C / C++ / MFC

Handling KeyBoard messages/accelerators handling in MFC dialog based applications

18-Aug-21 22:19

1. x -= y means subtract y from x and store the result in x.
2. The same for addition.
3. If not equals.
4. if equals.

A single = sign means assign the value on the right to the variable on the left.

ForNow30-Jul-21 4:07

Re: Handling KeyBoard messages/accelerators handling in MFC dialog based applications

30-Jul-21 4:07

I saw an article about this on the codeproject by

Nish Nishant

and it seems pretty simple first let me post his code

BOOL CPreTransTestApp::ProcessMessageFilter(int code, LPMSG lpMsg) 
{
    if(m_haccel)
    {
        if (::TranslateAccelerator(m_pMainWnd->m_hWnd, m_haccel, lpMsg)) 
            return(TRUE);
    }
	
    return CWinApp::ProcessMessageFilter(code, lpMsg);
}

Now let me expain my scenrio I am running a client server TCPI /IP program the server is a z/os mainframe and the client is a MFC C\C++ windows based program which displays data from the mainframe
I can have up to 4 modeless dialog boxes which display data in a rich edit their pointers live are my derived CWinApp

CDBGRApp

I did all the front end work created the accelarator in my resource file had it as selection in my menu "MENUITEM" and put the appropriate message map and message handler in derived CDialog CProgDebug

I then inserted the following code into my derived CWinAppp CDBGRApp

OOL CDBGRApp::ProcessMessageFilter(int code, LPMSG lpMsg)
{
	
	if (m_haccel)
	{
		if (debugger[0] == NULL);
		else
		{
			if (debugger[0]->m_hWnd == NULL);
			else
			{
			::TranslateAccelerator(debugger[0]->m_hWnd, m_haccel, lpMsg);
			return(TRUE);
			}

		}
	}
		return CWinApp::ProcessMessageFilter(code, lpMsg);
	}

debugger[0] is the first of an array defined as

CProgDebug *debugger[4];

After I created the CProgDebug with it rich edit the window didnt seem to take any input mouse or keyboard

Nish in his code didnt specify that after doing TranslateAccelrator and would have to do TranslateMessage and DispatchMessage from the msg structure as I assume that is being taken care of somewhere down the line by the frameWork

Graham Breach30-Jul-21 4:40

Re: Handling KeyBoard messages/accelerators handling in MFC dialog based applications

30-Jul-21 4:40

You missed out a test - you should only return TRUE if TranslateAccelerator() succeeds.

By the way, your if(something); else is quite confusing.

ForNow30-Jul-21 5:59

Re: Handling KeyBoard messages/accelerators handling in MFC dialog based applications

30-Jul-21 5:59

I am changing that so if I get a zero from from

TranslateAccelerator(

that means (and can you confirm this) it wasnt one the key strokes I defined right not necessarly an error I would get a zero from TranslateAccelerator maybe thats the problem in my logic

Graham Breach30-Jul-21 6:29

Re: Handling KeyBoard messages/accelerators handling in MFC dialog based applications

30-Jul-21 6:29

Here's the Windows docs page: TranslateAcceleratorA function (winuser.h) - Win32 apps | Microsoft Docs[^]

The function returns nonzero when it successfully translates the accelerator, which is when you should not pass the message through to the default handler. Your code is bypassing the default handler entirely when your h_accel and debug variables are set (without checking if the message was a translated keycode).

ForNow30-Jul-21 7:23

Re: Handling KeyBoard messages/accelerators handling in MFC dialog based applications

30-Jul-21 7:23

thanks if so this code by Nish

BOOL CPreTransTestApp::ProcessMessageFilter(int code, LPMSG lpMsg) 
{
    if(m_haccel)
    {
        if (::TranslateAccelerator(m_pMainWnd->m_hWnd, m_haccel, lpMsg)) 
            return(TRUE);
    }
	
    return CWinApp::ProcessMessageFilter(code, lpMsg);
}

is incorrect

this code from Microsoft docs is correct

MSG msg;
BOOL bRet;

while ( (bRet = GetMessage(&msg, (HWND) NULL, 0, 0)) != 0)
{
    if (bRet == -1) 
    {
        // handle the error and possibly exit
    }
    else
    { 
        // Check for accelerator keystrokes. 
     
        if (!TranslateAccelerator( 
                hwndMain,      // handle to receiving window 
                haccel,        // handle to active accelerator table 
                &msg))         // message data 
        {
            TranslateMessage(&msg); 
            DispatchMessage(&msg); 
        } 
    } 
}

as it has not TranlateAccelterator wouldnt you agree

Graham Breach30-Jul-21 8:17

Re: Handling KeyBoard messages/accelerators handling in MFC dialog based applications

30-Jul-21 8:17

They are both correct.

The first one skips the default handler if the accelerator has been translated.

The second one calls the default handler if the accelerator has not been translated.

ForNow30-Jul-21 8:28

Re: Handling KeyBoard messages/accelerators handling in MFC dialog based applications

30-Jul-21 8:28

thank you so much for your patience me However the way mine is set is INCORRECT as I dont have an IF testing for the validity of the TranlateAccelarator and that is why my keyboard gets locked becasue I havr return TRUE for all

Graham Breach30-Jul-21 8:49

Re: Handling KeyBoard messages/accelerators handling in MFC dialog based applications

30-Jul-21 8:49

Yes, that's right.

Richard MacCutchan30-Jul-21 4:56

Re: Handling KeyBoard messages/accelerators handling in MFC dialog based applications

30-Jul-21 4:56

C++

if (debugger[0] == NULL);
else
{

What is wrong with

C++

if (debugger[0] != NULL)
{

ForNow30-Jul-21 5:11

Re: Handling KeyBoard messages/accelerators handling in MFC dialog based applications

30-Jul-21 5:11

got a compile error when it I did that but I had semi colon after the open paren so the logic should work regardless I'll work to change it

thanks

Richard MacCutchan30-Jul-21 5:28

Re: Handling KeyBoard messages/accelerators handling in MFC dialog based applications

30-Jul-21 5:28

ForNow wrote:
I had semi colon after the open paren

Dave Kreskowiak30-Jul-21 6:10

Dave Kreskowiak

30-Jul-21 6:10

Not to mention the semi-colons on the end of the if line, essentially making it entirely useless.

Asking questions is a skill
CodeProject Forum Guidelines
Google: C# How to debug code
Seriously, go read these articles.

Dave Kreskowiak

Re: Handling KeyBoard messages/accelerators handling in MFC dialog based applications

Richard MacCutchan30-Jul-21 6:15

Dynamically creating CToolBar

30-Jul-21 6:15

Yes, I have never seen that done deliberately before.

Benjamin Bruno30-Jul-21 3:54

Benjamin Bruno

30-Jul-21 3:54

hi
I want to create CtoolBar dynamically, without the resource( RC file) entries.
Load image to Toolbar and set size based on certain condition.
RC file entries makes it predefined.

your help is much appreciated.

Re: Dynamically creating CToolBar

Richard MacCutchan30-Jul-21 4:52

Re: RGB image to CMYK gdi+

30-Jul-21 4:52

Then you need to write the code to create the buttons, allocate their ID values and images, and add them to the CToolBar object. See CToolBar Class | Microsoft Docs[^], and Toolbar - Win32 apps | Microsoft Docs[^].

RGB image to CMYK gdi+

Gopi Nath15-Jul-21 22:25

Gopi Nath

15-Jul-21 22:25

Hello,

I am trying to adjust the color balance (CYMK) of an image like this is in photoshop or some other applications.

From examples, i tried changing the current RGB to CMYK (for each pixel) using the below code.

for (int i = 0; i < width; i++)
	{
		for (int j = 0; j < height; j++)
		{
			tmpbmp->GetPixel(i, j, &clr);

			R = clr.GetR();
			G = clr.GetG();
			B = clr.GetB();

			c = _cyanclr / 255.0; // _cyanclr - user input in %
			m = _magentaclr / 255.0;
			y = _yellowclr / 255.0;
			k = _blackclr / 255.0;

			rr = c * (1.0 - k) + k;
			gg = m * (1.0 - k) + k;
			bb = y * (1.0 - k) + k;

			rr = (1.0 - rr) * 255.0 + 0.5;
			gg = (1.0 - gg) * 255.0 + 0.5;
			bb = (1.0 - bb) * 255.0 + 0.5;
			
           // here i dont know how to adjust new RGB with old one
			R += rr;
			G += gg;
			B += bb;

			R = R < 0 ? 0 : (R > 255) ? 255 : R;
			G = G < 0 ? 0 : (G > 255) ? 255 : G;
			B = B < 0 ? 0 : (B > 255) ? 255 : B;			

			output->SetPixel(i, j, Gdiplus::Color(R, G, B));
		}
	}

With this code, i am not getting the same result like in photoshop and other applications.

I am not sure whether I am doing in right method or not.

Please suggest.

I am using C++ and gdi+.

Regards,
Gopinath.

Richard MacCutchan17-Jul-21 6:15

Re: RGB image to CMYK gdi+

17-Jul-21 6:15

It is not clear exactly what your problem is or what adjustments you are trying to make to your colours. Maybe you could explain with some examples.

RedDk16-Oct-21 8:24

RedDk

16-Oct-21 8:24

Whatever works is the right method. There's no "not". Unless all one does is repost code they dug up from elsewhere and hasn't the foggiest idea what they're doing THAT for.
Thumbs Down | :thumbsdown:

Exception handler

Drugodrf14-Jul-21 6:39

Drugodrf

14-Jul-21 6:39

I'm looking for a way to catch exceptions due to software or hardware errors and prevent my solution from breaking brutally, but I can't find anything complete.
I have read the two main ways of handling exceptions, C ++ and SEH, but it seems to me that both do not include all cases that can happen.
Can anyone help me ?

Greg Utas14-Jul-21 9:15

Greg Utas

14-Jul-21 9:15

I think this article[^] might help.

Robust Services Core | Software Techniques for Lemmings | Articles
The fox knows many things, but the hedgehog knows one big thing.

SeeSharp214-Jul-21 10:31

SeeSharp2

14-Jul-21 10:31

Drugodrf wrote:
include all cases that can happen.

There is no way to handle all cases. For example, what it the power cord is pulled? Or the OS crashes?

Follow best practices and you'll get most all of the likely happenings.

Drugodrf15-Jul-21 6:15

Drugodrf

15-Jul-21 6:15

Greg Utas, thanks for article: i read it as soon as possible.

DevParty: ok, all cases is too much, but most of the cases?
I've tried both ways (exception C++ and SEH), but, for example, they catch division by zero, but not a string copy error.