OpenEuphoria

Re: Password prompt routine

• Posted by freeplay at mailandnews.com Aug 18, 2001
• 454 views

Hello again,

Thanks for all the suggestions.  In the end I worked out that a:

   printf(1, "\r", {})

puts the cursor back to the beginnning of the line.  So to erase the last
character printed I would need to goto the beginning of the line, print out
the line again but have the last character in the line be a space (to
erase) and then goto the beginning of the line again and reprint the line
minus the last character.  You can detect a bit of cursor flicker but it's
good enough for me 

Here is the revised routine:

function getpw(sequence prompt)
  sequence   pw
  integer    key
  integer    lenpw

  printf(1, "%s", {prompt})

  pw = ""

  while 1 do
    lenpw = length(pw)

    key = wait_key()

    if ( (key = 10) or (key = 13) ) then
      if lenpw > 0 then
        exit
      end if
    end if

    if ( (key = 8) or (key = 127) ) then
      if (lenpw > 0) then
        if (lenpw = 1) then
          pw = ""
        else
          pw = pw[2..lenpw]
        end if

        lenpw = lenpw - 1

        printf(1, "\r%s", {prompt})
        for i = 1 to lenpw do
          printf(1, "*", {})
        end for
        printf(1, " ", {})

        printf(1, "\r%s", {prompt})
        for i = 1 to lenpw do
          printf(1, "*", {})
        end for
      end if
    end if

    if ( (key >= 32) and (key <= 126) ) then
      if (lenpw < MAXPWLENGTH) then
        printf(1, "*", {})
        pw = append(pw, key)
      end if
    end if
  end while

  printf(1, "\n", {})

  return(pw)

end function

At 00:00 18/08/01 +0100, I wrote:
>
>Hello again folks!
>
>Ok I've got a routine I've called "getpw".  You give it a prompt string, it
>displays this prompt and then accepts a line of input which is terminated
>when you press return.  The routine returns the typed line.  When you type
>a character it prints a single '*' character so you know you've typed the
>character but has the nice effect that what you type is hidden from prying
>eyes.  Hence GET PassWord 
>
>I detect the backspace key (ASCII code 8) and deal with it accordingly
>(i.e. throw away the last character typed).  I was hoping to print a
>"backspace, space, backspace" sequence to rub out the last '*' character
>but can't get this to work.  Instead I'm currently printing a '#' character
>to indicate that the last character has been "erased".  If someone can help
>me achieve the "backspace, space, backspace" effect I'm after I'd be very
>grateful.
>
>Regards.
>
>FP.
<snipped>