Q44925: Status Line Input with a Blinking Cursor

Article: Q44925
Product(s): See article
Version(s): 1.00   | 1.00
Operating System(s): MS-DOS | OS/2
Keyword(s): ENDUSER | GETINPUT.ARC S12311.EXE | mspl13_basic
Last Modified: 13-SEP-1989

Question:

Is it possible in the Microsoft Editor to write an extension that will
accept a line of input from the user, preferably from the status line?

Response:

Version 1.02 of the Microsoft Editor offers a very convenient way to
do this. The GetString() callback function performs exactly this type
of input. Version 1.00 of the Editor, however, does not have such a
callback. It is possible to put together a routine that reads user
input using the ReadChar() function in M Version 1.00. However, since
ReadChar() waits for the next available character, there is no
convenient way to flash a cursor during input when using this
approach.

The function provided below is a status-line input routine that does
provide a flashing cursor. It uses the KbHook() and KbUnHook()
functions to prevent the editor from scanning the keyboard and then
reads the keyboard directly using the kbhit() and getch() functions
from the C run-time library.

An example C extension that demonstrates this function is available
in the Software\Data Library. This file can be found by searching on
the keyword GETINPUT, the Q number of this article, or S12311.
GETINPUT was archived using the PKware file-compression utility.

Status-Line Input Routine
-------------------------

#include "ext.h"
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <conio.h>

#define TRUE            1
#define FALSE           0

typedef unsigned        BOOL;

char *GetInput( int BufLen, char *theBuffer );

/* GetInput provides a means of getting user input from the status line
 * with a blinking cursor in a manner similar to M 1.02's GetString().
 * KbUnHook is used to capture keyboard input. KbHook restores normal
 * keyboard reading to the editor.
 *
 * Receives:    BufLen - Length of input buffer
 *              theBuffer - Pointer to input buffer
 *
 * Returns:     A pointer to the modified buffer, or NULL if ESC was
 *              used to cancel input.
 */
char *GetInput(
    int             BufLen,
    char            *theBuffer )
{
    char            Key;                        /* ASCII code of key */
    int             i = 0;                      /* Position in buffer */
    BOOL            CursorOn = TRUE;            /* State of cursor */
    int             FlashCount = 0;             /* Cursor state counter */
    int             CursorToggleCount = 100;    /* Iterations between changes
                                                   in cursor state */
    char            *r;                         /* Return pointer */

    /* Unhook the keyboard so that the editor no longer intercepts
     * keystrokes.
     */
    KbUnHook();

    /* Get keyboard input from user, stopping when ESC or ENTER is hit.
     * Characters not in the range of 32 to 127 are ignored.  Backspace
     * will work properly.  No more than (BufLen - 2) characters may
     * be entered.
     */
    do
    {
        /* Flash a cursor while waiting for the next keypress.
         */
        while( !kbhit() )
        {
            if( ++FlashCount == CursorToggleCount )
            {
                FlashCount = 0;
                CursorOn = !CursorOn;
                if( CursorOn )
                {
                    strcat( theBuffer, "_" );
                    DoMessage( theBuffer );
                }
                else
                {
                    theBuffer[i] = '\0';
                    DoMessage( theBuffer );
                }
            }
        }

        /* Snarf the key
         */
        Key = (char)getch();

        /* Handle backspace.
         */
        if( (Key == 8) && (i > 0) )
        {
            theBuffer[--i] = '\0';
            DoMessage( theBuffer );
        }

        /* Handle normal character.
         */
        if( (Key >=32) && (Key <= 127) && (i < BufLen - 2) )
        {
            theBuffer[i++] = Key;
            theBuffer[i] = '\0';
            DoMessage( theBuffer );
        }
    } while( (Key != 13) && (Key != 27) );

    /* If ESC was pressed, toss the input and NULL the input buffer,
     * else perform a little cleanup.
     */
    if( Key == 27 )
    {
        theBuffer[0] = '\0';
        DoMessage( theBuffer );
        r = NULL;
    }
    else
    {
        if( CursorOn )
            theBuffer[i] = '\0';
        DoMessage( theBuffer );
        r = theBuffer;
    }

    /* Restore normal keyboard input.
     */
    KbHook();

    return( r );
}

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