Re: MFC Custom Control in a MFC DLL

From:

Stephen Myers <""StephenMyers\"@discussions@microsoft.com">

Newsgroups:

microsoft.public.vc.mfc

Date:

Mon, 19 Oct 2009 09:39:29 -0500

Message-ID:

<eLxk4nMUKHA.4704@TK2MSFTNGP02.phx.gbl>

Luigino wrote:

On 16 Ott, 22:27, Joseph M. Newcomer <newco...@flounder.com> wrote:

I assumed the class had the appropriate AFX_EXT_CLASS or other suitable macro definition;
this should be added automatically when a project for an extension DLL is created. My
error. Of course, if the all-important source code had been included in the post, I might
have noticied this omission (but hey, why make it easy for the guys you are asking the
question of...?)
joe

On Fri, 16 Oct 2009 12:15:52 -0500, Stephen Myers

<""StephenMyers\"@discussi...@microsoft.com"> wrote:

Luigino wrote:

confusing the C++ compiler with the linker here. They are different, and what you do in
C++ has no implicit effect on the linker. Go to the Linker, Inputs, and add your .lib
file to the additional libraries line.

Ehm I did... I put under Linker-General in Additional Library
Directories the path of that Debug directory where the .lib file is
created once compiled the DLL and I added under Linker-Input, in
Additional Dependencies that CACharts.lib.....
So I also created now a control variable (from the class add variable
wizard) for this and implemented the code:
        CRect rect;
        c_MyStaticControl.GetWindowRect(&rect);
        ScreenToClient(&rect);
        CCaChart c_MyControl;
        c_MyControl.Create(rect, GetDlgItem
(c_MyStaticControl.GetDlgCtrlID()));
        c_MyStaticControl.DestroyWindow();
but I get these linker errors:
1>test_chartDlg.obj : error LNK2019: unresolved external symbol
"public: virtual __thiscall CCaChart::~CCaChart(void)" (??
1CCaChart@@UAE@XZ) referenced in function "protected: virtual int
__thiscall Ctest_chartDlg::OnInitDialog(void)" (?
OnInitDialog@Ctest_chartDlg@@MAEHXZ)
1>test_chartDlg.obj : error LNK2019: unresolved external symbol
"public: virtual int __thiscall CCaChart::Create(class CRect const
&,class CWnd *)" (?Create@CCaChart@@UAEHABVCRect@@PAVCWnd@@@Z)
referenced in function "protected: virtual int __thiscall
Ctest_chartDlg::OnInitDialog(void)" (?
OnInitDialog@Ctest_chartDlg@@MAEHXZ)
1>test_chartDlg.obj : error LNK2019: unresolved external symbol
"public: __thiscall CCaChart::CCaChart(void)" (??0CCaChart@@QAE@XZ)
referenced in function "protected: virtual int __thiscall
Ctest_chartDlg::OnInitDialog(void)" (?
OnInitDialog@Ctest_chartDlg@@MAEHXZ)
So, suspecting a possible issue of my VS2008, I tried to create from
scratch with class wizards a simple stupid DLL without adding or
modifying anything and trying to create a Test file from Visual Studio
IDE itself and when it asks me to choose the DLL project to test, it
returns "Unknown address 0"... then I try to create a test project for
the example, adding the .lib and I get same linker error I pasted
before...

I thought you needed to export the symbols in the library.
In CaChart.h
Something like
#ifdef MYLIB_BUILD
#define MYDLL_IO _declspec(dllexport) //conditional on MYLIB_BUILD
#else
#define MYDLL_IO _declspec(dllimport)
#endif
class MYDLL_IO CCaChart: public ...
Then add MYLIB_BUILD to the library project
Configuration Properties
    C/C++
        Preprocessor
           Preprocessor Defines
Steve

Joseph M. Newcomer [MVP]
email: newco...@flounder.com
Web:http://www.flounder.com
MVP Tips:http://www.flounder.com/mvp_tips.htm

In fact now it works.... just a thing that I'm trying to draw a filled
ellipse (where in the place I'll code the real component) and I
implemented an OnPaint, since I guess right after calling Create
function it should paint the DC on the parent but at debug it doesn't
fire...
I coded the OnPaint like this:

in the .h

     afx_msg void OnPaint();

in the .cpp

     added ON_WM_PAINT() in the MESSAGE_MAP routine

     void MyDLL::OnPaint()
    {
         CPaintDC dc(this);

         CDC MemDC;
         if (!MemDC.CreateCompatibleDC(&dc))
            return;

         CRect rect;
         GetClientRect(rect); // because it is a client
         MemDC.FillRect(rect, CBrush::FromHandle((HBRUSH)
GetStockObject(BLACK_BRUSH)));
         MemDC.Ellipse(rect);
    }

I tried also to move the creation thing to the test app in the way to
have an OnCreate(LPCREATESTRUCT lpCreateStruct) with same code of
OnPaint in the way to apply the drawing of the ellipse right after
creation of the DC and during Create(...) call it doesn't even fire
OnCreate(...) event to draw the ellipse, plus at SetWindowPos
execution I get an assert error on this line and at debug reports
passing the WndStatic variable (got by: CWnd* WndStatic = GetDlgItem
(c_MyStaticControl.GetDlgCtrlID()); since c_MyStaticControl control
variable is CStatic type), the m_hWnd in the function has value 0....
Shall I have missed something?....

Thanks
Ciao
Luigi

CWnd* WndStatic = GetDlgItem(c_MyStaticControl.GetDlgCtrlID());

is not at all the way things should be done. There is no reason to
create WndStatic. GetDlgItem should not be used in MFC. Check the
source of your code snippets. Chances are very good they are either not
written for MFC or written by someone who had not figured out what you
get with MFC.

Use c_MyStaticControl. instead of WndStatic->

This will not cirrect your problem.

I suspect that the real problem is due to accessing the control before
it is created (in OnInitDialog).

Steve