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ENC Kernel SDK

MFC Application Integration

A canonical pattern for embedding henc into an MFC SDI / MDI application via a CView subclass.

Header / members

Section titled “Header / members”
CEncView.h
#include "henc.h"
#include <gl/GL.h>


class CEncView : public CView
{
protected:
    HGLRC m_hRC;       // OpenGL context
    HDC   m_hDC;       // device context
    int   m_view;      // henc view handle
    bool  m_inited;


public:
    CEncView();
    virtual ~CEncView();


protected:
    afx_msg int  OnCreate(LPCREATESTRUCT lpCreateStruct);
    afx_msg void OnDestroy();
    afx_msg void OnSize(UINT nType, int cx, int cy);
    afx_msg void OnLButtonDown(UINT nFlags, CPoint point);
    afx_msg BOOL OnEraseBkgnd(CDC* pDC);
    virtual void OnDraw(CDC* pDC);


    DECLARE_MESSAGE_MAP()
};

Message map + OnCreate (henc init)

Section titled “Message map + OnCreate (henc init)”
CEncView.cpp
BEGIN_MESSAGE_MAP(CEncView, CView)
    ON_WM_CREATE()
    ON_WM_DESTROY()
    ON_WM_SIZE()
    ON_WM_LBUTTONDOWN()
    ON_WM_ERASEBKGND()
END_MESSAGE_MAP()


int CEncView::OnCreate(LPCREATESTRUCT lpCreateStruct)
{
    if (CView::OnCreate(lpCreateStruct) == -1) return -1;


    m_hDC = ::GetDC(m_hWnd);


    // Standard PIXELFORMATDESCRIPTOR + ChoosePixelFormat + SetPixelFormat
    PIXELFORMATDESCRIPTOR pfd = {};
    pfd.nSize = sizeof(pfd);
    pfd.nVersion = 1;
    pfd.dwFlags = PFD_DRAW_TO_WINDOW | PFD_SUPPORT_OPENGL | PFD_DOUBLEBUFFER;
    pfd.iPixelType = PFD_TYPE_RGBA;
    pfd.cColorBits = 32;
    pfd.cDepthBits = 24;


    int pf = ChoosePixelFormat(m_hDC, &pfd);
    SetPixelFormat(m_hDC, pf, &pfd);


    m_hRC = wglCreateContext(m_hDC);
    wglMakeCurrent(m_hDC, m_hRC);


    // henc init
    if (hencInit() != 0) {
        AfxMessageBox(_T("hencInit failed"));
        return -1;
    }
    m_view = hencCreate();
    hencSelect(m_view);


    // Default cell - load via a menu in a real app
    hencLoad("S57/KR4A4061.000");
    hencSetCenter(m_view, 129.42, 35.10);
    hencSetZoom(m_view, 12.0);


    m_inited = true;
    return 0;
}

OnSize: viewport sync

Section titled “OnSize: viewport sync”
void CEncView::OnSize(UINT nType, int cx, int cy)
{
    CView::OnSize(nType, cx, cy);
    if (!m_inited || cx <= 0 || cy <= 0) return;


    hencSetViewport(m_view, 0, 0, cx, cy);
    Invalidate(FALSE);
}

OnDraw: per-frame render

Section titled “OnDraw: per-frame render”
void CEncView::OnDraw(CDC* /*pDC*/)
{
    if (!m_inited) return;


    wglMakeCurrent(m_hDC, m_hRC);
    hencSelect(m_view);


    hencClearBackground(m_view);
    hencRender(m_view);
    hencSwapBuffer(m_view);
}


// Suppress CView's own background paint (avoids flicker)
BOOL CEncView::OnEraseBkgnd(CDC* /*pDC*/) { return TRUE; }

OnLButtonDown: object picking

Section titled “OnLButtonDown: object picking”
void CEncView::OnLButtonDown(UINT nFlags, CPoint point)
{
    if (!m_inited) { CView::OnLButtonDown(nFlags, point); return; }


    // Pick the closest S-57 object within ±8 px of the click
    int objHandle = hencPickObj(m_view, point.x, point.y, 8);
    if (objHandle >= 0) {
        char buf[2048];
        hencObjToString(objHandle, buf, sizeof(buf));
        CString msg(buf);
        AfxMessageBox(msg);
    }


    CView::OnLButtonDown(nFlags, point);
}

OnDestroy: teardown

Section titled “OnDestroy: teardown”
void CEncView::OnDestroy()
{
    if (m_inited) {
        hencDelete(m_view);
        hencDeinit();
    }


    wglMakeCurrent(NULL, NULL);
    if (m_hRC) wglDeleteContext(m_hRC);
    if (m_hDC) ::ReleaseDC(m_hWnd, m_hDC);


    CView::OnDestroy();
}

Common pitfalls

Section titled “Common pitfalls”
  • OnDraw fires but the view is blank: another context may be current. Re-call wglMakeCurrent at the start of OnDraw in apps with multiple views/dialogs.
  • OnSize reports 0×0: can happen on initial OnCreate. Guard with m_inited.
  • Flicker: must return TRUE from OnEraseBkgnd: the MFC default paints a white background.
  • Empty pick result: increase the pick radius (8 → 16 px) or use hencSelectObj with a rectangle.
Section titled “Related API”