DuiLib（四）——控件绘制

duilib的所有控件均绘制在唯一的真实窗口之中，本篇就具体看下这个绘制的过程。所有的绘制过程均在WM_PAINT消息处理过程中完成。由窗口及消息篇可以看到，窗口消息处理最终流到了CPaintManagerUI::MessageHandler中。包括WM_PAINT在内消息均在此函数中处理，我们仅关注WM_PAINT消息

     case WM_PAINT:
         {
             // Should we paint?
             RECT rcPaint = {  };
             if( !::GetUpdateRect(m_hWndPaint, &rcPaint, FALSE) ) return true;
             if( m_pRoot == NULL ) {
                 PAINTSTRUCT ps = {  };
                 ::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 = {  };
                 ::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, _T("windowinit"),  , , false);
                     }
                 }
             }
             // Set focus to first control?
             if( m_bFocusNeeded ) {
                 SetNextTabControl();
             }
             //
             // Render screen
             //
             // Prepare offscreen bitmap?
             if( m_bOffscreenPaint && m_hbmpOffscreen == NULL )
             {
                 RECT rcClient = {  };
                 ::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 = {  };
             ::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 = {  };
                         ::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);
                 }
                 m_pRoot->DoPaint(m_hDcOffscreen, ps.rcPaint);//绘制控件
                 for( int i = ; 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);
                 m_pRoot->DoPaint(ps.hdc, ps.rcPaint);//绘制控件
                 ::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;

在::BeginPaint(m_hWndPaint, &ps)和::EndPaint(m_hWndPaint, &ps)中间是窗口绘制部分，duilib包含了两种方式：双缓存方式（解决闪烁问题）和标准方式，默认为双缓存方式。两种方式最终都调用了m_pRoot->DoPaint，m_pRoot为控件容器，且DoPaint为虚函数，实际调用了CContainerUI::DoPaint

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

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

     if( m_items.GetSize() >  ) {
         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 = ; 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 = ; 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

 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 >  || m_cxyBorderRound.cy >  ) {
         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);
     }
 }

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。