c++ - Event in Maya Api to capture currentTime / frame change -

developing maya plugin. how can set-up callback gets fired each time frame number / current time changed in scene ?
had @ mscenemessage class, doesn't seem contain looking for.
thanks.

you can use meventmessage setup callback every time frame/current time changes. code speaks louder words, here's code comments interspersed illustrate how set up: (tldr impatient first, full code excerpt follow in next section)

tldr:

a code summary impatient:

    // ...      // our callback id array      // store ids of our callbacks     // later removal         mcallbackidarray mycallbackids;      // actual adding callback happens     // register our callback "timechanged" event     mcallbackid callbackid = meventmessage::addeventcallback("timechanged",  (mmessage::mbasicfunction) mysamplecmd::usercb);      // ...      if(mycallbackids.length() != 0)         // make sure remove callbacks added         stat = meventmessage::removecallbacks(mycallbackids); 

• reference meventmessage docs.
• the events listed here (in scriptjob command) can used meventmessage.

---

full(ish) code comments:

mysamplecommand.h

class mysamplecmd : public mpxcommand { public:                 mysamplecmd();     virtual     ~mysamplecmd();      // our callback - implemented static method     static      void usercb(void* clientdata);      mstatus     doit( const marglist& );     mstatus     redoit();     mstatus     undoit();        bool        isundoable() const;     static      void* creator();  public:      // our callback id array      // store ids of our callbacks     // later removal     mcallbackidarray mycallbackids; }; 

mysamplecommand.cpp (excerpt)

// constructor mysamplecmd::mysamplecmd() {      // clearing our callback id array     // housekeeping         mycallbackids.clear(); }  // destructor mysamplecmd::~mysamplecmd() {      // make sure remove callbacks added     // failing result in fatal error         if(mycallbackids.length() != 0)          // remove meventmessage callback         meventmessage::removecallbacks(mycallbackids); }  mstatus mysamplecmd::redoit() {      // actual adding callback happens     // register our callback "timechanged" event     mcallbackid callbackid = meventmessage::addeventcallback("timechanged",  (mmessage::mbasicfunction) mysamplecmd::usercb);      // append newly added callback's id our list of callback ids     // future removal     mycallbackids.append(callbackid);     return ms::ksuccess; }  mstatus mysamplecmd::undoit() {     mstatus stat;     if(mycallbackids.length() != 0)         // make sure remove callbacks added         stat = meventmessage::removecallbacks(mycallbackids);     return stat; }  // our callback function void safeselect::usercb(void* clientdata) {     mglobal::displayinfo( "callback usercb called!\n" );     return; }