Many applications of KDE on Windows project with graphical interface have the following issue: when they start a console process (that is, compiled with /SUBSYSTEM:CONSOLE) using QProcess::startDetached(), it doesn't run in the background, but its console windows pops up. After the discussion  we nailed the problem down to Qt.
Windows code for QProcess::start() checks if the caller app have a console window using GetConsoleWindow() system function. If it returns 0, qt arranges system flags accordingly so the console window isn't shown.
But QProcess::startDetached() does not perform such check and sets CREATE_NEW_CONSOLE flag unconditionally. Applying patch from  solves this issue for us, but we'd like to upstream this.
 : https://git.reviewboard.kde.org/r/124905/
 : https://git.reviewboard.kde.org/r/127962/diff/1#index_header
 : http://stackoverflow.com/questions/33874243/qprocessstartdetached-but-hide-console-window