action on pressing a key

[sdherzo]

hi
i am having an experiment with sensors. I calcualte the current distance top be d0 & print it out. But i need to get a reference point
So i want to set a reference point everytime i press a key& the distance then has to be caluculated
with "dref - do" .... & this " new" current distance has to be given out.Does anyone have ideas for the syntax !
thanks

case WM_PAINT:

...

...

d0 = s[1].d + (z_[0] * ( s[2].d - s[1].d )) + (z_[1] * ( s[3].d - s[1].d )) + (z_[2] * ( s[4].d - s[1].d ) )+ (z_[3] * ( s[5].d - s[1].d ));




y += CharHeight*2; /* Print */
sprintf (OutString,"d current = %lf ", d0);
TextOut(hDC, x, y, OutString, strlen (OutString));





SetTextAlign(hDC, TA_LEFT | TA_TOP);
EndPaint(hWndMain, &ps);
break;


case WM_KEYDOWN:

if (wParam == 'A') {


}

[danandu]

Initially set a reference point to your global static variable before you read the sensor data.
Then afterwards, use timer or threads to read keyboard input from the user to get a new reference value.

Always show the (Distance - Ref) on the screen.

Is this what you are looking for.

Please explain clearly

[sdherzo]

Initially set a reference point to your global static variable before you read the sensor data.
Then afterwards, use timer or threads to read keyboard input from the user to get a new reference value.

Always show the (Distance - Ref) on the screen.

Is this what you are looking for.

Please explain clearly

No . Let me try again :-)

Now i am giving out "d0" continuously on the screen. At a certain point i would like to save a particular value of d0 as my reference value"dref"by pressing a key.
The value that i would then like to output on the screen is "d0-dref"
where d0 is the values which i get continuooulsly & was shwoing earlier on teh screen & dref is the value i saved by pressing the key .

[danandu]

Handle the WM_KEYDOWN event and store the immediate value of d0 into a static dref.

Then from thereon, set a flag that a new ref has come.

Then always based on the flag's value

if flag is present
output d0 - dref
else
output d0 // only


...Also if you don't want to use the flag set dref initially to 0 and output always d0 - dref

simple!

[sdherzo]

thanks ! i think i will do it the second way ... first dref to 0 & then give dref a value...
but one question ; how should the key case look :
Like this ??

[code]
case WM_KEYDOWN:

if (wParam == 'A') {

d0 = dref ;
}

[code]

[zerver]

the other way,

dref = d0;

imho

[sdherzo]

hm ... this still does not work ... any suggestions ... ??

float dn,dref = 0;
 dn = d0-dref;

 d0 = s[1].d + (z_[0] * ( s[2].d - s[1].d )) + (z_[1] * ( s[3].d - s[1].d )) + (z_[2] * ( s[4].d - s[1].d ) )+ (z_[3] * ( s[5].d - s[1].d ));


y += CharHeight*2;            
sprintf (OutString,"d current = %lf    ", dn);           
  TextOut(hDC, x, y, OutString, strlen (OutString)); 

case WM_KEYDOWN:

       if (wParam == 'A')  {

        dref = d0;
	 }

[sdherzo]

still not working ... does anyone have an idea ??

my prob again ::

Now i am giving out "d0" continuously on the screen. At a certain point i would like to save a particular value of d0 as my reference value"dref"by pressing a key.
The value that i would then like to output on the screen is "d0-dref"
where d0 is the values which i get continuooulsly & was shwoing earlier on teh screen & dref is the value i saved by pressing the key .

[danandu]

Which project is this? is it a console project or an Win32 Application project.

You should handle the WM_KEYDOWN message from windows message handler which are available in the class wizard of MFC.

If you are using Win32, see MSDN to handle WM_KEYDOWN.

[sdherzo]

thanks i will try there. but isnt this the "WM_KEYDOWN" from msdn ?? i was just not sure what has to be written inside the Keydown ... i have called it from my winmessagehandler ...

[danandu]

yes it is!

[sdherzo]

thx ! i will try it !

[sdherzo]

hm .. i am doing something wrong i teh message handler ... i tried the method suggested by u & set d = d0- dref & set dref initially to 0 & put dref = d0 in the KEYDOWN message habndler ... still doesnt react on pressing the key
anyone sees the mistake ??

float dref = 0 ;

case WM_PAINT:
{
 d0 = ...;


 dn = (d0) - (dref);

            y += CharHeight*2;           
	   sprintf (OutString,"d current = %lf    ", dn);           
            TextOut(hDC, x, y, OutString, strlen (OutString)); 

}
case WM_KEYDOWN:

       if (wParam == 'A')  
	   
	  {


			
    dref = d0;

	  }

[zerver]

You need a break statement after each case in the switch...case block.

case WM_PAINT:
...
...
   break;

case WM_KEYDOWN:
...
...
   break;

[sdherzo]

i have a break ... just didnt post it here as i just wanted to post the important part of the code ;-) The problem lies inside my WM_KEYDOWN i think