Framework for task manager

Adds new classes:
- QgsTask. An interface for long-running background tasks
- QgsTaskManager. Handles groups of tasks - also available as a global
instance for tracking application wide tasks
- QgsTaskManagerWidget. A list view for showing active tasks and their
progress, and for cancelling them

A new dock widget has been added with a task manager widget showing
global tasks

python/core/core.sip

@@ -138,6 +138,7 @@
 %Include qgsstatisticalsummary.sip
 %Include qgsstringstatisticalsummary.sip
 %Include qgsstringutils.sip
+%Include qgstaskmanager.sip
 %Include qgstextrenderer.sip
 %Include qgstolerance.sip
 %Include qgstracer.sip

python/core/qgstaskmanager.sip

@@ -0,0 +1,174 @@
+/** \ingroup core
+ * \class QgsTask
+ * \brief Interface class for long running tasks which will be handled by a QgsTaskManager
+ * \note Added in version 2.16
+ */
+class QgsTask : QObject
+{
+
+%TypeHeaderCode
+#include <qgstaskmanager.h>
+%End
+  public:
+
+    //! Status of tasks
+    enum TaskStatus
+    {
+      Running, /*!< Task is currently running */
+      Complete, /*!< Task successfully completed */
+      Terminated, /*!< Task was terminated or errored */
+      // Paused,
+      // Queued,
+    };
+
+    /** Constructor for QgsTask.
+     * @param description text description of task
+     */
+    QgsTask( const QString& description = QString() );
+
+    //! Will be called when task has been terminated, either through
+    //! user interaction or other reason (eg application exit)
+    //! @note derived classes must ensure they call the base method
+    virtual void terminate();
+
+    //! Returns true if the task is active, ie it is not complete and has
+    //! not been terminated.
+    bool isActive() const;
+
+    //! Returns the current task status.
+    TaskStatus status() const;
+
+    //! Returns the task's description.
+    QString description() const;
+
+    //! Returns the task's progress (between 0.0 and 100.0)
+    double progress() const;
+
+  signals:
+
+    //! Will be emitted by task when its progress changes
+    //! @param progress percent of progress, from 0.0 - 100.0
+    //! @note derived classes should not emit this signal directly, instead they should call
+    //! setProgress()
+    void progressChanged( double progress );
+
+    //! Will be emitted by task when its status changes
+    //! @param status new task status
+    //! @note derived classes should not emit this signal directly, instead they should call
+    //! completed() or stopped()
+    void statusChanged( int status );
+
+    //! Will be emitted by task to indicate its completion.
+    //! @note derived classes should not emit this signal directly, instead they should call
+    //! completed()
+    void taskCompleted();
+
+    //! Will be emitted by task if it has terminated for any reason
+    //! other then completion.
+    //! @note derived classes should not emit this signal directly, instead they should call
+    //! stopped()//!
+    void taskStopped();
+
+  protected:
+
+    //! Sets the task's current progress. Should be called whenever the
+    //! task wants to update it's progress. Calling will automatically emit the progressChanged
+    //! signal.
+    //! @param progress percent of progress, from 0.0 - 100.0
+    void setProgress( double progress );
+
+    //! Sets the task as completed. Should be called when the task is complete.
+    //! Calling will automatically emit the statusChanged and taskCompleted signals.
+    void completed();
+
+    //! Sets the task as stopped. Should be called whenever the task ends for any
+    //! reason other than successful completion.
+    //! Calling will automatically emit the statusChanged and taskStopped signals.
+    void stopped();
+};
+
+/** \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.
+ * \note Added in version 2.16
+ */
+class QgsTaskManager : QObject
+{
+%TypeHeaderCode
+#include <qgstaskmanager.h>
+%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
+     */
+    QgsTaskManager( QObject* parent /TransferThis/ = nullptr );
+
+    virtual ~QgsTaskManager();
+
+    /** Adds a task to the manager. Ownership of the task is transferred
+     * to the manager.
+     * @param task task to add
+     * @returns unique task ID
+     */
+    long addTask( QgsTask* task /Transfer/ );
+
+    /** Deletes the specified task, first terminating it if it is currently
+     * running.
+     * @param id task ID
+     * @returns true if task was found and deleted
+     */
+    bool deleteTask( long id );
+
+    /** Deletes the specified task, first terminating it if it is currently
+     * running.
+     * @param task task to delete
+     * @returns true if task was contained in manager and deleted
+     */
+    bool deleteTask( QgsTask* task );
+
+    /** Returns the task with matching ID.
+     * @param id task ID
+     * @returns task if found, or nullptr
+     */
+    QgsTask* task( long id ) const;
+
+    /** Returns all tasks tracked by the manager.
+     */
+    QList<QgsTask*> tasks() const;
+
+    //! Returns the number of tasks tracked by the manager.
+    int count() const;
+
+    /** Returns the unique task ID corresponding to a task managed by the class.
+     * @param task task to find
+     * @returns task ID, or -1 if task not found
+     */
+    long taskId( QgsTask* task ) const;
+
+  signals:
+
+    //! Will be emitted when a task reports a progress change
+    //! @param taskId ID of task
+    //! @param progress percent of progress, from 0.0 - 100.0
+    void progressChanged( long taskId, double progress );
+
+    //! Will be emitted when a task reports a status change
+    //! @param taskId ID of task
+    //! @param status new task status
+    void statusChanged( long taskId, int status );
+
+    //! Emitted when a new task has been added to the manager
+    //! @param taskId ID of task
+    void taskAdded( long taskId );
+
+    //! Emitted when a task is about to be deleted
+    //! @param taskId ID of task
+    void taskAboutToBeDeleted( long taskId );
+
+};

python/gui/gui.sip

@@ -161,6 +161,7 @@
 %Include qgstablewidgetbase.sip
 %Include qgstabwidget.sip
 %Include qgstablewidgetitem.sip
+%Include qgstaskmanagerwidget.sip
 %Include qgstextannotationitem.sip
 %Include qgstextformatwidget.sip
 %Include qgstextpreview.sip

python/gui/qgstaskmanagerwidget.sip

@@ -0,0 +1,95 @@
+/** \ingroup gui
+ * \class QgsTaskManagerWidget
+ * A widget which displays tasks from a QgsTaskManager and allows for interaction with the manager
+ * @see QgsTaskManager
+ * @note introduced in QGIS 2.16
+ */
+class QgsTaskManagerWidget : QTreeView
+{
+%TypeHeaderCode
+#include <qgstaskmanagerwidget.h>
+%End
+  public:
+
+     /** Constructor for QgsTaskManagerWidget
+     * @param manager task manager associated with widget
+     * @param parent parent widget
+     */
+     QgsTaskManagerWidget( QgsTaskManager* manager, QWidget* parent /TransferThis/ = nullptr );
+
+};
+
+
+/** \ingroup gui
+ * \class QgsTaskManagerModel
+ * A model representing a QgsTaskManager
+ * @see QgsTaskManager
+ * @note introduced in QGIS 2.16
+ */
+class QgsTaskManagerModel: QAbstractItemModel
+{
+%TypeHeaderCode
+#include <qgstaskmanagerwidget.h>
+%End
+  public:
+
+    /** Constructor for QgsTaskManagerModel
+     * @param manager task manager for model
+     * @param parent parent object
+     */
+    explicit QgsTaskManagerModel( QgsTaskManager* manager, QObject* parent /TransferThis/ = nullptr );
+
+    //reimplemented QAbstractItemModel methods
+    QModelIndex index( int row, int column, const QModelIndex &parent = QModelIndex() ) const;
+    QModelIndex parent( const QModelIndex &index ) const;
+    int rowCount( const QModelIndex &parent = QModelIndex() ) const;
+    int columnCount( const QModelIndex &parent = QModelIndex() ) const;
+    QVariant data( const QModelIndex &index, int role = Qt::DisplayRole ) const;
+    Qt::ItemFlags flags( const QModelIndex & index ) const;
+    bool setData( const QModelIndex & index, const QVariant & value, int role = Qt::EditRole );
+
+};
+
+
+/** \ingroup gui
+ * \class QgsProgressBarDelegate
+ * A delegate for showing a progress bar within a view
+ * @note introduced in QGIS 2.16
+ */
+class QgsProgressBarDelegate : QStyledItemDelegate
+{
+%TypeHeaderCode
+#include <qgstaskmanagerwidget.h>
+%End
+  public:
+
+    /** Constructor for QgsProgressBarDelegate
+     * @param parent parent object
+     */
+    QgsProgressBarDelegate( QObject* parent /TransferThis/ = nullptr );
+
+    void paint( QPainter * painter, const QStyleOptionViewItem & option, const QModelIndex & index ) const;
+    QSize sizeHint( const QStyleOptionViewItem &option, const QModelIndex &index ) const;
+};
+
+/** \ingroup gui
+ * \class QgsProgressBarDelegate
+ * A delegate for showing task status within a view. Clicks on the delegate will cause the task to be cancelled (via the model).
+ * @note introduced in QGIS 2.16
+ */
+class QgsTaskStatusDelegate : QStyledItemDelegate
+{
+%TypeHeaderCode
+#include <qgstaskmanagerwidget.h>
+%End
+  public:
+
+    /** Constructor for QgsTaskStatusDelegate
+     * @param parent parent object
+     */
+    QgsTaskStatusDelegate( QObject* parent /TransferThis/ = nullptr );
+
+    void paint( QPainter * painter, const QStyleOptionViewItem & option, const QModelIndex & index ) const;
+    QSize sizeHint( const QStyleOptionViewItem &option, const QModelIndex &index ) const;
+    bool editorEvent( QEvent * event, QAbstractItemModel * model, const QStyleOptionViewItem & option, const QModelIndex & index );
+};

src/app/qgisapp.cpp

@@ -221,6 +221,8 @@
 #include "qgsstatusbarscalewidget.h"
 #include "qgsstyle.h"
 #include "qgssvgannotationitem.h"
+#include "qgstaskmanager.h"
+#include "qgstaskmanagerwidget.h"
 #include "qgssymbolselectordialog.h"
 #include "qgstextannotationitem.h"
 #include "qgstipgui.h"
@@ -851,6 +853,13 @@ QgisApp::QgisApp( QSplashScreen *splash, bool restorePlugins, bool skipVersionCh
   QMainWindow::addDockWidget( Qt::BottomDockWidgetArea, mUserInputDockWidget );
   mUserInputDockWidget->setFloating( true );
 
+  // create the task manager dock on starting QGIS - this is like the browser
+  mTaskManagerDock = new QDockWidget( tr( "Task Manager" ), this );
+  mTaskManagerDock->setObjectName( "TaskManager" );
+  addDockWidget( Qt::RightDockWidgetArea, mTaskManagerDock );
+  mTaskManagerDock->setWidget( new QgsTaskManagerWidget( QgsTaskManager::instance(), mTaskManagerDock ) );
+  mTaskManagerDock->hide();
+
   // create the GPS tool on starting QGIS - this is like the browser
   mpGpsWidget = new QgsGPSInformationWidget( mMapCanvas );
   //create the dock widget
@@ -1139,6 +1148,7 @@ QgisApp::QgisApp()
     , mOverviewDock( nullptr )
     , mpGpsDock( nullptr )
     , mLogDock( nullptr )
+    , mTaskManagerDock( nullptr )
     , mNonEditMapTool( nullptr )
     , mScaleWidget( nullptr )
     , mMagnifierWidget( nullptr )

src/app/qgisapp.h

@@ -1560,6 +1560,7 @@ class APP_EXPORT QgisApp : public QMainWindow, private Ui::MainWindow
     QgsDockWidget *mOverviewDock;
     QgsDockWidget *mpGpsDock;
     QgsDockWidget *mLogDock;
+    QDockWidget *mTaskManagerDock;
 
 #ifdef Q_OS_MAC
     //! Window menu action to select this window

src/core/CMakeLists.txt

@@ -211,6 +211,7 @@ SET(QGIS_CORE_SRCS
   qgsstatisticalsummary.cpp
   qgsstringstatisticalsummary.cpp
   qgsstringutils.cpp
+  qgstaskmanager.cpp
   qgstextlabelfeature.cpp
   qgstextrenderer.cpp
   qgstolerance.cpp
@@ -495,6 +496,7 @@ SET(QGIS_CORE_MOC_HDRS
   qgsrelationmanager.h
   qgsrunprocess.h
   qgssnappingutils.h
+  qgstaskmanager.h
   qgstracer.h
   qgstrackedvectorlayertools.h
   qgstransaction.h