*****************************************************************************
Move_Cursor:
		cs:move.w   4(si), ax                   ;Get the in/decrement.
		push.w      ax                          ;Save the (De/In)crement.
		
		cs:lds      HexSource, si               ;Get the screen position.
		cs:move.w   HexCursor, bx               ;Get the cursor position.

		or.w        ax, ax                      ;Clear AX.
		bpl.s       _Cursor_Down                ;Going up or down?

		neg.w       ax                          ;We want to see if the difference
		sub.w       si, bx                      ;between the screen start and the
		cmp.w       bx, ax                      ;cursor position is less than the
		ble.s       _On_Screen                  ;amount we want to move up the
		bra.s       _Off_Screen                 ;screen.

_Cursor_Down:
		sub.w       si, bx
		move.w      #!TOTALCHARS, cx
		sub.w       bx, cx
		
		cmp.w       cx, ax
		blt.s       _On_Screen

_Off_Screen: 
		pop.w       ax
		cs:add.w    ax, HexCursor
		add.w       ax, si
		cs:move.w   si, HexSource
		rts
*****************************************************************************
_On_Screen:
		pop.w       bx                          ; Set the new cursor
		cs:add.w    bx, HexCursor               ; Memory pointer.

		cs:move.b   CursorY, al                 ; See if we are stil
		and.w       #$ff, ax                    ; on the same X line.
		add.w       bx, ax
		bpl.s       _going_up
				
		add.w       #!NUM_CHARS*2, ax
		cs:div.b    CharsPerLine
		cs:sub.b    al, CursorX
		bra.s       _set_Y_pos
				
_going_up:
		cs:div.b    CharsPerLine
		cs:add.b    al, CursorX                 ; Save the new X pos.

_set_Y_pos:
		cs:move.b   ah, CursorY                 ; Save the new Y pos.
		rts
*****************************************************************************
HexDisplay:
		cs:les      TargetData, di
		cs:lds      HexSource, si
		eor.w       ax, ax                  ; Line number count
				
Hex_Display_lp:
		push.w      ax
		lea         160(di), di             ;Move to the next line.
		push.w      di

		bsr.w       Draw_Line               ;Do a line, ooops..
				
		pop.w       di
		pop.w       ax
		inc         ax
		cmp.w       #!NUM_LINES, ax
		blt.s       Hex_Display_lp
		rts
*****************************************************************************
Draw_Line:
		cs:move.b   AddrCol, ah             ;
		move.w      ds, bx                  ;
		move.w      #4, cx                  ;
		bsr.w       Print_Hex               ;
		bsr.w       Print_Colon1            ;
		cs:move.b   AddrCol, ah             ;
		move.w      si, bx                  ;
		move.w      #4, cx                  ;
		bsr.w       Print_Hex               ;
				
		dc.b        $66                     ; Extend...
		eor.w       ax, ax                  ; Clear AX
		dc.b        $66                     ; Extend...
		stos.w      #2, di                  ; Add a space.
		bsr.w       Print_Colon1            ; Print a colon.
		move.w      #0, dx                  ;
				
draw_lp:
		cs:cmp.w    HexCursor, si
		bne.s       _colour1
		move.b      #!HIGH_COL, ah
		bra.s       _colour_set
			  
_colour1:
		cs:move.b   HexColB, ah
		test.w      #1, si
		beq.s       _colour_set
		cs:move.b   HexColA, ah
				
_colour_set:    
		lods.b
		bsr.w       HPrint_Char

		move.b      al, bl
		move.b      #2, cl
		bsr.w       Print_Hex
				
		inc.b       dl
		cmp.b       #!NUM_CHARS, dl
		bne.s       draw_lp

		bsr.w       Print_Colon1            ; Print a colon.
		eor.w       ax,ax                   ; Clear AX.
		stos.w                              ; Print a space.
		rts
*****************************************************************************
HPrint_Char:
		push.w      di
		push.w      ax
		move.w      dx, bx
		rol         #1, bx
		lea         !NUM_CHARS*4+4(di), di
		sub.w       bx, di
		cmp.b       #32, al
		bge.s       Hprint_it
		move.b      #'.', al
Hprint_it:
		stos.w
		pop.w       ax
		pop.w       di
		rts
*****************************************************************************
IncSegment:
		bsr.w       GetSourceVar
		cs:inc.w    2(si)
		dc.b        $80,$FC,$91
		bne.s       _Inc_End
		cs:add.w    #99, 2(si)
_Inc_End:
		rts
*****************************************************************************
DecSegment:
		bsr.w       GetSourceVar
		cs:dec.w    2(si)
		dc.b        $80,$FC,$8D
		bne.s       _Dec_End
		cs:sub.w    #99, 2(si)
_Dec_End:
		rts
*****************************************************************************
Goto:
		bsr.w       GetSourceVar
		push.w      si                      ;Save SI.

		move.b      #!BC, ah
		move.w      #17, cx
		move.w      #1, bx
		bsr.w       DrawBox
		
		push.w      di
		sub.w       #160, di
		move.w      #GoPrompt, dx           ;The message.
		bsr.w       Print_String            ;Print it.
		pop.w       di
		lea         6(di), di

		move.b      #1, bh                  ;Set we allow a colon seperator
		move.w      #$404, cx               ;Set 4 characters either side of colon.
		bsr.w       Input_Hex               ;Get Hex input.

		pop.w       di                      ;Get our storage address.
		
		cmp.w       #$11b, ax               ;Escape aborts...
		beq.s       _Goto_Exit              ;Quit.

		move.w      dx, si                  ;Pre-load the data
		
		eor.w       bx, bx                  ;Clear our work space
		cmp.b       #4, ch                  ;Check if we have a segment
		beq.s       _Offset_lp              ;No segment to go

_GetSeg_lp:
		asl.w       #4, bx
		cs:move.b   (si), al
		or.b        al, bl
		inc.b       ch
		inc.w       si
		cmp.b       #4, ch
		bne.s       _GetSeg_lp
		
		cs:move.w   bx, 2(di)
		inc.w       si                      ;Set the segment.
		eor.w       bx, bx

_Offset_lp:
		asl.w       #4, bx
		cs:move.b   (si), al
		or.b        al, bl
		inc.b       cl
		inc.w       si
		cmp.b       #4, cl
		bne.s       _Offset_lp

		cmp.w       #CodSource, di          ;Check which display mode.
		beq.s       _Not_Hex

		cs:move.w   HexCursor, cx           ;A nifty trick...
		cs:sub.w    HexSource, cx           ;Add the screen to goto address.
		
		add.w       bx, cx
		cs:move.w   cx, HexCursor
_Not_Hex:
		cs:move.w   bx, (di)                ;Set the offset. 

_Goto_Exit:
		rts
*****************************************************************************
Input_Hex:
		move.w      #StackBot, si       ;Where to store the input.
		move.w      si, dx              ;Save the start address.
		
Input_Hex_lp:
		bsr.w       Get_KeyStroke       ;Get some input.
		
		or.w        ax, ax              ;Check for input...
		beq.s       Input_Hex_lp        ;None, so loop again.

		cmp.w       #$11b, ax           ;Escape pressed?
		beq.s       In_Hex_Out

		cmp.b       #$d, al             ;Carriage return?
		bne.s       _Check_Delete       ;Yep, so quit...
		cs:cmp.b    #':', -1(si)        ;Can't have a colon ending the address
		beq.s       Input_Hex_lp
		bra.s       In_Hex_Out
		
_Check_Delete:
		cmp.b       #8, al              ;Delete?
		bne.s       _Check_Colon        ;No, continue with checks...
		
		cmp.w       si, dx              ;Anything to delete?
		beq.s       Input_Hex_lp        ;Nope! loop again.
		dec.w       si                  ;Move back one.
		
		cs:cmp.b    #':', (si)          ;Was the last character a colon?
		bne.s       _sub_hexchar
		xchg.b      ch, cl              ;Swap the Lft/Rgt counters.
		inc.b       bh
		bra.s       _skip_hexchar       ;All done...

_sub_hexchar:
		inc.b       cl

_skip_hexchar:
		move.b      #!BC, ah
		eor.b       al, al
		sub.w       #2, di
		es:move.w   ax, (di)
		bra.s       Input_Hex_lp
		
_Check_Colon:
		cmp.b       #':', al
		bne.s       _Check_Hex
		
		or.b        bh, bh
		beq.s       Input_Hex_lp
		cmp.w       si, dx
		beq.s       Input_Hex_lp
		
		xchg.b      ch, cl
		dec.b       bh
		move.b      al, ah
		bra.s       In_Col_Prnt

_Check_Hex:
		or.b        cl, cl
		beq.s       Input_Hex_lp
		
		move.b      al, ah

		sub.b       #'0', ah
		bmi.s       Input_Hex_lp
		cmp.b       #9, ah
		ble.s       In_Hex_Prnt

		and.b       #$df, al
		move.b      al, ah
		sub.b       #$37, ah
		cmp.b       #$a, ah
		blt.s       Input_Hex_lp
		cmp.b       #$f, ah
		bgt.s       Input_Hex_lp

In_Hex_Prnt:
		dec.b       cl

In_Col_Prnt:
		cs:move.b   ah, (si)
		inc.w       si

		cs:move.b   #!BH, ah
		stos.w
		bra.w       Input_Hex_lp

In_Hex_Out:
		or.b        bh, bh
		bpl.s       _Skip_Swap
		xchg.b      cl, ch

_Skip_Swap:
		rts
*****************************************************************************
GetSourceVar:
		move.w      #CodSource, si
		dc.b        $2E,$81,$3E
		dc.w        PQ1-2, CodDisplay-PQ1
		beq.s       _Hex_Var
		move.w      #HexSource, si
_Hex_Var:
		rts
*****************************************************************************
GoPrompt        dc.b  " Enter Address ",0
CharsPerLine    dc.w  !NUM_CHARS
*****************************************************************************