walletview: make backupWallet() use GUIUtil::getSaveFileName()

- this allows removal of several Qt headers and makes use of a
  standardized function in GUIUtil
- adds selected path to the UI output

src/qt/walletview.cpp

@@ -18,16 +18,11 @@
 #include "overviewpage.h"
 #include "askpassphrasedialog.h"
 #include "ui_interface.h"
+#include "guiutil.h"
 
 #include <QHBoxLayout>
 #include <QVBoxLayout>
 #include <QAction>
-#if QT_VERSION < 0x050000
-#include <QDesktopServices>
-#else
-#include <QStandardPaths>
-#endif
-#include <QFileDialog>
 #include <QPushButton>
 
 WalletView::WalletView(QWidget *parent):
@@ -222,19 +217,19 @@ void WalletView::encryptWallet(bool status)
 
 void WalletView::backupWallet()
 {
-#if QT_VERSION < 0x050000
-    QString saveDir = QDesktopServices::storageLocation(QDesktopServices::DocumentsLocation);
-#else
-    QString saveDir = QStandardPaths::writableLocation(QStandardPaths::DocumentsLocation);
-#endif
-    QString filename = QFileDialog::getSaveFileName(this, tr("Backup Wallet"), saveDir, tr("Wallet Data (*.dat)"));
-    if (!filename.isEmpty()) {
+    QString filename = GUIUtil::getSaveFileName(this,
+        tr("Backup Wallet"), QString(),
+        tr("Wallet Data (*.dat)"));
+
+    if (filename.isEmpty())
+        return;
+
     if (!walletModel->backupWallet(filename)) {
-            emit message(tr("Backup Failed"), tr("There was an error trying to save the wallet data to the new location."),
+        emit message(tr("Backup Failed"), tr("There was an error trying to save the wallet data to %1.").arg(filename),
             CClientUIInterface::MSG_ERROR);
         }
-        else
-            emit message(tr("Backup Successful"), tr("The wallet data was successfully saved to the new location."),
+    else {
+        emit message(tr("Backup Successful"), tr("The wallet data was successfully saved to %1.").arg(filename),
             CClientUIInterface::MSG_INFORMATION);
     }
 }