func (tt *ToolTip) AddTool(tool Widget) error { hwnd := tool.Handle() var ti win.TOOLINFO ti.CbSize = uint32(unsafe.Sizeof(ti)) ti.Hwnd = hwnd ti.UFlags = win.TTF_IDISHWND | win.TTF_SUBCLASS ti.UId = uintptr(hwnd) if win.FALSE == tt.SendMessage(win.TTM_ADDTOOL, 0, uintptr(unsafe.Pointer(&ti))) { //return newError("TTM_ADDTOOL failed") return nil } return nil }