C / C++ / MFC

4-Aug-05 4:55

Some tools that draw selection rectangles over other windows have the same problem as yours, and I am seeing this with the ZoomIn enhancement I have been working on.
Typically, they invalidate the entire screen, which causes every piece of every window to redraw.
You might want to see what Jospeh Newcomer has done in his new ZoomIn tool he posted recently to CodeProject.
http://www.codeproject.com/tools/betterzoomin.asp[^]

MetaFiles

popo843-Aug-05 22:31

popo84

3-Aug-05 22:31

I currently developing a program and it is workable, but somehow when i turn on the program for a long time(15 minutes depends on how big the computer memory is) then it will hang. I check out that when i add a component which is inside my program, for example a bitmap file into my program. The computer memory starts to increase rapidly everytime i add a component. I been using meta files to store this added components but i have no idea how to remove the metafiles that is added, can anyone here help me. I'll be really grateful

From: Guibert Wink | ;)

Re: MetaFiles

badal_akr4-Aug-05 0:33

badal_akr

4-Aug-05 0:33

Same problem i faced yesterday and fixed it.
In my case i was creating a DISPLAY DC and one Compatible DC and one Bitmap memory through CreateDIBSection API call.

hdc = CreateDC("DISPLAY",NULL,NULL,NULL);
Bitmap = CreateDIBSection(hdc, pBMI, DIB_RGB_COLORS, (void**)&m_pVideoBits, 0, 0);
HDC hSrcDC = CreateCompatibleDC(hdc);
SelectObject(hSrcDC, m_hViewfinderBitmap);

while Deleting the Bitmap and DC you should follow the following way
DeleteDC(hSrcDC);
DeleteObject(Bitmap);
DeleteDC(hdc);

If your code also have some this kind of thing then please take care that, you should not clean a bitmap untill it is attached to the DC

Hope i could help you some way.

Regards

Anil Kumar

Structure Alignment?

badal_akr3-Aug-05 22:29

badal_akr

3-Aug-05 22:29

Can any body tell me why structure alignment is necessary in C/C++ and what it may cause?

Anil Kumar

Halawlaws3-Aug-05 23:08

Halawlaws

3-Aug-05 23:08

Hi Applications should generally align structure members at addresses that are "natural" for the data type and the processor involved. For example, a 4-byte data member should have an address that is a multiple of four.

This principle is especially important when you write code for porting to multiple processors. A misaligned 4-byte data member, which is on an address that is not a multiple of four, causes a performance penalty with an 80386 processor and a hardware exception with a MIPS® RISC processor. In the latter case, although the system handles the exception, the performance penalty is significantly greater.

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Halawlaws3-Aug-05 23:10

Halawlaws

3-Aug-05 23:10

Or maybe this can help too:

All modern CPUs expect that fundamental types like ints, longs and floats will be stored in memory at addresses that are multiples of their length.

CPUs are optimized for accessing memory aligned in this way.

Some CPUs:

allow unaligned access but at a performance penalty;

trap unaligned accesses to the operating system where they can either be ignored, simulated or reported as errors;

use unaligned addresses as a means of doing special operations during the load or store.

When a C compiler processes a structure declaration, it can:

add extra bytes between the fields to ensure that all fields requiring alignment are properly aligned;

ensure that instances of the structure as a whole are properly aligned. Malloc always returns memory pointers that are aligned for the strictest, fundamental machine type.

The specifications for C/C++ state that the existence and nature of these padding bytes are implementation defined. This means that each CPU/OS/Compiler combination is free to use whatever alignment and padding rules are best for their purposes. Programmers however are not supposed to assume that specific padding and alignment rules will be followed. There are no controls defined within the language for indicating special handling of alignment and padding although many compilers like gcc have non-standard extensions to permit this.

Summary

Structure Alignment
Structure alignment may be defined as the choice of rules which determine when and where padding is inserted together with the optimizations which the compiler is able to effect in generated code.

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badal_akr4-Aug-05 0:41

badal_akr

4-Aug-05 0:41

But as per my understanding the structure members are stored in the contigous memory locations for example

struct temp
{
char a,
int b,
float c,
};

if i declare temp *structPtr = 0x00000000 (Address of element a)
then what should be the address of element b if it is 0x00000002 then one byte is waisted.
According to you b should have address of multiple of 4.
So i can say that there is a trade of CPU performance vs Memory usage
Am i right please guide me.
Regards

Anil Kumar

Blake Miller4-Aug-05 5:04

4-Aug-05 5:04

Yes, memory usage versus performance.

In Visual Studio you can use the #pragma pack() to control memory alignment on a structure-by-structure basis.

problems while assigning CString object.

GKarRacer5-Aug-05 9:38

GKarRacer

5-Aug-05 9:38

Generally the default structure alignment (which you should use unless there is a compelling reason not to) is 8 bytes. This aligns all basic data types (up to doubles) to even multiples of their size.

Example (using 8 byte alignment):

struct test
{
    char    a;
    int     b;
    WORD    c;
    char    d;
    double  e;
};

The offset addresses are:

a = 0
b = 4
c = 8
d = 10
e = 16

Total size of the structure: 24 bytes

Notice there is some wasted space in there. You can add some variables to this and not increase the size of the structure at all. The following structure is still 24 bytes in size, but is now fully packed.

struct test2
{
    char    a;
    char    a2;
    WORD    a3;
    int     b;
    WORD    c;
    char    d;
    char    d2;
    int     d3;
    double  e;
};

a_david1233-Aug-05 22:03

a_david123

3-Aug-05 22:03

Respected All
Regards!

I have a CString object which has a value like

----------------------------------------
CString str=ss.find(0,4) //from this statment the str will be assign to

//file name ;

and now this "str" is a File name which i have to use in fileopen like

pFile=open("C:\\str.dat","r");

but it cant open str.dat as in the above satatment.now i think that i have to assign it to another string type variable and then can use it in opening a file.

but how i do it,,plz help me.

waiting for + response.

david

david

Re: problems while assigning CString object.

toxcct3-Aug-05 22:11

toxcct

3-Aug-05 22:11

i'm not sure i understand well, but what about this ?

pFile=open("C:\\" + str + ".dat","r");

TOXCCT >>> GEII power
[toxcct][VisualCalc]

Re: problems while assigning CString object.

Eytukan3-Aug-05 23:46

Eytukan

3-Aug-05 23:46

convert to char*
CString ss;//=xyz, david

char* str = ss.GetBuffer(cs.GetLength());

then construct ur file name.. with strcat(str,"//..dat"), so u wont get confused
then

pFile=fopen(str,"r");

am i right? Sniff | :^)

Close Open Windows with Escape-Key

Daniel Gerstner3-Aug-05 21:38

Daniel Gerstner

3-Aug-05 21:38

Hello,

I want to close all open Windows in my Application (not the MainWindow).
Unfortunately this Code fragment does not what I'm expecting Frown | :-(

Here is my Code:

//Test Only for 4 Windows

CWnd * pWnd = NULL;
pWnd = GetActiveWindow();

for(int i = 1; i < 4; i++)
{
pWnd = GetActiveWindow(); //I tried GetNextWindow too
if (pWnd != theApp.GetMainWnd())
{
pWnd->PostMessage(WM_KEYDOWN,VK_ESCAPE);
}
pWnd = NULL;
}

Thanks fpr your Help.
And greetings from Germany

Daniel Gerstner3-Aug-05 23:01

Daniel Gerstner

3-Aug-05 23:01

I have it!!

The Solution:

CWnd * pWnd = NULL;
pWnd = GetActiveWindow();

while(pWnd != theApp.GetMainWnd())
{
((CDialog*)pWnd)->EndDialog(IDCANCEL);
pWnd = GetActiveWindow();
}

Blake Miller4-Aug-05 5:06

4-Aug-05 5:06

You could also try to post the WM_CLOSE message to the windows.
If you notice strange side effects, you could consider doing the WM_CLOSE instead of calling EndDialog directly.

Daniel Gerstner4-Aug-05 19:02

Daniel Gerstner

4-Aug-05 19:02

Sends the WM_CLOSE Message IDCANCEL?
I would really like to use WM_CLOSE but I 'm not sure
if the Windows is closed with IDCANCEL. My solution has a
disadvantage it closes only Modal Dialogs Frown | :-(

Daniel

Blake Miller5-Aug-05 6:04