private void UpdateWindowProperties()

in src/Windows/Avalonia.Win32/WindowImpl.cs [1403:1551]
114 lines of code
34 McCabe index (conditional complexity)

        private void UpdateWindowProperties(WindowProperties newProperties, bool forceChanges = false)
        {
            var oldProperties = _windowProperties;

            // Calling SetWindowPos will cause events to be sent and we need to respond
            // according to the new values already.
            _windowProperties = newProperties;

            if (oldProperties.IsFullScreen == newProperties.IsFullScreen)
            {
                var exStyle = WindowStyles.WS_EX_WINDOWEDGE | (UseRedirectionBitmap ? 0 : WindowStyles.WS_EX_NOREDIRECTIONBITMAP);

                if ((oldProperties.ShowInTaskbar != newProperties.ShowInTaskbar) || forceChanges)
                {
                    if (newProperties.ShowInTaskbar)
                    {
                        exStyle |= WindowStyles.WS_EX_APPWINDOW;

                        if (_hiddenWindowIsParent)
                        {
                            // Can't enable the taskbar icon by clearing the parent window unless the window
                            // is hidden. Hide the window and show it again with the same activation state
                            // when we've finished. Interestingly it seems to work fine the other way.
                            var shown = IsWindowVisible(_hwnd);
                            var activated = GetActiveWindow() == _hwnd;

                            if (shown)
                                Hide();

                            _hiddenWindowIsParent = false;
                            SetParent(null);

                            if (shown)
                                Show(activated, false);
                        }
                    }
                    else
                    {
                        // To hide a non-owned window's taskbar icon we need to parent it to a hidden window.
                        if (_parent is null)
                        {
                            SetWindowLongPtr(_hwnd, (int)WindowLongParam.GWL_HWNDPARENT, OffscreenParentWindow.Handle);
                            _hiddenWindowIsParent = true;
                        }

                        exStyle &= ~WindowStyles.WS_EX_APPWINDOW;
                    }
                }

                if (newProperties.ShowInTaskbar)
                {
                    exStyle |= WindowStyles.WS_EX_APPWINDOW;
                }
                else
                {
                    exStyle &= ~WindowStyles.WS_EX_APPWINDOW;
                }

                WindowStyles style = WindowStyles.WS_CLIPCHILDREN | WindowStyles.WS_OVERLAPPEDWINDOW | WindowStyles.WS_CLIPSIBLINGS;

                if (this is EmbeddedWindowImpl)
                    style |= WindowStyles.WS_CHILD;

                if (IsWindowVisible(_hwnd))
                    style |= WindowStyles.WS_VISIBLE;

                if (newProperties.IsResizable || newProperties.WindowState == WindowState.Maximized)
                    style |= WindowStyles.WS_THICKFRAME;
                else
                    style &= ~WindowStyles.WS_THICKFRAME;

                if (newProperties.IsMinimizable)
                    style |= WindowStyles.WS_MINIMIZEBOX;
                else
                    style &= ~WindowStyles.WS_MINIMIZEBOX;

                if (newProperties.IsMaximizable || (newProperties.WindowState == WindowState.Maximized && newProperties.IsResizable))
                    style |= WindowStyles.WS_MAXIMIZEBOX;
                else
                    style &= ~WindowStyles.WS_MAXIMIZEBOX;

                const WindowStyles fullDecorationFlags = WindowStyles.WS_CAPTION | WindowStyles.WS_BORDER;

                if (newProperties.Decorations == SystemDecorations.Full)
                {
                    style |= fullDecorationFlags;
                }
                else
                {
                    style &= ~(fullDecorationFlags | WindowStyles.WS_THICKFRAME);

                    if (newProperties.Decorations == SystemDecorations.BorderOnly && newProperties.WindowState != WindowState.Maximized && newProperties.IsResizable)
                    {
                        style |= WindowStyles.WS_THICKFRAME | WindowStyles.WS_BORDER;
                    }
                    else if(newProperties.WindowState == WindowState.Maximized && _isClientAreaExtended)
                    {
                        style |= WindowStyles.WS_THICKFRAME;
                    }
                }

                var windowStates = GetWindowStateStyles();
                style &= ~WindowStateMask;
                style |= windowStates;

                _savedWindowInfo.Style = style;
                _savedWindowInfo.ExStyle = exStyle;

                if (WindowStylesCallback is { } callback)
                {
                    var (s, e) = callback((uint)style, (uint)exStyle);

                    style = (WindowStyles)s;
                    exStyle = (WindowStyles)e;
                }

                SetStyle(style);
                SetExtendedStyle(exStyle);
            }
            else
                SetFullScreen(newProperties.IsFullScreen);

            if (!_isFullScreenActive && ((oldProperties.Decorations != newProperties.Decorations) || forceChanges))
            {
                var margin = newProperties.Decorations == SystemDecorations.BorderOnly ? 1 : 0;

                var margins = new MARGINS
                {
                    cyBottomHeight = margin,
                    cxRightWidth = margin,
                    cxLeftWidth = margin,
                    cyTopHeight = margin
                };

                DwmExtendFrameIntoClientArea(_hwnd, ref margins);

                if (_shown || forceChanges)
                {
                    SetWindowPos(_hwnd, IntPtr.Zero, 0, 0, 0 ,0,
                        SetWindowPosFlags.SWP_NOZORDER | SetWindowPosFlags.SWP_NOACTIVATE |
                        SetWindowPosFlags.SWP_NOSIZE | SetWindowPosFlags.SWP_NOMOVE |
                        SetWindowPosFlags.SWP_FRAMECHANGED);
                }
            }

            // Ensure window state if decorations change
            if (_shown && oldProperties.Decorations != newProperties.Decorations)
                ShowWindow(WindowState, false);
        }