Reimplement click-to-pay links. Add OSX support.

Switch to using Qt's QLocalServer/QLocalSocket to handle bitcoin
payment links (bitcoin:... URIs)

Reason for switch: the boost::interprocess mechanism seemed flaky,
and doesn't mesh as well with "The Qt Way"

qtipcserver.cpp/h is replaced by paymentserver.cpp/h

Click-to-pay now also works on OSX, with a custom Info.plist
that registers Bitcoin-Qt as a handler for bitcoin: URLs and
an event listener on the main QApplication that handles
QFileOpenEvents (Qt translates 'url clicked' AppleEvents into
QFileOpenEvents automagically).

src/qt/paymentserver.cpp

@@ -0,0 +1,159 @@
+// Copyright (c) 2009-2012 The Bitcoin developers
+// Distributed under the MIT/X11 software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include "paymentserver.h"
+#include "guiconstants.h"
+#include "ui_interface.h"
+#include "util.h"
+
+#include <QApplication>
+#include <QByteArray>
+#include <QCoreApplication>
+#include <QDataStream>
+#include <QDebug>
+#include <QFileOpenEvent>
+#include <QHash>
+#include <QLocalServer>
+#include <QLocalSocket>
+#include <QStringList>
+#include <QUrl>
+
+using namespace boost;
+
+const int BITCOIN_IPC_CONNECT_TIMEOUT = 1000; // milliseconds
+const QString BITCOIN_IPC_PREFIX("bitcoin:");
+
+//
+// Create a name that is unique for:
+//  testnet / non-testnet
+//  data directory
+//
+static QString ipcServerName()
+{
+    QString name("BitcoinQt");
+
+    // Append a simple hash of the datadir
+    // Note that GetDataDir(true) returns a different path
+    // for -testnet versus main net
+    QString ddir(GetDataDir(true).string().c_str());
+    name.append(QString::number(qHash(ddir)));
+
+    return name;
+}
+
+//
+// This stores payment requests received before
+// the main GUI window is up and ready to ask the user
+// to send payment.
+//
+static QStringList savedPaymentRequests;
+
+//
+// Sending to the server is done synchronously, at startup.
+// If the server isn't already running, startup continues,
+// and the items in savedPaymentRequest will be handled
+// when uiReady() is called.
+//
+bool PaymentServer::ipcSendCommandLine()
+{
+    bool fResult = false;
+
+    const QStringList& args = QCoreApplication::arguments();
+    for (int i = 1; i < args.size(); i++)
+    {
+        if (!args[i].startsWith(BITCOIN_IPC_PREFIX, Qt::CaseInsensitive))
+            continue;
+        savedPaymentRequests.append(args[i]);
+    }
+
+    foreach (const QString& arg, savedPaymentRequests)
+    {
+        QLocalSocket* socket = new QLocalSocket();
+        socket->connectToServer(ipcServerName(), QIODevice::WriteOnly);
+        if (!socket->waitForConnected(BITCOIN_IPC_CONNECT_TIMEOUT))
+            return false;
+
+        QByteArray block;
+        QDataStream out(&block, QIODevice::WriteOnly);
+        out.setVersion(QDataStream::Qt_4_0);
+        out << arg;
+        out.device()->seek(0);
+        socket->write(block);
+        socket->flush();
+
+        socket->waitForBytesWritten(BITCOIN_IPC_CONNECT_TIMEOUT);
+        socket->disconnectFromServer();
+        delete socket;
+        fResult = true;
+    }
+    return fResult;
+}
+
+PaymentServer::PaymentServer(QApplication* parent) : QObject(parent), saveURIs(true)
+{
+    // Install global event filter to catch QFileOpenEvents on the mac (sent when you click bitcoin: links)
+    parent->installEventFilter(this);
+
+    QString name = ipcServerName();
+
+    // Clean up old socket leftover from a crash:
+    QLocalServer::removeServer(name);
+
+    uriServer = new QLocalServer(this);
+
+    if (!uriServer->listen(name))
+        qDebug() << tr("Cannot start bitcoin: click-to-pay handler");
+    else
+        connect(uriServer, SIGNAL(newConnection()), this, SLOT(handleURIConnection()));
+}
+
+bool PaymentServer::eventFilter(QObject *object, QEvent *event)
+{
+    // clicking on bitcoin: URLs creates FileOpen events on the Mac:
+    if (event->type() == QEvent::FileOpen)
+    {
+        QFileOpenEvent* fileEvent = static_cast<QFileOpenEvent*>(event);
+        if (!fileEvent->url().isEmpty())
+        {
+            if (saveURIs) // Before main window is ready:
+                savedPaymentRequests.append(fileEvent->url().toString());
+            else
+                emit receivedURI(fileEvent->url().toString());
+            return true;
+        }
+    }
+    return false;
+}
+
+void PaymentServer::uiReady()
+{
+    saveURIs = false;
+    foreach (const QString& s, savedPaymentRequests)
+        emit receivedURI(s);
+    savedPaymentRequests.clear();
+}
+
+void PaymentServer::handleURIConnection()
+{
+    QLocalSocket *clientConnection = uriServer->nextPendingConnection();
+
+    while (clientConnection->bytesAvailable() < (int)sizeof(quint32))
+        clientConnection->waitForReadyRead();
+
+    connect(clientConnection, SIGNAL(disconnected()),
+            clientConnection, SLOT(deleteLater()));
+
+    QDataStream in(clientConnection);
+    in.setVersion(QDataStream::Qt_4_0);
+    if (clientConnection->bytesAvailable() < (int)sizeof(quint16)) {
+        return;
+    }
+    QString message;
+    in >> message;
+
+    if (saveURIs)
+        savedPaymentRequests.append(message);
+    else
+        emit receivedURI(message);
+}