C / C++ / MFC Discussion Boards

Stephen Hewitt29-Mar-06 13:01

29-Mar-06 13:01

Calling TerminateProcess is meant as a last line of defense - In general it is not safe to go around terminating processes. If you must stop another process the correct technique is to ask it nicely to exit and only fall back on TerminateProcess if this doesn't succeed. See here[^] for some more info on this. If you do call TerminateProcess here's some possible ramifications in order of severity:
- Nothing bad happens.
- The program doesn't get a chance to clean up after itself - For example temporary files are left behind undeleted.
- The process corrupts data. This can occur if, say, the program was interrupted in the middle of an operation that should be atomic.
- If the process used shared memory, such if often the case when global hooks are used, the global data could be corrupted and effect other processes.

Steve

dialog not in taskbar

viperlogic29-Mar-06 4:55

viperlogic

29-Mar-06 4:55

I have a vc++6 MFC app, i have a main dialog that shows in the taskbar, the dialog can call a login dialog which also shows in the taskbar but i have the main callin another dialog but that doesnt show in the task bar. what is causing this

what part of the code actually makes a dialog show in the taskbar?

thx

Re: dialog not in taskbar

viperlogic29-Mar-06 5:04

viperlogic

29-Mar-06 5:04

i just found the line that does it in the .rc file

EXSTYLE WS_EX_APPWINDOW

i have added the above lines to the correct sections in the .rc file using notepad but how is this ment to be added when using visual studio 6

as the above way im sure isnt the right way

Re: dialog not in taskbar

toxcct29-Mar-06 5:06

toxcct

29-Mar-06 5:06

i'm quite sure you're calling that login dialog as modal from the Main dialog's OnInitDialog() function... aren't you ?!
Cool | :cool:

Re: dialog not in taskbar

viperlogic29-Mar-06 5:12

viperlogic

29-Mar-06 5:12

yes, that is correct, while the other dialog is called once a button is click in the main dialog

is this having an effect?

How to offer aticles here?

includeh1029-Mar-06 4:37

includeh10

29-Mar-06 4:37

I want to write some articles for the forum, how to do (publish) that?

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Includeh10

Re: How to offer aticles here?

Gavin Taylor29-Mar-06 4:44

Gavin Taylor

29-Mar-06 4:44

Check out http://codeproject.com/info/submit.asp[^]

Theres also a Submission Wizard here[^]

Gavin Taylor
w: http://www.gavspace.com

Re: How to offer aticles here?

includeh1029-Mar-06 5:03

includeh10

29-Mar-06 5:03

right, but how to navigate to these pages if not clicking links given by you?

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Includeh10

Re: How to offer aticles here?

Gavin Taylor29-Mar-06 5:08

Gavin Taylor

29-Mar-06 5:08

sorry, wasn't thinking... Smile | :)

Look at the top right hand menu on every page then Articles / Submit an Article

Gavin Taylor
w: http://www.gavspace.com

Copy contents of a window to the clipboard

anderslundsgard29-Mar-06 4:12

anderslundsgard

29-Mar-06 4:12

I like to do a “printscreen” on a window. Can I use the windows HWND to accomplish that in some way?

All tips are welcomed.

_____________________________

...and justice for all

APe

Re: Copy contents of a window to the clipboard

includeh1029-Mar-06 4:24

includeh10

29-Mar-06 4:24

search for "screen capture" in articles of the forum, u can find some samples - also in VC CD (samples).

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Includeh10

Re: Copy contents of a window to the clipboard

David Crow29-Mar-06 4:49

David Crow

29-Mar-06 4:49

See here.

"Let us be thankful for the fools. But for them the rest of us could not succeed." - Mark Twain

"There is no death, only a change of worlds." - Native American Proverb

What is the difference??

ashwath200529-Mar-06 3:33

ashwath2005

29-Mar-06 3:33

I have the below code:
There is a classs"CPaintDC".
Can anyone please tell me what is the difference between the following 2 statements:
1.)CPaintDC *pDC = new CPaintDC(this);
2.)CPaintDC* pDC=new CPaintDC;

Re: What is the difference??

toxcct29-Mar-06 3:53

toxcct

29-Mar-06 3:53

1. calls the CPaintDC contructor which receives a CWnd* parameter, and initializes it with the this pointer passed,

2. calls the CPaintDC default constructor...

Re: What is the difference??

includeh1029-Mar-06 4:43

includeh10

29-Mar-06 4:43

DC is related to Window, in other words, we say "a DC of a window".

1) the DC of "this" window - similar to ::GetDC(this->m_hWnd);
2) the DC of screen - similar to ::GetDC(0).

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Includeh10

Question

big_denny_20029-Mar-06 3:33

big_denny_200

29-Mar-06 3:33

Hi all

I have such question :

I often see following things in other people's code :

object.SomeFunction(BS_STYLE1 | BS_STYLE2 | BS_STYLE3)

and then after execution all those three styles are set to

the object.

How is this implemented inside the function ?

Can anybody clarify, or bring an example ?

thank you.

PS. For example this API uses such thing too :

ListView_SetExtendedListViewStyle(m_list, LVS_EX_FULLROWSELECT | LVS_EX_GRIDLINES );

Re: Question

khan++29-Mar-06 3:50

khan++

29-Mar-06 3:50

Actually it is a DWORD in the function:
void ListView_SetExtendedListViewStyle(HWND hwndLV,DWORD dwExStyle);
And this one is:
#define LVS_EX_FULLROWSELECT 0x00000020

this is this.

Re: Question

big_denny_20029-Mar-06 3:58

big_denny_200

29-Mar-06 3:58

thank you khan, but my question was how is it achieved inside the function that after writing

LVS_EX_FULLROWSELECT | LVS_EX_GRIDLINES

both styles are set.

And if I write only LVS_EX_FULLROWSELECT then only this style is set.

Re: Question

khan++29-Mar-06 4:08

khan++

29-Mar-06 4:08

Actually it is just a parameter like any other. The actual code inside the function handles the values passed, which can be anything.
It maybe like:

void func(DWORD dwStyle)
{
//save the dwStyle value to an internal variable maybe:
 m_dwStyle = dwStyle;
//Issue a redraw message to reflect the changed style.
 RedrawWindow();//etc

}

//some draw function for the control:

void Draw()
{
 if (m_dwStyle & LVS_EX_FULLROWSELECT)
 {
 //draw it differently
 }
 else
 {
 //draw it normally.
 }
}

this is this.

Re: Question

Gavin Taylor29-Mar-06 4:12

Gavin Taylor

29-Mar-06 4:12

It's called BitWise. CP has loads of articles on it if you do a search, however this is[^] a particulary good one.

All the function is doing is something like:

void SomeFunction( DWORD dwFlags )
{
	if( dwFlags & BS_STYLE2 )
	{ // Do something as style 2 was set
		DoSomething( );
	}
}

Gavin Taylor
w: http://www.gavspace.com

Re: Question

toxcct29-Mar-06 4:34

toxcct

29-Mar-06 4:34

i don't exactly get you ; however, if i understand well, you want to know this :
let go deeper in the instruction BS_STYLE1 | BS_STYLE3 | BS_STYLE6.

firstly, we need to know what are defined those constants like.
let's consider they're declared this way :

enum {
    BS_STYLE1 =  1,
    BS_STYLE2 =  2,
    BS_STYLE3 =  4,
    BS_STYLE4 =  8,
    BS_STYLE5 = 16,
    BS_STYLE6 = 32
};

to understand why these constants' values are chosen, we must go in binary representation to understand :

 1 -> 0b 00000000 00000000 00000000 00000001
 2 -> 0b 00000000 00000000 00000000 00000010
 4 -> 0b 00000000 00000000 00000000 00000100
 8 -> 0b 00000000 00000000 00000000 00001000
16 -> 0b 00000000 00000000 00000000 00010000
32 -> 0b 00000000 00000000 00000000 00100000

notice that for those special values that are multiples of 2, only one bit is set at a time, all the others are equal to 0.
the interrest in this is that each bit is a flag for a functionnality (style here), and we can mix them in once variable to avoid using as many booleans as we need flags.
for example, see the following case :

 0b 00000000 00000000 00000000 00100101
 
Flags of <code>Style6</code>, <code>Style3</code> and <code>Style1</code> are set

now, as we don't handle binary directly in C++, we use bitwise operators instead.
what you see as that vertical bar | is the bitwise OR operator.
the OR operator works like this :

 x y  |
--------
 0 0  0
 0 1  1
 1 0  1
 1 1  1

in the case of the instruction BS_STYLE1 | BS_STYLE3 | BS_STYLE6, it so ORs like this :

 0b 00000000 00000000 00000000 00000001   <- BS_STYLE1
 0b 00000000 00000000 00000000 00000100   <- BS_STYLE3
 0b 00000000 00000000 00000000 00100000   <- BS_STYLE6
-----------------------------------------------
 0b 00000000 00000000 00000000 00100101   <- BS_STYLE1 | BS_STYLE3 | BS_STYLE6

Now, the "mix value" is constructed, we can pass it to a function.
but how does the function know which bits are set, and which are not ?
easy... follow me !

Lets say we want to know if the bit of BS_STYLE1 is set from the mix we get in parameter (let's call it MIX_VAR.
we must create a maskwhich we'll AND with the :

STYLE1_MASK = 0b 00000000 00000000 00000000 00000001

as you see, the mask is the same as the STYLE constant, so in practice, you'll never see defined such mask :

MIX_VAR  -> 0b 00000000 00000000 00000000 00100101
MASK1    -> 0b 00000000 00000000 00000000 00000001
           ----------------------------------------
<code>Bitwise AND</code> 0b 00000000 00000000 00000000 00000001

if the result is equal to the STYLE1, then it is because the bit was set. otherwise, you get 0.

ok, now, in practice, here is how you'll often see it :

void fooFunc(DWORD dwMix) {
    if (BS_STYLE1 & dwMix) == BS_STYLE1) {
        //Apply style 1
    }
    else if (BS_STYLE2 & dwMix) == BS_STYLE2) {
        //Apply style 2
    }
    else if (BS_STYLE3 & dwMix) == BS_STYLE3) {
        //Apply style 3
    }
    //etc...
}