From fe5c019608f0b0d476877b9159c4e4876d675001 Mon Sep 17 00:00:00 2001
From: Robert Osfield <robert@openscenegraph.com>
Date: Thu, 3 Apr 2008 18:06:09 +0000
Subject: [PATCH] From Colin McDonald, "The X11WindowingSystemInterface in
 osgViewer/GraphicsWindowX11.cpp unconditionally sets the X11 error handler
 routine, replacing anything that was previously set.  This is a bit
 unfriendly, as the X11 error handler is a global attribute which the
 application, or the GUI toolkit being used, may well have set itself.

So I have modified X11WindowingSystemInterface to only replace the error
handler if it is the default i.e. if the application has not set it."
---
 src/osgViewer/GraphicsWindowX11.cpp | 49 +++++++++++++++++++++++++++--
 1 file changed, 46 insertions(+), 3 deletions(-)

diff --git a/src/osgViewer/GraphicsWindowX11.cpp b/src/osgViewer/GraphicsWindowX11.cpp
index 34d462c31..919a43159 100644
--- a/src/osgViewer/GraphicsWindowX11.cpp
+++ b/src/osgViewer/GraphicsWindowX11.cpp
@@ -1427,6 +1427,8 @@ void GraphicsWindowX11::requestWarpPointer(float x,float y)
 extern "C" 
 {
 
+typedef int (*X11ErrorHandler)(Display*, XErrorEvent*);
+
 int X11ErrorHandling(Display* display, XErrorEvent* event)
 {
     osg::notify(osg::NOTICE)<<"Got an X11ErrorHandling call display="<<display<<" event="<<event<<std::endl;
@@ -1543,12 +1545,37 @@ class X11WindowingSystemInterface : public osg::GraphicsContext::WindowingSystem
     }
 #endif
 
+protected:
+    bool _errorHandlerSet;
+    
+
 public:
     X11WindowingSystemInterface()
     {
         osg::notify(osg::INFO)<<"X11WindowingSystemInterface()"<<std::endl;
-    
-        XSetErrorHandler(X11ErrorHandling);
+
+
+        // Install an X11 error handler, if the application has not already done so.
+        
+        // Set default handler, and get pointer to current handler.
+        X11ErrorHandler currentHandler = XSetErrorHandler(NULL);
+        
+        // Set our handler, and get pointer to default handler.
+        X11ErrorHandler defHandler = XSetErrorHandler(X11ErrorHandling);
+
+        if ( currentHandler == defHandler )
+        {
+            // No application error handler, use ours.
+            // osg::notify(osg::INFO)<<"Set osgViewer X11 error handler"<<std::endl;
+            _errorHandlerSet = 1;
+        }
+        else
+        {
+            // Application error handler exists, leave it set.
+            // osg::notify(osg::INFO)<<"Existing application X11 error handler set"<<std::endl;
+            _errorHandlerSet = 0;
+            XSetErrorHandler(currentHandler);
+        }
     
 #if 0
         if (XInitThreads() == 0)
@@ -1572,7 +1599,23 @@ public:
         }
 
         //osg::notify(osg::NOTICE)<<"~X11WindowingSystemInterface()"<<std::endl;
-        XSetErrorHandler(0);
+
+        // Unset our X11 error handler, providing the application has not replaced it.
+
+        if ( _errorHandlerSet )
+        {
+            X11ErrorHandler currentHandler = XSetErrorHandler(NULL);
+            if ( currentHandler = X11ErrorHandling )
+            {
+                // osg::notify(osg::INFO)<<"osgViewer X11 error handler removed"<<std::endl;
+            }
+            else
+            {
+                // Not our error handler, leave it set.
+                // osg::notify(osg::INFO)<<"Application X11 error handler left"<<std::endl;
+                XSetErrorHandler(currentHandler);
+            }
+        }
     }
 
     virtual unsigned int getNumScreens(const osg::GraphicsContext::ScreenIdentifier& si)