From 4a2226af31f7f932ae65dee352a0cb40fb086d41 Mon Sep 17 00:00:00 2001
From: Nyall Dawson <nyall.dawson@gmail.com>
Date: Sun, 23 Apr 2017 13:07:04 +1000
Subject: [PATCH] Allow canceling background map renders

---
 python/core/qgsmaprenderertask.sip |  3 +++
 src/core/qgsmaprenderertask.cpp    | 27 ++++++++++++++++++++++++---
 src/core/qgsmaprenderertask.h      |  7 +++++++
 3 files changed, 34 insertions(+), 3 deletions(-)

diff --git a/python/core/qgsmaprenderertask.sip b/python/core/qgsmaprenderertask.sip
index 0fb5d5050fa..aa34a73f84e 100644
--- a/python/core/qgsmaprenderertask.sip
+++ b/python/core/qgsmaprenderertask.sip
@@ -47,6 +47,9 @@ class QgsMapRendererTask : QgsTask
  Adds ``annotations`` to be rendered on the map.
 %End
 
+    virtual void cancel();
+
+
   signals:
 
     void renderingComplete();
diff --git a/src/core/qgsmaprenderertask.cpp b/src/core/qgsmaprenderertask.cpp
index 6a42ea6ecf2..bd63124ba16 100644
--- a/src/core/qgsmaprenderertask.cpp
+++ b/src/core/qgsmaprenderertask.cpp
@@ -18,7 +18,6 @@
 #include "qgsannotation.h"
 #include "qgsannotationmanager.h"
 #include "qgsmaprenderertask.h"
-#include "qgsmaprenderercustompainterjob.h"
 
 
 QgsMapRendererTask::QgsMapRendererTask( const QgsMapSettings &ms, const QString &fileName, const QString &fileFormat )
@@ -47,6 +46,16 @@ void QgsMapRendererTask::addAnnotations( QList< QgsAnnotation * > annotations )
   }
 }
 
+void QgsMapRendererTask::cancel()
+{
+  mJobMutex.lock();
+  if ( mJob )
+    mJob->cancelWithoutBlocking();
+  mJobMutex.unlock();
+
+  QgsTask::cancel();
+}
+
 bool QgsMapRendererTask::run()
 {
   QImage img;
@@ -73,14 +82,26 @@ bool QgsMapRendererTask::run()
   if ( !destPainter )
     return false;
 
-  QgsMapRendererCustomPainterJob r( mMapSettings, destPainter );
-  r.renderSynchronously();
+  mJobMutex.lock();
+  mJob.reset( new QgsMapRendererCustomPainterJob( mMapSettings, destPainter ) );
+  mJobMutex.unlock();
+  mJob->renderSynchronously();
+
+  mJobMutex.lock();
+  mJob.reset( nullptr );
+  mJobMutex.unlock();
+
+  if ( isCanceled() )
+    return false;
 
   QgsRenderContext context = QgsRenderContext::fromMapSettings( mMapSettings );
   context.setPainter( destPainter );
 
   Q_FOREACH ( QgsAnnotation *annotation, mAnnotations )
   {
+    if ( isCanceled() )
+      return false;
+
     if ( !annotation || !annotation->isVisible() )
     {
       continue;
diff --git a/src/core/qgsmaprenderertask.h b/src/core/qgsmaprenderertask.h
index 941ee31c684..a94b010d18c 100644
--- a/src/core/qgsmaprenderertask.h
+++ b/src/core/qgsmaprenderertask.h
@@ -24,8 +24,10 @@
 #include "qgsannotationmanager.h"
 #include "qgsmapsettings.h"
 #include "qgstaskmanager.h"
+#include "qgsmaprenderercustompainterjob.h"
 
 #include <QPainter>
+class QgsMapRendererCustomPainterJob;
 
 /**
  * \class QgsMapRendererTask
@@ -65,6 +67,8 @@ class CORE_EXPORT QgsMapRendererTask : public QgsTask
      */
     void addAnnotations( QList< QgsAnnotation * > annotations );
 
+    void cancel() override;
+
   signals:
 
     /**
@@ -86,6 +90,9 @@ class CORE_EXPORT QgsMapRendererTask : public QgsTask
 
     QgsMapSettings mMapSettings;
 
+    QMutex mJobMutex;
+    std::unique_ptr< QgsMapRendererCustomPainterJob > mJob;
+
     QPainter *mPainter = nullptr;
 
     QString mFileName;