C / C++ / MFC

22-May-06 15:39

I am trying to use the EnumDisplayDevices function, but for some reason is giving me a undeclared Identifier:

#include <windows.h>
#include <iostream>
using namespace std;

void main()
{
DISPLAY_DEVICE dd;
DWORD i;

ZeroMemory(&dd, sizeof(dd));
dd.cb = sizeof(dd);

for(i=0; EnumDisplayDevices(NULL, i, &dd, 0); i++)
{
cout<

_anil_22-May-06 16:41

_anil_

22-May-06 16:41

Hi Though I can't exactly tell why the problem is occoring some of the resons are

UNICODE and WINVER definations. If you go to winuser.h you can see the defination of EnumDisplayDevice.
you can try as MSDN way. that is dynamically loding the funtion from DLL.

<br />
BOOL GetDisplayMonitorInfo(int nDeviceIndex, LPSTR lpszMonitorInfo)<br />
{<br />
    FARPROC EnumDisplayDevices;<br />
    HINSTANCE  hInstUser32;<br />
    DISPLAY_DEVICE DispDev; <br />
    char szSaveDeviceName[32];<br />
    BOOL bRet = TRUE;<br />
    <br />
    hInstUser32 = LoadLibrary("User32.DLL");<br />
    if (!hInstUser32) return FALSE;  <br />
    <br />
    // Get the address of the EnumDisplayDevices function<br />
    EnumDisplayDevices = (FARPROC)GetProcAddress(hInstUser32,"EnumDisplayDevicesA");<br />
    if (!EnumDisplayDevices) {<br />
        FreeLibrary(hInstUser32);<br />
        return FALSE;<br />
    }<br />
<br />
    ZeroMemory(&DispDev, sizeof(DISPLAY_DEVICE));<br />
    DispDev.cb = sizeof(DISPLAY_DEVICE); <br />
    <br />
    // After the first call to EnumDisplayDevices, <br />
    // DispDev.DeviceString is the adapter name<br />
    if (EnumDisplayDevices(NULL, nDeviceIndex, &DispDev, 0)) {  <br />
        lstrcpy(szSaveDeviceName, DispDev.DeviceName);<br />
        <br />
        // After second call, DispDev.DeviceString is the <br />
        // monitor name for that device <br />
        EnumDisplayDevices(szSaveDeviceName, 0, &DispDev, 0);   <br />
        <br />
        lstrcpy(lpszMonitorInfo, DispDev.DeviceString);<br />
    } else    {<br />
        bRet = FALSE;<br />
    }<br />
<br />
    FreeLibrary(hInstUser32);<br />
<br />
    return bRet;<br />
}<br />
<br />

Regards
Anil

zaro33323-May-06 4:56

23-May-06 4:56

Anil, Thank for your help, but this thing is starting to get on my nerves. I can not get it to work.

I try the above and nothing, then I try to simplify it and another error, see:

#include <windows.h>

BOOL GetDisplayMonitorInfo(int nDeviceIndex, LPSTR lpszMonitorInfo)
{
FARPROC EnumDisplayDevices;
HINSTANCE hInstUser32;
DISPLAY_DEVICE DispDev;
char szSaveDeviceName[32];
BOOL bRet = TRUE;

hInstUser32 = LoadLibrary("User32.DLL");
if (!hInstUser32) return FALSE;

// Get the address of the EnumDisplayDevices function
EnumDisplayDevices = (FARPROC)GetProcAddress(hInstUser32,"EnumDisplayDevicesA");

ZeroMemory(&DispDev, sizeof(DISPLAY_DEVICE));
DispDev.cb = sizeof(DISPLAY_DEVICE);

EnumDisplayDevices(szSaveDeviceName, 0, &DispDev, 0);

FreeLibrary(hInstUser32);

return bRet;
}

void main()
{
}
The error I get is:
error C2197: 'int (__stdcall *)(void)' : too many actual parameters on EnumDisplayDevices(szSave....)

I am thinking, I will not trying to get this function to work. Dead | X|

zaro33323-May-06 4:58

23-May-06 4:58

Anil, sorry for the above that says

#include it is missing <windows.h>

zaro33323-May-06 5:01

Re: EnumDisplayDevices [modified]

23-May-06 5:01

SOrry I did not know that this was taking HTML tags,

so the <> does not come out.

anyway it is #include <windows.h>

_anil_23-May-06 15:05

_anil_

23-May-06 15:05

I have just copy and paste the above code from MSDN
any way this time I changed it in my way and comiled it. Hope it will work.

<br />
<br />
typedef BOOL (WINAPI* EnumDisplayDevices) (<br />
											LPCTSTR lpDevice,                // device name<br />
											DWORD iDevNum,                   // display device<br />
											PDISPLAY_DEVICE lpDisplayDevice, // device information<br />
											DWORD dwFlags                    // reserved<br />
											);<br />
<br />
BOOL GetDisplayMonitorInfo(int nDeviceIndex, LPSTR lpszMonitorInfo)<br />
{<br />
	EnumDisplayDevices  pEnumDisplayDevices;<br />
	HINSTANCE hInstUser32;<br />
	DISPLAY_DEVICE DispDev;<br />
	char szSaveDeviceName[32];<br />
	BOOL bRet = TRUE;<br />
	<br />
	hInstUser32 = LoadLibrary("User32.DLL");<br />
	if (!hInstUser32) return FALSE;<br />
	<br />
	// Get the address of the EnumDisplayDevices function<br />
	pEnumDisplayDevices = (EnumDisplayDevices)GetProcAddress(hInstUser32,"EnumDisplayDevicesA");<br />
	<br />
	ZeroMemory(&DispDev, sizeof(DISPLAY_DEVICE));<br />
	DispDev.cb = sizeof(DISPLAY_DEVICE);<br />
	<br />
	pEnumDisplayDevices(szSaveDeviceName, 0, &DispDev, 0);<br />
	<br />
	FreeLibrary(hInstUser32);<br />
	<br />
	return bRet;<br />
}<br />
<br />
<br />
void main()<br />
{<br />
}<br />
<br />

Regards
Anil

-- modified at 21:05 Tuesday 23rd May, 2006

Re: EnumDisplayDevices [modified]

zaro33324-May-06 4:14

Embedded Chart Missing X-Axis Scale

24-May-06 4:14

Anil, THANK YOU VERYYYYYYYYYY MUCHHHHHH, YOU ARE ONE SMART PERSON, I REALLY WANT TO THANK YOU FOR YOUR HELP, I WAS ABLE TO USE THE CODE ABOVE AND IT WORKS. I JUST INCLUDED A COUT COMMAND TO PRINT OUT THE DEVICE INFORMATION. THANKS A LOT Cool | :cool:

if anything, this is how i change the code that Anil gave me, for other people looking at this question: [** I had the error for precompiler stdafx.h, so just go to settings and ignore the precompiler headers.]

#include <windows.h>
#include <iostream>
using namespace std;

typedef BOOL (WINAPI* EnumDisplayDevices) (
LPCTSTR lpDevice, // device name
DWORD iDevNum, // display device
PDISPLAY_DEVICE lpDisplayDevice, // device information
DWORD dwFlags // reserved
);

BOOL GetDisplayMonitorInfo()
{
EnumDisplayDevices pEnumDisplayDevices;
HINSTANCE hInstUser32;
DISPLAY_DEVICE DispDev;
char szSaveDeviceName[32];
BOOL bRet = TRUE;
DWORD i;

hInstUser32 = LoadLibrary("User32.DLL");
if (!hInstUser32) return FALSE;

// Get the address of the EnumDisplayDevices function
pEnumDisplayDevices = (EnumDisplayDevices)GetProcAddress(hInstUser32,"EnumDisplayDevicesA");

ZeroMemory(&DispDev, sizeof(DISPLAY_DEVICE));
DispDev.cb = sizeof(DISPLAY_DEVICE);

for(i=0;pEnumDisplayDevices(NULL/*szSaveDeviceName*/, i, &DispDev, 0);i++)
{
cout<

Jenleonard22-May-06 15:38

Jenleonard

22-May-06 15:38

Hi ~
I have an Excel Chart embedded in my program in a MFC Dialog. The x-axis scale shows dates from a time range selected by the user. The data is then drawn on the chart.

My problem is that in some cases the x-axis scale is missing. With the same data and scale, the data sometimes appears. If I have it redraw 10 times, the data is there some of the time.

Any ideas on what could be happening?
Thanks in advance!
Jen

C++ vs C# Performance

Ed K22-May-06 14:37

Ed K

22-May-06 14:37

Did some work for a friend over the weekend. Basic scenario was that he had a client who wanted to have a program built that processed some numbers. He wanted a test app built in Java, C#, VB.NET and C++. My friend had already developed the C# app so he sent me the code and I translated to C++. Initial testing looked like the C# app was as fast and sometimes faster than the C++ app...in debug and release.

I found that true until I stopped writing to the console. And even more so when I used profile guided optimization. At that point the C++ app embarrased the C# app. And in the same way C# cuts in half the time for VB.NET. The client decided not to look at Java knowing it didn't stand much chance.

C++
Total Time: 25.47ms
Per Tick: 0.00029ms // note that I had to extend this just to see the result!
Per 50K Ticks: 14.62ms

C#
Total Time: 185.10ms
Per Tick: 0.0021ms
Per 50K Ticks: 106.23ms

Bottom line for me is that the heavy lifting still belongs to C++!! Cool | :cool:

ed

~"Watch your thoughts; they become your words. Watch your words they become your actions.
Watch your actions; they become your habits. Watch your habits; they become your character.
Watch your character; it becomes your destiny."
-Frank Outlaw.

Re: C++ vs C# Performance [modified]

Nibu babu thomas22-May-06 17:14

Nibu babu thomas

22-May-06 17:14

Ed K wrote:
Bottom line for me is that the heavy lifting still belongs to C++!!

At last the truth! Jig | [Dance]

C and C++ Rules Smile | :)

.

PS: Sorry Ed. I clicked on 2 by mistake instead of clicking on 5. Sigh | :sigh:

Nibu thomas
A Developer

Programming tips[^] My site[^]

-- modified at 0:06 Tuesday 23rd May, 2006

bob1697222-May-06 17:15

bob16972

22-May-06 17:15

May I ask which version of VC++ you used? Reason I ask is because my time comparisons between VC++ 6.0 and VC++ 2003(Native) showed that the VC++ 2003 code embarassed the code from VC++ 6.0. This was without using any optimized compiler or settings. (Turning the optimized settings on VC++ 2003 and playing with the compiler optimization switches yielded less favorable results for some odd reason)

Since C# is from a newer generation of compilers, comparing it with VC++ 6.0 might not be as impressive for C++ programmers as comparing C# with VC++ 2003.

For what it's worth.

Anyway, thanks for sharing the results

Ed K23-May-06 14:06

Ed K

23-May-06 14:06

VS2005. I'm going to rewrite the code using C++/CLI just to see what it does. I'll put that up shortly.

ed

~"Watch your thoughts; they become your words. Watch your words they become your actions.
Watch your actions; they become your habits. Watch your habits; they become your character.
Watch your character; it becomes your destiny."
-Frank Outlaw.

Ryan Binns22-May-06 18:32

Ryan Binns

22-May-06 18:32

FWIW, I am a bit surprised by this. I would hesitate to suggest that perhaps the C# app hasn't been optimised very well or written as well as it could have been. I would expect the C++ app to be maybe 2 or 3 times faster, but not 7.

Ryan

"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"