FotS

At() - Screen positioning uses the “At” function for cursor positioning. It uses less program space and is arguably more intuitive than a stand-alone LOCATE command. Note that because it produces a string, strictly a ; or + should be used when printing following output, but because of a quirk in how lines are parsed when printing, it can be omitted resulting in the pleasing.

Print At(10,10) "fred"

VTKey$() - Key Scanning for non-ASCII keys (Function keys, Home, PageUp etc.) is a real pain in the neck. The Function VTKey$() can be used to replace Inkey$ and will return either the ASCII value of the key pressed or a predictable three-letter token for any of the special keys.

Your console emulator must support ANSI screen/keyboard codes - usually defined as VT52, VT100 etc. emulation. Personally I use PuTTY.

Dependancies

Option Base 0
Requires the LTrim and RTRIM Functions (VB work-a-like) or the equivalent LTrim RTrim CFunctions (note this latter does not treat TABs as white-space and so are not trimmed).

Example Usage

	Option Base 0
	InitVTKeys
	
Main:' just something to demonstrate usage

	Clr ' clear the screen

	For n=1 To 25 ' print out a diagonal line of numbers
		Print At(n,n);Str$(n)
	Next

	Window 6,10 ' define  window
	For n=1 To 25 ' demonstrate the contained area of the screen
		Print n
	Next
	
	Window 1,25
	
	Clr
	
	a$=StrEdit$("Fred",10,10,60)
	
	? At(1,1);a$

The Code

  Function At(v As Integer,h As Integer) As String
     At=Chr$(27)+"["+Str$(v)+";"+Str$(h)+"H"
  End Function

  Sub Clr
    Window 1,25' redefine the whole screen
    Print Chr$(27)+"[2J";
  End Sub

  Sub Window(Pt As Integer, Pb As Integer)
    'defines a window from line t to line b and positions the cursor in the start of it
    'Clr and At still work on the whole screen. Only when scrolling (or CRLF) enteres the
    'window does it capture the cursor. Note 0<Pt<Pb is enforced by the console emulator
     Print Chr$(27)+"["+Str$(Pt)+";"+Str$(Pb)+"r"+At(Pt,1);
  End Sub
	
  Function VTKey$() ' replaces Inkey$ and will return the character pressed or the special token _xx
     Local a$
     VTKey$=Inkey$
     Pause 25 ' give the remaining sequence (if any) time to arrive. 
              'Any less than 25 can give mis-reads of expanded tokens
     Do
       a$=Inkey$:If a$="" Then Exit Do  ' jump out when we are scanning ""
       VTKey$=VTKey$+a$                 ' build up the character codes
     Loop		
     If Len(VTKey$)>1 Then VTKey$=ExpandKey(VTKey$)
  End Function
	
  Function ExpandKey(c$) As String' called from VTKey$
    Local n
    For n=0 To Kct
	If KCode$(n)=c$ Then ExpandKey=KTkn$(n):Exit Function
    Next
    ExpandKey=""
  End Function

  Sub InitVTKeys
	Dim Integer Kct
	Local x$
	Local Integer q
KeyData:
	' <esc> [
	Data 27,91,68,0,"_LT"
	Data 27,91,67,0,"_RT"
	Data 27,91,65,0,"_UP"
	Data 27,91,66,0,"_DN"
	Data 27,91,49,126,0,"_HM"
	Data 27,91,50,126,0,"_IN"
	Data 27,91,51,126,0,"_DL"
	Data 27,91,52,126,0,"_ED"
	Data 27,91,53,126,0,"_PU"
	Data 27,91,54,126,0,"_PD"
	Data 27,91,55,126,0,"_HM"
	Data 27,91,56,126,0,"_ED"
	Data 27,91,49,49,126,0,"_F1"
	Data 27,91,49,50,126,0,"_F2"
	Data 27,91,49,51,126,0,"_F3"
	Data 27,91,49,52,126,0,"_F4"
	Data 27,91,49,53,126,0,"_F5"
	Data 27,91,49,55,126,0,"_F6"
	Data 27,91,49,56,126,0,"_F7"
	Data 27,91,49,57,126,0,"_F8"
	Data 27,91,50,48,126,0,"_F9"
	Data 27,91,50,49,126,0,"_FA"
	Data 27,91,50,51,126,0,"_FB"
	Data 27,91,50,52,126,0,"_FC"
	Data 255		

	Restore KeyData 'determine size of the key table
	Do
	  Read q
	  If q=255 Then Exit Do
	  If q=0 Then Kct=Kct+1:Read x$
	Loop

	Dim KCode$(Kct-1) Length 5
	Dim KTkn$(Kct-1) Length 3

	Restore KeyData
	Kct=0
	Do
	  Read q
	  If q=255 Then Kct=Kct-1:Exit Do ' adjust Kct to point at top of key array
	  If q=0 Then
	    Read KTkn$(Kct)
	    Kct=Kct+1
	  Else
	    KCode$(Kct)=KCode$(Kct)+Chr$(q)
	  EndIf
	Loop

	'Here Kode$(n) is the key sequences we get from the keypress
	'     KTkn$(n)  is the shorthand code name _xx
  End Sub

FotS

Table of Contents

VT Console Pack. Screen Positioning, Sane Key Scanning And a String Editing Routine

Dependancies

Example Usage

The Code