From 8d832d8aca7b29b67ef274f641a02ac3cc3c87d9 Mon Sep 17 00:00:00 2001
From: Martin Dobias <wonder.sk@gmail.com>
Date: Thu, 1 Sep 2016 21:43:40 +0800
Subject: [PATCH] Make sure we do not miss cancellation request at the
 beginning

---
 src/providers/wms/qgswmsprovider.cpp | 33 +++++++++++++++++++++++-----
 src/providers/wms/qgswmsprovider.h   |  2 ++
 2 files changed, 29 insertions(+), 6 deletions(-)

diff --git a/src/providers/wms/qgswmsprovider.cpp b/src/providers/wms/qgswmsprovider.cpp
index 35c4665a635..e6d732964c8 100644
--- a/src/providers/wms/qgswmsprovider.cpp
+++ b/src/providers/wms/qgswmsprovider.cpp
@@ -3337,7 +3337,18 @@ QgsWmsImageDownloadHandler::QgsWmsImageDownloadHandler( const QString& providerU
     : mProviderUri( providerUri )
     , mCachedImage( image )
     , mEventLoop( new QEventLoop )
+    , mFeedback( feedback )
 {
+  if ( feedback )
+  {
+    connect( feedback, SIGNAL( cancelled() ), this, SLOT( cancelled() ), Qt::QueuedConnection );
+
+    // rendering could have been cancelled before we started to listen to cancelled() signal
+    // so let's check before doing the download and maybe quit prematurely
+    if ( feedback->isCancelled() )
+      return;
+  }
+
   QNetworkRequest request( url );
   auth.setAuthorization( request );
   request.setAttribute( QNetworkRequest::CacheSaveControlAttribute, true );
@@ -3346,9 +3357,6 @@ QgsWmsImageDownloadHandler::QgsWmsImageDownloadHandler( const QString& providerU
   connect( mCacheReply, SIGNAL( downloadProgress( qint64, qint64 ) ), this, SLOT( cacheReplyProgress( qint64, qint64 ) ) );
 
   Q_ASSERT( mCacheReply->thread() == QThread::currentThread() );
-
-  if ( feedback )
-    connect( feedback, SIGNAL( cancelled() ), this, SLOT( cancelled() ), Qt::QueuedConnection );
 }
 
 QgsWmsImageDownloadHandler::~QgsWmsImageDownloadHandler()
@@ -3358,6 +3366,9 @@ QgsWmsImageDownloadHandler::~QgsWmsImageDownloadHandler()
 
 void QgsWmsImageDownloadHandler::downloadBlocking()
 {
+  if ( mFeedback && mFeedback->isCancelled() )
+    return; // nothing to do
+
   mEventLoop->exec( QEventLoop::ExcludeUserInputEvents );
 
   Q_ASSERT( !mCacheReply );
@@ -3497,6 +3508,16 @@ QgsWmsTiledImageDownloadHandler::QgsWmsTiledImageDownloadHandler( const QString&
     , mSmoothPixmapTransform( smoothPixmapTransform )
     , mFeedback( feedback )
 {
+  if ( feedback )
+  {
+    connect( feedback, SIGNAL( cancelled() ), this, SLOT( cancelled() ), Qt::QueuedConnection );
+
+    // rendering could have been cancelled before we started to listen to cancelled() signal
+    // so let's check before doing the download and maybe quit prematurely
+    if ( feedback->isCancelled() )
+      return;
+  }
+
   Q_FOREACH ( const TileRequest& r, requests )
   {
     QNetworkRequest request( r.url );
@@ -3513,9 +3534,6 @@ QgsWmsTiledImageDownloadHandler::QgsWmsTiledImageDownloadHandler( const QString&
 
     mReplies << reply;
   }
-
-  if ( feedback )
-    connect( feedback, SIGNAL( cancelled() ), this, SLOT( cancelled() ), Qt::QueuedConnection );
 }
 
 QgsWmsTiledImageDownloadHandler::~QgsWmsTiledImageDownloadHandler()
@@ -3525,6 +3543,9 @@ QgsWmsTiledImageDownloadHandler::~QgsWmsTiledImageDownloadHandler()
 
 void QgsWmsTiledImageDownloadHandler::downloadBlocking()
 {
+  if ( mFeedback && mFeedback->isCancelled() )
+    return; // nothing to do
+
   mEventLoop->exec( QEventLoop::ExcludeUserInputEvents );
 
   Q_ASSERT( mReplies.isEmpty() );
diff --git a/src/providers/wms/qgswmsprovider.h b/src/providers/wms/qgswmsprovider.h
index feb48d802c7..9a137faa260 100644
--- a/src/providers/wms/qgswmsprovider.h
+++ b/src/providers/wms/qgswmsprovider.h
@@ -571,6 +571,8 @@ class QgsWmsImageDownloadHandler : public QObject
     QImage* mCachedImage;
 
     QEventLoop* mEventLoop;
+
+    QgsRasterBlockFeedback* mFeedback;
 };