QgsTask::waitForFinished without event loop

because the old approach with using signals, using deleteLater and using an internal event loop is a very good recipe for big troubles.
qgis · Sep 21, 2017 · 88fcbb0 · 88fcbb0
1 parent 15e650d
commit 88fcbb0
Show file tree

Hide file tree

Showing 3 changed files with 28 additions and 21 deletions.
diff --git a/python/core/qgstaskmanager.sip b/python/core/qgstaskmanager.sip
@@ -170,10 +170,10 @@ class QgsTask : QObject
  :rtype: list of QgsMapLayer
 %End
 
-    bool waitForFinished( int timeout = 30000 );
+    bool waitForFinished( unsigned long timeout = 30000 );
 %Docstring
  Blocks the current thread until the task finishes or a maximum of ``timeout`` milliseconds.
- If the ``timeout`` is ``-1`` the thread will be blocked forever.
+ If ``timeout`` is ``0`` the thread will be blocked forever.
  In case of a timeout, the task will still be running.
  In case the task already is finished, the method will return immediately while
  returning ``true``.

diff --git a/src/core/qgstaskmanager.cpp b/src/core/qgstaskmanager.cpp
@@ -35,7 +35,9 @@ QgsTask::QgsTask( const QString &name, const Flags &flags )
   , mTotalProgress( 0.0 )
   , mShouldTerminate( false )
   , mStartCount( 0 )
-{}
+{
+  mNotFinishedMutex.lock();
+}
 
 QgsTask::~QgsTask()
 {
@@ -142,26 +144,19 @@ QList<QgsMapLayer *> QgsTask::dependentLayers() const
   return _qgis_listQPointerToRaw( mDependentLayers );
 }
 
-bool QgsTask::waitForFinished( int timeout )
+bool QgsTask::waitForFinished( unsigned long timeout )
 {
-  QEventLoop loop;
   bool rv = true;
-
-  connect( this, &QgsTask::taskCompleted, &loop, &QEventLoop::quit );
-  connect( this, &QgsTask::taskTerminated, &loop, &QEventLoop::quit );
-  QTimer timer;
-
-  if ( timeout != -1 )
+  if ( mOverallStatus == Complete || mOverallStatus == Terminated )
   {
-    timer.start( timeout );
-    connect( &timer, &QTimer::timeout, [&rv]() { rv = false; } );
-    connect( &timer, &QTimer::timeout, &loop, &QEventLoop::quit );
+    rv = true;
+  }
+  else
+  {
+    if ( timeout == 0 )
+      timeout = ULONG_MAX;
+    rv = mTaskFinished.wait( &mNotFinishedMutex, timeout );
   }
-
-  if ( status() == QgsTask::Complete || status() == QgsTask::Terminated )
-    return true;
-  loop.exec();
-
   return rv;
 }
 
@@ -249,9 +244,13 @@ void QgsTask::processSubTasksForCompletion()
   if ( mStatus == Complete && subTasksCompleted )
   {
     mOverallStatus = Complete;
+
     setProgress( 100.0 );
     emit statusChanged( Complete );
     emit taskCompleted();
+    mTaskFinished.wakeAll();
+    mNotFinishedMutex.unlock();
+    mTaskFinished.wakeAll();
   }
   else if ( mStatus == Complete )
   {
@@ -275,8 +274,12 @@ void QgsTask::processSubTasksForTermination()
   if ( mStatus == Terminated && subTasksTerminated && mOverallStatus != Terminated )
   {
     mOverallStatus = Terminated;
+
     emit statusChanged( Terminated );
     emit taskTerminated();
+    mTaskFinished.wakeAll();
+    mNotFinishedMutex.unlock();
+    mTaskFinished.wakeAll();
   }
   else if ( mStatus == Terminated && !subTasksTerminated )
   {

diff --git a/src/core/qgstaskmanager.h b/src/core/qgstaskmanager.h
@@ -188,14 +188,14 @@ class CORE_EXPORT QgsTask : public QObject
 
     /**
      * Blocks the current thread until the task finishes or a maximum of \a timeout milliseconds.
-     * If the \a timeout is ``-1`` the thread will be blocked forever.
+     * If \a timeout is ``0`` the thread will be blocked forever.
      * In case of a timeout, the task will still be running.
      * In case the task already is finished, the method will return immediately while
      * returning ``true``.
      *
      * The result will be false if the wait timed out and true in any other case.
      */
-    bool waitForFinished( int timeout = 30000 );
+    bool waitForFinished( unsigned long timeout = 30000 );
 
   signals:
 
@@ -290,13 +290,17 @@ class CORE_EXPORT QgsTask : public QObject
     //! Status of this task and all subtasks
     TaskStatus mOverallStatus;
 
+    QMutex mNotFinishedMutex;
+
     //! Progress of this (parent) task alone
     double mProgress;
     //! Overall progress of this task and all subtasks
     double mTotalProgress;
     bool mShouldTerminate;
     int mStartCount;
 
+    QWaitCondition mTaskFinished;
+
     struct SubTask
     {
       SubTask( QgsTask *task, QgsTaskList dependencies, SubTaskDependency dependency )