C / C++ / MFC

Difference between OLE and COM ???

15-Jun-09 21:34

Hey

Well, if you need to use forms I would suggest for you to use C# instead.
If there are things I have to do in C++ than you can always create a DLL with exports or COM DLL... depends on your requirements.

Anyway, if you want to create forms in C++ I would suggest using MFC (just follow the wizard in visual studio). Explaining exactly what is going on over there is a bit big for a that forum, but there are plenty of articles out there. Besides, I always believe that some trial and error is a good experience with new environments.

about reading and writing a file, you have several options:
- If you're using MFC, the easiest thing is to use MFC's CFILE class (I hardly use MFC so I can't really tell you much about that class, but I am sure it is easy to use this class).

- Another option is to use CATLFile, which is a class that literally wraps WIN32's read/write functions.

- You can use win32's read/write functions:
CreateFile()
ReadFile()
WriteFile()
you can see their signatures in MSDN (F1). There are some options for these functions and MSDN explain what each option means, if it gets a bit complicated, just ask...

- If you want a portable code (that will compile on windows and unix as well) you can use plain good old C functions: fopen() fread() fwrite().

Green Fuze15-Jun-09 12:50

15-Jun-09 12:50

Hi everybody

Can anyone please explain what is the difference between OLE and a COM?
I know that COM derives from OLE, but what OLE component lacks that doesn't make it a COM component?

In other words, I know what COM is, and I created several COM servers in C++, but I don't quite understand what is OLE...

Thanks A LOT in advance! Big Grin | :-D

Stuart Dootson15-Jun-09 14:57

15-Jun-09 14:57

Green Fuze wrote:
COM derives from OLE

Other way round. COM describes the concepts of interfaces, reference counting and a central registry. OLE uses those concepts to do the whole object linking and embedding thing.

Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p

Green Fuze15-Jun-09 21:23

15-Jun-09 21:23

Oh...! So now I know how to fit in that Corba thingy! Smile | :)

So OLE components are COM components that are being embedded into applications (for instance, for IE it is ActiveX) ???

Stuart Dootson15-Jun-09 22:02

15-Jun-09 22:02

Green Fuze wrote:
So OLE components are COM components that are being embedded into applications

That was the original meaning of OLE. The 'real' definition of OLE (I suppose) is that it's a defined set of COM interfaces that you can implement or consume to interact with other OLE objects. For example, if your application implements IOleClientSite (among others), you can host OLE objects.

Green Fuze wrote:
for instance, for IE it is ActiveX

Not quite - ActiveX was Microsoft's 'rebranding' of 'OLE custom controls'.

ActiveX got reused as a general adjective for technologies that used COM under the hood - ActiveX Data Objects (ADO), for example.

Green Fuze wrote:
So now I know how to fit in that Corba thingy

Corba's another similar but different thing again Smile | :)

It's probably most similar to COM, but it has a wider scope.

The Wikipedia pages on ActiveX, COM, OLE and Corba are probably worth reading.

Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p

Green Fuze15-Jun-09 23:29

how do i find who has focus?

15-Jun-09 23:29

Thanks!

I think I get it better now!

I'll also check Wikipedia.

Thanks again!

xchen199815-Jun-09 12:46

xchen1998

15-Jun-09 12:46

I created 2 edit boxes using CreateWindow..
In callback function, how can i know which edit box gets/loses focus/caret when clicking in one of the boxes?
Somehow, GetFocus() returns screen handle instead of edit box.

public delegate IntPtr WndProcCallback(IntPtr hWnd, uint Msg, IntPtr wParam, IntPtr lParam);
public IntPtr WndProc(IntPtr hWnd, uint uMsg, IntPtr wParam, IntPtr lParam)
{
switch (uMsg)
{
case WM_SETFOCUS:
//??? who gets focus
break;
case WM_KILLFOCUS:
///??? who loses focus
break;
default:
return CallWindowProc(lpWndProc, hWnd, uMsg, wParam, lParam);
}
return IntPtr.Zero;
}

Re: how do i find who has focus?

Stuart Dootson15-Jun-09 14:55

Desktop wallpaper/background

15-Jun-09 14:55

Look at the[^] documentation[^] - it's the window that gets the WM_SETFOCUS/WM_KILLFOCUS message that gets/loses focus respectively.

Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p

daavena15-Jun-09 12:27

daavena

15-Jun-09 12:27

Hi gentlemen,

is there an option how to obtain desktop wallpaper/background. I need to use it in the BitBlt function. I need to copy part of Desktop wallpaper/background to my appl.

I've tried:

hDesktopWindow = GetDesktopWindow();
HDC hdc = GetDC(hDesktopWindow)
or
HDC hdc = GetDC(NULL)

and than I used hdc in the BitBlt function as source hdc - but It doesn't work because I got desktop with all opened windows - I need only wallpaer without windows.

I've also tried PaintDesktop() function. It gets me the same result - results desktop with all windows.

or

HDC hdc = GetDC(GetDesktopWindow())

int iResult = GetObject(hdc,sizeof(HBITMAP), &hBitmap)

iResult is allways 0 and GetLastError gets 6 = ERROR_INVALID_HANDLE

Any idea?

Thanks.

Re: Desktop wallpaper/background

«_Superman_»15-Jun-09 16:37

«_Superman_»

15-Jun-09 16:37

daavena wrote:
HDC hdc = GetDC(GetDesktopWindow())

Try HDC hdc = CreateDC(TEXT("DISPLAY"),NULL,NULL,NULL) instead.

This will simply capture the existing screen on all monitors.

If you want to get the desktop wallpaper you should use
SystemParametersInfo(SPI_GETDESKWALLPAPER, ...

Look at the documentation of SystemParametersInfo Function[^]

«_Superman_»
I love work. It gives me something to do between weekends.

Re: Desktop wallpaper/background

daavena16-Jun-09 6:30

daavena

16-Jun-09 6:30

Hi,

thanks for your reply,

Try HDC hdc = CreateDC(TEXT("DISPLAY"),NULL,NULL,NULL) instead

but as you said this capture whole screen with all windows - I do not need this.

What I need is screen backgroud without any windows. Because I need copy a part of screen backgroud to my window.

I know SystemParametersInfo function. It gives me the name of wallpaper only.

How can I access a document member variable from a dialog window?

Darryl Bryk15-Jun-09 11:05

Darryl Bryk

15-Jun-09 11:05

In a multi-doc. app. with the view based on CScollView which is used to display images, I'd like to display a dialog window with some histogram graphics in it. The problem is the OnPaint function for the dialog needs a few of the document's variables to draw the image's histogram. Making the variables pulic doesn't help because the compiler says they're non-static. And I can't seem to get the GetDocument() function to work in the dialog class like it does for the View class. Is there a way to do this with GetDocument() or do I have to derive the dialog class to the View some how, or a ChildView? Any help would be appreciated.

Re: How can I access a document member variable from a dialog window?

Stuart Dootson15-Jun-09 14:53

Re: How can I access a document member variable from a dialog window?

15-Jun-09 14:53

Pass references or pointers to the variables into the dialog, either through a constructor or through accessors.

Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p

Darryl Bryk17-Jun-09 13:41

Darryl Bryk

17-Jun-09 13:41

Aha! I think that will work. Thanks!

Static function variable problem

alikalik15-Jun-09 8:18

alikalik

15-Jun-09 8:18

Hello,
I have a function that is called from a dll and contains static variable:

void myFn(double data)
{
	static double x;
	...
}

At each iteration x increases on some value.
The problem occurs when pass diffent data at the same time (i.e. call the function more than once at the same time), x variable mixes all values.

data1[] = 1,2,3
data2[] = 4,5,6

The result for the first call must be 1+2+3 = 6
The result for the second call must be 4+5+6 = 15

But now the result for the first call will be 1+4+2+5+... and so on.

How to avoid this problem?

David Crow15-Jun-09 10:03

David Crow

15-Jun-09 10:03

At first glance, your problem sounds like one of synchronization. But then I could not figure out how you were calling myFn(). It is expecting a single argument, yet you've shown two arrays. Are you passing one member of the array with each call to myFn()?

alikalik wrote:
The result for the first call must be 1+2+3 = 6
The result for the second call must be 4+5+6 = 15

But now the result for the first call will be 1+4+2+5+... and so on.

Nothing you've shown supports this. Confused | :confused:

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image processing toolkits | batch image processing

C^hris L^osinger15-Jun-09 10:04

C^hris L^osinger

15-Jun-09 10:04

alikalik wrote:
call the function more than once at the same time

are you calling the DLL from multiple threads ?

alikalik15-Jun-09 18:43

alikalik

15-Jun-09 18:43

I'm creating add-in for MS Excel.
The argument is a value in a cell.

So for instance, if I call MyFn(B11) and MyFn(B12), where B11 and B12 are cells, the result will be wrong.

led mike15-Jun-09 10:27

led mike

15-Jun-09 10:27

Try putting that code in your main() function.