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Most programming guidelines would go even further - Don't misuse dynamic_cast; use virtual functions instead.
Steve
-- modified at 1:35 Tuesday 18th April, 2006
i.e.
class CBaseView : public CView
{
public:
virtual bool CanClose() const = 0;
};
class CMyView1 : public CBaseView
{
public:
virtual bool CanClose() const
{
return false;
}
};
class CMyOtherViews : public CBaseView
{
public:
virtual bool CanClose() const
{
return true;
}
};
pView->CanClose();</code>
This is basic OO design and good use the C++'s features.
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Hi Stephen, Maxwell...
Thanks a lot for your immediate reply. It helped me to solve the problem.
Sarvan AL
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Sarvan AL wrote: warning C4541: 'typeid' used on polymorphic type 'class CView' with /GR-; unpredictable behavior may result
I believe it's telling you that the .rdata sections will increase in size, which may or may not be desirable. It might also have something to do with RTTI.
"Let us be thankful for the fools. But for them the rest of us could not succeed." - Mark Twain
"There is no death, only a change of worlds." - Native American Proverb
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While being handy and nice, the MFC CHotKeyCtrl class does act weird sometimes, for example, it does not recognize the "space" key, instead, it rejects the keystroke and cleans all existing contents just like I pressed the "backspace" key. Now the funny thing is that, if I set the "space" key programmatically m_wndHotkey1.SetHotkey(VK_SPACE, 0); it will work, just that it cannot be specified by user input.
Unfortunately I really want the "space" key to be one of the configurable hotkeys in my application. Do I have a way to work around this problem? Thank you.
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Try with:
UnregisterHotKey(...)
m_hotkey1.GetHotKey(...)
...
RegisterHotKey(...)
m_hotkey1.SetHotKey(...)
RegisterHotKey modifier flags defined in "CommCtrl.h" and "WinUser.h" are not same.
The values for fsModifiers are defined in "WinUser.h".
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Hi,
I would like to add drag/drop function to the CTreeCtrl class, just as the
Resource tree in Visual C++ environment. Are there any examples?
Thanks.
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Hi, friends,
I used to integrate the simulink package to my project, that is, I opened a
Simulink window and moved the window to the related view, assumed to be the CMHCSimPlatformView, the codes are referred to as follows:
//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
void CMHCSimPlatformView::OnStartMatlabEngine()
{
...
m_hSimulink = ::FindWindow(NULL,"Project_1 ");
if(::IsWindow(m_hSimulink))
{
//Set the CMHCSimPlatformView is the parent window for the simulink one
::SetParent(m_hSimulink,this->GetSafeHwnd());
CWnd * pWnd = NULL;
pWnd = FromHandle(m_hSimulink);
CRect rect;
GetClientRect(&rect);
//move the simulink window to the related area, that is to the
//client area of the CMHCSimPlatformView.
pWnd->MoveWindow(&rect,false);
//delete the catpion of the simulink interface
pWnd->ModifyStyle(WS_CAPTION|WS_BORDER,0);
//delte the system menu of the simulink interface
pWnd->SetMenu(NULL);
//delete the system toolbar of the simulink interface
HWND handToolbar = ::FindWindowEx(m_hSimulink,NULL,_T ToolbarWindow32"),NULL);
CWnd* pToolWnd;
pToolWnd = FromHandle(handToolbar);
pToolWnd->ShowWindow(FALSE);
CFrameWnd * pFrame=(CFrameWnd *)AfxGetMainWnd();
pFrame->GetActiveFrame()->UpdateWindow ();
UpdateData(true);
}
...
}
//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
where, Project_1 is the name of a simulink file opened before, and m_hSimulink is a variable of HWND.
Surely, the simulink window was moved to the CMHCSimPlatformView client area when the above codes are executed. However, after later opertions, the simulink window was often covered with the CMHCSimPlatformView window.
 How to ensure that the simulink window always stays on the top ?and how to
change the simulink window according to the CMHCSimPlatformView area?
Regards.
zhou_rusheng
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Please give me some ideas.
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I want to add ZoomIn/ZoomOut in my MFC Application, works on text and image, just like MSWORD, how can I get this??
thanks for your response
-- modified at 22:50 Monday 17th April, 2006
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MM_ISOTROPIC will get you zoom with minimal effort. You'll have to work a little though to get an app like MSWORD. I can't help you there.
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Here's a little to get you started. Start a new MFC/SDI app and plop this stuff in the appropriate locations. Set up menu/toolbar buttons for the zoomin/zoomout. Add some drawing code to your OnDraw and you should find that the drawing is fit_to_width in the view and it should be fit to width when printing. The rest is up to you. have fun...
(Let me know if I missed something)
///////////////////////////////////////////////
//Constants
const int MAX_SCALE = 20; // The maximum scale factor
//CDocument members...
protected:
CSize m_DocSize;
CSize CYourDoc::GetDocSize() const
{
return m_DocSize;
}
CYourDoc::CYourDoc()
{
// TODO: add one-time construction code here
m_DocSize=CSize(2000,2800);
}
//CScrollView members...
protected:
int m_Scale;
CYourView::CYourView()
{
// TODO: add construction code here
m_Scale=1; // Set scale factor 1:1
SetScrollSizes(MM_TEXT,CSize(0,0)); // Set arbitrary values
}
void CYourView::OnPrepareDC(CDC* pDC, CPrintInfo* pInfo)
{
CScrollView::OnPrepareDC(pDC);
// TODO: Add your specialized code here and/or call the base class
// Set up the DC for the current scale factor
int nExtentX;
int nExtentY;
CSize sizeDoc;
CRect rectClient;
// Allows the rectangle to include the bottom and rightmost logical unit
// SetGraphicsMode(pDC->m_hDC,GM_ADVANCED);
pDC->SetMapMode(MM_ISOTROPIC); // Allow scaling with aspect ratio preserved
// Get pertinent rectangle data
GetClientRect(&rectClient);
sizeDoc=GetDocument()->GetDocSize();
sizeDoc.cy=(-sizeDoc.cy); // Y goes down as it increments
pDC->SetWindowExt(sizeDoc); // Window extent is size of document
// Calculate viewport extent
nExtentX=(int)(GetScale()*rectClient.Width());
nExtentY=(int)((GetScale()*((nExtentX*sizeDoc.cy)/(sizeDoc.cx))));
// What kind of device context do we have?
if (pDC->IsPrinting()==TRUE) {
// Printer Context. Allow printing to edge of context. No scaling. Margins?
pDC->SetViewportExt(pDC->GetDeviceCaps(HORZRES),-pDC->GetDeviceCaps(VERTRES));
} else {
// Context is for screen
pDC->SetViewportExt(nExtentX,nExtentY);
}
}
int CYourView::GetScale()
{
return m_Scale;
}
void CYourView::SetScale(int nScaleFactor)
{
m_Scale=nScaleFactor;
ResetScrollBars(); // Adjust scrollbars to new scale
}
void CYourView::OnUpdateViewZoomout(CCmdUI* pCmdUI)
{
// TODO: Add your command update UI handler code here
if (GetScale()>=2) pCmdUI->Enable(TRUE);
else pCmdUI->Enable(FALSE);
}
void CYourView::OnUpdateViewZoomin(CCmdUI* pCmdUI)
{
// TODO: Add your command update UI handler code here
if (GetScale()<MAX_SCALE) pCmdUI->Enable(TRUE);
else pCmdUI->Enable(FALSE);
}
void CYourView::ResetScrollBars()
{
CSize sizeDoc;
CClientDC dc(this);
this->OnPrepareDC(&dc); // Update the device context
sizeDoc=GetDocument()->GetDocSize();
dc.LPtoDP(&sizeDoc); // Logical to device
this->SetScrollSizes(MM_TEXT,sizeDoc); // Update scrollbars
}
void CYourView::OnInitialUpdate()
{
CScrollView::OnInitialUpdate();
// TODO: calculate the total size of this view
ResetScrollBars();
}
void CYourView::OnSize(UINT nType, int cx, int cy)
{
CScrollView::OnSize(nType, cx, cy);
// TODO: Add your message handler code here
ResetScrollBars();
}
// Toolbar/menu button handler
void CYourView::OnViewZoomin()
{
// TODO: Add your command handler code here
if (GetScale()<MAX_SCALE) SetScale(GetScale()+1);
Invalidate();
}
// Toolbar/menu button handler
void CYourView::OnViewZoomout()
{
// TODO: Add your command handler code here
if (GetScale()>=2) SetScale(GetScale()-1);
Invalidate();
}
-- modified at 23:44 Monday 17th April, 2006
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really appreciate for your answer.
I add function TextOut in CMyView::OnDraw(), when I clicked ZoomIn, the view extended it's size, but the text in view still keeped it's size.
should I add some other code?
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I get it!
firt time I failed because I used Textout function without creating a CFont.
bob16972,thank you very much!!
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I'm glad it's working.
Take care.
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google offers a set of commands, such as link, pagerank, which can be used on google web-page.
my question is:
how to develop a VC program which uses google commands to retrieve google info of these commands?
any links, sample or comments?
thx
A special image tool for C++ programmers, don't miss it!
The world unique Software Label Maker is here for you and me ...
A nice hyper tool for optimizing your MS html-help contents.
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includeh10 wrote: how to develop a VC program which uses google commands to retrieve google info of these commands?
Google provide apis for same!, you can get that from google itself
"Opinions are neither right nor wrong. I cannot change your opinion. I can, however, change what influences your opinion." - David Crow
cheers,
Alok Gupta
VC Forum Q&A :- I/ IV
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Hi all,
Can Windows Media Player play from a buffer instead of a file?
Thanks!
Harshita
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I suspect it can render from an IStream interface. If this is the case all you have to do is implement an IStream that gets its data from a buffer. CreateStreamOnHGlobal and friends may be of interest.
Steve
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Thanks for your reply!
I have implemented an IStream that gets data from a buffer but I do not understand to which Media Player API should I feed this input?
I had gone through ReadFromStream sample of WMF 9 SDK. But, this sample takes an input from a file instead of IStream!
It would be great if you could provide some guideline. Thank again!
Harshita
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I was only guessing when I suggested using an IStream interface (as I indicated in the post). I would search the SDK for IStream, IStorage and IMoniker. If you do say and send my the results perhaps I can help.
Steve
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Thanks Steve!
Actually I even wanted to know that if I implement WMP to read from an IStream, is it important to have the knowledge of COM?
Regards,
Harshita
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IStream is a COM interface, so if you implement it yourself, yes. In my opinion knowledge of COM is essential knowledge for Windows developers. Especially if you write unmanaged code. In this instance you may be able to get away with using the CreateStreamOnHGlobal API and use a system supplied implementation however.
Steve
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Thanks again for your kind suggestion!
Can you suggest me some good URL for learning COM?
Regards,
Harshita
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Hello,
Visual Studio 2005
From the help on: Compiler Warning (level 2) C4356
If I modify that example like:
#include <iostream>
template <class T>
class C {
static int n;
};
class D : C<int> {};
int C<int>::n = 0;
if I take this code and put it in a DLL
like this:
# if defined(MYLIB_EXPORTS)
# define MYLIB_API __declspec(dllexport)
# else
# define MYLIB_API __declspec(dllimport)
# endif
template <class T>
class C {
static int n;
static void show() {
std::cout << "C:show()" << std::endl;
std::cout << n << std::endl;
}
};
class MYLIB_API D : C<int> {};
int C<int>::n = 3;
#include "mydll.h"
int main() {
int k1 = D::n;
int k2 = C<int>::n;
D::show();
}
The error I get, if I uncomment (a) or (b), is always:
1>myapp.obj : error LNK2001: unresolved external symbol "public: static int C<int>::n" (?n@?$C@H@@2HA)
This makes sense because I am not exporting C.
So the question is:
1.1) Why then method show() gets exported ?
1.2) In other words: Why the method gets exported and the data member not ?
2) Is there any way to export directly the data ?
( of course I could workaround the problem and access the static data member through a static method )
3) A last question, a little different, but maybe related:
If I try to export some data from a DLL, like:
// file mydll.h :
static MYLIB_API int mydata; // error C2201: 'mydata' : must have external linkage in order to be exported/imported
MYLIB_API static int mydata2; // error C2201: 'mydata' : must have external linkage in order to be exported/imported
I think that with vc70, if I remember well, I was not gettting any error message while compiling the DLL, but the LNK2001 error when linking the application.
In other words I am always forced to export data as static data member of a class, ( which is in some cases very unconvenient), like:
class MYLIB_API MyDataClass {
static int data;
};
int MyDataClass::data = 5;
Is there a way to do it without using a class ?
Thank you very much for any answer.
Marcello
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