Refresh CUPS printer list when QPrinterInfo.availablePrinters() is called.

Introduce freeCupsPrinters() thus fixing a bug in the old deallocation
code which would first set m_cupsPrintersCount = 0 and then
pass it to cupsFreeDests().

Task-number: QTBUG-33666
Change-Id: I94c51cb390761a669a9cbd589c1131cfb51354c3
Reviewed-by: Lars Knoll <lars.knoll@digia.com>

2 files changed, 19 insertions, 6 deletions

diff --git a/src/plugins/printsupport/cups/qcupsprintersupport.cpp b/src/plugins/printsupport/cups/qcupsprintersupport.cpp
index f41d4f5047..b9f0c394f8 100644
--- a/src/plugins/printsupport/cups/qcupsprintersupport.cpp
+++ b/src/plugins/printsupport/cups/qcupsprintersupport.cpp
@@ -66,8 +66,7 @@ QCupsPrinterSupport::QCupsPrinterSupport() : QPlatformPrinterSupport(),
 
 QCupsPrinterSupport::~QCupsPrinterSupport()
 {
-    if (cupsFreeDests)
-        cupsFreeDests(m_cupsPrintersCount, m_cupsPrinters);
+    freeCupsPrinters();
 }
 
 QPrintEngine *QCupsPrinterSupport::createNativePrintEngine(QPrinter::PrinterMode printerMode)
@@ -98,14 +97,20 @@ void QCupsPrinterSupport::loadCups()
     cupsGetOption = (CupsGetOption) m_cups.resolve("cupsGetOption");
 }
 
+void QCupsPrinterSupport::freeCupsPrinters()
+{
+    if (cupsFreeDests && m_cupsPrintersCount) {
+        cupsFreeDests(m_cupsPrintersCount, m_cupsPrinters);
+        m_cupsPrintersCount = 0;
+        m_cupsPrinters = 0;
+    }
+}
+
 void QCupsPrinterSupport::loadCupsPrinters()
 {
-    m_cupsPrintersCount = 0;
+    freeCupsPrinters();
     m_printers.clear();
 
-    if (cupsFreeDests)
-        cupsFreeDests(m_cupsPrintersCount, m_cupsPrinters);
-
     if (cupsGetDests)
         m_cupsPrintersCount = cupsGetDests(&m_cupsPrinters);
 
@@ -122,6 +127,12 @@ void QCupsPrinterSupport::loadCupsPrinters()
     }
 }
 
+QList<QPrinterInfo> QCupsPrinterSupport::availablePrinters()
+{
+    loadCupsPrinters();
+    return QPlatformPrinterSupport::availablePrinters();
+}
+
 QString QCupsPrinterSupport::printerOption(const QPrinterInfo &printer, const QString &key) const
 {
     return cupsOption(printerIndex(printer), key);
diff --git a/src/plugins/printsupport/cups/qcupsprintersupport_p.h b/src/plugins/printsupport/cups/qcupsprintersupport_p.h
index e9fe24203e..d42c0d2630 100644
--- a/src/plugins/printsupport/cups/qcupsprintersupport_p.h
+++ b/src/plugins/printsupport/cups/qcupsprintersupport_p.h
@@ -68,12 +68,14 @@ public:
     virtual QPaintEngine *createPaintEngine(QPrintEngine *printEngine, QPrinter::PrinterMode);
     virtual QList<QPrinter::PaperSize> supportedPaperSizes(const QPrinterInfo &) const;
     virtual QList<QPair<QString, QSizeF> > supportedSizesWithNames(const QPrinterInfo &) const;
+    virtual QList<QPrinterInfo> availablePrinters();
     virtual QString printerOption(const QPrinterInfo &printer, const QString &key) const;
     virtual PrinterOptions printerOptions(const QPrinterInfo &printer) const;
 
 private:
     void loadCups();
     void loadCupsPrinters();
+    void freeCupsPrinters();
     QString cupsOption(int i, const QString &key) const;
 
     QLibrary m_cups;