关于绘制文本的代码，看的不是很懂，麻烦标注一下。

    TCHAR szCaption[g_nCaptionLen] = {};
    GetWindowText(m_button, szCaption, g_nCaptionLen - 1);
    if (lstrlen(szCaption) > 0)
    {
        SetBkMode(hDC, TRANSPARENT);
        TCHAR* pReturnPos = NULL;
        HFONT hOldFont = (HFONT)SelectObject(hDC, m_hFont);
        if (pReturnPos = wcsstr(szCaption, L"\\r\\n"))
        {
            //pReturnPos[0] = '\r';
            //pReturnPos[1] = '\n';
            //strcpy(&pReturnPos[2], &pReturnPos[4]);
            TCHAR* pszSecondLine = pReturnPos + 4;
            rcWnd.bottom = (rcWnd.bottom + rcWnd.top) / 2;
            rcWnd.top += 1;
            DrawText(hDC, szCaption, pReturnPos - szCaption, &rcWnd, DT_CENTER);
            rcWnd.top -= 1;
            rcWnd.bottom = rcWnd.bottom * 2 - rcWnd.top;
            rcWnd.top = (rcWnd.bottom + rcWnd.top) / 2;
            rcWnd.top -= 1;
            DrawText(hDC, pszSecondLine, lstrlen(pszSecondLine), &rcWnd, DT_CENTER);
        }
        else
        {
            DrawText(hDC, szCaption, lstrlen(szCaption), &rcWnd, DT_CENTER | DT_VCENTER | DT_SINGLELINE);
        }
        SelectObject(hDC, hOldFont);
    }

这些都是win32 api函数，
GetWindowText(m_button, szCaption, g_nCaptionLen - 1);
获取现有窗体标题
if (pReturnPos = wcsstr(szCaption, L"\r\n"))
判断是不是最后一行
SetBkMode(hDC, TRANSPARENT);
这是设置背景透明
HFONT hOldFont = (HFONT)SelectObject(hDC, m_hFont);
这是设置字体
下面是计算坐标，然后
DrawText(hDC, szCaption, pReturnPos - szCaption, &rcWnd, DT_CENTER);
这是在居中的位置写字
SelectObject(hDC, hOldFont);
最后再恢复原先的字体