Prevent crash when going back from EraseDiskPage and then next.

This was caused by an invalid reference to a device model in the
partitioning preview widget after a PCM revert.

src/modules/partition/gui/EraseDiskPage.cpp

@@ -1,6 +1,6 @@
 /* === This file is part of Calamares - <http://github.com/calamares> ===
  *
- *   Copyright 2014, Teo Mrnjavac <teo@kde.org>
+ *   Copyright 2014-2015, Teo Mrnjavac <teo@kde.org>
  *
  *   Calamares is free software: you can redistribute it and/or modify
  *   it under the terms of the GNU General Public License as published by
@@ -38,6 +38,7 @@
 #include <QFormLayout>
 #include <QListView>
 #include <QLabel>
+#include <QMutexLocker>
 
 EraseDiskPage::EraseDiskPage( QWidget* parent )
     : QWidget( parent )
@@ -103,6 +104,9 @@ EraseDiskPage::init( PartitionCoreModule* core )
         if ( dev )
             doAutopartition( dev );
     } );
+
+    connect( m_core, &PartitionCoreModule::isDirtyChanged,
+             this, &EraseDiskPage::updatePreviews );
 }
 
 
@@ -187,11 +191,27 @@ EraseDiskPage::doAutopartition( Device* dev )
     PartitionInfo::setFormat( rootPartition, true );
     m_core->createPartition( dev, rootPartition );
 
+    updatePreviews();
 
-    {
+    m_core->dumpQueue();
+}
+
+
+void
+EraseDiskPage::updatePreviews()
+{
+    QMutexLocker( &EraseDiskPage::m_previewsMutex );
+
+    cDebug() << "Updating partitioning preview widgets.";
     qDeleteAll( m_previewFrame->children() );
     m_previewFrame->layout()->deleteLater();
 
+    if ( m_drivesView->selectionModel()->currentIndex() == QModelIndex() )
+    {
+        cDebug() << "No disk selected, bailing out.";
+        return;
+    }
+
     QFormLayout* layout = new QFormLayout;
     m_previewFrame->setLayout( layout );
     layout->setMargin( 0 );
@@ -213,6 +233,4 @@ EraseDiskPage::doAutopartition( Device* dev )
         info.partitionModelAfter->setParent( m_previewFrame );
         layout->addRow( tr( "After:" ), preview );
     }
-    }
-    m_core->dumpQueue();
 }

src/modules/partition/gui/EraseDiskPage.h

@@ -1,6 +1,6 @@
 /* === This file is part of Calamares - <http://github.com/calamares> ===
  *
- *   Copyright 2014, Teo Mrnjavac <teo@kde.org>
+ *   Copyright 2014-2015, Teo Mrnjavac <teo@kde.org>
  *
  *   Calamares is free software: you can redistribute it and/or modify
  *   it under the terms of the GNU General Public License as published by
@@ -19,6 +19,7 @@
 #ifndef ERASEDISKPAGE_H
 #define ERASEDISKPAGE_H
 
+#include <QMutex>
 #include <QWidget>
 
 class PartitionCoreModule;
@@ -41,11 +42,14 @@ signals:
 private:
     void setNextEnabled( bool enabled );
     void doAutopartition( Device* dev );
+    void updatePreviews();
 
     QListView* m_drivesView;
     PartitionCoreModule* m_core;
     QWidget* m_previewFrame;
 
+    QMutex m_previewsMutex;
+
     bool m_nextEnabled;
 };