duilib学习领悟(4)

　　使用duilib创建的主窗口绘制工作全都发生在一个 真实存在的主窗口句柄当中,这个绘制过程稍稍有些复杂,但再复杂也逃不过WM_PAINT消息,所有的绘制工作也都由这个WM_PAINT消息完成.在上几篇中,我们总结了,所有的窗口消息都被CPaintManager类拦截处理,它成为所有消息的路由中心,我们看看WM_PAINT消息的处理:

　　

    case WM_PAINT:
        {
            // Should we paint?
            RECT rcPaint = { 0 };
            if( !::GetUpdateRect(m_hWndPaint, &rcPaint, FALSE) ) return true;
            if( m_pRoot == NULL ) {
                PAINTSTRUCT ps = { 0 };
                ::BeginPaint(m_hWndPaint, &ps);
                ::EndPaint(m_hWndPaint, &ps);
                return true;
            }            
            // Do we need to resize anything?
            // This is the time where we layout the controls on the form.
            // We delay this even from the WM_SIZE messages since resizing can be
            // a very expensize operation.
            if( m_bUpdateNeeded ) {
                m_bUpdateNeeded = false;
                RECT rcClient = { 0 };
                ::GetClientRect(m_hWndPaint, &rcClient);
                if( !::IsRectEmpty(&rcClient) ) {
                    if( m_pRoot->IsUpdateNeeded() ) {
                        m_pRoot->SetPos(rcClient);
                        if( m_hDcOffscreen != NULL ) ::DeleteDC(m_hDcOffscreen);
                        if( m_hDcBackground != NULL ) ::DeleteDC(m_hDcBackground);
                        if( m_hbmpOffscreen != NULL ) ::DeleteObject(m_hbmpOffscreen);
                        if( m_hbmpBackground != NULL ) ::DeleteObject(m_hbmpBackground);
                        m_hDcOffscreen = NULL;
                        m_hDcBackground = NULL;
                        m_hbmpOffscreen = NULL;
                        m_hbmpBackground = NULL;
                    }
                    else {
                        CControlUI* pControl = NULL;
                        while( pControl = m_pRoot->FindControl(__FindControlFromUpdate, NULL, UIFIND_VISIBLE | UIFIND_ME_FIRST) ) {
                            pControl->SetPos( pControl->GetPos() );
                        }
                    }
                    // We'll want to notify the window when it is first initialized
                    // with the correct layout. The window form would take the time
                    // to submit swipes/animations.
                    if( m_bFirstLayout ) {
                        m_bFirstLayout = false;
                        SendNotify(m_pRoot, DUI_MSGTYPE_WINDOWINIT,  0, 0, false);
                    }
                }
            }
            // Set focus to first control?
            if( m_bFocusNeeded ) {
                SetNextTabControl();
            }
            //
            // Render screen
            //
            // Prepare offscreen bitmap?
            if( m_bOffscreenPaint && m_hbmpOffscreen == NULL )
            {
                RECT rcClient = { 0 };
                ::GetClientRect(m_hWndPaint, &rcClient);
                m_hDcOffscreen = ::CreateCompatibleDC(m_hDcPaint);
                m_hbmpOffscreen = ::CreateCompatibleBitmap(m_hDcPaint, rcClient.right - rcClient.left, rcClient.bottom - rcClient.top); 
                ASSERT(m_hDcOffscreen);
                ASSERT(m_hbmpOffscreen);
            }
            // Begin Windows paint
            PAINTSTRUCT ps = { 0 };
            ::BeginPaint(m_hWndPaint, &ps);
            if( m_bOffscreenPaint )
            {
                HBITMAP hOldBitmap = (HBITMAP) ::SelectObject(m_hDcOffscreen, m_hbmpOffscreen);
                int iSaveDC = ::SaveDC(m_hDcOffscreen);
                if( m_bAlphaBackground ) {
                    if( m_hbmpBackground == NULL ) {
                        RECT rcClient = { 0 };
                        ::GetClientRect(m_hWndPaint, &rcClient);
                        m_hDcBackground = ::CreateCompatibleDC(m_hDcPaint);;
                        m_hbmpBackground = ::CreateCompatibleBitmap(m_hDcPaint, rcClient.right - rcClient.left, rcClient.bottom - rcClient.top); 
                        ASSERT(m_hDcBackground);
                        ASSERT(m_hbmpBackground);
                        ::SelectObject(m_hDcBackground, m_hbmpBackground);
                        ::BitBlt(m_hDcBackground, ps.rcPaint.left, ps.rcPaint.top, ps.rcPaint.right - ps.rcPaint.left,
                            ps.rcPaint.bottom - ps.rcPaint.top, ps.hdc, ps.rcPaint.left, ps.rcPaint.top, SRCCOPY);
                    }
                    else
                        ::SelectObject(m_hDcBackground, m_hbmpBackground);
                    ::BitBlt(m_hDcOffscreen, ps.rcPaint.left, ps.rcPaint.top, ps.rcPaint.right - ps.rcPaint.left,
                        ps.rcPaint.bottom - ps.rcPaint.top, m_hDcBackground, ps.rcPaint.left, ps.rcPaint.top, SRCCOPY);
                }

                //绘制控件
                m_pRoot->DoPaint(m_hDcOffscreen, ps.rcPaint);
                for( int i = 0; i < m_aPostPaintControls.GetSize(); i++ ) {
                    CControlUI* pPostPaintControl = static_cast<CControlUI*>(m_aPostPaintControls[i]);
                    pPostPaintControl->DoPostPaint(m_hDcOffscreen, ps.rcPaint);
                }
                ::RestoreDC(m_hDcOffscreen, iSaveDC);
                ::BitBlt(ps.hdc, ps.rcPaint.left, ps.rcPaint.top, ps.rcPaint.right - ps.rcPaint.left,
                    ps.rcPaint.bottom - ps.rcPaint.top, m_hDcOffscreen, ps.rcPaint.left, ps.rcPaint.top, SRCCOPY);
                ::SelectObject(m_hDcOffscreen, hOldBitmap);

                if( m_bShowUpdateRect ) {
                    HPEN hOldPen = (HPEN)::SelectObject(ps.hdc, m_hUpdateRectPen);
                    ::SelectObject(ps.hdc, ::GetStockObject(HOLLOW_BRUSH));
                    ::Rectangle(ps.hdc, rcPaint.left, rcPaint.top, rcPaint.right, rcPaint.bottom);
                    ::SelectObject(ps.hdc, hOldPen);
                }
            }
            else
            {
                // A standard paint job
                int iSaveDC = ::SaveDC(ps.hdc);

                //绘制控件
                m_pRoot->DoPaint(ps.hdc, ps.rcPaint);
                ::RestoreDC(ps.hdc, iSaveDC);
            }
            // All Done!
            ::EndPaint(m_hWndPaint, &ps);
        }
        // If any of the painting requested a resize again, we'll need
        // to invalidate the entire window once more.
        if( m_bUpdateNeeded ) {
            ::InvalidateRect(m_hWndPaint, NULL, FALSE);
        }
        return true;

　　所有的绘制工作都会回到基类CControlUI的DoPaint() 代码如下:

void CControlUI::DoPaint(HDC hDC, const RECT& rcPaint)
{
    if( !::IntersectRect(&m_rcPaint, &rcPaint, &m_rcItem) ) return;

    // 绘制循序：背景颜色->背景图->状态图->文本->边框
    if( m_cxyBorderRound.cx > 0 || m_cxyBorderRound.cy > 0 ) {
        CRenderClip roundClip;
        CRenderClip::GenerateRoundClip(hDC, m_rcPaint,  m_rcItem, m_cxyBorderRound.cx, m_cxyBorderRound.cy, roundClip);
        PaintBkColor(hDC);
        PaintBkImage(hDC);
        PaintStatusImage(hDC);
        PaintText(hDC);
        PaintBorder(hDC);
    }
    else {
        PaintBkColor(hDC);
        PaintBkImage(hDC);
        PaintStatusImage(hDC);
        PaintText(hDC);
        PaintBorder(hDC);
    }
}

　　但是,这里又引出一个问题,绘制工作是如何路由到CControlUI的DoPaint()中的呢,如果程序中比较简单,就像我们现在这样,没有用到容器,只有一个按钮,那么就相对简单,调用m_pRoot->DoPaint()直到调用的就是基类的DoPaint():

　　假如我们的窗口中,使用的控件不只一个,必然用到容器,这时候再调用m_pRoot->DoPaint()就不是直接调用CControlUI::DoPaint()而是调用的容器类的DoPaint(),来看代码:

　　

    void CContainerUI::DoPaint(HDC hDC, const RECT& rcPaint)
    {
        RECT rcTemp = { 0 };
        if( !::IntersectRect(&rcTemp, &rcPaint, &m_rcItem) ) return;

        CRenderClip clip;
        CRenderClip::GenerateClip(hDC, rcTemp, clip);
        CControlUI::DoPaint(hDC, rcPaint);

        if( m_items.GetSize() > 0 ) {
            RECT rc = m_rcItem;
            rc.left += m_rcInset.left;
            rc.top += m_rcInset.top;
            rc.right -= m_rcInset.right;
            rc.bottom -= m_rcInset.bottom;
            if( m_pVerticalScrollBar && m_pVerticalScrollBar->IsVisible() ) rc.right -= m_pVerticalScrollBar->GetFixedWidth();
            if( m_pHorizontalScrollBar && m_pHorizontalScrollBar->IsVisible() ) rc.bottom -= m_pHorizontalScrollBar->GetFixedHeight();

            if( !::IntersectRect(&rcTemp, &rcPaint, &rc) ) {
                for( int it = 0; it < m_items.GetSize(); it++ ) {
                    CControlUI* pControl = static_cast<CControlUI*>(m_items[it]);
                    if( !pControl->IsVisible() ) continue;
                    if( !::IntersectRect(&rcTemp, &rcPaint, &pControl->GetPos()) ) continue;
                    if( pControl ->IsFloat() ) {
                        if( !::IntersectRect(&rcTemp, &m_rcItem, &pControl->GetPos()) ) continue;
                        pControl->DoPaint(hDC, rcPaint);
                    }
                }
            }
            else {
                CRenderClip childClip;
                CRenderClip::GenerateClip(hDC, rcTemp, childClip);
                for( int it = 0; it < m_items.GetSize(); it++ ) {
                    CControlUI* pControl = static_cast<CControlUI*>(m_items[it]);
                    if( !pControl->IsVisible() ) continue;
                    if( !::IntersectRect(&rcTemp, &rcPaint, &pControl->GetPos()) ) continue;
                    if( pControl ->IsFloat() ) {
                        if( !::IntersectRect(&rcTemp, &m_rcItem, &pControl->GetPos()) ) continue;
                        CRenderClip::UseOldClipBegin(hDC, childClip);
                        pControl->DoPaint(hDC, rcPaint);
                        CRenderClip::UseOldClipEnd(hDC, childClip);
                    }
                    else {
                        if( !::IntersectRect(&rcTemp, &rc, &pControl->GetPos()) ) continue;
                        pControl->DoPaint(hDC, rcPaint);
                    }
                }
            }
        }

        if( m_pVerticalScrollBar != NULL && m_pVerticalScrollBar->IsVisible() ) {
            if( ::IntersectRect(&rcTemp, &rcPaint, &m_pVerticalScrollBar->GetPos()) ) {
                m_pVerticalScrollBar->DoPaint(hDC, rcPaint);
            }
        }

        if( m_pHorizontalScrollBar != NULL && m_pHorizontalScrollBar->IsVisible() ) {
            if( ::IntersectRect(&rcTemp, &rcPaint, &m_pHorizontalScrollBar->GetPos()) ) {
                m_pHorizontalScrollBar->DoPaint(hDC, rcPaint);
            }
        }
    }

　　控件容器绘制完自己后，遍历子控件（包括子控件容器）调用其DoPaint，完成子控件绘制(代码已经在上上面贴出);

　　最终的绘制都是通过渲染引擎CRenderEngine实现的。

　　这样看来，整个绘制思路还是很清晰的：CPaintManagerUI::MessageHandler（WM_PAINT）--->CContainerUI::DoPaint--->CControlUI::DoPaint--->CRenderEngine。

　　OK绘制工作完成!