C / C++ / MFC

Re: How can I show my dialog on the TOP from other window dialog?

29-Jul-09 9:45

Why not just use a modal dialog that automatically closes itself after 2 seconds?

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THAQCD30-Jul-09 8:37

THAQCD

30-Jul-09 8:37

Can you provide any link how to show it in 2 seconds?

Re: How can I show my dialog on the TOP from other window dialog?

David Crow1-Aug-09 16:56

[MISC] - Operators - Meaning of operator &

1-Aug-09 16:56

See here.

Thang29-Jul-09 6:59

Thang

29-Jul-09 6:59

Dear everybody,
I have a question about the meaning of & operator in the following expression:
((WORD)(((DWORD)(l) >> 16) & 0xFFFF))

1) What role does the & operator do here ?
2) Why do programmers often use & with hexadecimal, not integer or long integer or double ?

I'm looking forward to seeing your reply soon.

Best regards,
Jetflower

David Crow29-Jul-09 7:05

29-Jul-09 7:05

Thang wrote:
1) What role does the & operator do here ?

Bitwise AND.

Thang wrote:
2) Why do programmers often use & with hexadecimal, not integer or long integer or double ?

Bits, bytes, and words are easier to visualize in base-16.

enhzflep29-Jul-09 8:27

enhzflep

29-Jul-09 8:27

Okay, lets say that l = 3131961357

This is the same as 0xBAADF00D
Which is the same as 10111010101011011111000000001101

Which means your expression looks a little something like this:

((WORD)(((DWORD)(0xBAADF00D) >> 16) & 0xFFFF))

3131961357 >> 16 = 47789
0xBAADF00D >> 16 = 0x0000BAAD
10111010101011011111000000001101 >> 16 = 00000000000000001011101010101101

47789 & 65535 = 47789
0x0000BAAD & 0x0000FFFF = 0x0000BAAD
00000000000000001011101010101101 & 00000000000000001111111111111111 = 00000000000000001011101010101101

Basically, the code simply takes a 32 bit number and returns the top (most significant) 16 bits of them.
The >> 16 followed by the & 0xFFFF is unnecessary - the bitshift right 16 bits automatically fills the top 16 bits with 0s.

This code is functionally the same:

(WORD)((DWORD)(l) >> 16)

See how much easier things are when we use hex/binary?

Edited && --> &

Maximilien29-Jul-09 9:48

Maximilien

29-Jul-09 9:48

We're lucky that

0XDEADBEEF != 0XBAADFOOD

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enhzflep29-Jul-09 10:00

enhzflep

29-Jul-09 10:00

Slider control on the status bar (where does WM_HSCROLL go?)

Thang30-Jul-09 6:10

Thang

30-Jul-09 6:10

Dear Mr enhzflep and Mr DavidCrow,
First of all, thank you so much about your clearly explanation.
I just still have a consideration, why the small expression (& 0xFFFF) has been still used in the expression ((l) >> 16) & 0xFFFF) here .
And this expression origins from window library, hix.
Why they still have used this expression if it was not necessary in here ?

Once again, thanks for your help, Mr enhzflep and Mr DavidCrow.

Best regards,
Duong Quoc Thang

BabakTaati29-Jul-09 5:46

BabakTaati

29-Jul-09 5:46

Hi,

I'm trying to place a slider control (CSliderCtrl) on the status bar. The slider bar appears fine and I can move it around (either manually or by calling SetPos). However, I can't find where the WM_HSCROLL messages from the slider bar are sent to! I set the parent of the slider control to the status bar, but no WM_HSCROLL is sent to that window! Any ideas?

Here's what my code looks like. First off, I derived a class from CStatusBar to handle WM_HSCROLL:

class CMyStatusBar : public CStatusBar 
{
public:
	DECLARE_MESSAGE_MAP()
	afx_msg void OnHScroll(UINT nSBCode, UINT nPos, CScrollBar* pScrollBar);
};

In my view class (e.g. CMySimpleProjctView) I added two members:

CSliderCtrl videoPosSlider;
CMyStatusBar statusBar;

and also a function called InitSliderBar() which is something like this:

void CMySimpleProjctView::InitSliderBar()
{
	CMainFrame* frame = (CMainFrame*) AfxGetApp()->m_pMainWnd; // get the main frame
	statusBar = (CMyStatusBar*)(frame->GetStatusBar()); // get the status bar

	// place a slide bar on the status bar, similar to http://support.microsoft.com/kb/142202
	RECT rc;
	statusBar->GetItemRect(0, &rc);
	VERIFY (videoPosSlider.Create(WS_CHILD | WS_VISIBLE, rc, statusBar, 1)); // parent of the slider = status bar

	videoPosSlider.SetRange(0, 50, 1);
	videoPosSlider.SetPos(5);
}

When I run the program, the slider bar appears and I can move it around, but CMyStatusBar::OnHScroll() is not called when I move the slider. To test if everything else is fine, I changed the parent of the slider control to the view window in the code as

VERIFY (videoPosSlider.Create(WS_CHILD | WS_VISIBLE, rc, m_hWnd, 1)); // parent of the slider = view window

and now CMySimpleProjctView::OnHScroll *is* called (but of course the slider bar appears at the wrong place, not on the status bar). I tried Spy++ to see where the WM_HSCROLL is sent to (when parent=status bar) but no WM_HSCROLL is sent at all! In fact no messages are passed when I move the slider around!!

Any ideas? thanks.

-Babak

(by the way, videoPosSlider.GetOwner() and videoPosSlider.GetParent() both return pointers that are identical to statusBar)

Reading from and writing to the registry in windows Vista

Sternocera29-Jul-09 5:00

Sternocera

29-Jul-09 5:00

Hello,

I'm maintaining an MFC application that reads and writes from/to the registry. Previously, it used the HKEY_LOCAL_MACHINE key. However, this meant that Vista users needed full OS administrative privileges, (and perhaps non-admin XP users, but there aren't a whole lot of those around) which isn't desirable. So, I changed the key used to HKEY_CURRENT_USER. This just appears to not work at all on Vista as a regular user, though it does work elsewhere.

How can I store values in the registry without administrative privileges?

Regards,
Sternocera

Re: Reading from and writing to the registry in windows Vista

David Crow29-Jul-09 5:47

Re: Reading from and writing to the registry in windows Vista

29-Jul-09 5:47

Sternocera wrote:
This just appears to not work at all on Vista as a regular user...

Do the registry functions fail?

bob1697229-Jul-09 5:53

bob16972

29-Jul-09 5:53

You need to include a security section in your manifest file to prevent Registry and File Virtualization for your application (or have the user turn User Access Control [UAC] off).

I would recommend the manifest resource file with the security section since it allows you to use registry and file functions without getting false positives from virtualization. I use "AsInvoker" for user apps.

"Windows via C/C++, Fifth Edition" by Richter has some good information on dealing with Vista and using manifests correctly.

The Microsoft endorsed way of properly designing an application for UAC is to use a security manifest section in your manifest file/resource.

Windows Vista Application Development Requirements for User Account Control Compatibility[^]

Create and Embed an application manifest[^]

Certified for Logo Test Case[^]

Re: Reading from and writing to the registry in windows Vista

Sternocera29-Jul-09 23:38

Sternocera

29-Jul-09 23:38

Bob,

Thanks for that, but all I want to do is stored some key:value pair application settings! Surely there is a simpler way?

bob16972 wrote:
You need to include a security section in your manifest file to prevent Registry and File Virtualization for your application (or have the user turn User Access Control [UAC] off).

Why? I thought that registry and file virtualisation where ways in which
Vista supported applications that used the registry.

Regards,
Sternocera

References

EliottA29-Jul-09 4:13

EliottA

29-Jul-09 4:13

Just brushing up my C++ here, and a quick question.

I see people pass by reference using the following methods

&int x;
int & x;
int &x;

Difference? Which is better practice? When declaring a function definition and you want that function to accept a reference, how do you define that function heading?

double myFunction(&int);

?

or do you include the variable name?

double myFunction(int &x);

Sorry to make you go over the basics, my book isn't very clear...

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C^hris L^osinger29-Jul-09 4:28

C^hris L^osinger

29-Jul-09 4:28

AFAIK, this: &int x; isn't valid C++.

the other two are identical.

double myFunction(&int);

that's not legal, either.

i always include the variable name, since the header is the first place i look when looking for documentation.

EliottA29-Jul-09 4:35

EliottA

29-Jul-09 4:35

Hey, thanks for the response.

So you include the variable name in the function definition? Seems like the smart thing to do I guess, I'll try to pick up on that habit.

Thanks for the reply. 5'ed.

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C^hris L^osinger29-Jul-09 4:40

C^hris L^osinger

29-Jul-09 4:40

EliottA wrote:

So you include the variable name in the function definition?

yeah. it's not strictly required, but it's really handy to people who want to use the function.

Maximilien29-Jul-09 7:59

Maximilien

29-Jul-09 7:59

Chris Losinger wrote:
but it's really handy to people who want to use the function.

especially when you have more than one parameter with the same type (as seen in our code)

void f(int, int, double, double, int, int& );
void f(int a, int b, double aa, double bb, int g, int& r){}

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