From ad9ebd4b545f68841f01268c8842ea2fbceee7a6 Mon Sep 17 00:00:00 2001
From: Artur Wieczorek <artwik@wp.pl>
Date: Sat, 16 Jul 2016 23:41:29 +0200
Subject: [PATCH] Fixed setting clipping box with negative size (wxDC, GTK).

Rectangular clipping region with negative size is accepted by wxDC::SetClippingRegion() (for compatibility with wxGCDC and Cairo) but for internal calculations we need to have this box defined by (x,y) at top-left corner and having non-negative size so we need to recalculate box's parameters in wxWindowDCImpl::DoSetClippingRegion() if necessary.
---
 src/gtk/dcclient.cpp | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/src/gtk/dcclient.cpp b/src/gtk/dcclient.cpp
index 1a3d60cc8e..507fd47769 100644
--- a/src/gtk/dcclient.cpp
+++ b/src/gtk/dcclient.cpp
@@ -1871,6 +1871,20 @@ void wxWindowDCImpl::DoSetClippingRegion( wxCoord x, wxCoord y, wxCoord width, w
 
     if (!m_gdkwindow) return;
 
+    // For internal calculations we need to have box definition
+    // in the canonical form, with (x,y) pointing to the top-left
+    // corner of the box and with non-negative width and height.
+    if ( width < 0 )
+    {
+        width = -width;
+        x -= (width - 1);
+    }
+    if ( height < 0 )
+    {
+        height = -height;
+        y -= (height - 1);
+    }
+
     wxRect rect;
     rect.x = XLOG2DEV(x);
     rect.y = YLOG2DEV(y);