Fix QPrintDialog with no parent and no active window

PrintDlgEx requires an non-null owner handle, otherwise it will fail
with an "Invalid Handle" error. This caused code which popped up a
print dialog as the only window in the application to fail silently
and immediately return Rejected from the exec() function. To continue
support for this somewhat unusual use case, we fall back to using the
print dialog itself as the owner of the print dialog sheet if all else
fails.

Reviewed-by: Trond

1 files changed, 6 insertions, 2 deletions

diff --git a/src/gui/dialogs/qprintdialog_win.cpp b/src/gui/dialogs/qprintdialog_win.cpp
index 1a3d2de..f66c27f 100644
--- a/src/gui/dialogs/qprintdialog_win.cpp
+++ b/src/gui/dialogs/qprintdialog_win.cpp
@@ -131,8 +131,8 @@ static void qt_win_setup_PRINTDLGEX(PRINTDLGEX *pd, QWidget *parent,
 
     if (d->ep->printToFile)
         pd->Flags |= PD_PRINTTOFILE;
-    Q_ASSERT(!parent ||parent->testAttribute(Qt::WA_WState_Created));
-    pd->hwndOwner = parent ? parent->winId() : 0;
+    Q_ASSERT(parent != 0 && parent->testAttribute(Qt::WA_WState_Created));
+    pd->hwndOwner = parent->winId();
     pd->lpPageRanges[0].nFromPage = qMax(pdlg->fromPage(), pdlg->minPage());
     pd->lpPageRanges[0].nToPage   = (pdlg->toPage() > 0) ? qMin(pdlg->toPage(), pdlg->maxPage()) : 1;
     pd->nCopies = d->ep->num_copies;
@@ -212,6 +212,10 @@ int QPrintDialogPrivate::openWindowsPrintDialogModally()
     else
         parent = QApplication::activeWindow();
 
+    // If there is no window, fall back to the print dialog itself
+    if (parent == 0)
+        parent = q;
+
     QWidget modal_widget;
     modal_widget.setAttribute(Qt::WA_NoChildEventsForParent, true);
     modal_widget.setParent(parent, Qt::Window);