_simple_new (ETableSimpleColumnCountFn col_count,
 				 ETableSimpleIsCellEditableFn is_cell_editable,
 				 ETableSimpleDuplicateValueFn duplicate_value,
 				 ETableSimpleFreeValueFn free_value,
+				 ETableSimpleInitializeValueFn initialize_value,
+				 ETableSimpleValueIsEmptyFn value_is_empty,
 				 ETableSimpleThawFn thaw,
 				 void *data);
 
diff --git a/widgets/e-table/e-table-size-test.c b/widgets/e-table/e-table-size-test.c
index d12a57fbbb..058429ca64 100644
--- a/widgets/e-table/e-table-size-test.c
+++ b/widgets/e-table/e-table-size-test.c
@@ -157,6 +157,20 @@ my_free_value (ETableModel *etc, int col, void *value, void *data)
 	g_free (value);
 }
 
+/* This function creates an empty value. */
+static void *
+my_initialize_value (ETableModel *etc, int col, void *data)
+{
+	return g_strdup ("");
+}
+
+/* This function reports if a value is empty. */
+static gboolean
+my_value_is_empty (ETableModel *etc, int col, const void *value, void *data)
+{
+	return !(value && *(char *)value);
+}
+
 /* This function is for when the model is unfrozen.  This can mostly
    be ignored for simple models.  */
 static void
@@ -179,7 +193,9 @@ create_table (void)
 	e_table_model = e_table_simple_new (
 					    my_col_count, my_row_count, my_value_at,
 					    my_set_value_at, my_is_cell_editable,
-					    my_duplicate_value, my_free_value, my_thaw, NULL);
+					    my_duplicate_value, my_free_value,
+					    my_initialize_value, my_value_is_empty,
+					    my_thaw, NULL);
 	/*
 	 * Next we create a header.  The ETableHeader is used in two
 	 * different way.  The first is the full_header.  This is the
diff --git a/widgets/e-table/e-table-subset.c b/widgets/e-table/e-table-subset.c
index b0c5671b65..a0add3b954 100644
--- a/widgets/e-table/e-table-subset.c
+++ b/widgets/e-table/e-table-subset.c
@@ -98,6 +98,22 @@ etss_free_value (ETableModel *etm, int col, void *value)
 	e_table_model_free_value (etss->source, col, value);
 }
 
+static void *
+etss_initialize_value (ETableModel *etm, int col)
+{
+	ETableSubset *etss = (ETableSubset *)etm;
+
+	return e_table_model_initialize_value (etss->source, col);
+}
+
+static gboolean
+etss_value_is_empty (ETableModel *etm, int col, const void *value)
+{
+	ETableSubset *etss = (ETableSubset *)etm;
+
+	return e_table_model_value_is_empty (etss->source, col, value);
+}
+
 static void
 etss_thaw (ETableModel *etm)
 {
@@ -120,6 +136,8 @@ etss_class_init (GtkObjectClass *klass)
 	table_class->is_cell_editable = etss_is_cell_editable;
 	table_class->duplicate_value  = etss_duplicate_value;
 	table_class->free_value       = etss_free_value;
+	table_class->initialize_value = etss_initialize_value;
+	table_class->value_is_empty   = etss_value_is_empty;
 	table_class->thaw             = etss_thaw;
 }
 
diff --git a/widgets/e-table/test-check.c b/widgets/e-table/test-check.c
index 3a32098245..300ebf7a7e 100644
--- a/widgets/e-table/test-check.c
+++ b/widgets/e-table/test-check.c
@@ -1,3 +1,4 @@
+/* -*- Mode: C; tab-width: 8; indent-tabs-mode: t; c-basic-offset: 8 -*- */
 /*
  * Test code for the ETable package
  *
@@ -66,7 +67,7 @@ set_value_at (ETableModel *etc, int col, int row, const void *val, void *data)
 	g_assert (col < 2);
 	g_assert (row < LINES);
 
-	if (col == 0){
+	if (col == 0) {
 		my_table [row].value = GPOINTER_TO_INT (val);
 		printf ("Value at %d,%d set to %d\n", col, row, GPOINTER_TO_INT (val));
 	} else {
@@ -84,19 +85,37 @@ is_cell_editable (ETableModel *etc, int col, int row, void *data)
 static void *
 duplicate_value (ETableModel *etc, int col, const void *value, void *data)
 {
-  if (col == 0){
-    return (void *) value;
-  } else {
-    return g_strdup (value);
-  }
+	if (col == 0) {
+		return (void *) value;
+	} else {
+		return g_strdup (value);
+	}
 }
 
 static void
 free_value (ETableModel *etc, int col, void *value, void *data)
 {
-  if (col != 0){
-    g_free (value);
-  }
+	if (col != 0) {
+		g_free (value);
+	}
+}
+
+static void *
+initialize_value (ETableModel *etc, int col, void *data)
+{
+	if (col == 0)
+		return NULL;
+	else
+		return g_strdup ("");
+}
+
+static gboolean
+value_is_empty (ETableModel *etc, int col, const void *value, void *data)
+{
+	if (col == 0)
+		return value == NULL;
+	else
+		return !(value && *(char *)value);
 }
 
 static void
@@ -128,7 +147,9 @@ check_test (void)
 	e_table_model = e_table_simple_new (
 		col_count, row_count, value_at,
 		set_value_at, is_cell_editable, 
-		duplicate_value, free_value, thaw, NULL);
+		duplicate_value, free_value, 
+		initialize_value, value_is_empty,
+		thaw, NULL);
 
 	/*
 	 * Header
diff --git a/widgets/e-table/test-cols.c b/widgets/e-table/test-cols.c
index 6756511fb4..e34e477dae 100644
--- a/widgets/e-table/test-cols.c
+++ b/widgets/e-table/test-cols.c
@@ -1,3 +1,4 @@
+/* -*- Mode: C; tab-width: 8; indent-tabs-mode: t; c-basic-offset: 8 -*- */
 /*
  * Test code for the ETable package
  *
@@ -84,19 +85,37 @@ is_cell_editable (ETableModel *etc, int col, int row, void *data)
 static void *
 duplicate_value (ETableModel *etc, int col, const void *value, void *data)
 {
-  if (col == 0){
-    return (void *)value;
-  } else {
-    return g_strdup (value);
-  }
+	if (col == 0){
+		return (void *)value;
+	} else {
+		return g_strdup (value);
+	}
 }
 
 static void
 free_value (ETableModel *etc, int col, void *value, void *data)
 {
-  if (col != 0){
-    g_free (value);
-  }
+	if (col != 0){
+		g_free (value);
+	}
+}
+
+static void *
+initialize_value (ETableModel *etc, int col, void *data)
+{
+	if (col == 0)
+		return NULL;
+	else
+		return g_strdup ("");
+}
+
+static gboolean
+value_is_empty (ETableModel *etc, int col, const void *value, void *data)
+{
+	if (col == 0)
+		return value == NULL;
+	else
+		return !(value && *(char *)value);
 }
 
 static void
@@ -128,6 +147,7 @@ multi_cols_test (void)
 		col_count, row_count, value_at,
 		set_value_at, is_cell_editable,
 		duplicate_value, free_value,
+		initialize_value, value_is_empty,
 		thaw, NULL);
 
 	/*
diff --git a/widgets/e-table/test-table.c b/widgets/e-table/test-table.c
index a882b8dbdf..724090d904 100644
--- a/widgets/e-table/test-table.c
+++ b/widgets/e-table/test-table.c
@@ -190,6 +190,18 @@ free_value (ETableModel *etc, int col, void *value, void *data)
 	g_free (value);
 }
 
+static void *
+initialize_value (ETableModel *etc, int col, void *data)
+{
+	return g_strdup ("");
+}
+
+static gboolean
+value_is_empty (ETableModel *etc, int col, const void *value, void *data)
+{
+	return !(value && *(char *)value);
+}
+
 static void
 thaw (ETableModel *etc, void *data)
 {
@@ -220,7 +232,9 @@ table_browser_test (void)
 	e_table_model = e_table_simple_new (
 		col_count, row_count, value_at,
 		set_value_at, is_cell_editable,
-		duplicate_value, free_value, thaw, NULL);
+		duplicate_value, free_value,
+		initialize_value, value_is_empty,
+		thaw, NULL);
 
 	/*
 	 * Header
@@ -315,7 +329,8 @@ do_e_table_demo (const char *spec)
 		e_table_model = 
 			e_table_simple_new (col_count, row_count, value_at,
 					    set_value_at, is_cell_editable,
-					    duplicate_value, free_value, 
+					    duplicate_value, free_value,
+					    initialize_value, value_is_empty,
 					    thaw, NULL);
 
 	full_header = e_table_header_new ();
diff --git a/widgets/table/e-table-example-1.c b/widgets/table/e-table-example-1.c
index 70689c2953..fbaa3389a2 100644
--- a/widgets/table/e-table-example-1.c
+++ b/widgets/table/e-table-example-1.c
@@ -157,6 +157,20 @@ my_free_value (ETableModel *etc, int col, void *value, void *data)
 	g_free (value);
 }
 
+/* This function creates an empty value. */
+static void *
+my_initialize_value (ETableModel *etc, int col, void *data)
+{
+	return g_strdup ("");
+}
+
+/* This function reports if a value is empty. */
+static gboolean
+my_value_is_empty (ETableModel *etc, int col, const void *value, void *data)
+{
+	return !(value && *(char *)value);
+}
+
 /* This function is for when the model is unfrozen.  This can mostly
    be ignored for simple models.  */
 static void
@@ -184,7 +198,9 @@ create_table (void)
 	e_table_model = e_table_simple_new (
 					    my_col_count, my_row_count, my_value_at,
 					    my_set_value_at, my_is_cell_editable,
-					    my_duplicate_value, my_free_value, my_thaw, NULL);
+					    my_duplicate_value, my_free_value, 
+					    my_initialize_value, my_value_is_empty,
+					    my_thaw, NULL);
 	/*
 	 * Next we create a header.  The ETableHeader is used in two
 	 * different way.  The first is the full_header.  This is the
diff --git a/widgets/table/e-table-example-2.c b/widgets/table/e-table-example-2.c
index 5bc6910437..c318507ea4 100644
--- a/widgets/table/e-table-example-2.c
+++ b/widgets/table/e-table-example-2.c
@@ -121,66 +121,90 @@ my_col_count (ETableModel *etc, void *data)
 static int
 my_row_count (ETableModel *etc, void *data)
 {
-  return ROWS;
+	return ROWS;
 }
 
 static void *
 my_value_at (ETableModel *etc, int col, int row, void *data)
 {
-  if (col == COLOR_COLUMN){
-    if (importance_data[row]){
-      return color1;
-    } else {
-      return color2;
-    }
-  } else if (col == IMPORTANCE_COLUMN){
-    return (gpointer) importance_data[row];
-  } else {
-	return (void *) table_data [row][col];
-  }
+	if (col == COLOR_COLUMN){
+		if (importance_data[row]){
+			return color1;
+		} else {
+			return color2;
+		}
+	} else if (col == IMPORTANCE_COLUMN){
+		return (gpointer) importance_data[row];
+	} else {
+		return (void *) table_data [row][col];
+	}
 }
 
 static void
 my_set_value_at (ETableModel *etc, int col, int row, const void *val, void *data)
 {
-  if (col == COLOR_COLUMN){ 
-  } else if (col == IMPORTANCE_COLUMN){
-    importance_data[row] = (gboolean) val;
-  } else {
-	g_free (table_data [row][col]);
-	table_data [row][col] = g_strdup (val);
-  }
+	if (col == COLOR_COLUMN){ 
+	} else if (col == IMPORTANCE_COLUMN){
+		importance_data[row] = (gboolean) val;
+	} else {
+		g_free (table_data [row][col]);
+		table_data [row][col] = g_strdup (val);
+	}
 }
 
 static gboolean
 my_is_cell_editable (ETableModel *etc, int col, int row, void *data)
 {
-  if (col == IMPORTANCE_COLUMN)
-    return FALSE;
-  else
-    return TRUE;
+	if (col == IMPORTANCE_COLUMN)
+		return FALSE;
+	else
+		return TRUE;
 }
 
 static void *
 my_duplicate_value (ETableModel *etc, int col, const void *value, void *data)
 {
-  if (col == COLOR_COLUMN){
-    return (void *) value;
-  } else if (col == IMPORTANCE_COLUMN){
-    return (void *) value;
-  } else {
-    return g_strdup (value);
-  }
+	if (col == COLOR_COLUMN){
+		return (void *) value;
+	} else if (col == IMPORTANCE_COLUMN){
+		return (void *) value;
+	} else {
+		return g_strdup (value);
+	}
 }
 
 static void
 my_free_value (ETableModel *etc, int col, void *value, void *data)
 {
-  if (col == COLOR_COLUMN){
-  } else if (col == IMPORTANCE_COLUMN){
-  } else {
-    g_free (value);
-  }
+	if (col == COLOR_COLUMN){
+	} else if (col == IMPORTANCE_COLUMN){
+	} else {
+		g_free (value);
+	}
+}
+
+static void *
+my_initialize_value (ETableModel *etc, int col, void *data)
+{
+	if (col == COLOR_COLUMN){
+		return NULL;
+	} else if (col == IMPORTANCE_COLUMN){
+		return NULL;
+	} else {
+		return g_strdup ("");
+	}
+}
+
+static gboolean
+my_value_is_empty (ETableModel *etc, int col, const void *value, void *data)
+{
+	if (col == COLOR_COLUMN){
+		return value == NULL;
+	} else if (col == IMPORTANCE_COLUMN){
+		return value == NULL;
+	} else {
+		return !(value && *(char *)value);
+	}
 }
 
 static void
@@ -213,7 +237,9 @@ create_table ()
 	e_table_model = e_table_simple_new (
 					    my_col_count, my_row_count, my_value_at,
 					    my_set_value_at, my_is_cell_editable,
-					    my_duplicate_value, my_free_value, my_thaw, NULL);
+					    my_duplicate_value, my_free_value,
+					    my_initialize_value, my_value_is_empty,
+					    my_thaw, NULL);
 	/*
 	  Next we create a header.  The ETableHeader is used in two
 	  different way.  The first is the full_header.  This is the
diff --git a/widgets/table/e-table-model.c b/widgets/table/e-table-model.c
index 3ea01c05e1..7ed8a9ba5f 100644
--- a/widgets/table/e-table-model.c
+++ b/widgets/table/e-table-model.c
@@ -107,6 +107,30 @@ e_table_model_free_value (ETableModel *e_table_model, int col, void *value)
 		ETM_CLASS (e_table_model)->free_value (e_table_model, col, value);
 }
 
+void *
+e_table_model_initialize_value (ETableModel *e_table_model, int col)
+{
+	g_return_val_if_fail (e_table_model != NULL, NULL);
+	g_return_val_if_fail (E_IS_TABLE_MODEL (e_table_model), NULL);
+
+	if (ETM_CLASS (e_table_model)->initialize_value)
+		return ETM_CLASS (e_table_model)->initialize_value (e_table_model, col);
+	else
+		return NULL;
+}
+
+gboolean
+e_table_model_value_is_empty (ETableModel *e_table_model, int col, const void *value)
+{
+	g_return_val_if_fail (e_table_model != NULL, FALSE);
+	g_return_val_if_fail (E_IS_TABLE_MODEL (e_table_model), FALSE);
+
+	if (ETM_CLASS (e_table_model)->value_is_empty)
+		return ETM_CLASS (e_table_model)->value_is_empty (e_table_model, col, value);
+	else
+		return FALSE;
+}
+
 static void
 e_table_model_destroy (GtkObject *object)
 {
@@ -117,6 +141,7 @@ e_table_model_destroy (GtkObject *object)
 static void
 e_table_model_class_init (GtkObjectClass *object_class)
 {
+	ETableModelClass *klass = E_TABLE_MODEL_CLASS(object_class);
 	e_table_model_parent_class = gtk_type_class (gtk_object_get_type ());
 	
 	object_class->destroy = e_table_model_destroy;
@@ -162,6 +187,22 @@ e_table_model_class_init (GtkObjectClass *object_class)
 				GTK_TYPE_NONE, 1, GTK_TYPE_INT);
 
 	gtk_object_class_add_signals (object_class, e_table_model_signals, LAST_SIGNAL);
+
+	klass->column_count = NULL;     
+	klass->row_count = NULL;        
+	klass->value_at = NULL;         
+	klass->set_value_at = NULL;     
+	klass->is_cell_editable = NULL; 
+	klass->duplicate_value = NULL;  
+	klass->free_value = NULL;       
+	klass->initialize_value = NULL; 
+	klass->value_is_empty = NULL;   
+	klass->thaw = NULL;             
+	klass->model_changed = NULL;    
+	klass->model_row_changed = NULL;
+	klass->model_cell_changed = NULL;
+	klass->model_row_inserted = NULL;
+	klass->model_row_deleted = NULL;
 }
 
 
diff --git a/widgets/table/e-table-model.h b/widgets/table/e-table-model.h
index e542754f22..0c8d51b882 100644
--- a/widgets/table/e-table-model.h
+++ b/widgets/table/e-table-model.h
@@ -28,8 +28,14 @@ typedef struct {
 	void        (*set_value_at)     (ETableModel *etm, int col, int row, const void *value);
 	gboolean    (*is_cell_editable) (ETableModel *etm, int col, int row);
 
-	void       *(*duplicate_value)   (ETableModel *etm, int col, const void *value);
-	void        (*free_value)        (ETableModel *etm, int col, void *value);
+	/* Allocate a copy of the given value. */
+	void       *(*duplicate_value)  (ETableModel *etm, int col, const void *value);
+	/* Free an allocated value. */
+	void        (*free_value)       (ETableModel *etm, int col, void *value);
+	/* Return an allocated empty value. */
+	void	   *(*initialize_value) (ETableModel *etm, int col);
+	/* Return TRUE if value is equivalent to an empty cell. */
+	gboolean    (*value_is_empty)   (ETableModel *etm, int col, const void *value);
 	
 	void        (*thaw)             (ETableModel *etm);
 	/*
@@ -62,6 +68,8 @@ gboolean    e_table_model_is_cell_editable (ETableModel *e_table_model, int col,
 
 void       *e_table_model_duplicate_value  (ETableModel *e_table_model, int col, const void *value);
 void        e_table_model_free_value       (ETableModel *e_table_model, int col, void *value);
+void       *e_table_model_initialize_value (ETableModel *e_table_model, int col);
+gboolean    e_table_model_value_is_empty   (ETableModel *e_table_model, int col, const void *value);
 
 void        e_table_model_freeze           (ETableModel *e_table_model);
 void        e_table_model_thaw             (ETableModel *e_table_model);
diff --git a/widgets/table/e-table-simple.c b/widgets/table/e-table-simple.c
index e8c4d1debb..7e0135b21e 100644
--- a/widgets/table/e-table-simple.c
+++ b/widgets/table/e-table-simple.c
@@ -18,63 +18,103 @@
 static int
 simple_column_count (ETableModel *etm)
 {
-	ETableSimple *simple = (ETableSimple *)etm;
+	ETableSimple *simple = E_TABLE_SIMPLE(etm);
 
-	return simple->col_count (etm, simple->data);
+	if (simple->col_count)
+		return simple->col_count (etm, simple->data);
+	else
+		return 0;
 }
 
 static int
 simple_row_count (ETableModel *etm)
 {
-	ETableSimple *simple = (ETableSimple *)etm;
+	ETableSimple *simple = E_TABLE_SIMPLE(etm);
 
-	return simple->row_count (etm, simple->data);
+	if (simple->row_count)
+		return simple->row_count (etm, simple->data);
+	else
+		return 0;
 }
 
 static void *
 simple_value_at (ETableModel *etm, int col, int row)
 {
-	ETableSimple *simple = (ETableSimple *)etm;
+	ETableSimple *simple = E_TABLE_SIMPLE(etm);
 
-	return simple->value_at (etm, col, row, simple->data);
+	if (simple->value_at)
+		return simple->value_at (etm, col, row, simple->data);
+	else
+		return NULL;
 }
 
 static void
 simple_set_value_at (ETableModel *etm, int col, int row, const void *val)
 {
-	ETableSimple *simple = (ETableSimple *)etm;
+	ETableSimple *simple = E_TABLE_SIMPLE(etm);
 
-	simple->set_value_at (etm, col, row, val, simple->data);
+	if (simple->set_value_at)
+		simple->set_value_at (etm, col, row, val, simple->data);
 }
 
 static gboolean
 simple_is_cell_editable (ETableModel *etm, int col, int row)
 {
-	ETableSimple *simple = (ETableSimple *)etm;
+	ETableSimple *simple = E_TABLE_SIMPLE(etm);
 
-	return simple->is_cell_editable (etm, col, row, simple->data);
+	if (simple->is_cell_editable)
+		return simple->is_cell_editable (etm, col, row, simple->data);
+	else
+		return FALSE;
 }
 
+/* The default for simple_duplicate_value is to return the raw value. */
 static void *
 simple_duplicate_value (ETableModel *etm, int col, const void *value)
 {
-	ETableSimple *simple = (ETableSimple *)etm;
+	ETableSimple *simple = E_TABLE_SIMPLE(etm);
 
-	return simple->duplicate_value (etm, col, value, simple->data);
+	if (simple->duplicate_value)
+		return simple->duplicate_value (etm, col, value, simple->data);
+	else
+		return (void *)value;
 }
 
 static void
 simple_free_value (ETableModel *etm, int col, void *value)
 {
-	ETableSimple *simple = (ETableSimple *)etm;
+	ETableSimple *simple = E_TABLE_SIMPLE(etm);
 
-	simple->free_value (etm, col, value, simple->data);
+	if (simple->free_value)
+		simple->free_value (etm, col, value, simple->data);
+}
+
+static void *
+simple_initialize_value (ETableModel *etm, int col)
+{
+	ETableSimple *simple = E_TABLE_SIMPLE(etm);
+	
+	if (simple->initialize_value)
+		return simple->initialize_value (etm, col, simple->data);
+	else
+		return NULL;
+}
+
+static gboolean
+simple_value_is_empty (ETableModel *etm, int col, const void *value)
+{
+	ETableSimple *simple = E_TABLE_SIMPLE(etm);
+	
+	if (simple->value_is_empty)
+		return simple->value_is_empty (etm, col, value, simple->data);
+	else
+		return FALSE;
 }
 
 static void
 simple_thaw (ETableModel *etm)
 {
-	ETableSimple *simple = (ETableSimple *)etm;
+	ETableSimple *simple = E_TABLE_SIMPLE(etm);
 
 	simple->thaw (etm, simple->data);
 }
@@ -91,6 +131,8 @@ e_table_simple_class_init (GtkObjectClass *object_class)
 	model_class->is_cell_editable = simple_is_cell_editable;
 	model_class->duplicate_value = simple_duplicate_value;
 	model_class->free_value = simple_free_value;
+	model_class->initialize_value = simple_initialize_value;
+	model_class->value_is_empty = simple_value_is_empty;
 	model_class->thaw = simple_thaw;
 }
 
@@ -125,6 +167,8 @@ e_table_simple_new (ETableSimpleColumnCountFn col_count,
 		    ETableSimpleIsCellEditableFn is_cell_editable,
 		    ETableSimpleDuplicateValueFn duplicate_value,
 		    ETableSimpleFreeValueFn free_value,
+		    ETableSimpleInitializeValueFn initialize_value,
+		    ETableSimpleValueIsEmptyFn value_is_empty,
 		    ETableSimpleThawFn thaw,
 		    void *data)
 {
@@ -137,9 +181,11 @@ e_table_simple_new (ETableSimpleColumnCountFn col_count,
 	et->value_at = value_at;
 	et->set_value_at = set_value_at;
 	et->is_cell_editable = is_cell_editable;
-	et->thaw = thaw;
 	et->duplicate_value = duplicate_value;
 	et->free_value = free_value;
+	et->initialize_value = initialize_value;
+	et->value_is_empty = value_is_empty;
+	et->thaw = thaw;
 	et->data = data;
 	
 	return (ETableModel *) et;
diff --git a/widgets/table/e-table-simple.h b/widgets/table/e-table-simple.h
index 51134f45aa..ab97452f10 100644
--- a/widgets/table/e-table-simple.h
+++ b/widgets/table/e-table-simple.h
@@ -4,14 +4,22 @@
 
 #include "e-table-model.h"
 
-typedef int         (*ETableSimpleColumnCountFn)    (ETableModel *etm, void *data);
-typedef	int         (*ETableSimpleRowCountFn)       (ETableModel *etm, void *data);
-typedef	void       *(*ETableSimpleValueAtFn)        (ETableModel *etm, int col, int row, void *data);
-typedef	void        (*ETableSimpleSetValueAtFn)     (ETableModel *etm, int col, int row, const void *val, void *data);
-typedef	gboolean    (*ETableSimpleIsCellEditableFn) (ETableModel *etm, int col, int row, void *data);
-typedef	void       *(*ETableSimpleDuplicateValueFn) (ETableModel *etm, int col, const void *val, void *data);
-typedef	void        (*ETableSimpleFreeValueFn)      (ETableModel *etm, int col, void *val, void *data);
-typedef void        (*ETableSimpleThawFn)           (ETableModel *etm, void *data);
+#define E_TABLE_SIMPLE_TYPE        (e_table_simple_get_type ())
+#define E_TABLE_SIMPLE(o)          (GTK_CHECK_CAST ((o), E_TABLE_SIMPLE_TYPE, ETableSimple))
+#define E_TABLE_SIMPLE_CLASS(k)    (GTK_CHECK_CLASS_CAST((k), E_TABLE_SIMPLE_TYPE, ETableSimpleClass))
+#define E_IS_TABLE_SIMPLE(o)       (GTK_CHECK_TYPE ((o), E_TABLE_SIMPLE_TYPE))
+#define E_IS_TABLE_SIMPLE_CLASS(k) (GTK_CHECK_CLASS_TYPE ((k), E_TABLE_SIMPLE_TYPE))
+
+typedef int         (*ETableSimpleColumnCountFn)     (ETableModel *etm, void *data);
+typedef	int         (*ETableSimpleRowCountFn)        (ETableModel *etm, void *data);
+typedef	void       *(*ETableSimpleValueAtFn)         (ETableModel *etm, int col, int row, void *data);
+typedef	void        (*ETableSimpleSetValueAtFn)      (ETableModel *etm, int col, int row, const void *val, void *data);
+typedef	gboolean    (*ETableSimpleIsCellEditableFn)  (ETableModel *etm, int col, int row, void *data);
+typedef	void       *(*ETableSimpleDuplicateValueFn)  (ETableModel *etm, int col, const void *val, void *data);
+typedef	void        (*ETableSimpleFreeValueFn)       (ETableModel *etm, int col, void *val, void *data);
+typedef void       *(*ETableSimpleInitializeValueFn) (ETableModel *etm, int col, void *data);
+typedef gboolean    (*ETableSimpleValueIsEmptyFn)    (ETableModel *etm, int col, const void *val, void *data);
+typedef void        (*ETableSimpleThawFn)            (ETableModel *etm, void *data);
 
 typedef struct {
 	ETableModel parent;
@@ -23,6 +31,8 @@ typedef struct {
 	ETableSimpleIsCellEditableFn is_cell_editable;
 	ETableSimpleDuplicateValueFn duplicate_value;
 	ETableSimpleFreeValueFn      free_value;
+	ETableSimpleInitializeValueFn initialize_value;
+	ETableSimpleValueIsEmptyFn value_is_empty;
 	ETableSimpleThawFn           thaw;
 	void *data;
 } ETableSimple;
@@ -40,6 +50,8 @@ ETableModel *e_table_simple_new (ETableSimpleColumnCountFn col_count,
 				 ETableSimpleIsCellEditableFn is_cell_editable,
 				 ETableSimpleDuplicateValueFn duplicate_value,
 				 ETableSimpleFreeValueFn free_value,
+				 ETableSimpleInitializeValueFn initialize_value,
+				 ETableSimpleValueIsEmptyFn value_is_empty,
 				 ETableSimpleThawFn thaw,
 				 void *data);
 
diff --git a/widgets/table/e-table-size-test.c b/widgets/table/e-table-size-test.c
index d12a57fbbb..058429ca64 100644
--- a/widgets/table/e-table-size-test.c
+++ b/widgets/table/e-table-size-test.c
@@ -157,6 +157,20 @@ my_free_value (ETableModel *etc, int col, void *value, void *data)
 	g_free (value);
 }
 
+/* This function creates an empty value. */
+static void *
+my_initialize_value (ETableModel *etc, int col, void *data)
+{
+	return g_strdup ("");
+}
+
+/* This function reports if a value is empty. */
+static gboolean
+my_value_is_empty (ETableModel *etc, int col, const void *value, void *data)
+{
+	return !(value && *(char *)value);
+}
+
 /* This function is for when the model is unfrozen.  This can mostly
    be ignored for simple models.  */
 static void
@@ -179,7 +193,9 @@ create_table (void)
 	e_table_model = e_table_simple_new (
 					    my_col_count, my_row_count, my_value_at,
 					    my_set_value_at, my_is_cell_editable,
-					    my_duplicate_value, my_free_value, my_thaw, NULL);
+					    my_duplicate_value, my_free_value,
+					    my_initialize_value, my_value_is_empty,
+					    my_thaw, NULL);
 	/*
 	 * Next we create a header.  The ETableHeader is used in two
 	 * different way.  The first is the full_header.  This is the
diff --git a/widgets/table/e-table-subset.c b/widgets/table/e-table-subset.c
index b0c5671b65..a0add3b954 100644
--- a/widgets/table/e-table-subset.c
+++ b/widgets/table/e-table-subset.c
@@ -98,6 +98,22 @@ etss_free_value (ETableModel *etm, int col, void *value)
 	e_table_model_free_value (etss->source, col, value);
 }
 
+static void *
+etss_initialize_value (ETableModel *etm, int col)
+{
+	ETableSubset *etss = (ETableSubset *)etm;
+
+	return e_table_model_initialize_value (etss->source, col);
+}
+
+static gboolean
+etss_value_is_empty (ETableModel *etm, int col, const void *value)
+{
+	ETableSubset *etss = (ETableSubset *)etm;
+
+	return e_table_model_value_is_empty (etss->source, col, value);
+}
+
 static void
 etss_thaw (ETableModel *etm)
 {
@@ -120,6 +136,8 @@ etss_class_init (GtkObjectClass *klass)
 	table_class->is_cell_editable = etss_is_cell_editable;
 	table_class->duplicate_value  = etss_duplicate_value;
 	table_class->free_value       = etss_free_value;
+	table_class->initialize_value = etss_initialize_value;
+	table_class->value_is_empty   = etss_value_is_empty;
 	table_class->thaw             = etss_thaw;
 }
 
diff --git a/widgets/table/test-check.c b/widgets/table/test-check.c
index 3a32098245..300ebf7a7e 100644
--- a/widgets/table/test-check.c
+++ b/widgets/table/test-check.c
@@ -1,3 +1,4 @@
+/* -*- Mode: C; tab-width: 8; indent-tabs-mode: t; c-basic-offset: 8 -*- */
 /*
  * Test code for the ETable package
  *
@@ -66,7 +67,7 @@ set_value_at (ETableModel *etc, int col, int row, const void *val, void *data)
 	g_assert (col < 2);
 	g_assert (row < LINES);
 
-	if (col == 0){
+	if (col == 0) {
 		my_table [row].value = GPOINTER_TO_INT (val);
 		printf ("Value at %d,%d set to %d\n", col, row, GPOINTER_TO_INT (val));
 	} else {
@@ -84,19 +85,37 @@ is_cell_editable (ETableModel *etc, int col, int row, void *data)
 static void *
 duplicate_value (ETableModel *etc, int col, const void *value, void *data)
 {
-  if (col == 0){
-    return (void *) value;
-  } else {
-    return g_strdup (value);
-  }
+	if (col == 0) {
+		return (void *) value;
+	} else {
+		return g_strdup (value);
+	}
 }
 
 static void
 free_value (ETableModel *etc, int col, void *value, void *data)
 {
-  if (col != 0){
-    g_free (value);
-  }
+	if (col != 0) {
+		g_free (value);
+	}
+}
+
+static void *
+initialize_value (ETableModel *etc, int col, void *data)
+{
+	if (col == 0)
+		return NULL;
+	else
+		return g_strdup ("");
+}
+
+static gboolean
+value_is_empty (ETableModel *etc, int col, const void *value, void *data)
+{
+	if (col == 0)
+		return value == NULL;
+	else
+		return !(value && *(char *)value);
 }
 
 static void
@@ -128,7 +147,9 @@ check_test (void)
 	e_table_model = e_table_simple_new (
 		col_count, row_count, value_at,
 		set_value_at, is_cell_editable, 
-		duplicate_value, free_value, thaw, NULL);
+		duplicate_value, free_value, 
+		initialize_value, value_is_empty,
+		thaw, NULL);
 
 	/*
 	 * Header
diff --git a/widgets/table/test-cols.c b/widgets/table/test-cols.c
index 6756511fb4..e34e477dae 100644
--- a/widgets/table/test-cols.c
+++ b/widgets/table/test-cols.c
@@ -1,3 +1,4 @@
+/* -*- Mode: C; tab-width: 8; indent-tabs-mode: t; c-basic-offset: 8 -*- */
 /*
  * Test code for the ETable package
  *
@@ -84,19 +85,37 @@ is_cell_editable (ETableModel *etc, int col, int row, void *data)
 static void *
 duplicate_value (ETableModel *etc, int col, const void *value, void *data)
 {
-  if (col == 0){
-    return (void *)value;
-  } else {
-    return g_strdup (value);
-  }
+	if (col == 0){
+		return (void *)value;
+	} else {
+		return g_strdup (value);
+	}
 }
 
 static void
 free_value (ETableModel *etc, int col, void *value, void *data)
 {
-  if (col != 0){
-    g_free (value);
-  }
+	if (col != 0){
+		g_free (value);
+	}
+}
+
+static void *
+initialize_value (ETableModel *etc, int col, void *data)
+{
+	if (col == 0)
+		return NULL;
+	else
+		return g_strdup ("");
+}
+
+static gboolean
+value_is_empty (ETableModel *etc, int col, const void *value, void *data)
+{
+	if (col == 0)
+		return value == NULL;
+	else
+		return !(value && *(char *)value);
 }
 
 static void
@@ -128,6 +147,7 @@ multi_cols_test (void)
 		col_count, row_count, value_at,
 		set_value_at, is_cell_editable,
 		duplicate_value, free_value,
+		initialize_value, value_is_empty,
 		thaw, NULL);
 
 	/*
diff --git a/widgets/table/test-table.c b/widgets/table/test-table.c
index a882b8dbdf..724090d904 100644
--- a/widgets/table/test-table.c
+++ b/widgets/table/test-table.c
@@ -190,6 +190,18 @@ free_value (ETableModel *etc, int col, void *value, void *data)
 	g_free (value);
 }
 
+static void *
+initialize_value (ETableModel *etc, int col, void *data)
+{
+	return g_strdup ("");
+}
+
+static gboolean
+value_is_empty (ETableModel *etc, int col, const void *value, void *data)
+{
+	return !(value && *(char *)value);
+}
+
 static void
 thaw (ETableModel *etc, void *data)
 {
@@ -220,7 +232,9 @@ table_browser_test (void)
 	e_table_model = e_table_simple_new (
 		col_count, row_count, value_at,
 		set_value_at, is_cell_editable,
-		duplicate_value, free_value, thaw, NULL);
+		duplicate_value, free_value,
+		initialize_value, value_is_empty,
+		thaw, NULL);
 
 	/*
 	 * Header
@@ -315,7 +329,8 @@ do_e_table_demo (const char *spec)
 		e_table_model = 
 			e_table_simple_new (col_count, row_count, value_at,
 					    set_value_at, is_cell_editable,
-					    duplicate_value, free_value, 
+					    duplicate_value, free_value,
+					    initialize_value, value_is_empty,
 					    thaw, NULL);
 
 	full_header = e_table_header_new ();