fix default suffixes in save dialog in GNOME, make it more clear that PNG is used (solves #833)

src/qt/guiutil.cpp

@@ -15,6 +15,8 @@
 #include <QAbstractItemView>
 #include <QApplication>
 #include <QClipboard>
+#include <QFileDialog>
+#include <QDesktopServices>
 
 QString GUIUtil::dateTimeStr(qint64 nTime)
 {
@@ -121,3 +123,50 @@ void GUIUtil::copyEntryData(QAbstractItemView *view, int column, int role)
         QApplication::clipboard()->setText(selection.at(0).data(role).toString());
     }
 }
+
+QString GUIUtil::getSaveFileName(QWidget *parent, const QString &caption,
+                                 const QString &dir,
+                                 const QString &filter,
+                                 QString *selectedSuffixOut)
+{
+    QString selectedFilter;
+    QString myDir;
+    if(dir.isEmpty()) // Default to user documents location
+    {
+        myDir = QDesktopServices::storageLocation(QDesktopServices::DocumentsLocation);
+    }
+    else
+    {
+        myDir = dir;
+    }
+    QString result = QFileDialog::getSaveFileName(parent, caption, myDir, filter, &selectedFilter);
+
+    /* Extract first suffix from filter pattern "Description (*.foo)" or "Description (*.foo *.bar ...) */
+    QRegExp filter_re(".* \\(\\*\\.(.*)[ \\)]");
+    QString selectedSuffix;
+    if(filter_re.exactMatch(selectedFilter))
+    {
+        selectedSuffix = filter_re.cap(1);
+    }
+
+    /* Add suffix if needed */
+    QFileInfo info(result);
+    if(!result.isEmpty())
+    {
+        if(info.suffix().isEmpty() && !selectedSuffix.isEmpty())
+        {
+            /* No suffix specified, add selected suffix */
+            if(!result.endsWith("."))
+                result.append(".");
+            result.append(selectedSuffix);
+        }
+    }
+
+    /* Return selected suffix if asked to */
+    if(selectedSuffixOut)
+    {
+        *selectedSuffixOut = selectedSuffix;
+    }
+    return result;
+}
+