这段代码时什么意思看了好长时间看不懂

Question

这段代码时什么意思看了好长时间看不懂

    case WM_DRAWITEM:
    {
        DRAWITEMSTRUCT* pDrawItemSturct = (DRAWITEMSTRUCT*)lParam;

        if (pDrawItemSturct->itemState & ODS_FOCUS)
        {
            RECT rtFocus = pDrawItemSturct->rcItem;
            rtFocus.left += 3;
            rtFocus.top += 3;
            rtFocus.right -= 3;
            rtFocus.bottom -= 3;
            _this->DrawFocusRect(pDrawItemSturct->hDC, rtFocus);
        }
        //_this->Draw(pDrawItemSturct->hDC);
    }

Answer 1

case WM_DRAWITEM:
    {
        DRAWITEMSTRUCT* pDrawItemSturct = (DRAWITEMSTRUCT*)lParam;//获取自绘控件信息

        if (pDrawItemSturct->itemState & ODS_FOCUS)//判断控件是否获得焦点
        {
            RECT rtFocus = pDrawItemSturct->rcItem;//获取控件区域并存储在rtFocus
            rtFocus.left += 3;
            rtFocus.top += 3;
            rtFocus.right -= 3;
            rtFocus.bottom -= 3;//更改区域大小
            _this->DrawFocusRect(pDrawItemSturct->hDC, rtFocus);//画焦点矩形
        }
        //_this->Draw(pDrawItemSturct->hDC);//绘图
    }