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Where's the C++ question?
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~<br />
Peter Weyzen<br />
Staff Engineer<br />
<A HREF="http://www.soonr.com">SoonR Inc -- PC Power delivered to your phone</A>
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Hi, I'm wondering which of these is more efficient in C code:
Let's say I have a function:
int check(int x)<br />
{<br />
int var;<br />
<br />
var = calc_var(x);<br />
<br />
return var;<br />
}
Is it more efficient to make that "int var;" into "static int var;" or is it better to keep it as non-static? This is a single-threaded program and the "calc_var" function always returns a value so changing var to static will have exactly the same programmatic behavior, I'm just wondering which is actually a more efficient way to do it, since this "check(int x)" function is called all over the place constantly, sometimes hundreds of times per second.
Thanks!
KR
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In my humble opinion negligible change in efficiency. The way to get more efficient code in that case is to do this
__inline int check(int x) { return calc_var(x); }
provided the compiler complies with the __inline hint it will remove "sometimes hundreds of times per second" of constructing and releasing a stackframe around the unnecessary function call.
Or even, at the risk of incurring the wrath of some of the other members here
#define check(x) calc_var(x)
which will guarantee the unnecessary function call and stackframe are eliminated
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int check(int x)
{
return calc_var(x);
}
would be better as the int is only copied once. If you need the value of calc_var() for further processing in check() I'd avoid a static as you will probably end up confusing the optimiser and wind up with worse machine code. In my limited experiance spending time on questions like this is often a waste of time.
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Sorry, I was sort of unclear with my question; the check function I posted is a simplistic example, the real function is about 600 lines long and is a lot more complex than just returning another function, so it's not as easy as just eliminating a variable declaration.
KR
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A local variable is likely in the cache, so it is more effiecint.
A static one may be far from the current instruction.
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KellyR wrote: Is it more efficient ...
You can only find that out by testing. Testing with real data, that is.
And before you spend time for this, you should really be sure that this function call is a bottleneck of your application.
So - profile it! While processing real data!
Let's think the unthinkable, let's do the undoable, let's prepare to grapple with the ineffable itself, and see if we may not eff it after all.
Douglas Adams, "Dirk Gently's Holistic Detective Agency"
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I want to put it at the top part of client for the customer to pick up thumbnail to the client. Like this:
/-------------------------------------------------------\
| /--------------------------------------------------\ |
| |:laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh:| |
| |--------------------------------------------------| |
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\-------------------------------------------------------/
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Do you want to have thumbnails of images on the listctrl of left to right?
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On the Listctrl you have a option its name is Alignment you can set it to top or left.
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Hi,
I am converting my MFC project from a dialog-based application to a single document interface. My dialog box contains a button which calls DoModal() on a Server-site dialog written by our company. Normally, this would bring up a window showing all of the services available on a server. This works fine and dandy in my dialog-based version of the project; however, in my new SDI application (in which the main dialog window from the first project fills the child view), calling DoModal() no longer brings up another window. I tried putting DoModal() code for both the server-site dialog and some of my own process status threads all over the project (inside the main dialog class, inside the child view class, and inside the application class), and nothing works. The only modal dialog I can bring up in the entire project is the about box which was already pre-coded. If anyone has any clue as to why DoModal() fails in my SDI application, please let me know.
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Can you put a bit of code, about how are you doing that?
If you are in MFC (I guess with wizard, because of the About.. box) it should be easy to do. The easiest way is to make the dialog in the resource editor, then create a class to that dialog and then make the call like:
OnButtonClick ()
{
CMyDialog newDlg;
if (IDCANCEL == newDlg.DoModal ())
{
return;
}
return;
}
Greetings.
--------
M.D.V. 
If something has a solution... Why do we have to worry about?. If it has no solution... For what reason do we have to worry about?
Help me to understand what I'm saying, and I'll explain it better to you
“The First Rule of Program Optimization: Don't do it. The Second Rule of Program Optimization (for experts only!): Don't do it yet.” - Michael A. Jackson
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I am writing exactly what you put, yet it does not bring up a modal dialog box. If I debug, I can step into the DoModal() function to see what's wrong, and it looks like it fails when checking if lpDialogTemplate is NULL:
<br />
INT_PTR CDialog::DoModal()<br />
{<br />
ASSERT(m_lpszTemplateName != NULL || m_hDialogTemplate != NULL ||<br />
m_lpDialogTemplate != NULL);<br />
<br />
LPCDLGTEMPLATE lpDialogTemplate = m_lpDialogTemplate;<br />
HGLOBAL hDialogTemplate = m_hDialogTemplate;<br />
HINSTANCE hInst = AfxGetResourceHandle();<br />
if (m_lpszTemplateName != NULL)<br />
{<br />
hInst = AfxFindResourceHandle(m_lpszTemplateName, RT_DIALOG);<br />
HRSRC hResource = ::FindResource(hInst, m_lpszTemplateName, RT_DIALOG);<br />
hDialogTemplate = LoadResource(hInst, hResource);<br />
}<br />
if (hDialogTemplate != NULL)<br />
lpDialogTemplate = (LPCDLGTEMPLATE)LockResource(hDialogTemplate);<br />
<br />
if (lpDialogTemplate == NULL)<br />
return -1;<br />
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Errr...sorry about that code snippet, I evidently used the wrong tags. By the way, this code is from dlgcore.cpp. Also, the code continues past the return -1 statement, I just didn't include it because it stops right there.
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I was wondering how I could take screenshots using PrintWindow() on Windows XP and get the transparency information, so I don't get an ugly black border around all my individual window screenshots. This seems to be possible from looking at other programs (e.g. TopDesk, http://www.otakusoftware.com/topdesk/). I played with calling GetLayeredWindowAttributes to find out transparency information, but it only succeeds for app that initially set the transparency information in the first place.
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I haven't tried this, but what happens if you create a 32-bit ARGB DIB section and select it into the destination DC?
Fill it with transparent pixels before the PrintWindow() call.
Of course, to preserve the transparency when saving to a file, you'll need to use a file
format that supports transparency, like PNG or TIFF.
Mark
Mark Salsbery
Microsoft MVP - Visual C++
![Java | [Coffee]](https://www.codeproject.com/script/Forums/Images/coffee.gif)
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I'm using C# with interop. I'm not too sure what you mean by "dib section," although I am creating a 32-bit ARGB bitmap where the image is written to. I tried making the bitmap transparent first, and also tried something like coloring all the pixels red first. Neither worked; every pixel is always overwritten. There is always a black border, and when I try to access the pixel at 0,0 (which on my computer should be transparent, because its a Windows XP rounded corner), it is always black with an alpha value of 255.
My C# code looks like this:
Rect rc;
GetWindowRect(hwnd, out rc);
if (rc.Width == 0 && rc.Height == 0)
{
return null;
}
System.Drawing.Bitmap bitmap = new System.Drawing.Bitmap((int)rc.Width, (int)rc.Height, System.Drawing.Imaging.PixelFormat.Format32bppArgb);
bitmap.MakeTransparent();
System.Drawing.Graphics gfxBitmap = System.Drawing.Graphics.FromImage(bitmap);
IntPtr hdcBitmap = gfxBitmap.GetHdc();
PrintWindow(hwnd, hdcBitmap, 0);
gfxBitmap.ReleaseHdc(hdcBitmap);
gfxBitmap.Dispose();
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You're doing the same thing I was referring to 
MakeTransparent() isn't going to help here. I would try actually clearing the bitmap to
transparent pixels with a transparent brush before calling PrintWindow().
What are you doing after the code you've shown? How do you check and see the undesired black border?
Mark
Mark Salsbery
Microsoft MVP - Visual C++
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Ok, I think I figured it out. The reason why the windows I was interested in were transparent wasn't because they were layered-- they had clipping window regions! Your hint about clearing the bitmap to transparent pixels was also helpful (I was drawing a transparent rectangle, but that doesn't work; you need to call clear).
Here is my final code. You can get the Win32/GDI functions through pinvoke.net
Rect rc;
GetWindowRect(hwnd, out rc);
if (rc.Width == 0 && rc.Height == 0)
{
return null;
}
System.Drawing.Bitmap bitmap = new System.Drawing.Bitmap((int)rc.Width, (int)rc.Height, System.Drawing.Imaging.PixelFormat.Format32bppArgb);
System.Drawing.Graphics gfxBitmap = System.Drawing.Graphics.FromImage(bitmap);
IntPtr hdcBitmap = gfxBitmap.GetHdc();
PrintWindow(hwnd, hdcBitmap, 0);
gfxBitmap.ReleaseHdc(hdcBitmap);
IntPtr hRgn = CreateRectRgn(0, 0, 0, 0);
GetWindowRgn(new IntPtr(hwnd), hRgn);
System.Drawing.Region region = System.Drawing.Region.FromHrgn(hRgn);
if (!region.IsEmpty(gfxBitmap))
{
gfxBitmap.ExcludeClip(region);
gfxBitmap.Clear(System.Drawing.Color.Transparent);
}
gfxBitmap.Dispose();
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Cool! Thanks for the update
I'll try to remember that the next time it comes up!
Cheers,
Mark
Mark Salsbery
Microsoft MVP - Visual C++
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Dear All
i am about to start a project something like download manager Like FlashGet....etc
i need to know how to start ??
i need any info. about the following :
"limit download speed"
"resume, pause, stop"
i need any tips
thanks
bye
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Adore C++ wrote: i need to know how to start ??
Maybe with something a little less ambitious. Not to dull your knife or anything, but you can't jump into the deep end of the pool and then immediately ask for help. Start small and build upon that.
"Normal is getting dressed in clothes that you buy for work and driving through traffic in a car that you are still paying for, in order to get to the job you need to pay for the clothes and the car and the house you leave vacant all day so you can afford to live in it." - Ellen Goodman
"To have a respect for ourselves guides our morals; to have deference for others governs our manners." - Laurence Sterne
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DavidCrow wrote: you can't jump into the deep end of the pool and then immediately ask for help.
Sweet, let's make an acronym out of that: The Internet
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