如何使用纯win32api不使用MFC来自绘非客户区

Question

想用纯winapi写一个美化桌面窗口，但是出现了很多小问题

case WM_NCPAINT:
    { 
        int tbheight, tbwidth;
        RECT wndrect, clientrect;
        GetWindowRect(hwnd, &wndrect);
        GetClientRect(hwnd, &clientrect);
        tbheight = GetSystemMetrics(SM_CYSIZE);//标题栏宽度
        //end 得到系统标题栏的信息
        //填充标题栏
        RECT rcWindow;
        GetWindowRect(hwnd, &rcWindow);
        HDC hDc = GetWindowDC(hwnd);
        HBRUSH hBrush = CreateSolidBrush(RGB(25, 0, 255));
        HBRUSH hOldbrush = (HBRUSH)SelectObject(hDc, (HGDIOBJ)hBrush);
        PatBlt(hDc, 0, 0, wndrect.right - wndrect.left, tbheight, PATCOPY);
        //end 填充标题栏
            //填充边框
        NONCLIENTMETRICS  nonmet;
        nonmet.cbSize = sizeof(NONCLIENTMETRICS);
        SystemParametersInfo(SPI_GETNONCLIENTMETRICS, sizeof(NONCLIENTMETRICS), &nonmet, 0);

        RECT borderleft, borderright, bordertop, borderbottom;
        borderleft.left = 0;
        borderleft.right = wndrect.left + 7;
        borderleft.top = tbheight;
        borderleft.bottom = wndrect.bottom;
        hBrush = CreateSolidBrush(RGB(200, 0, 0));
        SelectObject(hDc, (HGDIOBJ)hBrush);
        PatBlt(hDc, borderleft.left, borderleft.top, nonmet.iPaddedBorderWidth + 4, borderleft.bottom - borderleft.top, PATCOPY);
        SelectObject(hDc, (HGDIOBJ)hOldbrush);

        bordertop.left = 0;
        bordertop.bottom = wndrect.top + nonmet.iCaptionHeight + nonmet.iPaddedBorderWidth + 4;
        bordertop.right = wndrect.right;
        bordertop.top = nonmet.iCaptionHeight;
        hBrush = CreateSolidBrush(RGB(0, 200, 0));
        SelectObject(hDc, (HGDIOBJ)hBrush);
        PatBlt(hDc, bordertop.left, bordertop.top, bordertop.right - bordertop.left, nonmet.iPaddedBorderWidth + 5, PATCOPY);
        SelectObject(hDc, (HGDIOBJ)hOldbrush);

        borderright.left = wndrect.right - wndrect.left - nonmet.iPaddedBorderWidth - 4;
        borderright.top = nonmet.iCaptionHeight;
        borderright.bottom = wndrect.bottom;
        borderright.right = wndrect.right - wndrect.left;
        hBrush = CreateSolidBrush(RGB(0, 100, 200));
        SelectObject(hDc, (HGDIOBJ)hBrush);
        PatBlt(hDc, borderright.left, borderright.top, nonmet.iPaddedBorderWidth + 4, borderright.bottom - borderright.top, PATCOPY);


        borderbottom.bottom = wndrect.bottom;
        borderbottom.left = nonmet.iPaddedBorderWidth + 4;
        borderbottom.right = wndrect.right - wndrect.left - nonmet.iPaddedBorderWidth - 4;
        borderbottom.top = wndrect.bottom - wndrect.top - nonmet.iPaddedBorderWidth - 4;
        hBrush = CreateSolidBrush(RGB(100, 80, 80));
        SelectObject(hDc, (HGDIOBJ)hBrush);
        PatBlt(hDc, borderbottom.left, borderbottom.top, borderbottom.right - borderbottom.left, nonmet.iPaddedBorderWidth + 4, PATCOPY);
        //end 填充边框
        SelectObject(hDc, (HGDIOBJ)hOldbrush);
        ReleaseDC(hwnd, hDc);
        //DefWindowProc(hwnd,uMsg,wParam,lParam);
        RECT btnrect;
        btnrect.bottom = nonmet.iCaptionHeight + nonmet.iBorderWidth;
        btnrect.left = wndrect.right - wndrect.left - nonmet.iCaptionHeight * 3 - nonmet.iBorderWidth;
        btnrect.right = btnrect.left + nonmet.iCaptionHeight * 3;
        btnrect.top = nonmet.iBorderWidth;

        HDC hcomdc = CreateCompatibleDC(hDc);
        HBITMAP hbmp = LoadBitmap(g_hInstance, MAKEINTRESOURCE(IDB_BITMAP));
        HBITMAP holdbmp = (HBITMAP)SelectObject(hcomdc, (HGDIOBJ)hbmp);
        StretchBlt(hDc, btnrect.left - nonmet.iPaddedBorderWidth - 14, btnrect.top + nonmet.iPaddedBorderWidth + 4, nonmet.iCaptionHeight * 3 + 12, nonme  t.iCaptionHeight, hcomdc, 0, 0, 60, 20, SRCCOPY);

源码是参考https://www.cnblogs.com/ddx-deng/p/3755833.html的
但是
第一，标题栏按钮还是没显示出来？
第二，窗口置于底层就原型毕露了？
第三，标题栏如何用位图填充？