From c46b9f0eefbaa1e586af56762ec35700df641002 Mon Sep 17 00:00:00 2001
From: Karl Tomlinson <karlt+@karlt.net>
Date: Fri, 25 Mar 2011 16:38:59 +1300
Subject: [PATCH] b=576933 use a separate display to make protocol requests
 within X error handler r=roc

--HG--
extra : transplant_source : %E9%20K%F1d6%08%3D%05%FE%5B%7F%E0%18%EFQ%92%A0%9AM
---
 toolkit/xre/nsX11ErrorHandler.cpp | 52 ++++++++++++++++---------------
 1 file changed, 27 insertions(+), 25 deletions(-)

diff --git a/toolkit/xre/nsX11ErrorHandler.cpp b/toolkit/xre/nsX11ErrorHandler.cpp
index 4bfd81d5c9f..ee806d2eee6 100644
--- a/toolkit/xre/nsX11ErrorHandler.cpp
+++ b/toolkit/xre/nsX11ErrorHandler.cpp
@@ -54,24 +54,15 @@ using mozilla::plugins::PluginProcessChild;
 #define BUFSIZE 2048 // What Xlib uses with XGetErrorDatabaseText
 
 extern "C" {
-static int
-IgnoreError(Display *display, XErrorEvent *event) {
-  return 0; // This return value is ignored.
-}
-
 static int
 X11Error(Display *display, XErrorEvent *event) {
   nsCAutoString notes;
   char buffer[BUFSIZE];
 
   // Get an indication of how long ago the request that caused the error was
-  // made.  Do this before querying extensions etc below.
+  // made.
   unsigned long age = NextRequest(display) - event->serial;
 
-  // Ignore subsequent errors, which may get processed during the extension
-  // queries below for example.
-  XSetErrorHandler(IgnoreError);
-
   // Get a string to represent the request that caused the error.
   nsCAutoString message;
   if (event->request_code < 128) {
@@ -79,22 +70,33 @@ X11Error(Display *display, XErrorEvent *event) {
     message.AppendInt(event->request_code);
   } else {
     // Extension request
-    int nExts;
-    char** extNames = XListExtensions(display, &nExts);
-    if (extNames) {
-      for (int i = 0; i < nExts; ++i) {
-        int major_opcode, first_event, first_error;
-        if (XQueryExtension(display, extNames[i],
-                            &major_opcode, &first_event, &first_error)
-            && major_opcode == event->request_code) {
-          message.Append(extNames[i]);
-          message.Append('.');
-          message.AppendInt(event->minor_code);
-          break;
-        }
-      }
 
-      XFreeExtensionList(extNames);
+    // man XSetErrorHandler says "the error handler should not call any
+    // functions (directly or indirectly) on the display that will generate
+    // protocol requests or that will look for input events" so we use another
+    // temporary Display to request extension information.  This assumes on
+    // the DISPLAY environment variable has been set and matches what was used
+    // to open |display|.
+    Display *tmpDisplay = XOpenDisplay(NULL);
+    if (tmpDisplay) {
+      int nExts;
+      char** extNames = XListExtensions(tmpDisplay, &nExts);
+      if (extNames) {
+        for (int i = 0; i < nExts; ++i) {
+          int major_opcode, first_event, first_error;
+          if (XQueryExtension(tmpDisplay, extNames[i],
+                              &major_opcode, &first_event, &first_error)
+              && major_opcode == event->request_code) {
+            message.Append(extNames[i]);
+            message.Append('.');
+            message.AppendInt(event->minor_code);
+            break;
+          }
+        }
+
+        XFreeExtensionList(extNames);
+      }
+      XCloseDisplay(tmpDisplay);
     }
   }