C / C++ / MFC

Re: How to Resize Static Window Objects

10-Mar-13 23:29

Your question could do with a bit more detail; what exactly are you trying to do? You can use the CStatic Class[^] for static text, and that is resizable (as is any window).

Use the best guess

Richard Andrew x6411-Mar-13 2:13

Richard Andrew x64

11-Mar-13 2:13

Thanks.

I assumed there was no MFC class because the "Add Variable" wizard did not present me with one.

I've created a small class that automatically resizes and repositions controls when a window is resized, and I inherited from classes liked CComboBox, CListBox but I didn't see the CStatic class.

Thanks again.

The difficult we do right away...
...the impossible takes slightly longer.

Re: How to Resize Static Window Objects

Richard MacCutchan11-Mar-13 2:47

[Challenge/Puzzle] Implement reinterpret_cast

11-Mar-13 2:47

Richard Andrew x64 wrote:
I assumed

Never assume anything with MFC. I have also found in the past that the Wizard does not always list every possibility, even though MFC wraps all the standard Windows and has a number of custom types.

Use the best guess

Why moniker?

Vaclav_10-Mar-13 5:46

Vaclav_

10-Mar-13 5:46

This is not a programming "how to", just looking for short explanation/ verification of usage of "moniker".
My basic understanding is that it's function is similar to DOS path, allowing access to an object.
Now it this particular sequence I do not get the enumeration, followed by getting the first moniker and bind it to , I guess filter.
This is part of my code to get data from USB camera and I am still learning how to put all this COM and DirectShow stuff together.
This is what I understand so far – the enumeration identify the “object class” in my case USB cameras and than I can select which one using the Next in loop ( this snippet gets only the first one) and than let the filter “connect / bind “ to the selected camera.
This is still plain COM code , no DirectShow.
Am I right so far?
Thanks for reading.
Cheers Vaclav

TRACE("\nObtain a category enumerator by calling ICreateDevEnum::CreateClassEnumerator with the CLSID of the desired category");
IEnumMoniker* cams = 0;
hr = devs?devs->CreateClassEnumerator (CLSID_VideoInputDeviceCategory, &cams, 0) Blush | :O

;
if (FAILED(hr))
{
TRACE("\nFailed devs->CreateClassEnumerator (CLSID_VideoInputDeviceCategory");
return;
}
ASSERT(cams); // redundant

TRACE("\nget first found capture device (webcam?)");
// moniker - similar to DOS path to get info on object
IMoniker* mon = 0;
hr = cams->Next (1,&mon,0); // get first found capture device (webcam?)
if (FAILED(hr))
{
TRACE("\nFailed get first found capture device (webcam?)");
return;
}
ASSERT( mon);

TRACE("\nBind moniker ( mon) to object ( cam)");
IBaseFilter* cam = 0;
hr = mon->BindToObject(0,0,IID_IBaseFilter, (void**)&cam);
if (FAILED(hr))
{
TRACE("\nFailed Bind moniter ( mon) to object ( cam)");
return;
}
ASSERT( cam);

Re: Why moniker?

dusty_dex10-Mar-13 6:45

dusty_dex

10-Mar-13 6:45

Your friend is MSDN

Monikers (COM)

Smile | :)

Q. Hey man! have you sorted out the finite soup machine?

A. Why yes, it's celery or tomato.

Re: Why moniker?

Vaclav_10-Mar-13 7:25

Vaclav_

10-Mar-13 7:25

"A moniker in COM is not only a way to identify an object—a moniker is <b>also implemented as an object</b>. "

What a startling, useful and unexpected information!( SARCASM)

Seriously, thanks for your reply. It is helpful.

Re: Why moniker?

dusty_dex10-Mar-13 7:32

dusty_dex

10-Mar-13 7:32

COM has been evolving since before Windows 3, so there's stuff lingers on because of backward compatibility that won't break existing code.

Q. Hey man! have you sorted out the finite soup machine?

A. Why yes, it's celery or tomato.

MicroVirus10-Mar-13 3:55

10-Mar-13 3:55

Hey coders,

I came up with a little puzzle/challenge for C++, so for those interested, my challenge to you is this:

Using any C++ constructs, other than any of the casting constructs*, reimplement the following code:

C++

int i = someIntValue();
int *pint = reinterpret_cast<int*>(i)

Or in words, find a way to reinterpret_cast an integer into a pointer without casting (implicitly, or explicitly!). You may assume that sizeof(int)==sizeof(int*).

I hope to be surprised by answers I hadn't thought of Smile | :)

* with casting constructs, I mean any form of implicit casts (e.g. int to long int), C-style casts (e.g. (int*)i) and C++-style casts (e.g. reinterpet_cast<int*>(i)); and also any functions/macro's/API calls (such as STL implementations) which rely internally on casts.

Best Regards,

Richard

Richard MacCutchan10-Mar-13 8:07

10-Mar-13 8:07

This forum is for serious questions, the Lounge is the place for quizzes.

Use the best guess

MicroVirus10-Mar-13 10:57

10-Mar-13 10:57

Hmmm

Didn't realise that.

I felt it was more in place in a C++ specific message board than in a lounge, as I do find such challenges to be stimulating myself.

Brandon-X1200010-Mar-13 11:32

Brandon-X12000

10-Mar-13 11:32

Richard MacCutchan wrote:
This forum is for serious questions, the Lounge is the place for quizzes.

I deem this is technically appropriate (by the definitions of the rules), it is C++/C code.

Where in the rules up at the very top posted by Admin Chris Maunder, does it directly say that is for serious questions.

Keep in mind a quiz is a question, you are giving an answer.

EDIT:

Chris Maunder wrote:
Please do not post links to your question in one forum from another, unrelated forum (such as the lounge). It will be deleted.

And you said...

Richard MacCutchan wrote:
the Lounge is the place for quizzes.

Trying to guide him in the wrong path Wink | ;)

, consider re-reading the rules.

Simple Thanks and Regards,
Brandon T. H.

Programming in C and C++ now, now developing applications, services and drivers (and maybe some kernel modules...psst kernel-mode drivers...psst).

Many of life's failures are people who did not realize how close they were to success when they gave up. - Thomas Edison

Richard MacCutchan10-Mar-13 23:17

10-Mar-13 23:17

Brandon-X12000 wrote:
I deem this is technically appropriate

I suspect you are in a minority.

Brandon-X12000 wrote:
Trying to guide him in the wrong path

Not at all, the Lounge is the place for such questions; even Chris posts them there.

Use the best guess

Matthew Faithfull11-Mar-13 1:44

Matthew Faithfull

11-Mar-13 1:44

You could do something like:-

int i = 42;
int* pint = 0;
int** ppint = 0;
ppint += &i;
pint = *ppint;

If I'm not mistaken pint is now an int pointer to address 42 and no casting as such has taken place.

"The secret of happiness is freedom, and the secret of freedom, courage."
Thucydides (B.C. 460-400)

Stefan_Lang11-Mar-13 23:18

11-Mar-13 23:18

Matthew Faithfull wrote:
ppint += &i;

Doesn't work - you only can add integral types (size_t and anything that implicitely converts to size_t) to a pointer.

Also, as Harold Aptroot pointed out in response to my variant, even if it would work as intended, pint would point to 42*sizeof(int), not 42.

Matthew Faithfull11-Mar-13 23:40

Matthew Faithfull

11-Mar-13 23:40

I haven't tried it as it's, as you point out, not of practical use but &i is certainly integral. Another step may be needed to get around restrictions on adding pointers to pointers but the principle is the same. The multiplication by sizeof(int) is not an really issue as this can be overcome without any casting.
The addition was a syntactic nicety to explain what I was doing anyway and is not strictly necessary. How about:-

int i = 42;
int** ppint = &i;
int* pint = *ppint;

which is shorter and doesn't do pointer arithmetic.

"The secret of happiness is freedom, and the secret of freedom, courage."
Thucydides (B.C. 460-400)

MicroVirus13-Mar-13 11:12

13-Mar-13 11:12

Dear Matthew,

Thanks for submitting your solution. Unfortunately, ppint is of type int**, whereas &i returns an int*, so this will not work without casting int* to int**.

Matthew Faithfull13-Mar-13 11:18

Matthew Faithfull

13-Mar-13 11:18

I would like to see the assmebler generated for the cast from int* to int**. My expectation is that it would consist of 0 instructions or at most a nop. If no actual cast takes place and none is specified in the code then I say the challenge is met. Assignment from int* to int** is certainly valid. In reality at the backend of most compilers I suspect int* and int** will be same thing anyway. Smile | :)

"The secret of happiness is freedom, and the secret of freedom, courage."
Thucydides (B.C. 460-400)

MicroVirus13-Mar-13 11:29

13-Mar-13 11:29

It's true that in many implementations of C/C++ a pointer to one type is technically (in terms of generated code and storage needs) the same as a pointer to any other type.
But in terms of the language, int* is certainly not an int**. At the very least, the compiler will give you an error on the line int **ppi = &i, saying there is no conversion from int* to int**. But ok, that's the compiler, so maybe it's just being annoying? One nice way, I think, of realising these two (int* and int**) are two very different objects is the following:

C++

int* pi = ...;
int** ppi = ...;
*pi; *ppi; // These two are both valid C++ and we know what this means
**ppi; // This is also valid, but the following:
**pi; // Is not valid, and it is not clear what it's suppose to mean; *pi gives an integer value, so what is the dereference of an integer?

So I'd say that int* and int** can't be the same thing, because the one can do something the other can't Wink | ;)

Stefan_Lang11-Mar-13 3:29

11-Mar-13 3:29

C++

int i = someIntValue();
int *pint = 0;
pint += i;

Note that this doesn't even require sizeof(int)==sizeof(int*), as i will be cast to the correct size implicitely.

harold aptroot11-Mar-13 9:03

harold aptroot

11-Mar-13 9:03

But it will also be multiplied by sizeof(int) implicitly..

And if you divide by sizeof(int) first, it kills the lowest bit(s).

Stefan_Lang11-Mar-13 22:30

11-Mar-13 22:30

Ah, you're right on both accounts.

Not that it would make much sense to have an incorrectly aligned pointer, but then the challenge didn't make much sense for practical use anyway...

Stefan_Lang12-Mar-13 0:09

12-Mar-13 0:09

The following code compiles and it does return the correct values:

C++

int* f1(int i) { return 0; }
int* f2(int* pi) { return pi; }
union UPointers {
   int*(*ag1[2])(int i);
   struct SPointers {
      int*(*g1)(int i);
      int*(*g2)(int* pi);
   } my_spointers;
} my_pointers;
int* foo(int i) {
   int* (*h1)(int i);
   my_pointers.my_spointers.g1 = &f1;
   my_pointers.my_spointers.g2 = &f2;
   h1 = my_pointers.ag1[1];
   return h1(i);
}
int _tmain(int argc, _TCHAR* argv[])
{
   for (int i = 12; i < 15; ++i) {
      int* pi = foo(i);
      std::cout << i << ' ' << pi << std::endl;
   }
   return 0;
}

The output is:

12 0000000C
13 0000000D
14 0000000E

The idea is to abuse a function pointer that is supposed to pass an int argument by assigning it to a function that expects an int*. I'm almost sure there is no implicit conversion involved, but I'm not too familiar with function pointers to be sure.

The 'conversion' happens when the function call writes the int argument to the stack, but the function that is called interprets it as a int*.

MicroVirus13-Mar-13 11:19