A previous article shows how to use D2D MFC classes for easily make a simple image viewer. As said there, it can be made even easier.

Enabling D2D support in MFC

1. In the WM_CREATE message handler call CWnd::EnableD2DSupport.
   
   C++

   int CDemoView::OnCreate(LPCREATESTRUCT lpCreateStruct) { if (CScrollView::OnCreate(lpCreateStruct) == -1) return -1; EnableD2DSupport(); // Enable D2D support for this window: return 0; }

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   int CDemoView::OnCreate(LPCREATESTRUCT lpCreateStruct) {     if (CScrollView::OnCreate(lpCreateStruct) == -1)         return -1;           EnableD2DSupport(); // Enable D2D support for this window:       return 0; }

2. In the overridden CView::OnUpdate load the bitmap from the current document’s file.
   
   C++

   void CDemoView::OnUpdate(CView* pSender, LPARAM lHint, CObject* pHint) { CDemoDoc* pDoc = GetDocument(); ASSERT_VALID(pDoc); CSize sizeImage(100, 100); delete m_pBitmap; m_pBitmap = NULL; const CString& strFile = pDoc->GetPathName(); if(! strFile.IsEmpty()) { CHwndRenderTarget* pRenderTarget = this->GetRenderTarget(); ASSERT_VALID(pRenderTarget); m_pBitmap = new CD2DBitmap(pRenderTarget, strFile); HRESULT hr = m_pBitmap->Create(pRenderTarget); if(m_pBitmap->IsValid()) { CD2DSizeF size = m_pBitmap->GetSize(); sizeImage.SetSize(static_cast<int>(size.width), static_cast<int>(size.height)); } } SetScrollSizes(MM_TEXT, sizeImage); ScrollToPosition(CPoint(0, 0)); }

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   void CDemoView::OnUpdate(CView* pSender, LPARAM lHint, CObject* pHint) {     CDemoDoc* pDoc = GetDocument();     ASSERT_VALID(pDoc);       CSize sizeImage(100, 100);     delete m_pBitmap;     m_pBitmap = NULL;       const CString& strFile = pDoc->GetPathName();     if(! strFile.IsEmpty())     {         CHwndRenderTarget* pRenderTarget = this->GetRenderTarget();         ASSERT_VALID(pRenderTarget);           m_pBitmap = new CD2DBitmap(pRenderTarget, strFile);         HRESULT hr = m_pBitmap->Create(pRenderTarget);         if(m_pBitmap->IsValid())         {             CD2DSizeF size = m_pBitmap->GetSize();             sizeImage.SetSize(static_cast<int>(size.width), static_cast<int>(size.height));         }     }    SetScrollSizes(MM_TEXT, sizeImage);    ScrollToPosition(CPoint(0, 0)); }

3. Map AFX_WM_DRAW2D registered message which is sent by the framework if D2D support is enabled. Perform all Direct2D painting in the AFX_WM_DRAW2D message handler.
   
   C++

   LRESULT CDemoView::OnDrawUsingDirect2D(WPARAM wParam, LPARAM lParam) { CHwndRenderTarget* pRenderTarget = (CHwndRenderTarget*)lParam; ASSERT_VALID(pRenderTarget); if(pRenderTarget->IsValid()) { D2D1_COLOR_F color = {1.f, 1.f, 1.f, 1.f}; // r, g, b, a pRenderTarget->Clear(color); if((nullptr != m_pBitmap) && m_pBitmap->IsValid()) { // apply translation transform according to view's scroll position CPoint point = GetScrollPosition(); D2D1_MATRIX_3X2_F matrix = D2D1::Matrix3x2F::Translation((float)-point.x, (float)-point.y); pRenderTarget->SetTransform(matrix); // draw the bitmap CD2DSizeF size = m_pBitmap->GetSize(); pRenderTarget->DrawBitmap(m_pBitmap, CD2DRectF(0, 0, size.width, size.height)); } } return TRUE; }

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   LRESULT CDemoView::OnDrawUsingDirect2D(WPARAM wParam, LPARAM lParam) {     CHwndRenderTarget* pRenderTarget = (CHwndRenderTarget*)lParam;     ASSERT_VALID(pRenderTarget);       if(pRenderTarget->IsValid())     {         D2D1_COLOR_F color = {1.f, 1.f, 1.f, 1.f}; // r, g, b, a         pRenderTarget->Clear(color);         if((nullptr != m_pBitmap) && m_pBitmap->IsValid())         {             // apply translation transform according to view's scroll position             CPoint point = GetScrollPosition();             D2D1_MATRIX_3X2_F matrix = D2D1::Matrix3x2F::Translation((float)-point.x, (float)-point.y);             pRenderTarget->SetTransform(matrix);             // draw the bitmap             CD2DSizeF size = m_pBitmap->GetSize();             pRenderTarget->DrawBitmap(m_pBitmap, CD2DRectF(0, 0, size.width, size.height));         }     }     return TRUE; }

That’s all. No need to create a render target, resize it, recreating it when nesessary, calling BeginDraw, EndDraw, etc. All is done in the MFC framework if D2D support is enabled for a window.

Demo project

Download: Image VIewer - Enabling D2D Support for MFC.zip (1666)

Resources and related articles

• Codexpert blog: MFC Support for Direct2D topics
• MSDN: CWnd::EnableD2DSupport
• MSDN: Adding a D2D Object to an MFC Project
• Codexpert blog: MFC Support for Direct2D – Part 1