More panda3d.exe robustness: make sure contents.xml is fresh if core API fails hash check

direct/src/plugin_standalone/panda3d.cxx

@@ -356,6 +356,7 @@ bool Panda3D::
 get_plugin() {
   // First, look for the existing contents.xml file.
   bool success = false;
+  bool is_fresh = false;
 
   Filename contents_filename = Filename(Filename::from_os_specific(_root_dir), "contents.xml");
   if (_verify_contents != P3D_VC_force) {
@@ -370,6 +371,38 @@ get_plugin() {
   if (!success) {
     // Couldn't read it (or it wasn't current enough), so go get a new
     // one.
+    if (!download_contents_file(contents_filename)) {
+      // We don't have a usable contents.xml file.
+      return false;
+    }
+    is_fresh = true;
+  }
+
+  // Now that we've downloaded the contents file successfully, start
+  // the Core API.
+  if (!get_core_api()) {
+      // We failed.  Make sure contents.xml is up-to-date and try again.
+    if (!is_fresh && download_contents_file(contents_filename) && get_core_api()) {
+      return true;
+    } else {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+////////////////////////////////////////////////////////////////////
+//     Function: Panda3D::download_contents_file
+//       Access: Protected
+//  Description: Redownloads the contents.xml file from the named
+//               URL without first checking if it is up to date.
+//               Returns true if we have a contents.xml file that
+//               might be usable, false otherwise.
+////////////////////////////////////////////////////////////////////
+bool Panda3D::
+download_contents_file(const Filename &contents_filename) {
+  bool success = false;
   HTTPClient *http = HTTPClient::get_global_ptr();
 
   // Try the super_mirror first.
@@ -433,13 +466,6 @@ get_plugin() {
 
     tempfile.unlink();
   }
-  }
-
-  if (success) {
-    // Now that we've downloaded the contents file successfully, start
-    // the Core API.
-    success = get_core_api();
-  }
 
   return success;
 }
@@ -835,7 +861,6 @@ download_core_api() {
   }
 
   if (!success) {
-    cerr << "Couldn't download core API.\n";
     return false;
   }
 

direct/src/plugin_standalone/panda3d.h

@@ -42,6 +42,7 @@ public:
 protected:
   bool post_arg_processing();
   bool get_plugin();
+  bool download_contents_file(const Filename &contents_filename);
   bool read_contents_file(const Filename &contents_filename, bool fresh_download);
   void find_host(TiXmlElement *xcontents);
   void read_xhost(TiXmlElement *xhost);