(destroy_all_children): New arg first_child_to_destroy.

(make_menu_in_widget): New arg keep_first_children.
(xm_update_menu): Preserve the first children even if later ones
have a structural change.
(update_one_menu_entry): Use this_one_change field.

1 files changed, 88 insertions, 41 deletions

diff --git a/lwlib/lwlib-Xm.c b/lwlib/lwlib-Xm.c
index 26ac76fad9e..72700641d2d 100644
--- a/lwlib/lwlib-Xm.c
+++ b/lwlib/lwlib-Xm.c
@@ -147,9 +147,13 @@ resource_motif_string (widget, name)
   return result;
 }
 
+/* Destroy all of the children of WIDGET
+   starting with number FIRST_CHILD_TO_DESTROY.  */
+
 static void
-destroy_all_children (widget)
+destroy_all_children (widget, first_child_to_destroy)
      Widget widget;
+     int first_child_to_destroy;
 {
   Widget* children;
   unsigned int number;
@@ -158,17 +162,14 @@ destroy_all_children (widget)
   children = XtCompositeChildren (widget, &number);
   if (children)
     {
+      XtUnmanageChildren (children + first_child_to_destroy,
+			  number - first_child_to_destroy);
+
       /* Unmanage all children and destroy them.  They will only be 
-       * really destroyed when we get out of DispatchEvent. */
-      for (i = 0; i < number; i++)
-	{
-	  Widget child = children [i];
-	  if (!child->core.being_destroyed)
-	    {
-	      XtUnmanageChild (child);
-	      XtDestroyWidget (child);
-	    }
-	}
+	 really destroyed when we get out of DispatchEvent.  */
+      for (i = first_child_to_destroy; i < number; i++)
+	XtDestroyWidget (children[i]);
+
       XtFree ((char *) children);
     }
 }
@@ -337,11 +338,14 @@ all_dashes_p (s)
   return True;
 }
 
+/* KEEP_FIRST_CHILDREN gives the number of initial children to keep.  */
+
 static void
-make_menu_in_widget (instance, widget, val)
+make_menu_in_widget (instance, widget, val, keep_first_children)
      widget_instance* instance;
      Widget widget;
      widget_value* val;
+     int keep_first_children;
 {
   Widget* children = 0;
   int num_children;
@@ -353,6 +357,11 @@ make_menu_in_widget (instance, widget, val)
   int ac;
   Boolean menubar_p;
 
+  Widget* old_children;
+  unsigned int old_num_children;
+
+  old_children = XtCompositeChildren (widget, &old_num_children);
+
   /* Allocate the children array */
   for (num_children = 0, cur = val; cur; num_children++, cur = cur->next);
   children = (Widget*)XtMalloc (num_children * sizeof (Widget));
@@ -368,7 +377,18 @@ make_menu_in_widget (instance, widget, val)
     XtAddCallback (XtParent (widget), XmNpopdownCallback,
 		   xm_pop_down_callback, (XtPointer)instance);
 
-  for (child_index = 0, cur = val; cur; child_index++, cur = cur->next)
+  /* Preserve the first KEEP_FIRST_CHILDREN old children.  */
+  for (child_index = 0, cur = val; child_index < keep_first_children;
+       child_index++, cur = cur->next)
+    children[child_index] = old_children[child_index];
+
+  /* Check that those are all we have
+     (the caller should have deleted the rest).  */
+  if (old_num_children != keep_first_children)
+    abort ();
+
+  /* Create the rest.  */
+  for (child_index = keep_first_children; cur; child_index++, cur = cur->next)
     {    
       ac = 0;
       XtSetArg (al [ac], XmNsensitive, cur->enabled); ac++;
@@ -405,7 +425,7 @@ make_menu_in_widget (instance, widget, val)
       else
 	{
 	  menu = XmCreatePulldownMenu (widget, cur->name, NULL, 0);
-	  make_menu_in_widget (instance, menu, cur->contents);
+	  make_menu_in_widget (instance, menu, cur->contents, 0);
 	  XtSetArg (al [ac], XmNsubMenuId, menu); ac++;
 	  button = XmCreateCascadeButton (widget, cur->name, al, ac);
 
@@ -430,6 +450,8 @@ make_menu_in_widget (instance, widget, val)
     }
 
   XtFree ((char *) children);
+  if (old_children)
+    XtFree ((char *) old_children);
 }
 
 static void
@@ -444,7 +466,7 @@ update_one_menu_entry (instance, widget, val, deep_p)
   Widget menu;
   widget_value* contents;
 
-  if (val->change == NO_CHANGE)
+  if (val->this_one_change == NO_CHANGE)
     return;
 
   /* update the sensitivity and userdata */
@@ -455,7 +477,7 @@ update_one_menu_entry (instance, widget, val, deep_p)
 		 0);
 
   /* update the menu button as a label. */
-  if (val->change >= VISIBLE_CHANGE)
+  if (val->this_one_change >= VISIBLE_CHANGE)
     xm_update_label (instance, widget, val);
 
   /* update the pulldown/pullaside as needed */
@@ -471,7 +493,7 @@ update_one_menu_entry (instance, widget, val, deep_p)
       if (contents)
 	{
 	  menu = XmCreatePulldownMenu (XtParent (widget), XtName (widget), NULL, 0);
-	  make_menu_in_widget (instance, menu, contents);
+	  make_menu_in_widget (instance, menu, contents, 0);
 	  ac = 0;
 	  XtSetArg (al [ac], XmNsubMenuId, menu); ac++;
 	  XtSetValues (widget, al, ac);
@@ -495,39 +517,64 @@ xm_update_menu (instance, widget, val, deep_p)
      widget_value* val;
      Boolean deep_p;
 {
+  Widget* children;
+  unsigned int num_children;
+  int num_children_to_keep = 0;
+  int i;
+  widget_value* cur;
+
+  children = XtCompositeChildren (widget, &num_children);
+
   /* Widget is a RowColumn widget whose contents have to be updated
    * to reflect the list of items in val->contents */
-  if (val->contents->change == STRUCTURAL_CHANGE)
-    {
-      destroy_all_children (widget);
-      make_menu_in_widget (instance, widget, val->contents);
-    }
-  else
-    {
-      /* Update all the buttons of the RowColumn in order. */
-      Widget* children;
-      unsigned int num_children;
-      int i;
-      widget_value* cur;
 
-      children = XtCompositeChildren (widget, &num_children);
+  /* See how many buttons we can keep, and how many we
+     must completely replace.  */
+  if (val->contents == 0)
+    num_children_to_keep = 0;
+  else if (val->contents->change == STRUCTURAL_CHANGE)
+    {
       if (children)
 	{
-	  for (i = 0, cur = val->contents; i < num_children; i++)
+	  for (i = 0, cur = val->contents; i < num_children;
+	       i++, cur = cur->next)
 	    {
-	      if (!cur)
-		abort ();
-	      if (children [i]->core.being_destroyed
-		  || strcmp (XtName (children [i]), cur->name))
-		continue;
-	      update_one_menu_entry (instance, children [i], cur, deep_p);
-	      cur = cur->next;
+	      if (cur->this_one_change == STRUCTURAL_CHANGE)
+		break;
 	    }
-	  XtFree ((char *) children);
+
+	  num_children_to_keep = i;
+	}
+    }
+  else
+    num_children_to_keep = num_children;
+
+  /* Update all the buttons of the RowColumn, in order,
+     except for those we are going to replace entirely.  */
+  if (children)
+    {
+      for (i = 0, cur = val->contents; i < num_children_to_keep; i++)
+	{
+	  if (!cur)
+	    abort ();
+	  if (children [i]->core.being_destroyed
+	      || strcmp (XtName (children [i]), cur->name))
+	    continue;
+	  update_one_menu_entry (instance, children [i], cur, deep_p);
+	  cur = cur->next;
 	}
-      if (cur)
-	abort ();
     }
+
+  /* Now replace from scratch all the buttons after the last
+     place that the top-level structure changed.  */
+  if (val->contents->change == STRUCTURAL_CHANGE)
+    {
+      destroy_all_children (widget, num_children_to_keep);
+      make_menu_in_widget (instance, widget, val->contents,
+			   num_children_to_keep);
+    }
+
+  XtFree ((char *) children);
 }