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/*

 * This file is part of the LibreOffice project.

 *

 * This Source Code Form is subject to the terms of the Mozilla Public

 * License, v. 2.0. If a copy of the MPL was not distributed with this

 * file, You can obtain one at http://mozilla.org/MPL/2.0/.

 *

 * This file incorporates work covered by the following license notice:

 *

 *   Licensed to the Apache Software Foundation (ASF) under one or more

 *   contributor license agreements. See the NOTICE file distributed

 *   with this work for additional information regarding copyright

 *   ownership. The ASF licenses this file to you under the Apache

 *   License, Version 2.0 (the "License"); you may not use this file

 *   except in compliance with the License. You may obtain a copy of

 *   the License at http://www.apache.org/licenses/LICENSE-2.0 .

 */

#ifndef INCLUDED_VCL_TASK_HXX

#define INCLUDED_VCL_TASK_HXX

#include <vcl/dllapi.h>

struct ImplSchedulerData;

enum class TaskPriority

{

    HIGHEST,       ///< These events should run very fast!

    DEFAULT,       ///< Default priority used, e.g. the default timer priority

    // Input from the OS event queue is processed before HIGH_IDLE tasks.

    HIGH_IDLE,     ///< Important idle events to be run before processing drawing events

    RESIZE,        ///< Resize runs before repaint, so we won't paint twice

    REPAINT,       ///< All repaint events should go in here

    SKIA_FLUSH,    ///< tdf#165277 Skia needs to flush immediately before POST_PAINT tasks on macOS

    POST_PAINT,    ///< Everything running directly after painting

    DEFAULT_IDLE,  ///< Default idle priority

    LOWEST,        ///< Low, very idle cleanup tasks

    TOOLKIT_DEBUG  ///< Do not use. Solely for IdleTask::waitUntilIdleDispatched

};

#define PRIO_COUNT (static_cast<int>(TaskPriority::TOOLKIT_DEBUG) + 1)

class VCL_DLLPUBLIC Task

{

    friend class Scheduler;

    friend struct ImplSchedulerData;

    ImplSchedulerData *mpSchedulerData; ///< Pointer to the element in scheduler list

    const char        *mpDebugName;     ///< Useful for debugging

    TaskPriority       mePriority;      ///< Task priority

    bool               mbActive;        ///< Currently in the scheduler

    bool               mbStatic;        ///< Is a static object

protected:

    static void StartTimer( sal_uInt64 nMS );

    const ImplSchedulerData* GetSchedulerData() const { return mpSchedulerData; }

    virtual void SetDeletionFlags();

    /**

     * How long (in MS) until the Task is ready to be dispatched?

     *

     * Simply return Scheduler::ImmediateTimeoutMs if you're ready, like an

     * Idle. If you have to return Scheduler::InfiniteTimeoutMs, you probably

     * need another mechanism to wake up the Scheduler or rely on other

     * Tasks to be scheduled, or simply use a polling Timer.

     *

     * @param nTimeNow the current time

     * @return the sleep time of the Task to become ready

     */

    virtual sal_uInt64 UpdateMinPeriod( sal_uInt64 nTimeNow ) const = 0;

public:

    Task( const char *pDebugName );

    Task( const Task& rTask );

    virtual ~Task();

    Task& operator=( const Task& rTask );

    void            SetPriority(TaskPriority ePriority);

    TaskPriority    GetPriority() const { return mePriority; }

    const char     *GetDebugName() const { return mpDebugName; }

    virtual bool DecideTransferredExecution();

    // Call handler

    virtual void    Invoke() = 0;

    /**

     * Schedules the task for execution

     *

     * If the timer is already active, it's reset!

     * Check with Task::IsActive() to prevent reset.

     *

     * If you unset bStartTimer, the Task must call Task::StartTimer(...) to be correctly scheduled!

     * Otherwise it might just be picked up when the Scheduler runs the next time.

     *

     * @param bStartTimer if false, don't schedule the Task by calling Task::StartTimer(0).

     */

    virtual void Start(bool bStartTimer = true);

    void            Stop();

    bool            IsActive() const { return mbActive; }

    /**

     * This function must be called for static tasks, so the Task destructor

     * ignores the scheduler mutex, as it may not be available anymore.

     * The cleanup is still correct, as it has already happened in

     * DeInitScheduler call well before the static destructor calls.

     */

    void            SetStatic() { mbStatic = true; }

    bool            IsStatic() const { return mbStatic; }

};

#endif // INCLUDED_VCL_TASK_HXX

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