Fixed issue #223. Attempt to remove stale lock file.

--HG--
branch : develop

src/app/core/vapplication.cpp

@@ -339,6 +339,43 @@ double VApplication::fromPixel(double pix) const
     return fromPixel(pix, _patternUnit);
 }
 
+//---------------------------------------------------------------------------------------------------------------------
+bool VApplication::TryLock(QLockFile *lock)
+{
+    if (lock == nullptr)
+    {
+        return false;
+    }
+
+    if (lock->tryLock())
+    {
+        return true;
+    }
+    else
+    {
+        if (lock->error() == QLockFile::LockFailedError)
+        {
+            // This happens if a stale lock file exists and another process uses that PID.
+            // Try removing the stale file, which will fail if a real process is holding a
+            // file-level lock. A false error is more problematic than not locking properly
+            // on corner-case systems.
+            if (lock->removeStaleLockFile() == false || lock->tryLock() == false)
+            {
+                return false;
+            }
+            else
+            {
+                return true;
+            }
+        }
+        else
+        {
+            return false;
+        }
+        return false;
+    }
+}
+
 //---------------------------------------------------------------------------------------------------------------------
 QString VApplication::pathToTables() const
 {
@@ -461,7 +498,7 @@ void VApplication::BeginLogging()
         qInstallMessageHandler(noisyFailureMsgHandler);
         logLock = new QLockFile(LogPath()+".lock");
         logLock->setStaleLockTime(0);
-        if (logLock->tryLock())
+        if (TryLock(logLock))
         {
             qCDebug(vApp) << "Log file"<<LogPath()<<"was locked.";
         }
@@ -495,7 +532,7 @@ void VApplication::ClearOldLogs() const
         {
             QFileInfo info(allFiles.at(i));
             QLockFile *lock = new QLockFile(info.absoluteFilePath() + ".lock");
-            if (lock->tryLock())
+            if (TryLock(lock))
             {
                 qCDebug(vApp) << "Locked file"<<info.absoluteFilePath();
                 QFile oldLog(allFiles.at(i));
@@ -2118,7 +2155,7 @@ void VApplication::GatherLogs() const
                 }
                 QLockFile *logLock = new QLockFile(info.absoluteFilePath()+".lock");
                 logLock->setStaleLockTime(0);
-                if (logLock->tryLock())
+                if (TryLock(logLock))
                 {
                     *out <<"--------------------------" << endl;
                     QFile logFile(info.absoluteFilePath());

src/app/core/vapplication.h

@@ -70,6 +70,8 @@ public:
     double             fromPixel(double pix, const Unit &unit) const;
     double             fromPixel(double pix) const;
 
+    static bool        TryLock(QLockFile *lock);
+
     static const qreal PrintDPI;
     QString            translationsPath() const;
     QString            pathToTables() const;

src/app/mainwindow.cpp

@@ -2365,7 +2365,7 @@ void MainWindow::LoadPattern(const QString &fileName)
     qCDebug(vMainWindow)<<"Loking file";
     lock = new QLockFile(fileName+".lock");
     lock->setStaleLockTime(0);
-    if (lock->tryLock())
+    if (VApplication::TryLock(lock))
     {
         qCDebug(vMainWindow) << "Pattern file"<<fileName<<"was locked.";
     }
@@ -2477,7 +2477,7 @@ QStringList MainWindow::GetUnlokedRestoreFileList() const
             // Seeking file that realy need reopen
             QLockFile *lock = new QLockFile(files.at(i)+".lock");
             lock->setStaleLockTime(0);
-            if (lock->tryLock())
+            if (VApplication::TryLock(lock))
             {
                 restoreFiles.append(files.at(i));
             }