C / C++ / MFC

Having trouble with c++ templates

21-Sep-15 20:50

LVS_EX_HEADERDRAGDROP is a extended style, that is why should be setup not there, but using SetExtendedStyle method:

C++

ListCtrl.SetExtendedStyle(LVS_EX_HEADERDRAGDROP);

I don't know Win32, but I am sure there is SetExtendedStyle Win32 function ...

BobInNJ21-Sep-15 12:48

BobInNJ

21-Sep-15 12:48

I have a c++ class that contains the following:

template<class T> class Poly {
public:
Poly<T>(int order = 0)
{
this->order = order;
coeffs = new double[order+1];
for( int i = 0;i<=order; i++ )
coeffs[i] = 0;
}
Poly<T>( int order, T *coeffs);
Poly<T>( Poly &poly );

~Poly()
{
delete []coeffs;
}

// other member functions are not shown.

friend ostream &operator << ( ostream &out,
Poly<T> &poly );
private:

// data members not show.

};

This class is defined in a file called poly.h. In the file poly.cpp, I have the following function definition:

template<class T>
ostream & operator << ( ostream &out, Poly<T> &poly )
{
bool printedCoeff = false;
.
.
.
return out;
}

In a third file called test.cpp, I have:

double coeffs[] = { 3, 1, 2, 1 };
Poly<double> p1(3,coeffs), p2;

cout << p1 << endl;

I am using the Microsoft Visual Studio and I get a linker error because of the statement:
cout << p1 << endl;

I believe that my definition of the function overloading << is
not properly getting instantiated. How do I fix this?

Bob

Re: Having trouble with c++ templates

CPallini21-Sep-15 21:45

CPallini

21-Sep-15 21:45

Have alook at: "[34.12] Why can't I separate the definition of my templates class from it's declaration and put it inside a .cpp file?"[^] and also at [34.13] of the same document.

Calling GDI+ DrawImage function throws _BLOCK_TYPE_IS_VALID error

Kiran Satish21-Sep-15 7:39

Kiran Satish

21-Sep-15 7:39

I am trying to use GDI+ within my MFC dialog based application with multiple child dialogs. On one of the child dialogs, I am trying to draw an image from an array of 8 bit BYTE pixel data. Here is how my flow process is for this-

Variables declared in my child dialog's header file.

CSS

LONG	DIBSecWidth;
LONG	DIBSecHeight;
LONG	BitsPerPixel;
LONG        Stride;
BITMAPINFO* bmi;
BYTE*       pDIBSectionBits;
HBITMAP     hbm;
Graphics*   imagedisp;
Bitmap*     offscreenBitmap;
RECT        m_imagedisp_rect;
BOOL        m_BUpdate;

Then in my OnInitDialog() function, I do the following

CSS

DIBSecWidth = 512;
DIBSecHeight = 512;
BitsPerPixel = 8;

Stride = ((DIBSecWidth* BitsPerPixel + 31L) & (~31L)) / 8L;	
	
bmi = (BITMAPINFO *)new BYTE[sizeof(BITMAPINFO) + UCHAR_MAX * sizeof(RGBQUAD)];
bmi->bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
bmi->bmiHeader.biWidth = DIBSecWidth;
bmi->bmiHeader.biHeight = DIBSecHeight;
bmi->bmiHeader.biPlanes = 1;
bmi->bmiHeader.biBitCount = (WORD)BitsPerPixel;
bmi->bmiHeader.biCompression = BI_RGB;
bmi->bmiHeader.biSizeImage = 0;
bmi->bmiHeader.biXPelsPerMeter = 0;
bmi->bmiHeader.biYPelsPerMeter = 0;
bmi->bmiHeader.biClrUsed = 0;
bmi->bmiHeader.biClrImportant = 0;
memcpy(bmi->bmiColors, summercmap, 256*sizeof(RGBQUAD)); //summercmap is a color table of 256 RGB (COLORREF) values
	
hbm = ::CreateDIBSection(NULL, bmi, DIB_RGB_COLORS, (void**)&pDIBSectionBits, NULL, 0);
	
offscreenBitmap = new Bitmap(bmi, pDIBSectionBits);
ImageDisplay.GetClientRect(&m_imagedisp_rect);
imagedisp = new Graphics(ImageDisplay.GetDC()->GetSafeHdc());
m_BUpdate = true;

and in OnPaint() message handler I have the following

CSS

CPaintDC dc(this); // device context for painting
// TODO: Add your message handler code here
if (m_BUpdate)
{
BYTE *pCurRowPixel = (BYTE *)(pDIBSectionBits);
memcpy(pCurRowPixel, m_pImgBuffPrc, DIBSecWidth*DIBSecHeight);
imagedisp->DrawImage(offscreenBitmap, 0, 0, DIBSecWidth, DIBSecWidth);
m_BUpdate = false;
delete pCurRowPixel;
}

Whenever I run my application, it throws an error at imagedisplay->DrawImage function, if I comment it out it doesn't throw the error. I am sure there is something simple that I am missing here or the way I am trying to draw is not right, any ideas/suggestions?
thanks

PKNT

modified 21-Sep-15 13:49pm.

Re: Calling GDI+ DrawImage function throws _BLOCK_TYPE_IS_VALID error

CPallini21-Sep-15 21:50

CPallini

21-Sep-15 21:50

Quote:
delete pCurRowPixel;

What's the purpose of the above line? It looks plain wrong, to me.

Re: Calling GDI+ DrawImage function throws _BLOCK_TYPE_IS_VALID error

Jochen Arndt21-Sep-15 21:54

Re: Calling GDI+ DrawImage function throws _BLOCK_TYPE_IS_VALID error

21-Sep-15 21:54

I saw that too. But it is guarded by m_BUpdate.

CPallini21-Sep-15 22:01

CPallini

21-Sep-15 22:01

The crashing call too is guarded by m_BUpdate.
Anyway, it is wrong calling delete on the memory allocated via CreateDIBSection.

Re: Calling GDI+ DrawImage function throws _BLOCK_TYPE_IS_VALID error

Jochen Arndt21-Sep-15 22:14

21-Sep-15 22:14

CPallini wrote:
Anyway, it is wrong calling delete on the memory allocated via CreateDIBSection.

Which might be the reason for the exception because <code>_BLOCK_TYPE_IS_VALID is thrown when trying to delete memory that wasn't allocated using new.

Shift + VK_LEFT

_Flaviu20-Sep-15 21:44

20-Sep-15 21:44

Is there any possibility to catch shift + left key without mess up PreTranslateMessage ? I have tried this:

C++

void CGridCtrlExt::OnKeyDown(UINT nChar, UINT nRepCnt, UINT nFlags) 
{
	// TODO: Add your message handler code here and/or call default

	if(VK_LEFT == nChar || VK_RIGHT == nChar)
		TRACE1(">>>%d", nChar);

	CGridCtrl::OnKeyDown(nChar, nRepCnt, nFlags);
}

I see TRACE message ... but when I wrote:

C++

void CGridCtrlExt::OnKeyDown(UINT nChar, UINT nRepCnt, UINT nFlags) 
{
	// TODO: Add your message handler code here and/or call default

	if((VK_LEFT == nChar || VK_RIGHT == nChar) && GetKeyState(VK_SHIFT) < 0)
		TRACE1(">>>%d", nChar);

	CGridCtrl::OnKeyDown(nChar, nRepCnt, nFlags);
}

I saw nothing ... can you help me out, please ? Thank you.

Jochen Arndt20-Sep-15 22:19

20-Sep-15 22:19

It should work that way. But it will not work if those key combinations are "eaten" by an existing pre-translation. You may test that by using the first version with an extended trace:

TRACE1(">>>%d, state %x", nChar, GetKeyState(VK_SHIFT));

If the above is not called with shift key down, it is probably "eaten". Then you must use PreTranslateMessage or try to disable the existing translation.

_Flaviu20-Sep-15 22:24

20-Sep-15 22:24

I was just made the same test:

C++

TRACE("%d|%d\n", IsSHIFTpressed(), nChar);

but no, with shift key pressed, the keydown handler seem not calling ... I have to see what happen above this class. Thank you, and I'll come back with feedback.

_Flaviu20-Sep-15 22:39

20-Sep-15 22:39

Strange ... I have checked if parent of CGridCtrlExt (CGridCtrl), has PreTranslateMessage, but no, has not ... more over, I override CGridCtrlExt::OnChar, CGridCtrlExt::OnSysChar, CGridCtrlExt::OnSysKeyDown, none of them tell me when I press the shift key ... weird ... I don't know where to search the issue ...

Jochen Arndt20-Sep-15 22:51

20-Sep-15 22:51

I don't know which CGridCtrl you are using. The keys may be also catched by an underlying Windows control so that you don't see the translator source.

If there is some action associated, you should recognize it. What happens when pressing Shift Left/Right on a wide item?

You may spend some more time for investigation or just implement your own PreTranslateMessage handler.

_Flaviu20-Sep-15 23:04

20-Sep-15 23:04

"I don't know which CGridCtrl you are using"
I am using this[^] one.

Jochen Arndt20-Sep-15 23:14

20-Sep-15 23:14

I have not used that so far. But I'm quite sure that the arrow keys are used to select cells when the Shift key is pressed too.

_Flaviu20-Sep-15 23:14

20-Sep-15 23:14

I guess it is my mistake !!! : I already have an accelerator, shift + left key, on menu item command ... if this is the cause, is there any possibility to know in CGridCtrlExt, of on CDialog which contain this control, to know when I pressed Shift and left key ?

Jochen Arndt20-Sep-15 23:21

20-Sep-15 23:21

If you have a global accelerator you have three options:

From the accelerator handling check if your grid control is active and pass the message to that if so
Add another accelerator table to your grid control
Use PreTranslateMessage in your grid control

_Flaviu20-Sep-15 23:23

20-Sep-15 23:23

I will try your first solution. I'll come back.

_Flaviu21-Sep-15 22:13

21-Sep-15 22:13

Because left/right key combined with shift/ctrl key are used to mark grid cells, I have chose to use F7/F8 key for my needs. Thank you all of you for patience and attention. Bye.

Richard MacCutchan20-Sep-15 22:32

Richard MacCutchan

20-Sep-15 22:32

I have just tried this and it all works as per the documentation. I can only assume that these keys are being trapped by the CGridCtrlExt control somehow.

_Flaviu20-Sep-15 22:53