Custom Window Border

[dot97]

Hello,

I currently try to create a QMainWindow with an custom window border on Windows. My current code is:

bool MainWindow::nativeEvent(const QByteArray &eventType,
    void *msg, long *result) {
    auto win_msg = static_cast<MSG*>(msg);
    auto message = win_msg->message;
    auto wParam = win_msg->wParam;
    auto lParam = win_msg->lParam;

    if (message == WM_CREATE)
        int i = 0;

    if (message == WM_CREATE || message == WM_ACTIVATE
        || message == WM_NCCALCSIZE || message == WM_NCHITTEST) {
        auto forward = true;
        auto win_result = (LRESULT)0;
        auto hwnd = (HWND)winId();
        auto dwm_enabled = (BOOL)FALSE;
        auto hr = DwmIsCompositionEnabled(&dwm_enabled);
        if (SUCCEEDED(hr)) {
            forward = !DwmDefWindowProc(hwnd, message,
                wParam, lParam, &win_result);

            switch (message) {
            case WM_CREATE: {
                RECT rcClient;
                GetWindowRect(hwnd, &rcClient);

                // Inform application of the frame change.
                SetWindowPos(hwnd, NULL,
                    rcClient.left, rcClient.top,
                    rcClient.right - rcClient.left,
                    rcClient.bottom - rcClient.top,
                    SWP_FRAMECHANGED);

                forward = true;
                win_result = 0;
                break;
            }
            case WM_ACTIVATE: {
                MARGINS margins;

                margins.cxLeftWidth = 0;
                margins.cxRightWidth = 0;
                margins.cyBottomHeight = 0;
                margins.cyTopHeight = 0;

                hr = DwmExtendFrameIntoClientArea(hwnd, &margins);

                if (!SUCCEEDED(hr))
                {
                    // Handle error.
                }

                forward = true;
                win_result = 0;
                break;
            }
            case WM_NCCALCSIZE: {
                if (wParam == TRUE) {
                    NCCALCSIZE_PARAMS *params =
                        reinterpret_cast<NCCALCSIZE_PARAMS*>(lParam);
                    params->rgrc[0].left = params->rgrc[0].left + 5;
                    params->rgrc[0].top = params->rgrc[0].top + 0;
                    params->rgrc[0].right = params->rgrc[0].right - 5;
                    params->rgrc[0].bottom = params->rgrc[0].bottom - 5;
                    forward = false;
                    win_result = 0;
                }
                break;
            }
            case WM_NCHITTEST: {
                if (win_result == 0) {
                    auto mouse_pos = POINT{ LOWORD(lParam), HIWORD(lParam) };
                    RECT window_rect;
                    GetWindowRect(hwnd, &window_rect);
                    RECT frame_rect = { 0 };
                    AdjustWindowRectEx(&frame_rect,
                        WS_OVERLAPPEDWINDOW & ~WS_CAPTION, FALSE, NULL);
                    auto row = (USHORT)1;
                    auto col = (USHORT)1;
                    auto resize_border = false;
                    if (mouse_pos.y >= window_rect.top
                        && mouse_pos.y < window_rect.top + 30) {
                        resize_border =
                            (mouse_pos.y < (window_rect.top - frame_rect.top));
                        row = 0;
                    }
                    else
                        if (mouse_pos.y < window_rect.bottom
                            && mouse_pos.y >= window_rect.bottom)
                            row = 2;
                    if (mouse_pos.x >= window_rect.left
                        && mouse_pos.x < window_rect.left)
                        col = 0;
                    else
                        if (mouse_pos.x < window_rect.right
                            && mouse_pos.x >= window_rect.right)
                            col = 2;

                    LRESULT result_map[3][3] = {
                        { HTTOPLEFT, resize_border ? HTTOP : HTCAPTION, HTTOPRIGHT },
                        { HTLEFT, HTNOWHERE, HTRIGHT },
                        { HTBOTTOMLEFT, HTBOTTOM, HTBOTTOMRIGHT },
                    };

                    win_result = result_map[row][col];
                    if (win_result != HTNOWHERE)
                        forward = false;
                }
                break;
            }
            }
        }

        if (!forward) {
            *result = win_result;
            return true;
        }
    }

    return QWidget::nativeEvent(eventType, msg, result);
}

void MainWindow::paintEvent(QPaintEvent *event) {
    QPainter p(this);
    p.setPen(Qt::NoPen);

    p.setBrush(QBrush(QColor("#bbdefb")));
    p.drawRect(0, 0, geometry().width(), geometry().height());

    p.setBrush(QBrush(QColor("#2196f3")));
    p.drawRect(0, 0, geometry().width(), 30);

    QMainWindow::paintEvent(event);
}

The problem is, them main winow then looks like this:

So it seems, that the sizes of the drawing area are not calculated correctly given the customizations I made.
Does anybody know a solution to this?

Regards

[A Former User]

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