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Can I resiza a column in a DataGrid control (whriting a code of cource)
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I am trying to write a safe DC class, so I can avoid the hassle of keeping track of pens and brushes returned to me, as well as a one step create/select bitmap process.
Here is what I am doing:
CPen* CGDC::SafeSelect( CPen* pPen )
{
if (m_pOldPen)
{
return SelectObject(pPen);
}
else
{
m_pOldPen = SelectObject(pPen);
return m_pOldPen;
}
}
CBrush* CGDC::SafeSelect( CBrush* pBrush )
{
if (m_pOldBrush)
return SelectObject(pBrush);
else
{
m_pOldBrush = SelectObject(pBrush);
return m_pOldBrush;
}
}
m_pOldPen and m_pOldBrush are both NULL, I have stepped through and both functions behave as I would expect, as does the destructor:
CGDC::~CGDC()
{
if (m_pOldPen)
SelectObject(m_pOldPen);
if (m_pOldBrush)
SelectObject(m_pOldBrush);
if (m_pOldFont)
SelectObject(m_pOldFont);
DeleteDC();
}
Here's the thing. I tested it with this:
// for (int j = 0; j < 500; j++)
{
CGDC dc;
for (int i =0; i<500; i++)
{
CPen pen;
pen.CreatePen(PS_SOLID, 1, RGB(0,0,0));
/*CPen* pPen = */dc.SafeSelect(&pen);
CBrush brush;
brush.CreateSolidBrush(RGB(0,0,0));
dc.SafeSelect(&brush);
// dc.SelectObject(pPen);
}
}
Now, no matter which loop I comment in, if I comment out the SafeSelect on the pen it works fine. If I include the pen select and the call to SelectObject, it works fine. If I declare pPen here or not, if I call SafeSelect on the pen, it doesn't matter if I grab pPen here or not - unless I select it here, although it gets selected in CGDC, I lose about 30% of my GDI rsources when this code is called.
I have checked using GDI usage and the number of sequential ( in memory ) pens I leak varies, but is between 450 and 470. I don't leak any brushes. Can anyone tell me what is going on ? I have experimented with deleteobject, etc., but the fact is I seem to do the same thing inside the class and outside, but inside works for brushes, not pens.
Thanks
Christian
The content of this post is not necessarily the opinion of my yadda yadda yadda.
To understand recursion, we must first understand recursion.
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Modify your SafeSelect functions like this:
if (m_pOldPen!=NULL) SelectObject(m_pOldPen);
if (pPen!=NULL) m_pOldPen = SelectObject(pPen); else m_pOldPen=NULL;
return m_pOldPen;
Same for the brush version.
Now, if you are detaching the DC handle from the CDC base class, then your destructor is worthless, since the DC handle is gone.
The other problem is that I did not see a constructor for your CGDC class. Assuming that you're using the base CDC, then the DC handle is null, and SelectObject will either (a) do nothing (b) bomb (c) leak.
Just my $0.02
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Thanks for the comment, but apart from the fact that I'd not yet checked for NULL 'incoming', I had tried doing it this way previously, tried it again with your code, and it still leaks pens like craazy, but not brushes.
Here is my constructor:
CGDC::CGDC(CDC* pDC /* = NULL */)
{
CreateCompatibleDC(pDC);
SetStretchBltMode(COLORONCOLOR);
m_pOldBitmap = NULL;
m_pOldBrush = NULL;
m_pOldPen = NULL;
m_pOldFont = NULL;
}
P.S. Why won't Code Project remember me under IE 4 ?
Christian
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Heck it doesn't remember it under IE55 either.
I think I spotted your problem; it's in the loop:
for (int i=0;i<500;i++)
{
CPen pen;
pen.CreatePen(PS_SOLID, 1, RGB(0,0,0));
dc.SafeSelect(&pen);
/* Okay, here is the problem as I see it: the first time this is called, there is no pen to release, so the pen handle is selected into the device context, which basically takes ownership of it. Then your loop exits, and the CPen object is destroyed, taking the handle with it - but more than likly just a COPY of the handle, leaving the other one still selected into the device context, since it was never selected out. Then the 2nd time into the loop you create a new CPen, and then select it in, but you never got rid of the other one. */
}
I've never written code like this; I've always done it like, the scope of the function:
CPen *pOldPen = dc.SelectObject(&pen);
...dowhatever....
dc.SelectObject(pOldPen);
If I was going to attempt to re-write the SafeSelect, I would probably NOT do it like this (IMHO), but instead, make a helper class (or nested class) that does the need balanced SelectObject's on construct and destruct.
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That is how I have done it in the past too, but what I do not understand is why recreating this process in my class works for brushes, but not pens.
If you follow my logic, I am doing the exact same thing in safeselect for brushes ( which work ) and pens ( which don't ) and the same thing as what I do externally ( which works ). I tried Deleteing whatever gets returned to me in SafeSelect, which does not leak, so I may think along those lines instead.
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Actually, it's not really necessary to remember to reselect the original pens. All you need to do is use the SaveDC() and RestoreDC() functions at the beginning and end of your draw routines.
Unfortunately, it's hard to build these into your DC class because pens allocated on the stack might get destroyed before you DC class gets destroyed, and if those pens are currently selected, then you get a resource leak. You have to call RestoreDC() before the objects go out of scope.
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I put a CDialog into a dll, exported the dialog class and attempted to call it from the application program.
Ok so far. But the DoModal() method always returns -1. I stepped through MS DoModal() code and found
out that it cannot find the template. When called from within the dll it works ok. I also tried passing the 'this'
pointer in my app to the dialog's constructor, but that didn't help either. Any ideas how to make this work?
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I have recently found that at least in my enviroment I cannot arbitrarly find a color that looks ok on my development machine and count that it will even show (other than black or white) on other machines the application is installed on.
I had been just defining a color with the RGB function:
CBrush PageBg;
PageBg.CreateSolidBrush(RGB(255,200,200));
When I do the above, the color may or may not map to anything but black or white.
I am using Chris Maunders ColourPopup and since it is also using defined colors via the RGB funciton, the base choices it shows are often only showing up as black and white.
I have modified this so the user can set ther own colors via a dialog box and then these are read each time the application starts.
CBrush PageBg;
PageBg.CreateSolidBrush(clrSheet);
This is fine for user customization, how ever it really is not how I want the inital exposure to the application to be. If this does not look right go try something and here is a dialog box to see what works 
I would appreciate any comments (suggestions or pointers) on how does one set basic colors that they can count on being displayable.
How likely is it that the machines do not have the correct video drives for the cards installed. I know the general approach here is to use some stock setup disk images that are copied to the machines prior to delivery and I do not know how much updating is being done based on the actual hardware. Or am I to quick to pass the problem with this question? I still have to find a solution for my problem in any case.
Thanks Mike
Michael A Barnhart
mabtech@swbell.net
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all i can think is that some users are running in crappy color modes ... some companies tech guys let the machines run in god awful modes (256 colors or worse) so check that first ... the app i'm working on uses hi-color buttons on the toolbar and other bits and it generally looks ok on a 256 color mode but on less it looks godawful
"every year we invent better idiot proof systems and every year they invent better idiots"
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The modes is not the issue. I have verified several machines and all are at least "True Color" 16 bit.
Thanks,
Michael A Barnhart
mabtech@swbell.net
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errr ... what kind of status you looking for?
"every year we invent better idiot proof systems and every year they invent better idiots"
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hmmmm
i dont know for sure about this ... think about it ... an app goes funny and sits in an endless loop ... how would the system know it wasn't doing something it meant to do ... i can only guess that you would attach a hook dll to its main window and peek its message queue ... if it didn't process any for a given time period you could assume it wasn't responding ... god knows what that time out would be but i guess maybe 10 or 15 seconds would be a fair start
if there's a better way i'd like to know too
"every year we invent better idiot proof systems and every year they invent better idiots"
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ID: Q231844
They suggest using SendMessageTimeout() and if it times out you know it is not
responding.
Stephen Kellett
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Hello,
I was wondering if anyone knows of a way to get some kind of system id from a PC. I've looked at:
- GetVolumeInformation to get the hard-drive serial number but this is often the same if drives are ghosted from the same image.
- Netbios to get the MAC Address of the Ethernet Adapter. The problem is that Microsoft says that this "does not work reliably on Windows 95 or Windows 98".
Thanks,
Raed
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How to write a WIN NT Service using MFC which will execute an application at bootup time?.
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Hi ,
ODBC drivers Microsoft ODBC driver for Oracle or Oracle ODBC driver , which is best?
Thanks,
Kannan.A.
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Anyone can tell me how i can compare the caption of string table element with a CString??
Thanks![Rose | [Rose]](https://codeproject.global.ssl.fastly.net/script/Forums/Images/rose.gif)
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Guess you could load the caption of the string resource into another CString with CString::LoadString(UINT nID) and go from there.
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Hi,
I'm desperately seeking for a link where all DLL's are listed, installed by the Windows Installer.
Hope u can help me.
--
Alex Marbus
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Hmmm...
On NT, in the Winnt\repair dir, there is a hidden setup.log file that might be useful if you're trying to see what windows itself has accumulated.
You'll have to weed through a lot of other files to find the dlls. I think there might be a reader utility somewhere - shouldn't be hard to write. Basically an .ini file with path, name, and checksum of installed files in the [Files.Winnt] section.
Also look for "Active Setup.log" on both NT and w2k.
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i coded an application using hook events but when I trace events in debug mode, only the events sent by this application are catched!! The application doesn't catch others events from windows!!
My hook functions are in a dll, I don't understand!!
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Hi
Anyone can tell me how i can grayed a Menu.
The problem is i don't have the ID
How can i do that.
Thanks
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I look for a code sample using SetWineventHook() and SetWindowsEvent(). I've already samples from MSDN... Thanks!
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hi,
Win2k protects the system files by detecting changes and replacing changed files from a cache. I see that there are ways to disable this feature. But is there a way to just disable this feature for one single file insted of all system files ?
thanks
karthik
ps: reason being inetinfo dlls stack size is set to 40000 , but some of my dlls need a stack size of 100000 ,so I want to change the stack size of this dll alone. win2k will not allow me to use this modified dll.
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