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-   -   how to get the last key pressed without stopping the programm ? (http://www.daniweb.com/forums/thread17356.html)

WARburg Jan 22nd, 2005 11:05 am
how to get the last key pressed without stopping the programm ?
 
Hello Everyone!
That's my first post on this forum and I'd like to greet Everyone

I got a question about getting the last key pressed without stopping the programm. I know that getchar(), cin, getch() commands don't allow to do that. Have You any idea how to solve this problem?

I 'd like to do sth like that:

while(play){
char a;
a=get_last_key_without_stopping_the_programm(); // Do You know a function similiar to that?
switch(a){
case: 'W' :
do_sth();
break;
case 'S' :
do_sth_else();
break;
default:
do_default();
break;
}
a='*';
}

Narue Jan 22nd, 2005 11:09 am
Re: how to get the last key pressed without stopping the programm ?
 
>I know that getchar(), cin, getch() commands don't allow to do that.
getch (and getche) does, but it isn't a standard function and won't exist on all implementations. What compiler and operating system do you use?

Emmitt310 Jan 22nd, 2005 11:10 pm
Re: how to get the last key pressed without stopping the programm ?
 
Well, i think i know what you mean but it may help to know what kind of program you want to make. If it's a win32 application, checking for keyboard input during a loop is easy, but if this isnt a win32 application, keyboard input can still be checked, its just a bit more complicated.

mango_maniac Jan 22nd, 2005 11:29 pm
Re: how to get the last key pressed without stopping the programm ?
 
Quote:
Originally Posted by Emmitt310
Well, i think i know what you mean but it may help to know what kind of program you want to make. If it's a win32 application, checking for keyboard input during a loop is easy, but if this isnt a win32 application, keyboard input can still be checked, its just a bit more complicated.
First post here...I found this site looking for similar information. I'm using win32, but am totally unfamilliar with the windows.h header. I currently only know standard c++. How would one go about capturing keystrokes without waiting for <return> to be pressed. If you could demonstrate a compilable snippet, I'd be grateful.

MM

Emmitt310 Jan 22nd, 2005 11:51 pm
Re: how to get the last key pressed without stopping the programm ?
 
Ok well, the reason why it's easy in win32 to check for keyboard input is because you can check for a window message WM_KEYDOWN. Each key has a specific virtual key code, but, you can figure that out. Heres a simple code snippet that checks for if the key pressed was the esc key. (this is compilable if you know where to put it in your program)

switch(message)

{

     case WM_KEYDOWN:

          switch(wParam)

          {

               case VK_ESCAPE: //the virutal key code for esc

                    PostQuitMessage(0);

               break;

          }

     break;

     /*

     rest of the window procedure

     */

}

mango_maniac Jan 23rd, 2005 1:47 am
Re: how to get the last key pressed without stopping the programm ?
 
Quote:
Originally Posted by Emmitt310
Ok well, the reason why it's easy in win32 to check for keyboard input is because you can check for a window message WM_KEYDOWN. Each key has a specific virtual key code, but, you can figure that out. Heres a simple code snippet that checks for if the key pressed was the esc key. (this is compilable if you know where to put it in your program)

switch(message)

{

     case WM_KEYDOWN:

          switch(wParam)

          {

               case VK_ESCAPE: //the virutal key code for esc

                    PostQuitMessage(0);

               break;

          }

     break;

     /*

     rest of the window procedure

     */

}
Thanks for your help. I ended up doing it another way. I'm going to use something like the following. Do you see problems other than non-portability to systems that don't use ascii 13 for <return>?
#include <windows.h> 

#include <string>

#include <iostream>



using namespace std;



string getPassword();



int main(){

    

    string password("true");

    

    while (true){

        

        cout << " Input Password: ";

        password = getPassword();

        

        cout << "Verify Password: ";

        string pwverify = getPassword();

        

        if(password == pwverify) {break;}

        cout << "\nPassword mismatch.  Try again\n";

    }

    

    cout  << password << endl << password.size() << endl;

    

    system("pause");      

} 





string getPassword(){ 

    CHAR buffer[1] = ""; 

    DWORD w; 

    HANDLE console = GetStdHandle(STD_OUTPUT_HANDLE); 

    HANDLE keyboard = GetStdHandle(STD_INPUT_HANDLE); 

    INPUT_RECORD input[1]; 

    

    string pw;

    

     while(true) { 

        // Read an input record. 

        ReadConsoleInput(keyboard, input, 1, &w); 

         

        // Process a key down input event. 

        if(input[0].EventType == KEY_EVENT 

           && input[0].Event.KeyEvent.bKeyDown)

        { 

         

            // Retrieve the character that was pressed. 

            buffer[0] = input[0].Event.KeyEvent.uChar.AsciiChar; 

            

            if(buffer[0] == 13){ break;}  // enter pressed

            if(buffer[0] == 8){           // backspace

                pw.erase(pw.size()-1, 1);

                cout << "\b \b";

                continue;

            }

            

            if(buffer[0] != 0) {  // 0 is function keys, shift, ctrl, etc.

               cout << '*';

               pw += buffer[0];

            }

        } 

    }

    cout << endl;

    return pw;

}

WARburg Jan 23rd, 2005 10:09 am
Re: how to get the last key pressed without stopping the programm ?
 
Quote:
Originally Posted by Narue
>I know that getchar(), cin, getch() commands don't allow to do that.
getch (and getche) does, but it isn't a standard function and won't exist on all implementations. What compiler and operating system do you use?
I use Linux and Windows OS both and I'd like to make an application that is compatible with both of them(or needs just a few little changes). I try to make some snake-similar game in ASII. Compiler for Windows I use is Borland c++ builder 6.0 and for Linux g++).

Quetzalcoatl Jun 22nd, 2005 11:40 pm
Re: how to get the last key pressed without stopping the programm ?
 
How would I do a similar thing using TC(required for school), which cannot use Windows.h? (Uses DOS)

Marcosp Apr 7th, 2006 5:22 pm
Re: how to get the last key pressed without stopping the programm ?
 
About the solution given by Mango Maniac, does anyone knows how to do the same but using a Matlab mex file? I runned a modified version of his program in Visual C++ and it worked, but when I put the same code in the Matlab "mexfuction" the program compile and runs, but it doesn't respond when I press the keys. Here is the code:

#include <windows.h>
#include <string>
#include <iostream>
#include <stdio.h>
#include "C:\MATLAB7\extern\include\mex.h"


CHAR buffer[1] = "";
DWORD w;
HANDLE console = GetStdHandle(STD_OUTPUT_HANDLE);
HANDLE keyboard = GetStdHandle(STD_INPUT_HANDLE);
INPUT_RECORD input[1];

void mexFunction(int nlhs, mxArray *plhs[],int nrhs, const mxArray *prhs[]) {



mexPrintf("para cima");
while (1) {
ReadConsoleInput(keyboard, input, 1, &w);
if(input[0].EventType == KEY_EVENT && input[0].Event.KeyEvent.bKeyDown) {
buffer[0] = input[0].Event.KeyEvent.uChar.AsciiChar;
if(buffer[0] == 13) { break;}
if(buffer[0] == 56) {mexPrintf("para cima");}
if(buffer[0] == 50) {mexPrintf("para baixo");}
if(buffer[0] == 52) {mexPrintf("esquerda");}
if(buffer[0] == 54) {mexPrintf("direita");}

}
}
}

I'm using a windows XP, Matlab 7 and Visual C++ 6.0


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