Remove QgsTaskManager singleton, and instead attach an instance

to QgsApplication.

ie instead of QgsTaskManager.instance(), use
QgsApplication.taskManager()

Author: nyalldawson

python/core/qgsapplication.sip

@@ -374,6 +374,13 @@ static void qtgui_UpdatePyArgv(PyObject *argvlist, int argc, char **argv)
      * @note added in 2.4 */
     static void setMaxThreads( int maxThreads );
 
+    /**
+     * Returns the application's task manager, used for managing application
+     * wide background task handling.
+     * @note added in QGIS 3.0
+     */
+    static QgsTaskManager* taskManager();
+
 %If(ANDROID)
     //dummy method to workaround sip generation issue issue
     bool x11EventFilter ( XEvent * event );

python/core/qgstaskmanager.sip

@@ -251,10 +251,6 @@ class QgsTaskManager : QObject
 %End
   public:
 
-    /** Returns the global task manager instance pointer, creating the object on the first call.
-     */
-    static QgsTaskManager * instance();
-
     /** Constructor for QgsTaskManager.
      * @param parent parent QObject
      */

src/app/qgisapp.cpp

@@ -2410,7 +2410,7 @@ void QgisApp::createStatusBar()
   connect( mMapCanvas, SIGNAL( renderStarting() ), this, SLOT( canvasRefreshStarted() ) );
   connect( mMapCanvas, SIGNAL( mapCanvasRefreshed() ), this, SLOT( canvasRefreshFinished() ) );
 
-  mTaskManagerWidget = new QgsTaskManagerStatusBarWidget( QgsTaskManager::instance(), statusBar() );
+  mTaskManagerWidget = new QgsTaskManagerStatusBarWidget( QgsApplication::taskManager(), statusBar() );
   statusBar()->addPermanentWidget( mTaskManagerWidget, 0 );
 
   // Bumped the font up one point size since 8 was too

src/core/qgsapplication.cpp

@@ -25,6 +25,7 @@
 #include "qgsexpression.h"
 #include "qgsactionscoperegistry.h"
 #include "qgsruntimeprofiler.h"
+#include "qgstaskmanager.h"
 
 #include <QDir>
 #include <QFile>
@@ -105,6 +106,9 @@ QgsApplication::QgsApplication( int & argc, char ** argv, bool GUIenabled, const
 {
   sPlatformName = platformName;
 
+  // don't use initializer lists or scoped pointers - as more objects are added here we
+  // will need to be careful with the order of creation/destruction
+  mTaskManager = new QgsTaskManager();
   mProfiler = new QgsRuntimeProfiler();
   mActionScopeRegistry = new QgsActionScopeRegistry();
 
@@ -239,6 +243,7 @@ void QgsApplication::init( QString customConfigPath )
 QgsApplication::~QgsApplication()
 {
   delete mActionScopeRegistry;
+  delete mTaskManager;
   delete mProfiler;
 }
 
@@ -1407,6 +1412,11 @@ void QgsApplication::setMaxThreads( int maxThreads )
   QgsDebugMsg( QString( "set QThreadPool max thread count to %1" ).arg( QThreadPool::globalInstance()->maxThreadCount() ) );
 }
 
+QgsTaskManager* QgsApplication::taskManager()
+{
+  return instance()->mTaskManager;
+}
+
 void QgsApplication::emitSettingsChanged()
 {
   emit settingsChanged();

src/core/qgsapplication.h

@@ -24,6 +24,7 @@
 
 class QgsActionScopeRegistry;
 class QgsRuntimeProfiler;
+class QgsTaskManager;
 
 /** \ingroup core
  * Extends QApplication to provide access to QGIS specific resources such
@@ -366,6 +367,13 @@ class CORE_EXPORT QgsApplication : public QApplication
      * @note added in 2.4 */
     static void setMaxThreads( int maxThreads );
 
+    /**
+     * Returns the application's task manager, used for managing application
+     * wide background task handling.
+     * @note added in QGIS 3.0
+     */
+    static QgsTaskManager* taskManager();
+
 #ifdef ANDROID
     //dummy method to workaround sip generation issue issue
     bool x11EventFilter( XEvent * event )
@@ -456,6 +464,7 @@ class CORE_EXPORT QgsApplication : public QApplication
 
     QgsActionScopeRegistry* mActionScopeRegistry;
     QgsRuntimeProfiler* mProfiler;
+    QgsTaskManager* mTaskManager;
 };
 
 #endif

src/core/qgstaskmanager.cpp

@@ -110,18 +110,6 @@ void QgsTask::terminated()
 // QgsTaskManager
 //
 
-// Static calls to enforce singleton behaviour
-QgsTaskManager *QgsTaskManager::sInstance = nullptr;
-QgsTaskManager *QgsTaskManager::instance()
-{
-  if ( !sInstance )
-  {
-    sInstance = new QgsTaskManager();
-  }
-
-  return sInstance;
-}
-
 QgsTaskManager::QgsTaskManager( QObject* parent )
     : QObject( parent )
     , mTaskMutex( new QMutex( QMutex::Recursive ) )

src/core/qgstaskmanager.h

@@ -273,7 +273,7 @@ typedef QList< QgsTask* > QgsTaskList;
 /** \ingroup core
  * \class QgsTaskManager
  * \brief Task manager for managing a set of long-running QgsTask tasks. This class can be created directly,
- * or accessed via a global instance.
+ * or accessed via QgsApplication::taskManager().
  * \note Added in version 3.0
  */
 class CORE_EXPORT QgsTaskManager : public QObject
@@ -282,10 +282,6 @@ class CORE_EXPORT QgsTaskManager : public QObject
 
   public:
 
-    /** Returns the global task manager instance pointer, creating the object on the first call.
-     */
-    static QgsTaskManager * instance();
-
     /** Constructor for QgsTaskManager.
      * @param parent parent QObject
      */
@@ -405,8 +401,6 @@ class CORE_EXPORT QgsTaskManager : public QObject
 
   private:
 
-    static QgsTaskManager *sInstance;
-
     struct TaskInfo
     {
       TaskInfo( QgsTask* task = nullptr )

tests/src/core/testqgsapplication.cpp

@@ -83,7 +83,6 @@ void TestQgsApplication::platformName()
   QCOMPARE( QgsApplication::platform(), QString( "desktop" ) );
 }
 
-
 void TestQgsApplication::checkPaths()
 {
   QString myPath = QgsApplication::authorsFilePath();

tests/src/core/testqgstaskmanager.cpp

@@ -150,6 +150,7 @@ class FinishTask : public QgsTask
 class TestQgsTaskManager : public QObject
 {
     Q_OBJECT
+  public:
 
   private slots:
     void initTestCase();// will be called before the first testfunction is executed.
@@ -159,7 +160,6 @@ class TestQgsTaskManager : public QObject
     void task();
     void taskResult();
     void taskFinished();
-    void createInstance();
     void addTask();
     //void taskTerminationBeforeDelete();
     void taskId();
@@ -171,8 +171,6 @@ class TestQgsTaskManager : public QObject
     void dependancies();
     void layerDependencies();
 
-  private:
-
 };
 
 void TestQgsTaskManager::initTestCase()
@@ -279,12 +277,6 @@ void TestQgsTaskManager::taskResult()
   QCOMPARE( task->status(), QgsTask::Terminated );
 }
 
-void TestQgsTaskManager::createInstance()
-{
-  QgsTaskManager* manager = QgsTaskManager::instance();
-  QVERIFY( manager );
-}
-
 void TestQgsTaskManager::addTask()
 {
   //create an empty manager

tests/src/python/test_qgstaskmanager.py

@@ -17,7 +17,8 @@
 
 from qgis.core import (
     QgsTask,
-    QgsTaskManager
+    QgsTaskManager,
+    QgsApplication
 )
 from qgis.PyQt.QtCore import (QCoreApplication)
 
@@ -91,7 +92,7 @@ def testTaskFromFunction(self):
         """ test creating task from function """
 
         task = QgsTask.fromFunction('test task', run, 20)
-        QgsTaskManager.instance().addTask(task)
+        QgsApplication.taskManager().addTask(task)
         while task.status() not in [QgsTask.Complete, QgsTask.Terminated]:
             pass
 
@@ -101,7 +102,7 @@ def testTaskFromFunction(self):
 
         # try a task which cancels itself
         bad_task = QgsTask.fromFunction('test task2', run, None)
-        QgsTaskManager.instance().addTask(bad_task)
+        QgsApplication.taskManager().addTask(bad_task)
         while bad_task.status() not in [QgsTask.Complete, QgsTask.Terminated]:
             pass
 
@@ -113,7 +114,7 @@ def testTaskFromFunctionWithKwargs(self):
         """ test creating task from function using kwargs """
 
         task = QgsTask.fromFunction('test task3', run_with_kwargs, result=5, password=1)
-        QgsTaskManager.instance().addTask(task)
+        QgsApplication.taskManager().addTask(task)
         while task.status() not in [QgsTask.Complete, QgsTask.Terminated]:
             pass
 
@@ -124,14 +125,14 @@ def testTaskFromFunctionWithKwargs(self):
     def testTaskFromFunctionIsCancellable(self):
         """ test that task from function can check cancelled status """
         bad_task = QgsTask.fromFunction('test task4', cancellable)
-        QgsTaskManager.instance().addTask(bad_task)
+        QgsApplication.taskManager().addTask(bad_task)
         while bad_task.status() != QgsTask.Running:
             pass
 
         bad_task.cancel()
         while bad_task.status() == QgsTask.Running:
             pass
-        while QgsTaskManager.instance().countActiveTasks() > 0:
+        while QgsApplication.taskManager().countActiveTasks() > 0:
             QCoreApplication.processEvents()
 
         self.assertEqual(bad_task.status(), QgsTask.Terminated)
@@ -140,7 +141,7 @@ def testTaskFromFunctionIsCancellable(self):
     def testTaskFromFunctionCanSetProgress(self):
         """ test that task from function can set progress """
         task = QgsTask.fromFunction('test task5', progress_function)
-        QgsTaskManager.instance().addTask(task)
+        QgsApplication.taskManager().addTask(task)
         while task.status() != QgsTask.Running:
             pass
 
@@ -152,16 +153,16 @@ def testTaskFromFunctionCanSetProgress(self):
         task.cancel()
         while task.status() == QgsTask.Running:
             pass
-        while QgsTaskManager.instance().countActiveTasks() > 0:
+        while QgsApplication.taskManager().countActiveTasks() > 0:
             QCoreApplication.processEvents()
 
     def testTaskFromFunctionFinished(self):
         """ test that task from function can have callback finished function"""
         task = QgsTask.fromFunction('test task', run_no_result, on_finished=finished_no_val)
-        QgsTaskManager.instance().addTask(task)
+        QgsApplication.taskManager().addTask(task)
         while task.status() not in [QgsTask.Complete, QgsTask.Terminated]:
             pass
-        while QgsTaskManager.instance().countActiveTasks() > 0:
+        while QgsApplication.taskManager().countActiveTasks() > 0:
             QCoreApplication.processEvents()
 
         # check that the finished function was called
@@ -172,10 +173,10 @@ def testTaskFromFunctionFinished(self):
     def testTaskFromFunctionFinishedWithVal(self):
         """ test that task from function can have callback finished function and is passed result values"""
         task = QgsTask.fromFunction('test task', run_single_val_result, on_finished=finished_single_value_result)
-        QgsTaskManager.instance().addTask(task)
+        QgsApplication.taskManager().addTask(task)
         while task.status() not in [QgsTask.Complete, QgsTask.Terminated]:
             pass
-        while QgsTaskManager.instance().countActiveTasks() > 0:
+        while QgsApplication.taskManager().countActiveTasks() > 0:
             QCoreApplication.processEvents()
 
         # check that the finished function was called
@@ -186,10 +187,10 @@ def testTaskFromFunctionFinishedWithVal(self):
     def testTaskFromFunctionFinishedWithMultipleValues(self):
         """ test that task from function can have callback finished function and is passed multiple result values"""
         task = QgsTask.fromFunction('test task', run_multiple_val_result, on_finished=finished_multiple_value_result)
-        QgsTaskManager.instance().addTask(task)
+        QgsApplication.taskManager().addTask(task)
         while task.status() not in [QgsTask.Complete, QgsTask.Terminated]:
             pass
-        while QgsTaskManager.instance().countActiveTasks() > 0:
+        while QgsApplication.taskManager().countActiveTasks() > 0:
             QCoreApplication.processEvents()
 
         # check that the finished function was called