Qt 5.2 has built in support for indicating progress and other states in Windows Taskbar icon.
I followed Qt Doc on
QWinTaskbarProgress given here
Seems like their example is not working for me. So I created a demo program which demonstrates on how to show progress and states using Taskbar.
Here is the preview of my demo app.
You can browse and download the complete project from Github/mdminhazulhaque.