From 37ac409586f564db0e487f3d5b44b3a612d62438 Mon Sep 17 00:00:00 2001
From: ehofman <ehofman>
Date: Sun, 19 Dec 2004 10:19:14 +0000
Subject: [PATCH] Melchior FRANZ:

fgLoadFlight() loads a property file ("fgfs.sav") to a new property tree,
and then copies that over to the main tree. copyProperties() didn't know
how to handle type SGPropertyNode::ALIAS and hence threw an exception that
made fgfs abort.

The attached patch adds support for ALIAS to copyProperties(): aliased
nodes are created in the target tree if necessary, and then linked like in
the source tree. It seemed useful to add an optional argument to
props.[ch]xx/getType() that would indeed return the property type "ALIAS"
for aliased nodes, and not the type of the node that it refers to. The patch
also fixes a bug in writeNode() that caused extra lines after alias entries.

If there's resistance to the change to getType() (David?) I can easily use
isAlias(). This just makes copyProperties() a tad uglier, but I can live with
it. It's useful for scanning a tree, though, if an alias node can be treated
exactly like all other nodes, without automatic redirection.
---
 simgear/props/props.cxx    |  4 ++--
 simgear/props/props.hxx    |  4 +++-
 simgear/props/props_io.cxx | 11 +++++++++--
 3 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/simgear/props/props.cxx b/simgear/props/props.cxx
index 60a19aa4..50b412cb 100644
--- a/simgear/props/props.cxx
+++ b/simgear/props/props.cxx
@@ -969,9 +969,9 @@ SGPropertyNode::getPath (bool simplify) const
 }
 
 SGPropertyNode::Type
-SGPropertyNode::getType () const
+SGPropertyNode::getType (bool deref_alias) const
 {
-  if (_type == ALIAS)
+  if (_type == ALIAS && deref_alias)
     return _value.alias->getType();
   else
     return _type;
diff --git a/simgear/props/props.hxx b/simgear/props/props.hxx
index a08d6ffa..c800f29d 100644
--- a/simgear/props/props.hxx
+++ b/simgear/props/props.hxx
@@ -850,8 +850,10 @@ public:
 
   /**
    * Get the type of leaf value, if any, for this node.
+   * When applied to an ALIAS node, deref_alias decides if the type
+   * of the referred node is to be returned (default), or ALIAS.
    */
-  Type getType () const;
+  Type getType (bool deref_alias = true) const;
 
 
   /**
diff --git a/simgear/props/props_io.cxx b/simgear/props/props_io.cxx
index e936f5b0..ec549011 100644
--- a/simgear/props/props_io.cxx
+++ b/simgear/props/props_io.cxx
@@ -368,6 +368,7 @@ getTypeName (SGPropertyNode::Type type)
   case SGPropertyNode::STRING:
     return "string";
   case SGPropertyNode::ALIAS:
+    return "alias";
   case SGPropertyNode::NONE:
     return "unspecified";
   }
@@ -483,7 +484,7 @@ writeNode (ostream &output, const SGPropertyNode * node,
   }
 
 				// If there are children, write them next.
-  if (nChildren > 0 || node->isAlias()) {
+  if (nChildren > 0) {
     doIndent(output, indent);
     output << '<' << name;
     writeAtts(output, node);
@@ -550,7 +551,7 @@ copyProperties (const SGPropertyNode *in, SGPropertyNode *out)
 				// First, copy the actual value,
 				// if any.
   if (in->hasValue()) {
-    switch (in->getType()) {
+    switch (in->getType(false)) {
     case SGPropertyNode::BOOL:
       if (!out->setBoolValue(in->getBoolValue()))
 	retval = false;
@@ -579,6 +580,12 @@ copyProperties (const SGPropertyNode *in, SGPropertyNode *out)
       if (!out->setUnspecifiedValue(in->getStringValue()))
 	retval = false;
       break;
+    case SGPropertyNode::ALIAS: {
+      const char *path = in->getAliasTarget()->getPath();
+      SGPropertyNode *node = out->getRootNode()->getNode(path, true);
+      out->alias(node);
+      break;
+    }
     default:
       string message = "Unknown internal SGPropertyNode type";
       message += in->getType();