c++ - How to animate two values using QTimeLine -

i have qgraphicsitem want animate size change. because of this, need vary both height , width of object on time. have used qtimeline in past single-variable animations , use here two-variable if possible. however, don't see qtimeline::setframerange() works 2 variables.

how can accomplish this? there better qt class this?

since animations have attached objects, graphics item qgraphicsobject, can expose relevant properties qt property system.

since you're animating amounts qsizef, simplest way expose single property , use qpropertyanimation.

in general, if have animate multiple properties in parallel, set them individual qpropertyanimations. run in parallel using qparallelanimationgroup.

it's of course possible use qtimeline, have interpolate between endpoints manually, basing on frame number, example. why bother.

below complete example shows how animate 3 properties @ once: pos, size , rotation.

main.cpp

#include <qgraphicsscene> #include <qgraphicsview> #include <qpropertyanimation> #include <qparallelanimationgroup> #include <qsequentialanimationgroup> #include <qgraphicsobject> #include <qpainter> #include <qapplication>  class item : public qgraphicsobject {     q_object     qreal m_pen;     qsizef m_size;     q_property(qsizef size read size write setsize notify newsize)     q_signal void newsize();     qreal width() const { return m_size.width() + m_pen; }     qreal height() const { return m_size.height() + m_pen; } public:     explicit item(qgraphicsitem *parent = 0) :         qgraphicsobject(parent), m_pen(5.0), m_size(50.0, 50.0) {}     qsizef size() const { return m_size; }     void setsize(const qsizef & size) {         if (m_size != size) {             m_size = size;             update();             emit newsize();         }     }     qrectf boundingrect() const {         return qrectf(-width()/2, -height()/2, width(), height());     }     void paint(qpainter *p, const qstyleoptiongraphicsitem *, qwidget *) {         p->setpen(qpen(qt::black, m_pen));         p->drawellipse(qpointf(0,0), width()/2, height()/2);         p->setpen(qpen(qt::red, m_pen));         p->drawline(0, 0, 0, height()/2);     } };  void animate(qobject * obj) {     qparallelanimationgroup * group = new qparallelanimationgroup(obj);     qpropertyanimation * pos = new qpropertyanimation(obj, "pos", obj);     qpropertyanimation * size = new qpropertyanimation(obj, "size", obj);     qpropertyanimation * rot= new qpropertyanimation(obj, "rotation", obj);     pos->setduration(3000);     pos->setloopcount(-1);     pos->seteasingcurve(qeasingcurve::inoutcubic);     pos->setstartvalue(qpointf(-50, -50));     pos->setendvalue(qpointf(50, 50));     size->setduration(1500);     size->setloopcount(-1);     size->seteasingcurve(qeasingcurve::inoutelastic);     size->setstartvalue(qsizef(100, 100));     size->setendvalue(qsizef(100, 30));     rot->setduration(1000);     rot->setloopcount(-1);     rot->setstartvalue(0.0);     rot->setendvalue(360.0);     group->addanimation(pos);     group->addanimation(size);     group->addanimation(rot);     group->start(); }  int main(int argc, char *argv[]) {     qapplication a(argc, argv);     qgraphicsscene s;     qgraphicsview v(&s);     item * item = new item;     s.additem(item);     v.setrenderhint(qpainter::antialiasing);     v.setscenerect(-125, -125, 300, 300);     v.show();     animate(item);     return a.exec(); }  #include "main.moc"