[mutter/wip/ui-on-own-connection: 6/13] errors: Copy error trap code from GDK into mutter

[Jasper St. Pierre <jstpierre src gnome org>]

commit cc6becb163f87cf676465a4e564cda7af3ba4c3a
Author: Jasper St. Pierre <jstpierre mecheye net>
Date:   Sun Apr 6 15:51:11 2014 -0400

    errors: Copy error trap code from GDK into mutter
    
    In order to kill off using GDK for event handling in X11, we're going
    to need to stop using GDK primitives.

 src/core/display-private.h |    2 +
 src/core/errors.c          |  263 ++++++++++++++++++++++++++++++++++++++++----
 2 files changed, 241 insertions(+), 24 deletions(-)
---
diff --git a/src/core/display-private.h b/src/core/display-private.h
index 84ee5a8..26b83a0 100644
--- a/src/core/display-private.h
+++ b/src/core/display-private.h
@@ -253,6 +253,8 @@ struct _MetaDisplay
   /* Closing down the display */
   int closing;
 
+  GSList *error_traps;
+
   /* Managed by group.c */
   GHashTable *groups_by_leader;
 
diff --git a/src/core/errors.c b/src/core/errors.c
index f199c69..2e855f2 100644
--- a/src/core/errors.c
+++ b/src/core/errors.c
@@ -1,9 +1,8 @@
 /* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*- */
 
-/* 
- * Copyright (C) 2001 Havoc Pennington, error trapping inspired by GDK
- * code copyrighted by the GTK team.
- * 
+/*
+ * Copyright (C) 2014 Red Hat
+ *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License as
  * published by the Free Software Foundation; either version 2 of the
@@ -13,9 +12,11 @@
  * WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * General Public License for more details.
- * 
+ *
  * You should have received a copy of the GNU General Public License
- * along with this program; if not, see <http://www.gnu.org/licenses/>.
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+ * 02111-1307, USA.
  */
 
 /**
@@ -27,36 +28,250 @@
 #include <config.h>
 #include <meta/errors.h>
 #include "display-private.h"
-#include <errno.h>
-#include <stdlib.h>
-#include <gdk/gdk.h>
-
-/* In GTK+-3.0, the error trapping code was significantly rewritten. The new code
- * has some neat features (like knowing automatically if a sync is needed or not
- * and handling errors asynchronously when the error code isn't needed immediately),
- * but it's basically incompatible with the hacks we played with GTK+-2.0 to
- * use a custom error handler along with gdk_error_trap_push().
- *
- * Since the main point of our custom error trap was to get the error logged
- * to the right place, with GTK+-3.0 we simply omit our own error handler and
- * use the GTK+ handling straight-up.
- * (See https://bugzilla.gnome.org/show_bug.cgi?id=630216 for restoring logging.)
- */
+
+/* This is a copy-paste of the error handling code in GDK, modified
+ * so that it works with mutter's internal structures, since we don't
+ * have a GDK display open. */
+
+/* compare X sequence numbers handling wraparound */
+#define SEQUENCE_COMPARE(a,op,b) (((long) (a) - (long) (b)) op 0)
+
+typedef struct _GdkErrorTrap  GdkErrorTrap;
+
+struct _GdkErrorTrap
+{
+  /* Next sequence when trap was pushed, i.e. first sequence to
+   * ignore
+   */
+  gulong start_sequence;
+
+  /* Next sequence when trap was popped, i.e. first sequence
+   * to not ignore. 0 if trap is still active.
+   */
+  gulong end_sequence;
+
+  /* Most recent error code within the sequence */
+  int error_code;
+};
+
+/* delivers an error event from the error handler in gdkmain-x11.c */
+static void
+meta_display_error_event (MetaDisplay *display,
+                          XErrorEvent *error)
+{
+  GSList *tmp_list;
+  gboolean ignore;
+
+  ignore = FALSE;
+  for (tmp_list = display->error_traps;
+       tmp_list != NULL;
+       tmp_list = tmp_list->next)
+    {
+      GdkErrorTrap *trap;
+
+      trap = tmp_list->data;
+
+      if (SEQUENCE_COMPARE (trap->start_sequence, <=, error->serial) &&
+          (trap->end_sequence == 0 ||
+           SEQUENCE_COMPARE (trap->end_sequence, >, error->serial)))
+        {
+          ignore = TRUE;
+          trap->error_code = error->error_code;
+          break; /* only innermost trap gets the error code */
+        }
+    }
+
+  if (!ignore)
+    {
+      gchar buf[64];
+      gchar *msg;
+
+      XGetErrorText (display->xdisplay, error->error_code, buf, 63);
+
+      msg =
+        g_strdup_printf ("mutter received an X Window System error: %s\n"
+                         "  (Details: serial %ld error_code %d request_code %d minor_code %d)\n",
+                         buf,
+                         error->serial,
+                         error->error_code,
+                         error->request_code,
+                         error->minor_code);
+
+      g_error ("%s", msg);
+    }
+}
+
+static int
+gdk_x_error (Display    *xdisplay,
+             XErrorEvent *error)
+{
+  MetaDisplay *display = meta_display_for_x_display (xdisplay);
+  meta_display_error_event (display, error);
+  return 0;
+}
+
+/* non-GDK previous error handler */
+typedef int (*GdkXErrorHandler) (Display *, XErrorEvent *);
+static GdkXErrorHandler _gdk_old_error_handler;
+/* number of times we've pushed the GDK error handler */
+static int _gdk_error_handler_push_count = 0;
+
+static void
+_gdk_x11_error_handler_push (void)
+{
+  GdkXErrorHandler previous;
+
+  previous = XSetErrorHandler (gdk_x_error);
+
+  if (_gdk_error_handler_push_count > 0)
+    {
+      if (previous != gdk_x_error)
+        g_warning ("XSetErrorHandler() called with a GDK error trap pushed. Don't do that.");
+    }
+  else
+    {
+      _gdk_old_error_handler = previous;
+    }
+
+  _gdk_error_handler_push_count += 1;
+}
+
+static void
+_gdk_x11_error_handler_pop  (void)
+{
+  g_return_if_fail (_gdk_error_handler_push_count > 0);
+
+  _gdk_error_handler_push_count -= 1;
+
+  if (_gdk_error_handler_push_count == 0)
+    {
+      XSetErrorHandler (_gdk_old_error_handler);
+      _gdk_old_error_handler = NULL;
+    }
+}
+
+static void
+delete_outdated_error_traps (MetaDisplay *display)
+{
+  GSList *tmp_list;
+  gulong processed_sequence;
+
+  processed_sequence = XLastKnownRequestProcessed (display->xdisplay);
+
+  tmp_list = display->error_traps;
+  while (tmp_list != NULL)
+    {
+      GdkErrorTrap *trap = tmp_list->data;
+
+      if (trap->end_sequence != 0 &&
+          SEQUENCE_COMPARE (trap->end_sequence, <=, processed_sequence))
+        {
+          GSList *free_me = tmp_list;
+
+          tmp_list = tmp_list->next;
+          display->error_traps = g_slist_delete_link (display->error_traps, free_me);
+          g_slice_free (GdkErrorTrap, trap);
+        }
+      else
+        {
+          tmp_list = tmp_list->next;
+        }
+    }
+}
 
 void
 meta_error_trap_push (MetaDisplay *display)
 {
-  gdk_error_trap_push ();
+  GdkErrorTrap *trap;
+
+  delete_outdated_error_traps (display);
+
+  /* set up the Xlib callback to tell us about errors */
+  _gdk_x11_error_handler_push ();
+
+  trap = g_slice_new0 (GdkErrorTrap);
+
+  trap->start_sequence = XNextRequest (display->xdisplay);
+  trap->error_code = Success;
+
+  display->error_traps =
+    g_slist_prepend (display->error_traps, trap);
+}
+
+static gint
+meta_error_trap_pop_internal (MetaDisplay *display,
+                              gboolean     need_code)
+{
+  GdkErrorTrap *trap;
+  GSList *tmp_list;
+  int result;
+
+  g_return_val_if_fail (display->error_traps != NULL, Success);
+
+  /* Find the first trap that hasn't been popped already */
+  trap = NULL; /* quiet gcc */
+  for (tmp_list = display->error_traps;
+       tmp_list != NULL;
+       tmp_list = tmp_list->next)
+    {
+      trap = tmp_list->data;
+
+      if (trap->end_sequence == 0)
+        break;
+    }
+
+  g_return_val_if_fail (trap != NULL, Success);
+  g_assert (trap->end_sequence == 0);
+
+  /* May need to sync to fill in trap->error_code if we care about
+   * getting an error code.
+   */
+  if (need_code)
+    {
+      gulong processed_sequence;
+      gulong next_sequence;
+
+      next_sequence = XNextRequest (display->xdisplay);
+      processed_sequence = XLastKnownRequestProcessed (display->xdisplay);
+
+      /* If our last request was already processed, there is no point
+       * in syncing. i.e. if last request was a round trip (or even if
+       * we got an event with the serial of a non-round-trip)
+       */
+      if ((next_sequence - 1) != processed_sequence)
+        {
+          XSync (display->xdisplay, False);
+        }
+
+      result = trap->error_code;
+    }
+  else
+    {
+      result = Success;
+    }
+
+  /* record end of trap, giving us a range of
+   * error sequences we'll ignore.
+   */
+  trap->end_sequence = XNextRequest (display->xdisplay);
+
+  /* remove the Xlib callback */
+  _gdk_x11_error_handler_pop ();
+
+  /* we may already be outdated */
+  delete_outdated_error_traps (display);
+
+  return result;
 }
 
 void
 meta_error_trap_pop (MetaDisplay *display)
 {
-  gdk_error_trap_pop_ignored ();
+  meta_error_trap_pop_internal (display, FALSE);
 }
 
 int
 meta_error_trap_pop_with_return  (MetaDisplay *display)
 {
-  return gdk_error_trap_pop ();
+  return meta_error_trap_pop_internal (display, TRUE);
 }