[EDIT]: I found a better workaround for my own C++ code. Add one line to the main() function, like this (or use the second line with the desired style name):

int main(int argc, char *argv[]) { qputenv("QT_STYLE_OVERRIDE",""); // qputenv("QT_STYLE_OVERRIDE","Fusion"); ....

[OLD ANSWER]:

Error message: QApplication: invalid style override passed, ignoring it. To remove this error message: In Qt Creator (ver 4.4.1) Select "Projects" (wrench icon on left edge) Under "Build & Run" (left pane) Select "Run" Under "Run Settings" (right pane) Under "Run Environment" Select "Details" (drop down list) Scroll down to "QT_STYLE_OVERRIDE" Click it to highlight it Then click "Unset" button (right side) Click "Details" to close the list Now when you run the application you shouldn't see this error message.

I'll stick with Qt 5.6.2 until 5.8 is released.

Thanks a lot for all you help SGaist. I didn't have a clue what was going wrong and wouldn't have found the source of the problem with your assistance.

Thanks again.

@mrjj

Your welcome,
it can be a pain to find answers at times, so having a guide near the IDE for odd errors helps in getting stuff done quicker for those odd errors

I downloaded and compiled opencv3 with gtk3 on, and then I installed Qt and had the same issue.

I found a work around for this is to recompile opencv with cmake and set: WITH_GTK3=OFF. And reinstall the library.

After that my Qt application work fine. Hope this helps