C / C++ / MFC

26-Apr-05 17:48

In your CView-derived class's OnDraw:

CBitmap bmp;
if (bmp.LoadBitmap(IDB_BITMAP1))
{
   // Get the size of the bitmap
   BITMAP bmpInfo;
   bmp.GetBitmap(&bmpInfo);

   // Create an in-memory DC compatible with the
   // display DC we're using to paint
   CDC dcMemory;
   dcMemory.CreateCompatibleDC(pDC);

   // Select the bitmap into the in-memory DC
   CBitmap* pOldBitmap = dcMemory.SelectObject(&bmp);

   // Find a centerpoint for the bitmap in the client area
   CRect rect;
   GetClientRect(&rect);
   int nX = rect.left + (rect.Width() - bmpInfo.bmWidth) / 2;
   int nY = rect.top + (rect.Height() - bmpInfo.bmHeight) / 2;

   // Copy the bits from the in-memory DC into the on-
   // screen DC to actually do the painting. Use the centerpoint
   // we computed for the target offset.
   pDC->BitBlt(nX, nY, bmpInfo.bmWidth, bmpInfo.bmHeight, &dcMemory,
      0, 0, SRCCOPY);

   dcMemory.SelectObject(pOldBitmap);
}

PeterRitchie.com

system files

trupgmtuf26-Apr-05 11:46

trupgmtuf

26-Apr-05 11:46

Hi,
In my program I need a windows system file say mouhid.sys, for example.
I found that file inside the cab file in windows\driver cache\i386\driver.cab. If I give this as my source path in my program, it is not detecting the file( I think because of cabinet file).
Is there any way to tell the system to take from that cab file automatically or any spl path that we can mention so that the system automatically detects the file.
Thanks a lot.

Re: system files

Peter Ritchie26-Apr-05 17:51

BrowseFolders Dialog on Win2k/IE5?

26-Apr-05 17:51

See SetupIterateCabinet[^]

PeterRitchie.com

Ingmar326-Apr-05 11:07

Ingmar3

26-Apr-05 11:07

Hello,

I've got a class to browse folders similiar to CSXBrowseFolder here on code-project. It worked fine until I needed to run my software on a fresh installed Windows 2000 with IE5.
Selecting e.g. "My Documents" gives me not the real path but an Id like "::{xxxxxxxxx}".
I'm not sure if I'm right, but I think I need to resolve this "link" using the shell functions. But whatever I tried it didn't work.
If I select a usual folder (e.g. c:\test) it works like expected.

I found a message on MSDN, that win2k/ie5 doesn't follow these links. But newer versions do so. Seems I get the Id of the not real existing folder, while IE6 resolves these links automatically.

Maybe someone can give me hint how to solve this problem? Thanks in advance!
Ingmar

Peter Ritchie26-Apr-05 17:20

26-Apr-05 17:20

You can convert the file object's display name into a path with the following:

<FONT COLOR=GREEN>/// <summary>
/// Sample that converts a textual file/folder object display name
/// (::{GUID} format) to a physical path (if possible)
/// </summary>
/// <author> Peter A. Ritchie</author>
/// <date type="creation">26-Apr-2005</date>
</FONT>CComPtr<FONT COLOR=BLUE><</FONT>IShellFolder<FONT COLOR=BLUE>></FONT> pshf <FONT COLOR=BLUE>=</FONT> NULL<FONT COLOR=BLUE>;</FONT>

<FONT COLOR=BLUE>:</FONT><FONT COLOR=BLUE>:</FONT>SHGetDesktopFolder<FONT COLOR=BLUE>(</FONT><FONT COLOR=BLUE>&</FONT>pshf<FONT COLOR=BLUE>)</FONT><FONT COLOR=BLUE>;</FONT>
LPITEMIDLIST pidlDocFiles<FONT COLOR=BLUE>;</FONT>
ULONG cbEaten<FONT COLOR=BLUE>;</FONT>
pshf<FONT COLOR=BLUE>-</FONT><FONT COLOR=BLUE>></FONT>ParseDisplayName<FONT COLOR=BLUE>(</FONT>NULL<FONT COLOR=BLUE>,</FONT> <ul>	NULL<FONT COLOR=BLUE>,</FONT> 
	L<FONT COLOR=PURPLE>"::{450d8fba-ad25-11d0-98a8-0800361b1103}"</FONT><FONT COLOR=BLUE>,</FONT> 
	<FONT COLOR=BLUE>&</FONT>cbEaten<FONT COLOR=BLUE>,</FONT> 
	<FONT COLOR=BLUE>&</FONT>pidlDocFiles<FONT COLOR=BLUE>,</FONT> 
	NULL<FONT COLOR=BLUE>)</FONT><FONT COLOR=BLUE>;</FONT>
</ul>
TCHAR szPath<FONT COLOR=BLUE>[</FONT>MAX_PATH<FONT COLOR=BLUE>]</FONT> <FONT COLOR=BLUE>=</FONT> _T<FONT COLOR=BLUE>(</FONT><FONT COLOR=PURPLE>""</FONT><FONT COLOR=BLUE>)</FONT><FONT COLOR=BLUE>;</FONT>

<FONT COLOR=BLUE>:</FONT><FONT COLOR=BLUE>:</FONT>SHGetPathFromIDList<FONT COLOR=BLUE>(</FONT>pidlDocFiles<FONT COLOR=BLUE>,</FONT> szPath<FONT COLOR=BLUE>)</FONT><FONT COLOR=BLUE>;</FONT>

But, I'm curious, how are you getting the display name "::{GUID}"? Are you using SHBrowseForFolder? If so, what are you doing with the PIDL?

PeterRitchie.com

Ingmar326-Apr-05 21:18

Ingmar3

26-Apr-05 21:18

Thanks for the help. I tried it out, but if gives me the same GUID back again I put in?!

For your question, I use
itemIDList = SHBrowseForFolder(&browseInfo);
...do some checks and then
SHGetPathFromIDList(itemIDList, szPathBuffer);

And at this point I've got that GUID in szPathBuffer. I found so many samples, everyone does it that way, but I already tested on 2 win2k machines and it doesn't work. (Except I update to IE6, but this is currently not an option).
Maybe something is wrong with my browseinfo structure? I did nothing special, maybe some flags are needed I didn't set?

Ingmar

Peter Ritchie29-Apr-05 5:26

29-Apr-05 5:26

Then you've got a GUID to a virtual folder that does not have a physical location for it.

PeterRitchie.com

Ingmar313-May-05 1:40

Ingmar3

13-May-05 1:40

I tested some things, and it seems the problem isn't SHBrowseForFolder itself. But it's more strange: A simple BrowseForFolder-application works well on 2k, but my real application doesn't! I did try and error and I found out, that I get a good path, when I run SHBroswForFolder before I open a database via ODBC (CDatabase) ?!?!

Don't have a good idea now, but it has definitly to do with the DB-Open. Maybe it's a bug? This works great on XP or better on any machine with IE>5.

Ingmar

delete this questions

Steve Messer26-Apr-05 10:42

Steve Messer

26-Apr-05 10:42

It is my understanding the using the following line of code is bad pratice.

delete this;

Is there ever a good reason to use this construct?

Thanks

PJ Arends26-Apr-05 11:17

26-Apr-05 11:17

Like anything else, if it is used properly it has its uses, but used improperly it can be disatrous. I use it for classes that are to be self deleting, and always make sure it is the very last command the class executes.

"You're obviously a superstar." - Christian Graus about me - 12 Feb '03

"Obviously ??? You're definitely a superstar!!!" mYkel - 21 Jun '04

Within you lies the power for good - Use it!

Honoured as one of The Most Helpful Members of 2004

Anonymous26-Apr-05 11:27

Anonymous

26-Apr-05 11:27

It's how COM object lifetime is managed. Last one to call Release(), essentially tells the object to delete itself. For instance:

ULONG Release(void)
{
    ULONG lResult = InterlockedDecrement(&m_dwRef);
    if (lResult == 0) delete this;
    return lResult;
}

Steve Messer26-Apr-05 12:02

Steve Messer

26-Apr-05 12:02

Okay so COM makes use of it and also with self deleting classes.

I understand the COM aspect but what is a self deleting class?

Let me clarify the question a little. Is there a general rule? When would you use delete this?

Thanks

PJ Arends26-Apr-05 12:16

26-Apr-05 12:16

smesser wrote:
what is a self deleting class?

A class that deletes itself. Examples are CFrameWnd and CWinThread (when m_bAutoDelete is TRUE).

"You're obviously a superstar." - Christian Graus about me - 12 Feb '03

"Obviously ??? You're definitely a superstar!!!" mYkel - 21 Jun '04

Within you lies the power for good - Use it!

Honoured as one of The Most Helpful Members of 2004

Steve Messer26-Apr-05 12:28

Steve Messer

26-Apr-05 12:28

Yeah, but that is framework stuff. When as a programmer have you used:

delete this;

Steve

PJ Arends26-Apr-05 12:54

26-Apr-05 12:54

http://www.codeproject.com/miscctrl/windowscroller.asp[^]

"You're obviously a superstar." - Christian Graus about me - 12 Feb '03

"Obviously ??? You're definitely a superstar!!!" mYkel - 21 Jun '04

Within you lies the power for good - Use it!

Honoured as one of The Most Helpful Members of 2004

Maximilien26-Apr-05 12:10

Maximilien

26-Apr-05 12:10

with MFC, it's used to delete a modeless dialog.

Maximilien Lincourt
Your Head A Splode - Strong Bad

Brian R26-Apr-05 12:45

Brian R

26-Apr-05 12:45

I have been programming with c++ since the Cfront "compiler" came out of ATT. I have never found a circumstance where delete this seemed like a correct solution. My impresssion is that it is an artifact of bad design. The fact that the MFC and COM implementation require it is not a surprise Wink | ;-)

Along the same line, throwing an exception via a pointer is equally dangerous in my book!

PJ Arends26-Apr-05 13:21

26-Apr-05 13:21

Brian R wrote:
it is an artifact of bad design

It is a tool that makes it easier to use and then dispose of one time objects without having to keep track of the pointers and memory yourself. Using it is a design decision, not "bad design". Abusing it is bad design, but then abusing anything is.

"You're obviously a superstar." - Christian Graus about me - 12 Feb '03

"Obviously ??? You're definitely a superstar!!!" mYkel - 21 Jun '04

Within you lies the power for good - Use it!

Honoured as one of The Most Helpful Members of 2004

Mayur Mahajan26-Apr-05 17:57

Mayur Mahajan

26-Apr-05 17:57

PJ Arends wrote:
Using it is a design decision, not "bad design". Abusing it is bad design, but then abusing anything is

I am in 100% agreement with you. Even the infamous 'goto' is cursed as a bad design paradigm. But circumstances govern their use in a few specialized cases. After all 'delete this' has certainly come to my rescue when I had to monitor the lifetime of an object using a reference counter similar to the COM classes. I seem a fair use of 'delete this' in such case. Also there are so many things in C++ that if abused screw up the program, better curse programming skill than curse a language

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

David Crow27-Apr-05 2:54

David Crow

27-Apr-05 2:54

Mayur Mahajan wrote:
But circumstances govern their use in a few specialized cases.

A paper put together in 1966 by BÖhm, Corrado, and Guiseppe proved theoretically that the GOTO statement was unnecessary; Dijkstra considered it harmful; and Knuth said it might be useful in some circumstances.

"Ideas are a dime a dozen. People who put them into action are priceless." - Unknown