From e6b337e32312772a3450e4b5bd6c9720c2a99dcb Mon Sep 17 00:00:00 2001
From: Martin Dobias <wonder.sk@gmail.com>
Date: Wed, 4 Jun 2014 19:00:53 +0700
Subject: [PATCH] Trying to fix #10164 (crash on zoom in/out)

This happens due to infinite recursion when syncing extent between
map canvas and map renderer. Not entirely sure why, seems to happen
only on 32bit systems.
---
 src/gui/qgsmapcanvas.cpp | 13 +++++++++++++
 src/gui/qgsmapcanvas.h   |  2 ++
 2 files changed, 15 insertions(+)

diff --git a/src/gui/qgsmapcanvas.cpp b/src/gui/qgsmapcanvas.cpp
index 713a9de771f..849776f15d1 100755
--- a/src/gui/qgsmapcanvas.cpp
+++ b/src/gui/qgsmapcanvas.cpp
@@ -89,6 +89,7 @@ QgsMapCanvasRendererSync::QgsMapCanvasRendererSync( QgsMapCanvas* canvas, QgsMap
     : QObject( canvas )
     , mCanvas( canvas )
     , mRenderer( renderer )
+    , mSyncingExtent( false )
 {
   connect( mCanvas, SIGNAL( extentsChanged() ), this, SLOT( onExtentC2R() ) );
   connect( mRenderer, SIGNAL( extentsChanged() ), this, SLOT( onExtentR2C() ) );
@@ -109,12 +110,24 @@ QgsMapCanvasRendererSync::QgsMapCanvasRendererSync( QgsMapCanvas* canvas, QgsMap
 
 void QgsMapCanvasRendererSync::onExtentC2R()
 {
+  // protection against possible bounce back
+  if ( mSyncingExtent )
+    return;
+
+  mSyncingExtent = true;
   mRenderer->setExtent( mCanvas->mapSettings().extent() );
+  mSyncingExtent = false;
 }
 
 void QgsMapCanvasRendererSync::onExtentR2C()
 {
+  // protection against possible bounce back
+  if ( mSyncingExtent )
+    return;
+
+  mSyncingExtent = true;
   mCanvas->setExtent( mRenderer->extent() );
+  mSyncingExtent = false;
 }
 
 void QgsMapCanvasRendererSync::onMapUnitsC2R()
diff --git a/src/gui/qgsmapcanvas.h b/src/gui/qgsmapcanvas.h
index fdb943affe4..243135109db 100755
--- a/src/gui/qgsmapcanvas.h
+++ b/src/gui/qgsmapcanvas.h
@@ -662,6 +662,8 @@ class QgsMapCanvasRendererSync : public QObject
   protected:
     QgsMapCanvas* mCanvas;
     QgsMapRenderer* mRenderer;
+
+    bool mSyncingExtent;
 };