How to remove the default menu on the left side of the title bar - Qt?

Code:

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Qt :: WindowFlags flags = 0;
 
    // Makes the Pomodoro stay on the top of all windows.
    flags |= Qt :: WindowStaysOnTopHint;
 
    // Removes minimize, maximize, and close buttons.
    flags |= Qt :: WindowTitleHint | Qt :: CustomizeWindowHint;
 
    window->setWindowFlags (flags);
    window->setWindowTitle ("Failing to plan is planning to fail");

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This removes minimize, maximize, and close buttons. The default menu on the left is still there. How to get rid of that?

I want the title bar to be there, but just want the menu to be removed.

Default menu contains: Minimize, Maximize, Move etc options.

On what system?

Code:

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this->setWindowFlags( Qt :: WindowStaysOnTopHint | Qt::WindowTitleHint | Qt::CustomizeWindowHint );

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works as you want on W7 and Ubuntu.