Let us say you have two qt application on click of a button on one application window you want to bring the other application window on top. You can use any method of IPC between these two applications.
In windows above is not possible directly with qt you can bang your head with all feature of qt to send a window on top give it focus make it active but to no avail. The window will remain on back.
You need to have a hack around to make this possible.
One peculiar observation was on the first try window was not coming on front but in next all try it comes in the front. So you can open close the window fast for the first time and going forward you have resolved the problem.
There are some other workaround mentioned on qt forum but it didn’t worked for me. I tried with registry setting but didn’t wanted to restart the system so not sure whether it works or not.
// HACK: bringing window to top
// from QT documentation:
// void QWidget::activateWindow ()
// On Windows, if you are calling this when the application is not currently
// the active one then it will not make it the active window. It will change
// the color of the taskbar entry to indicate that the window has changed in
// some way. This is because Microsoft do not allow an application to
// interrupt what the user is currently doing in another application.
My hack was very simple by using windows API to bring a window on top
SetWindowPos((HWND)viewer->winId(), HWND_TOPMOST, 0, 0, 0, 0, SWP_NOMOVE | SWP_NOSIZE);
Giving it focus is still not working for me for my particular application so I have to try the first hack also opening and closing the window fast. You can make this a very small window and put it in some weird position so no one can notice. Also this is needed only once so you can do it when your second application starts(whose window you want to bring in front from another app trigger).