Example of using a multimedia timer in QT windows

Source code analysis in qtimer (using Windows as an example)
In the article, we see the usage of timer in Windows using QT:

• When the interval is zero, QT does not use the system timer.
• Non-zero Interval
  • The multimedia timer is used when the interval is less than 20 ms and the system supports multimedia timers.
  • Otherwise, use a common timer.

Qt's policy should be able to meet our needs well, but a user on qtcn was expecting to call the system's multimedia timer directly. In this case, write your own Timer class.

Code

• The code is relatively simple. The header file mmtimer. H is as follows:

#ifndef MMTIMER_H#define MMTIMER_H#include <qt_windows.h>#include <QtCore/QObject>class MMTimer : public QObject{    Q_OBJECTpublic:    explicit MMTimer(int interval, QObject *parent = 0);    ~MMTimer();signals:    void timeout();public slots:    void start();    void stop();friend void WINAPI CALLBACK mmtimer_proc(uint, uint, DWORD_PTR, DWORD_PTR, DWORD_PTR);private:    int m_interval;    int m_id;};#endif // MMTIMER_H

• The source code file mmtimer. cpp is as follows:

#include "mmtimer.h"#include <MMSystem.h>#ifdef __MINGW32__ //w32api bug#define TIME_KILL_SYNCHRONOUS 0x0100#endifvoid WINAPI CALLBACK mmtimer_proc(uint timerId, uint, DWORD_PTR user, DWORD_PTR, DWORD_PTR){    MMTimer *t = reinterpret_cast<MMTimer*>(user);    emit t->timeout();}MMTimer::MMTimer(int interval, QObject *parent) :    QObject(parent),m_interval(interval),m_id(0){}MMTimer::~MMTimer(){    stop();}void MMTimer::start(){    m_id = timeSetEvent(m_interval, 1, mmtimer_proc, (DWORD_PTR)this,                 TIME_CALLBACK_FUNCTION | TIME_PERIODIC | TIME_KILL_SYNCHRONOUS);}void MMTimer::stop(){    if (m_id){        timeKillEvent(m_id);        m_id = 0;    }}

Description

The above Code does not need to be explained:

• For more information about timesetevent and timekillevent, see msdn.
• In addition, the WIN32API package of mingw does not define time_kill_synchronous, and some modifications are made in the Code.

Make sure that the required libraries are correctly linked.

LIBS += -lwinmm

Note: This is what msdn says in its introduction to timesetevent (this is not a comment)

Note  This function is obsolete. New applications should use CreateTimerQueueTimer to create a timer-queue timer.