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Used by the routines at MAIN_EXEC and INPUT.
The editor is called on two occasions:
First the 'error stack pointer' is saved and an alternative address provided.
EDITOR 03884 LD HL,(23613) The current value of ERR-SP is saved on the machine stack.
03887 PUSH HL
This entry point is used by the routine at ED_ERROR.
ED_AGAIN 03888 LD HL,4223 This is ED_ERROR.
03891 PUSH HL Any event that leads to the error handling routine (see ERR-SP) being used will come back to ED_ERROR.
03892 LD (23613),SP
A loop is now entered to handle each keystroke.
ED_LOOP 03896 CALL WAIT_KEY Return once a key has been pressed.
03899 PUSH AF Save the code temporarily.
03900 LD D,0 Fetch the duration of the keyboard click (PIP).
03902 LD E,(IY-1)
03905 LD HL,200 And the pitch.
03908 CALL BEEPER Now make the 'pip'.
03911 POP AF Restore the code.
03912 LD HL,3896 Pre-load the machine stack with the address of ED_LOOP.
03915 PUSH HL
Now analyse the code obtained.
03916 CP 24 Accept all character codes, graphic codes and tokens.
03920 CP 7 Also accept ','.
03924 CP 16 Jump forward if the code represents an editing key.
03926 JR C,ED_KEYS
The control keys - INK to TAB - are now considered.
03928 LD BC,2 INK and PAPER will require two locations.
03931 LD D,A Copy the code to D.
03932 CP 22 Jump forward with INK and PAPER.
AT and TAB would be handled as follows:
03936 INC BC Three locations required.
03937 BIT 7,(IY+55) Jump forward unless dealing with 'INPUT LINE...' (bit 7 of FLAGX set).
03944 CALL WAIT_KEY Get the second code and put it in E.
03947 LD E,A
The other bytes for the control characters are now fetched.
ED_CONTR 03948 CALL WAIT_KEY Get another code.
03951 PUSH DE Save the previous codes.
03952 LD HL,(23643) Fetch K-CUR.
03955 RES 0,(IY+7) Signal 'K mode' (reset bit 0 of MODE).
03959 CALL MAKE_ROOM Make two or three spaces.
03962 POP BC Restore the previous codes.
03963 INC HL Point to the first location.
03964 LD (HL),B Enter first code.
03965 INC HL Then enter the second code which will be overwritten if there are only two codes - i.e. with INK and PAPER.
03966 LD (HL),C
03967 JR ADD_CH_1 Jump forward.
This entry point is used by the routine at ED_SYMBOL.
The address of this entry point is found in the initial channel information table.
The following subroutine actually adds a code to the current EDIT or INPUT line.
ADD_CHAR 03969 RES 0,(IY+7) Signal 'K mode' (reset bit 0 of MODE).
03973 LD HL,(23643) Fetch the cursor position (K-CUR).
03976 CALL ONE_SPACE Make a single space.
ADD_CH_1 03979 LD (DE),A Enter the code into the space and set K-CUR to signal that the cursor is to occur at the location after. Then return indirectly to ED_LOOP.
03980 INC DE
03981 LD (23643),DE
03985 RET
The editing keys are dealt with as follows:
ED_KEYS 03986 LD E,A The code is transferred to the DE register pair.
03987 LD D,0
03989 LD HL,3993 The base address of the editing keys table.
03992 ADD HL,DE The entry is addressed and then fetched into E.
03993 LD E,(HL)
03994 ADD HL,DE The address of the handling routine is saved on the machine stack.
03995 PUSH HL
03996 LD HL,(23643) The HL register pair is set to K-CUR and an indirect jump made to the required routine.
03999 RET
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