gfx/src/X11Util.h
author Benoit Jacob <bjacob@mozilla.com>
Mon, 06 Dec 2010 06:34:34 -0500
changeset 58663 056814244cebfe62d9a2dfd20e4d0160b04b1e7a
parent 46351 6a6fbf66e1e01b945cfa1b59d2a9e7717504b8b1
child 58728 686e646d23004d082909149f04b4aa0cd35b9200
permissions -rw-r--r--
Bug 613079 - WebGL crash [@mozilla::gl::GLContextProviderGLX::CreateOffscreen] - r=mattwoodrow, a=blocking-betaN

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
 * vim: sw=2 ts=8 et :
 */
/* ***** BEGIN LICENSE BLOCK *****
 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at:
 * http://www.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is Mozilla Code.
 *
 * The Initial Developer of the Original Code is
 *   The Mozilla Foundation
 * Portions created by the Initial Developer are Copyright (C) 2010
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *
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 * either the GNU General Public License Version 2 or later (the "GPL"), or
 * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 * in which case the provisions of the GPL or the LGPL are applicable instead
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#ifndef mozilla_X11Util_h
#define mozilla_X11Util_h

// Utilities common to all X clients, regardless of UI toolkit.

#if defined(MOZ_WIDGET_GTK2)
#  include <gdk/gdkx.h>
#elif defined(MOZ_WIDGET_QT)
// X11/X.h has #define CursorShape 0, but Qt's qnamespace.h defines
//   enum CursorShape { ... }.  Good times!
#undef CursorShape
#  include <QX11Info>
#  include <X11/Xlib.h>
#else
#  error Unknown toolkit
#endif 

#include "nsDebug.h"

namespace mozilla {

/**
 * Return the default X Display created and used by the UI toolkit.
 */
inline Display*
DefaultXDisplay()
{
#if defined(MOZ_WIDGET_GTK2)
  return GDK_DISPLAY();
#elif defined(MOZ_WIDGET_QT)
  return QX11Info::display();
#endif
}

/**
 * Invoke XFree() on a pointer to memory allocated by Xlib (if the
 * pointer is nonnull) when this class goes out of scope.
 */
template<typename T>
struct ScopedXFree
{
  ScopedXFree() : mPtr(NULL) {}
  ScopedXFree(T* aPtr) : mPtr(aPtr) {}

  ~ScopedXFree() { Assign(NULL); }

  ScopedXFree& operator=(T* aPtr) { Assign(aPtr); return *this; }

  operator T*() const { return get(); }
  T* operator->() const { return get(); }
  T* get() const { return mPtr; }

private:
  void Assign(T* aPtr)
  {
    NS_ASSERTION(!mPtr || mPtr != aPtr, "double-XFree() imminent");

    if (mPtr)
      XFree(mPtr);
    mPtr = aPtr;
  }

  T* mPtr;

  // disable these
  ScopedXFree(const ScopedXFree&);
  ScopedXFree& operator=(const ScopedXFree&);
  static void* operator new (size_t);
  static void operator delete (void*);
};

/**
 * On construction, set a graceful X error handler that doesn't crash the application and records X errors.
 * On destruction, restore the X error handler to what it was before construction.
 * 
 * The SyncAndGetError() method allows to know whether a X error occurred, optionally allows to get the full XErrorEvent,
 * and resets the recorded X error state so that a single X error will be reported only once.
 *
 * Nesting is correctly handled: multiple nested ScopedXErrorHandler's don't interfere with each other's state. However,
 * if SyncAndGetError is not called on the nested ScopedXErrorHandler, then any X errors caused by X calls made while the nested
 * ScopedXErrorHandler was in place may then be caught by the other ScopedXErrorHandler. This is just a result of X being
 * asynchronous and us not doing any implicit syncing: the only method in this class what causes syncing is SyncAndGetError().
 *
 * This class is not thread-safe at all. It is assumed that only one thread is using any ScopedXErrorHandler's. Given that it's
 * not used on Mac, it should be easy to make it thread-safe by using thread-local storage with __thread.
 */
class ScopedXErrorHandler
{
    // trivial wrapper around XErrorEvent, just adding ctor initializing by zero.
    struct ErrorEvent
    {
        XErrorEvent m_error;

        ErrorEvent()
        {
            memset(this, 0, sizeof(ErrorEvent));
        }
    };

    // this ScopedXErrorHandler's ErrorEvent object
    ErrorEvent m_xerror;

    // static pointer for use by the error handler
    static ErrorEvent* s_xerrorptr;

    // what to restore s_xerrorptr to on destruction
    ErrorEvent* m_oldxerrorptr;

    // what to restore the error handler to on destruction
    int (*m_oldErrorHandler)(Display *, XErrorEvent *);

public:

    static int
    ErrorHandler(Display *, XErrorEvent *ev)
    {
        s_xerrorptr->m_error = *ev;
        return 0;
    }

    ScopedXErrorHandler()
    {
        // let s_xerrorptr point to this object's m_xerror object, but don't reset this m_xerror object!
        // think of the case of nested ScopedXErrorHandler's.
        m_oldxerrorptr = s_xerrorptr;
        s_xerrorptr = &m_xerror;
        m_oldErrorHandler = XSetErrorHandler(ErrorHandler);
    }

    ~ScopedXErrorHandler()
    {
        s_xerrorptr = m_oldxerrorptr;
        XSetErrorHandler(m_oldErrorHandler);
    }

    /** \returns true if a X error occurred since the last time this method was called on this ScopedXErrorHandler object.
     *
     * \param ev this optional parameter, if set, will be filled with the XErrorEvent object
     */
    bool SyncAndGetError(Display *dpy, XErrorEvent *ev = nsnull)
    {
        XSync(dpy, False);
        bool retval = m_xerror.m_error.error_code != 0;
        if (ev)
            *ev = m_xerror.m_error;
        m_xerror = ErrorEvent(); // reset
        return retval;
    }
};


} // namespace mozilla

#endif  // mozilla_X11Util_h