C / C++ / MFC

read and write the structure to file

9-Aug-05 9:20

I see Jose Lamas Rios already gave a reasonable answer. Even without the automatic destuction in the post-increment code it is still possible for your code to increment passed the end (off into la la land). A normal interator does basicaly that, except it has a specific (invalid) ending point that you can check to see if you are done.

As for pre-increment and post-increment operator: You are not correct about what the compiler can do. A compiler can shape the code on known types such as int, double, ect..; it is incapable of determining how to convert a post-increment to a pre-increment for user defined types. Therefore, you should make using a pre-increment a habit or you'll constantly be making (hidden) temporary copies of what ever you are incrementing.

INTP
"The more help VB provides VB programmers, the more miserable your life as a C++ programmer becomes."
Andrew W. Troelsen

Re: Weird Memory Issues

cmk9-Aug-05 1:03

cmk

9-Aug-05 1:03

Without knowing how Iterator was written it's hard to say what's wrong.

The (*iterator)++ looks weird on an object pointer - i hope Iterator overloads operator ++ () and/or operator ++ (int).

...cmk

Save the whales - collect the whole set

Re: Weird Memory Issues

LighthouseJ9-Aug-05 5:06

LighthouseJ

9-Aug-05 5:06

Yes, I got example code for doing both pre- and post-increment from a site on the web and used that code in my project.

pnpfriend8-Aug-05 12:58

pnpfriend

8-Aug-05 12:58

Hi,
I have

========================
in vb.net
========================
Public Structure aStructure
public k as short
public b as short
public c as string
End Structure

Sub WriteStructure()
Dim txtfName As String
txtfName = "c:\rStruct.txt"
FileOpen(FreeFile(), txtfName, OpenMode.Binary, OpenAccess.Write)
FilePut(1, rStructure)
FileClose(1)
End Sub

================================
in c++, read in the structure
================================
struct astruct
{
int k;
int b;
CString c;
};
void main()
{
astruct *rStructure = new(struct astruct);
CString fName = "c:\\rStruct.txt";
aStructure = new(struct astruct);
FILE *rFile
rFile = fopen(fName, "r");
if(File)
{
fread(rStructure,sizeof(struct astruct),1,rFile);
fclose(rFile);
}
}

Do not really know why the structure wasnt' fill in right when it reads in (c++ code)? Only the first member 'k' was read in right. what am I doing wrong?

Thank you.

Re: read and write the structure to file

Tim Smith8-Aug-05 13:15

Tim Smith

8-Aug-05 13:15

k,b are ints where in VB they are shorts. Also, you can't read a VB string into a CString like that.

Tim Smith

I'm going to patent thought. I have yet to see any prior art.

Re: read and write the structure to file

pnpfriend9-Aug-05 3:37

pnpfriend

9-Aug-05 3:37

so how should I read then?

GDI Object leak detection

prcarp8-Aug-05 11:37

prcarp

8-Aug-05 11:37

First, I appologize if the answer is here somewhere but I couldn't find it. I am trying to find out where in my program I have a GDI object leak. As I run my program, the task manager reports that my GDI object count is rising. I have been programming VC++ since 4.0 and I am very verse in deleting my objects when I am done with them. However, I have run into a case where I believe it is in a Win32 call that may make a copy. I just don't know which one.

For example, I just learned that CStatic::SetIcon makes a copy. I have an array of HICONs that are loaded in App::InitInstance and destroyed in App:ExitInstance. Everytime I call a CStatic::SetIcon with one of these icon handles, the GDI object count increases. The fix was to do a GetIcon first, and DeleteObject on the icon handle it returns. Program is happy now in that regard.

But I still am missing some and I was wondering where. The program is graphic intensive and would be tough to start selectively commenting out the graphic calls.

Any thoughts?

Blake Miller8-Aug-05 12:02

Blake Miller

8-Aug-05 12:02

Are you running the debug kernel of windows?

In the old days (I mean 1994/1995) if you did so, when your process exited, if you had not freed all the GDI objects, you would get a dump when running your process under debug mode of all the GDI object you failed to 'free'.

You might also find this utility helpful:
http://msdn.microsoft.com/msdnmag/issues/03/01/GDILeaks/default.aspx[^]

prcarp9-Aug-05 2:34

prcarp

9-Aug-05 2:34

I am using WindowsXP with latest patches, etc. The task manager GDI Object count increases when I open a particular dialog box, for example. This dialog box has many CStatic-based elements which I use for some icon displays (that change based on some user WM_ events). It also has CButton-based elements for some metal-looking buttons with regions and icons. I started commenting out different pieces, trying to isolate the issue. The icons change while the dialog is open and the GDI Object count increases. It stays at that level when the dialog is closed but goes up yet again when the dialog is re-opened. To complicate matters more, I use a CMemDC to draw on before BitBlt-ing onto the CDC provided in the OnDraw.

I wouldn't necessarily have an issue with this but if the program runs for hours, I get low system resource errors, the program fails to paint windows, and eventually locks up. It seems to happen more frequently when I am in front of customers. Smile | :)

Task manager is the only way to kill it.

I will look into the article you mentioned. I also looked at different tools (Rational Purify, Numega, etc.) but they are expensive.... I may have no alternative.

Thanks!

cmk8-Aug-05 15:17

cmk

8-Aug-05 15:17

MFC uses a lot of object caching.

As a result, you can't use the values in the Task Mgr as an accurate account of what 'you' have freed as MFC may still have the object cached. It makes it rather hard to find any real leaks.

...cmk

Save the whales - collect the whole set

prcarp9-Aug-05 2:38

prcarp

9-Aug-05 2:38

I was wondering about that. I did see some cases where the count would linger before going down. However, I have some cases where it jumps up by 30 to 40 and then stays put (see response to Blake above). It gets bigger and bigger as the program stays running and eventually I get system resource errors and the program hangs.

John R. Shaw8-Aug-05 19:39

mr MFC please do something when I press a key

8-Aug-05 19:39

prcarp wrote:
appologize

No need! If you feel the need, it implies you know what you're doing, but have not figured out the answer yet!

It would help if you posted the leak error message.

If it is happening in debug mode, the odds are that the leak reported is invalid. Since the task manager reports that the count is rising, then it probably is real. Before assuming the task manager is telling you the entire truth: give it a few minutes or try closing the IDE, to see if the task manager stops reporting the same count. If the task manager does report the same count, then try running a release version of your application and see if the same thing is still happening.

Assuming (ass-u-me) that the problem is in the code you wrote, then I would put a TRACE(...) statement wherever you create a GDI object as well as where you release/free the GDI object (to see if they match).

There is also the possibility that you selected a pen, brush, ect... and did not restore the original (unlikely).

Oh Well! I dought if any of this helped (you already knew it).

INTP
"The more help VB provides VB programmers, the more miserable your life as a C++ programmer becomes."
Andrew W. Troelsen

Spiritofamerica8-Aug-05 10:29

Spiritofamerica

8-Aug-05 10:29

hello

I am making a program in MFC

I have a class for a window
I want to achieve this: when a key is pressed something happens.

To achieve this I did this
I went to class view I right clicked on my class and clicked on propreties
I clciked on messages
I selected WM_KEYDOWN and from the right column I selected
Add OnKeyDown

this created a new function:

void CViewListaLocatari::OnKeyDown(UINT nChar, UINT nRepCnt, UINT nFlags)
{
MessageBox("toader","toader",MB_OK);

if (nChar==VK_DELETE)
OnBnSterge();
else
CFormView::OnKeyUp(nChar, nRepCnt, nFlags);

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

and this line appeared in the message map

ON_WM_KEYDOWN()

I changed it to this

ON_WM_KEYDOWN(WM_KEYDOWN,OnKeyDown)

because it made more sense for it to be like that although I don't know if I did right

anyway it doesn't work
and no messagebox appears even

how do I make it work?

or do you know another way to do this?

Stober8-Aug-05 11:02

Stober

8-Aug-05 11:02

First -- don't screw around with the code that ClassWizard writes unles you know what you are doing. Change it back the way it was.

WM_KEYDOWN events are not handled by CDialog-derived classes. You have to use PreTranslateMessage() to capture the key events. Key events always go to the window that has focus.

Michael Kane9-Aug-05 4:48

Michael Kane

9-Aug-05 4:48

Thank you. It works fine.

Spiritofamerica13-Aug-05 9:46

Spiritofamerica

13-Aug-05 9:46

can you please elaborate on this

PreTranslateMessage()

where exactly should I put this ?

It is not a method that I can use

can you please explain more please

Rick York8-Aug-05 11:44

Rick York

8-Aug-05 11:44

Have you tried catching WM_CHAR ?

Drawing Text into a Bitmap with GDI

Spiritofamerica13-Aug-05 9:49

Spiritofamerica

13-Aug-05 9:49

Rick York wrote:
Have you tried catching WM_CHAR ?

doesn't work

wookie1828-Aug-05 8:56

wookie182

8-Aug-05 8:56

Hello,

I want to draw some text into a bitmap image. The image is stored in the memory. I just want to place some text in there. Afterwards it should be processed by a DirectShow pipeline but this doesn't matter here....

I tried a lot with GDI, but it doesn't work so far. Here is my code:

unsigned __int8 pBuffer; //pointer to image data<br />
int m_ImageWidth = 1024; //dimensions of the image<br />
int m_ImageHeight = 1024;<br />
<br />
BITMAP bmp = {0,m_ImageWidth,m_ImageHeight,m_ImageWidth,1,8,pBuffer};<br />
HBITMAP hBMP = CreateBitmapIndirect(&bmp);<br />
HDC hDC_bmp = CreateCompatibleDC(0);<br />
HBITMAP hBMPc = CreateCompatibleBitmap(hDC_bmp,m_ImageWidth,m_ImageHeight);<br />
HGDIOBJ x =	SelectObject(hDC_bmp, hBMPc);<br />
<br />
<br />
<br />
HDC hDC_txt = CreateCompatibleDC(0);<br />
int b = BitBlt(hDC_bmp,0,0,200,200,hDC_txt,0,0,BLACKNESS);<br />
<br />
char text_tag[16];<br />
sprintf(text_tag,"0123456789");<br />
RECT rect = {0,0,200,200};<br />
	<br />
int a = DrawText(hDC_txt,TEXT(text_tag),1,&rect,DT_LEFT);<br />
<br />
BITMAPINFO bmInfo;<br />
memset(&bmInfo.bmiHeader,0,sizeof(BITMAPINFOHEADER));<br />
bmInfo.bmiHeader.biSize=sizeof(BITMAPINFOHEADER);<br />
bmInfo.bmiHeader.biWidth=m_ImageWidth;<br />
bmInfo.bmiHeader.biHeight=m_ImageHeight;<br />
bmInfo.bmiHeader.biPlanes=1;<br />
bmInfo.bmiHeader.biBitCount=24;<br />
	<br />
HBITMAP g = CreateDIBitmap(hDC_txt,&bmInfo.bmiHeader,0,0,0,DIB_RGB_COLORS);<br />
<br />
int c = GetObject(g,1024*1024,(void*)pBuffer);

After processing these lines i think I should have the image with the text in the Buffer "pBuffer". But I don't have. Can anyone tell me why and how it works??? I am also open to a different method which just puts text into my bitmap.

Thanks for help
chris

C^hris L^osinger8-Aug-05 10:07

C^hris L^osinger

8-Aug-05 10:07

wookie182 wrote:
HDC hDC_txt = CreateCompatibleDC(0);
int b = BitBlt(hDC_bmp,0,0,200,200,hDC_txt,0,0,BLACKNESS);

this is a problem.

before you Blt to a DC, that DC needs to have a bitmap selected into it.

but, i'm not sure why you need hDC_txt in the first place. you should be able to do a DrawText onto hDC_bmp (after selecting your bitmap into hDC_bmp, of course).

Cleek | Image Toolkits | Thumbnail maker

wookie1828-Aug-05 10:27

wookie182

8-Aug-05 10:27

Well if I do without the hDC_txt it produces the same result. Only 24byte (nonsens) are writen in the Buffer. My new code looked like this

<br />
...<br />
	BITMAP bmp = {0,m_ImageWidth,m_ImageHeight,m_ImageWidth,1,8,pBuffer};<br />
	HBITMAP hBMP = CreateBitmapIndirect(&bmp);<br />
	HDC hDC_bmp = CreateCompatibleDC(0);<br />
	HBITMAP hBMPc = CreateCompatibleBitmap(hDC_bmp,m_ImageWidth,m_ImageHeight);<br />
	HGDIOBJ x =	SelectObject(hDC_bmp, hBMPc);<br />
<br />
	char text_tag[16];<br />
	sprintf(text_tag,"0123456789");<br />
	RECT rect = {0,0,200,200};<br />
	<br />
	int a = DrawText(hDC_bmp,TEXT(text_tag),1,&rect,DT_LEFT);<br />
<br />
        BITMAPINFO bmInfo;<br />
        memset(&bmInfo.bmiHeader,0,sizeof(BITMAPINFOHEADER));<br />
        bmInfo.bmiHeader.biSize=sizeof(BITMAPINFOHEADER);<br />
        bmInfo.bmiHeader.biWidth=m_ImageWidth;<br />
        bmInfo.bmiHeader.biHeight=m_ImageHeight;<br />
        bmInfo.bmiHeader.biPlanes=1;<br />
        bmInfo.bmiHeader.biBitCount=8;<br />
	<br />
	HBITMAP g = CreateDIBitmap(hDC_bmp,&bmInfo.bmiHeader,0,0,0,DIB_RGB_COLORS);<br />
<br />
	int c = GetObject(g,1024*1024,(void*)pBuffer__);<br />

I'm very new to this GDI stuff. And I don't exactly know what I'm actually doing. I just want to have text in my bitmap.... so please tolerate some stupid misstakes and questions...

Thanks
Chris

John R. Shaw8-Aug-05 20:02

8-Aug-05 20:02

Ahhh, you almost lost me entirely here "__int8 pBuffer" (that makes no since). Then I glanced at the rest of the code, which almost(!) looks reasonable(?).

wookie182 wrote:
I tried a lot with GDI, but it doesn't work so far.

Sorry, but that is because you do not know what your are doing!

INTP
"The more help VB provides VB programmers, the more miserable your life as a C++ programmer becomes."
Andrew W. Troelsen

Anonymous9-Aug-05 2:44

Anonymous

9-Aug-05 2:44

Of course I am NOT using an uninitialized Pointer!!! There is some code before, which allocates memory and puts data to this buffer. I am just new to this GDI stuff and I believe there must be something wrong in these lines....

John R. Shaw9-Aug-05 9:48