Improved Windows printer support and fixed crashes due to NULL devMode

With certain printer drivers, the PRINTER_INFO_2 can return NULL for
the pDevMode member in the call to GetPrinter() as mentioned on MSDN:
https://msdn.microsoft.com/en-us/library/windows/desktop/dd144911
In many places, Qt first checks that devMode isn't NULL before
dereferencing it.  In other places it does not (such as when it
actually attempts to print in QWin32PrintEngine::begin()).  Checking
every dereference aside, most printer functionality is removed without
access to the DEVMODE structure.  This fix uses DocumentProperties()
to get the DEVMODE information when the first method fails.

[ChangeLog][QtPrintSupport][QPrinter][Windows] Improved Windows printer
support and fixed crashes due to NULL devMode

Task-number: QTBUG-44349
Task-number: QTBUG-43877
Task-number: QTBUG-2251
Change-Id: Iafa337055d967c70f2096dcde4cc9c8ca8a0d252
Reviewed-by: Andy Shaw <andy.shaw@digia.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/src/printsupport/dialogs/qpagesetupdialog_win.cpp b/src/printsupport/dialogs/qpagesetupdialog_win.cpp
index 9185705bcf..baa8f93454 100644
--- a/src/printsupport/dialogs/qpagesetupdialog_win.cpp
+++ b/src/printsupport/dialogs/qpagesetupdialog_win.cpp
@@ -134,6 +134,13 @@ int QPageSetupDialog::exec()
 
         // copy from our temp DEVMODE struct
         if (!engine->globalDevMode() && hDevMode) {
+            // Make sure memory is allocated
+            if (ep->ownsDevMode && ep->devMode)
+                free(ep->devMode);
+            ep->devMode = (DEVMODE *) malloc(devModeSize);
+            ep->ownsDevMode = true;
+
+            // Copy
             void *src = GlobalLock(hDevMode);
             memcpy(ep->devMode, src, devModeSize);
             GlobalUnlock(hDevMode);