qtgain skip flac patch

--- a/src/QtGain.cpp
+++ b/src/QtGain.cpp
@@ -270,7 +270,13 @@ void QtGain::processFiles_TrackGain(){
     }

     // Check output of replay gain tools
-    processOutput();
+    if (this->m_lastFileSkipped) {
+        addSkippedFiles();
+        if (isLogSkippedFiles()) addToErrorlog(tr("<font color='green'>File already gained -> skipped</font> :: %1<br>").arg(currentFileName()));
+    } else {
+        processOutput();
+    }
+    this->m_lastFileSkipped = false;

     if (finishedFiles() < allFiles.size()){

@@ -305,8 +311,17 @@ void QtGain::processFiles_TrackGain(){
         // FLAC
         else if (allFiles[finishedFiles()].endsWith(".flac", Qt::CaseInsensitive)){
             ui.FileFormatIcon->setPixmap(QPixmap(":/Icons/flac.png"));
-            Parameter << "--add-replay-gain" << allFiles[finishedFiles()];
-            TrackGainProcess->start(FlacGainBinaryPath(), Parameter);
+            // Check if flac file is already gained, metaflac does not do this by itself
+            QProcess checkProcess;
+            checkProcess.start(FlacGainBinaryPath(), QStringList() << "--show-tag" << "REPLAYGAIN_TRACK_GAIN" << allFiles[finishedFiles()]);
+            checkProcess.waitForFinished();
+            QString output(checkProcess.readAllStandardOutput());
+            if (output.contains("REPLAYGAIN_TRACK_GAIN=")) {
+                this->m_lastFileSkipped = true;
+            } else {
+                Parameter << "--add-replay-gain" << allFiles[finishedFiles()];
+                TrackGainProcess->start(FlacGainBinaryPath(), Parameter);
+            }
         }
     }

@@ -347,6 +362,8 @@ void QtGain::processFiles_TrackGain(){
     else {
         setCurrentFileName(allFiles[finishedFiles()]);
         addFinishedFiles();
+        if (this->m_lastFileSkipped)
+            QMetaObject::invokeMethod( this, "processFiles_TrackGain", Qt::QueuedConnection);
     }
 }

@@ -499,6 +516,7 @@ void QtGain::processFoundFiles(){
         }

         setGUI_To(BUSY);
+        this->m_lastFileSkipped = false;
         isTrackGain() ? processFiles_TrackGain() : processFiles_AlbumGain();
     } else {
         setGUI_To(IDLE, tr("No media files found..."));
--- a/src/QtGain.h
+++ b/src/QtGain.h
@@ -51,6 +51,7 @@ private:
     QAction  *actionQuit;
     QString m_Errorlog;
     QString m_lastAlbumGainOutput;
+    bool    m_lastFileSkipped;

     void startupInitiations();
     void processOutput();