Allow task priority to be specified

qgis · Dec 5, 2016 · 4dc3dd9 · 4dc3dd9
1 parent 9b76374
commit 4dc3dd9
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Showing 3 changed files with 29 additions and 20 deletions.
diff --git a/python/core/qgstaskmanager.sip b/python/core/qgstaskmanager.sip
@@ -311,18 +311,21 @@ class QgsTaskManager : QObject
 
     /** Adds a task to the manager. Ownership of the task is transferred
      * to the manager, and the task manager will be responsible for starting
-     * the task.
+     * the task. The priority argument can be used to control the run queue's
+     * order of execution.
      * @returns unique task ID
      */
-    long addTask( QgsTask* task /Transfer/ );
+    long addTask( QgsTask* task /Transfer/, int priority = 0 );
 
     /**
      * Adds a task to the manager, using a full task definition (including dependancy
      * handling). Ownership of the task is transferred to the manager, and the task
-     * manager will be responsible for starting the task.
+     * manager will be responsible for starting the task. The priority argument can
+     * be used to control the run queue's order of execution.
      * @returns unique task ID
      */
-    long addTask( const TaskDefinition& task /Transfer/ );
+    long addTask( const TaskDefinition& task /Transfer/, int priority = 0 );
+
 
     /** Returns the task with matching ID.
      * @param id task ID

diff --git a/src/core/qgstaskmanager.cpp b/src/core/qgstaskmanager.cpp
@@ -40,7 +40,7 @@ QgsTask::QgsTask( const QString &name, const Flags& flags )
 
 QgsTask::~QgsTask()
 {
-  Q_ASSERT_X( mStatus == Queued || mStatus == Terminated || mStatus == Complete, "delete", QString( "status was %1" ).arg( mStatus ).toLatin1() );
+  Q_ASSERT_X( mStatus != Running, "delete", QString( "status was %1" ).arg( mStatus ).toLatin1() );
 
   QThreadPool::globalInstance()->cancel( this );
 
@@ -333,25 +333,26 @@ QgsTaskManager::~QgsTaskManager()
   delete mLayerDependenciesMutex;
 }
 
-long QgsTaskManager::addTask( QgsTask* task )
+long QgsTaskManager::addTask( QgsTask* task, int priority )
 {
-  return addTaskPrivate( task, QgsTaskList(), false );
+  return addTaskPrivate( task, QgsTaskList(), false, priority );
 }
 
-long QgsTaskManager::addTask( const QgsTaskManager::TaskDefinition& definition )
+long QgsTaskManager::addTask( const QgsTaskManager::TaskDefinition& definition, int priority )
 {
   return addTaskPrivate( definition.task,
                          definition.dependencies,
-                         false );
+                         false,
+                         priority );
 }
 
 
-long QgsTaskManager::addTaskPrivate( QgsTask* task, QgsTaskList dependencies, bool isSubTask )
+long QgsTaskManager::addTaskPrivate( QgsTask* task, QgsTaskList dependencies, bool isSubTask, int priority )
 {
   long taskId = mNextTaskId++;
 
   mTaskMutex->lockForWrite();
-  mTasks.insert( taskId, task );
+  mTasks.insert( taskId, TaskInfo( task, priority ) );
   mTaskMutex->unlock();
 
   if ( isSubTask )
@@ -387,7 +388,7 @@ long QgsTaskManager::addTaskPrivate( QgsTask* task, QgsTaskList dependencies, bo
         break;
     }
     //recursively add sub tasks
-    addTaskPrivate( subTask.task, subTask.dependencies, true );
+    addTaskPrivate( subTask.task, subTask.dependencies, true, priority );
   }
 
   if ( !dependencies.isEmpty() )
@@ -735,7 +736,7 @@ void QgsTaskManager::processQueue()
     QgsTask* task = it.value().task;
     if ( task && task->mStatus == QgsTask::Queued && dependenciesSatisified( it.key() ) && it.value().added.testAndSetRelaxed( 0, 1 ) )
     {
-      QThreadPool::globalInstance()->start( task );
+      QThreadPool::globalInstance()->start( task, it.value().priority );
     }
 
     if ( task && ( task->mStatus != QgsTask::Complete && task->mStatus != QgsTask::Terminated ) )

diff --git a/src/core/qgstaskmanager.h b/src/core/qgstaskmanager.h
@@ -386,18 +386,20 @@ class CORE_EXPORT QgsTaskManager : public QObject
 
     /** Adds a task to the manager. Ownership of the task is transferred
      * to the manager, and the task manager will be responsible for starting
-     * the task.
+     * the task. The priority argument can be used to control the run queue's
+     * order of execution.
      * @returns unique task ID
      */
-    long addTask( QgsTask* task );
+    long addTask( QgsTask* task, int priority = 0 );
 
     /**
      * Adds a task to the manager, using a full task definition (including dependancy
      * handling). Ownership of the task is transferred to the manager, and the task
-     * manager will be responsible for starting the task.
+     * manager will be responsible for starting the task. The priority argument can
+     * be used to control the run queue's order of execution.
      * @returns unique task ID
      */
-    long addTask( const TaskDefinition& task );
+    long addTask( const TaskDefinition& task, int priority = 0 );
 
     /** Returns the task with matching ID.
      * @param id task ID
@@ -498,12 +500,14 @@ class CORE_EXPORT QgsTaskManager : public QObject
 
     struct TaskInfo
     {
-      TaskInfo( QgsTask* task = nullptr )
+      TaskInfo( QgsTask* task = nullptr, int priority = 0 )
           : task( task )
-          , added( false )
+          , added( 0 )
+          , priority( priority )
       {}
       QgsTask* task;
       QAtomicInt added;
+      int priority;
     };
 
     mutable QReadWriteLock* mTaskMutex;
@@ -531,7 +535,8 @@ class CORE_EXPORT QgsTaskManager : public QObject
 
     long addTaskPrivate( QgsTask* task,
                          QgsTaskList dependencies,
-                         bool isSubTask );
+                         bool isSubTask,
+                         int priority );
 
     bool cleanupAndDeleteTask( QgsTask* task );