When the user clicks the title bar, the title-bar control sends a WM_TRACKFRAME message to its owner (the frame window). When the frame window receives the WM_TRACKFRAME message, the frame sends a WM_QUERYTRACKINFO message to itself to fill in a TRACKINFO structure that defines the tracking parameters and boundaries. To modify the default behavior, an application must subclass the frame window, intercept the WM_QUERYTRACKINFO message, and modify the TRACKINFO structure. If the application returns TRUE for the WM_QUERYTRACKINFO message, the tracking operation proceeds according to the information in the TRACKINFO structure. If the application returns FALSE, no tracking occurs.