C / C++ / MFC

Harsha Gopal15-Jun-03 15:27

Harsha Gopal

15-Jun-03 15:27

Intercept the WM_CLOSE message and return false. If you are using MFC, goto classwizard and add WM_CLOSE message handler to that particular window and remove the CDialog::OnClose() statement.

Harsha
----------------------------------
http://www.ece.arizona.edu/~hpg
----------------------------------

Anonymous15-Jun-03 17:34

Anonymous

15-Jun-03 17:34

That's right, Make more programs that require a hard reset to get out of.
MS finally makes a reasonably stable OS (XP) and then you go and disable essential escape funtionality. Try disabling Alt-Tab and Ctrl-Alt-Del as well (I don't think you will, but would be a good challenge)
Alt F4 is there for a reason!

Head retracted now (I'm sure you have a legit reason for doing this)! Eek! | :eek:

Ryan Binns15-Jun-03 17:50

Ryan Binns

15-Jun-03 17:50

Anonymous wrote:
I'm sure you have a legit reason for doing this

Smile | :)

There are plenty of reasons. I wrote a little app a while ago for a church for controlling a LCD projector (turning it on/off etc.). It was an appbar that ran at startup and was permanently set at the top of the screen, and they didn't want people to be able to close it, because then they couldn't control the projector. So I had to do this. I did it in a slightly different way, though.

Ryan

Being little and getting pushed around by big guys all my life I guess I compensate by pushing electrons and holes around. What a bully I am, but I do enjoy making subatomic particles hop at my bidding - Roger Wright (2^nd April 2003, The Lounge)

Punctuality is only a virtue for those who aren't smart enough to think of good excuses for being late - John Nichol "Point Of Impact"

Joan M16-Jun-03 0:48

Joan M

16-Jun-03 0:48

If you must let people interact with your app, then you should think about setting a system wide keyboard hook in order to avoid all the "strange" keypresses (Ctrl + shift + esc...) and also to implement a gina dll in order to avoid Ctrl+alt+del... you can say then that you control the PC and that you can be sure that people won't touch things that shouldn't...

hope this helps.

Couple of questions concerning bits

Ryan Binns16-Jun-03 1:01

Ryan Binns

16-Jun-03 1:01

Joan Murt wrote:
hope this helps.

Confused | :confused:

I never asked a question! Confused | :confused:

All I had to do was prevent one app from being closed. Task Manager was disabled by system policies, so all I had to do was prevent Alt+F4 and Escape (it was a dialog app). Setting a system-wide keyboard hook would have been massive overkill.

Ryan

Being little and getting pushed around by big guys all my life I guess I compensate by pushing electrons and holes around. What a bully I am, but I do enjoy making subatomic particles hop at my bidding - Roger Wright (2^nd April 2003, The Lounge)

Punctuality is only a virtue for those who aren't smart enough to think of good excuses for being late - John Nichol "Point Of Impact"

georgiek5015-Jun-03 11:27

georgiek50

15-Jun-03 11:27

I was under the impression (according to my programming book) that a left shift on a byte caused the bits on the left to "fall off" and zeros inserted to the right:

eg. 0x1F << 2 = 0xC0

but it equals 0x7C0

Why is this?

My reason for asking this question is that I am trying to find a four byte sequence within a file (MPEG-1) that doesn't seem to byte aligned. I wrote a little function to do a "bit by bit" search but since the above statement is not true it fails, here is my code (I feed it 64 bits at a time):

int FindSequenceHeader(unsigned char *str)
{
	// Does a bit by bit search for the sequence header

	char ch[4];

	DWORD dwValue;

	for (int x = 0; x < 4; x++)
	{
		for (int i = 0; i < 8; i++)
		{
			ch[0] = ( (str[x + 0] << (0 + i)) | (str[x + 1] >> (8 - i)) );
			ch[1] = ( (str[x + 1] << (0 + i)) | (str[x + 2] >> (8 - i)) );
			ch[2] = ( (str[x + 2] << (0 + i)) | (str[x + 3] >> (8 - i)) );
			ch[3] = ( (str[x + 3] << (0 + i)) | (str[x + 4] >> (8 - i)) );

			dwValue = ( ch[0] | (ch[1] << 8) | (ch[2] << 16) | (ch[3] << 24) );

			switch (dwValue)
			{
				case 0x000001b3:
					cout << "Video Sequence Header Found" << endl;

					return 0;

					break;

				default:
	
					break;
			}
		}
	}

	// Found nothing...
	return 1;
}

which then leads me to ask why this standard routine i've seen in many sample codes works:

DWORD MakeDword(unsigned char *str)
{
	return ( str[0] | (str[1] << 8) | (str[2] << 16) | (str[3] << 24) );
}

any thoughts?

adamUK15-Jun-03 11:52

adamUK

15-Jun-03 11:52

georgiek50 wrote:
eg. 0x1F << 2 = 0xC0

but it equals 0x7C0

georgiek50 wrote:
Why is this?

Because it is the right answer.

0x1F = 0001 1111

shift it left a coupla times and put zeros in on the right

0111 1100 = 0x7C

0000 = 0
0001 = 1
0010 = 2
0011 = 3
0100 = 4
0101 = 5
0110 = 6
0111 = 7
1000 = 8
1001 = 9
1010 = A
1011 = B
1100 = C
1101 = D
1110 = E
1111 = F

cheers!!

Adam.

My world tour
What I do now..

"I spent a lot of my money on booze, birds and fast cars. The rest I just squandered"
George Best.

Toni7815-Jun-03 12:07

Toni78

15-Jun-03 12:07

georgiek50 wrote:
I was under the impression (according to my programming book) that a left shift on a byte caused the bits on the left to "fall off" and zeros inserted to the right:
eg. 0x1F << 2 = 0xC0
but it equals 0x7C0

That's not the right answer. 0x1F << 2 = 0x7C.But in any case to ensure that you receive only the last 8 bits you can AND a byte with 0x0FF. For example:

char[ 0 ] = 0x1F;
DWORD dwVar = char[ 0 ];
dwVar = (dwVar << 2) & 0x0FF  // dwVar = 0x7C

georgiek50 wrote:
dwValue = ( ch[0] | (ch[1] << 8) | (ch[2] << 16) | (ch[3] << 24) );

The compiler will get each character in ch and store it into a register because that's the only place where shift operations can be performed. For example if you would see the above code written in machine language it would look like this:

mov eax, ch[0];    // ch[0] = byte ptr address in memory
mov edx, ch[1];    // same thing for ch[1]
shl edx, 8;        // ch1[] << 8
or eax, edx;       // ch[0] | (ch[1] << 8)
mov edx, ch[2];    // edx = ch[2]
shl edx, 16;       // ch[2] << 16
or eax, edx;       // ch[0] | (ch[1] << 8) | (ch[2] << 16 );
and so on....

The final result in eax will be moved to a dword ptr memory location that corresponds to dwValue. All the registers are 4 bytes long (32 bits) and a DWORD data type is a 32 bit unsigned integer. That's why this works.

// Afterall I realized that even my comment lines have bugs

georgiek5015-Jun-03 12:58

georgiek50

15-Jun-03 12:58

Sorry, what I meant to write was 0x1f << 6 (instead of 2)= 0x7c0 where I was expecting just 0xc0 according to this logic:

<br />
0x1F = 00011111<br />
0x1F << 6 = 11000000 or 0xC0<br />

I think my understanding of shifting is very off!

Harsha Gopal15-Jun-03 15:42

Harsha Gopal

15-Jun-03 15:42

The compiler assumes it as a 16-bit number. So,

0x1F = 0000000000011111
0x1F << 6 = 0000011111000000 = 0x7C0.

So, for 8 - bit operation may be u can write as
unsigned long a = 0x1F;
a=LOBYTE(a<<6);

It gives the desired result....You can fit it into your program...

Harsha
----------------------------------
http://www.ece.arizona.edu/~hpg
----------------------------------

georgiek5015-Jun-03 15:53

georgiek50

15-Jun-03 15:53

Thanks...and you clarified for me what hi and lo - byte means, I was wondering about that for some time!

Text Object Model(Urgent)

peterchen15-Jun-03 23:49

peterchen

15-Jun-03 23:49

Be aware that:
a) Bytes get int-expanded when shifting things around
b) char, int etc. are signed - which makes the shift "arithmetic", i.e. the highest order bit remains set.

So a) use unsigned char, and b) cast th shift result back to unsigned char.

"Der Geist des Kriegers ist erwacht / Ich hab die Macht" StS

sighist | Agile Programming | doxygen

Asad Rasheed15-Jun-03 11:22

Asad Rasheed

15-Jun-03 11:22

Hello,
where can i get "tom.h". I have visual studio 6.0 enterprice eddition and sp5. but there is no such file.

Thanks in Advance to solve this problem.

Thank you

Asad Rasheed

Re: Text Object Model(Urgent)

Ryan Binns15-Jun-03 17:55

Ryan Binns

15-Jun-03 17:55

Download the Platform SDK.

Ryan

Being little and getting pushed around by big guys all my life I guess I compensate by pushing electrons and holes around. What a bully I am, but I do enjoy making subatomic particles hop at my bidding - Roger Wright (2^nd April 2003, The Lounge)

Punctuality is only a virtue for those who aren't smart enough to think of good excuses for being late - John Nichol "Point Of Impact"

How Can i detect a radion button is clicked

snipes15-Jun-03 11:14

snipes

15-Jun-03 11:14

Hi , I wanted to know what is the function that detect a radio button is detected
example : in A Wizard the next button is disabled
what'is the function that enable the next button if a radio is checked.
Please Help,
Thanks
Bye Confused | :confused:

Re: How Can i detect a radion button is clicked

adamUK15-Jun-03 11:58

adamUK

15-Jun-03 11:58

If you are using MFC then using classwizard, assign a member variable to the first radio button in the group.

Then, handle the BN_CLICKED message for each radio button in your group. Check the state of the member variable (having called UpdateData()). If it the right value then enable your Next button.

hope this helps

Adam.

My world tour
What I do now..

"I spent a lot of my money on booze, birds and fast cars. The rest I just squandered"
George Best.

Re: How Can i detect a radion button is clicked

basementman16-Jun-03 4:20

basementman

16-Jun-03 4:20

Or, just give each radio button a unique id. (IDC_RADIO1, IDC_RADIO2) Then, you can map a OnClick handler for the ID and no member variable is required. In your handler, you can always ask the button whether it is checked or not as follows:

<br />
void MyClass::OnRadio2Clicked()<br />
{<br />
  BOOL bChecked = SendDlgItemMessage(IDC_RADIO2,BM_GETCHECK);<br />
<br />
  if (bChecked)<br />
    //enable something<br />
  else<br />
    // <br />
}

onwards and upwards...

Web Browser control (questions)

Member 43908315-Jun-03 10:29

Member 439083

15-Jun-03 10:29

I am developing an application in MFC, using the Microsoft Web Browser control, embedded in a CFormView. I have two specific questions related to using the browser control:

1) How do I retrieve the HTML text that is currently being displayed in the web browser? Specifically, when the OnDocumentComplete message fires, I would like to retrieve the HTML currently in the browser, and do some custom parsing on it.

2) None of the standard accelerator keys (ctrl-c, ctrl-v, etc.) work when the web browser control has focus. The only way I can perform these standard operations is to use the context menu (right-click), which is somewhat time consuming for many users.

Thanks in advance!

Brian

Tarundeep Singh Kalra16-Jun-03 3:53

Tarundeep Singh Kalra

16-Jun-03 3:53

see this
http://msdn.microsoft.com/library/default.asp?url=/workshop/browser/mshtml/reference/commandids.asp

Member 43908316-Jun-03 13:07

Member 439083

16-Jun-03 13:07

Thanks, I will check it out.

Neville Franks16-Jun-03 12:14

Neville Franks

16-Jun-03 12:14

1) Try GetouterHTML().

2) In an app I'm slowly working on I grab the keystrokes in Javascript code embedded in the page and send them back to my C++ code.

For an excellent resource on this subject see:
http://www.beginthread.com/Topic/MSVC[^]

Hope that helps.

Neville Franks, Author of ED for Windows. Free Trial at www.getsoft.com

knappbl16-Jun-03 13:01

knappbl

16-Jun-03 13:01

I don't see 'GetouterHTML' as a member of the HTML browser class that was generated for me when I added the browser control to my project.

I will take a look at the URL you posted - thanks.

Brian

Member 43908316-Jun-03 13:08

Member 439083

16-Jun-03 13:08

Sorry, that was me.

Please respond to *this* post, so I will get an email notification.

Sorry.