From 5c3ddb7a7f56e18f890504b46b37addba00c70b2 Mon Sep 17 00:00:00 2001
From: Graham Dawes <graham.dawes@geoteric.com>
Date: Thu, 20 Dec 2018 13:41:02 +0000
Subject: [PATCH] Prevent crash when attempting to clear a DC with not device
 under wxQT

---
 src/qt/dc.cpp | 40 ++++++++++++++++++++++++++++++++++++----
 1 file changed, 36 insertions(+), 4 deletions(-)

diff --git a/src/qt/dc.cpp b/src/qt/dc.cpp
index e5405276cd..5cd918ba2c 100644
--- a/src/qt/dc.cpp
+++ b/src/qt/dc.cpp
@@ -115,14 +115,46 @@ bool wxQtDCImpl::CanGetTextExtent() const
 
 void wxQtDCImpl::DoGetSize(int *width, int *height) const
 {
-    if (width)  *width  = m_qtPainter->device()->width();
-    if (height) *height = m_qtPainter->device()->height();
+    QPaintDevice *pDevice = m_qtPainter->device();
+
+    int deviceWidth;
+    int deviceHeight;
+
+    if (pDevice)
+    {
+        deviceWidth = pDevice->width();
+        deviceHeight = pDevice->height();
+    }
+    else
+    {
+        deviceWidth = 0;
+        deviceHeight = 0;
+
+    }
+    if (width) *width  = deviceWidth;
+    if (height) *height = deviceHeight;
 }
 
 void wxQtDCImpl::DoGetSizeMM(int* width, int* height) const
 {
-    if (width)  *width  = m_qtPainter->device()->widthMM();
-    if (height) *height = m_qtPainter->device()->heightMM();
+    QPaintDevice *pDevice = m_qtPainter->device();
+
+    int deviceWidthMM;
+    int deviceHeightMM;
+
+    if (pDevice)
+    {
+        deviceWidthMM = pDevice->widthMM();
+        deviceHeightMM = pDevice->heightMM();
+    }
+    else
+    {
+        deviceWidthMM = 0;
+        deviceHeightMM = 0;
+    }
+
+    if (width)  *width  = deviceWidthMM;
+    if (height) *height = deviceHeightMM;
 }
 
 int wxQtDCImpl::GetDepth() const