Question

Seems you can only use QPropertyAnimation with drop-down style animation , am I wrong ?

I want the window to be visible from a straight line , to full size , expand in both sides.

Answer 1

Looks like you want to animate widget’s size property.
As such QPropertyAnimation can be used to animate any property of widget.

For your purpose you can use geometry property of QWidget. Following code will animate geometry changes, you can modify start value and end value for effect you want.

 QPropertyAnimation *animation = new QPropertyAnimation(myWidget, "geometry");
 animation->setDuration(10000);
 animation->setStartValue(QRect(0, 0, 100, 30));
 animation->setEndValue(QRect(250, 250, 100, 30));

 animation->start();