More ROM Font Tweaks

- Add a signature to the start of the font map table to prevent accidentally applying/decompressing invalid font data.
- Improve Z280 font byte retrieval to properly restore the user mode bank.

Source/HBIOS/hbios.asm

@@ -8312,6 +8312,21 @@ FNT_SELECT:
 	LD	(FNT_BID),A		; SAVE IN WORKING VARIABLE
 	LD	D,FNT_BNKID		; D = BANK FOR FONT DATA
 	LD	HL,FNT_MAP		; POINT TO START OF MAP
+;
+	; FONT MAP TABLE BEGINS WITH A 2 BYTE SIGNATURE.  ATTEMPTING
+	; TO DECOMPRESS INVALID DATA WOULD BE VERY BAD.
+	CALL	FNT_BYTE		; FIRST SIGNATURE BYTE
+	;;;CALL	PC_SPACE		; ** DEBUG ***
+	;;;CALL	COUT			; ** DEBUG ***
+	INC	HL			; BUMP PTR
+	CP	'F'			; SHOULD BE 'F'
+	JR	NZ,FNT_SELECT_ERR	; IF MISMATCH, BAIL OUT W/ ERR
+	CALL	FNT_BYTE		; SECOND SIGNATURE BYTE
+	;;;CALL	COUT			; ** DEBUG ***
+	INC	HL			; BUMP PTR
+	CP	'M'			; SHOULD BE 'M'
+	JR	NZ,FNT_SELECT_ERR	; IF MISMATCH, BAIL OUT W/ ERR
+;	
 FNT_SELECT0:
 	CALL	FNT_BYTE		; LOAD THE FONT ID FROM MAP
 	;;;CALL	PC_SPACE		; ** DEBUG ***
@@ -8337,7 +8352,7 @@ FNT_SELECT1:
 	CALL	FNT_BYTE		; HI BYTE OF ADDRESS
 	LD	D,A			; PUT IN D
 	EX	DE,HL			; FULL ADDRESS TO HL
-
+;
 ;;;#IF ROMFONTS
 ;;;	CALL	PC_SPACE		; ** DEBUG ***
 ;;;	LD	A,'R'			; ** DEBUG ***
@@ -8347,7 +8362,7 @@ FNT_SELECT1:
 ;;;	LD	A,'H'			; ** DEBUG ***
 ;;;	CALL	COUT                    ; ** DEBUG ***
 ;;;#ENDIF
-
+;
 	POP	AF			; RECOVER FONT ID
 	AND	$80			; COMPRESSED FONT DATA?
 	JR	Z,FNT_SELECT2		; IF NOT, SKIP DECOMP
@@ -8383,8 +8398,6 @@ FNT_SELECT1:
 	LD	(FNT_BID),A		; UPDATE FNT_BID
 	LD	HL,$E000		; DEOMP BUF ADR TO HL
   #ELSE
-	;;;LD	A,'I'			; ** DEBUG ***
-	;;;CALL	COUT			; ** DEBUG ***
 	LD	DE,$E000		; DECOMP BUF ADR TO DE
 	CALL	DLZSA2			; DECOMPRESS
 	LD	HL,$E000		; DECOMP BUF ADR TO HL
@@ -8431,17 +8444,33 @@ FNT_BYTE:
 #IF (MEMMGR == MM_Z280)
 	; HBX_PEEK FOR Z280 DOES NOT WORK WHEN INVOKED WHILE IN
 	; SYSTEM MODE.  THIS SHOULD BE REVISITED.
-	LD	A,(FNT_BID)
-	PUSH	BC
-	PUSH	DE
-	PUSH	HL
-	LD	B,$00
-	CALL	Z280_BNKSEL
-	POP	HL
-	POP	DE
-	POP	BC
-	LDUP	A,(HL)
-	RET
+	;
+	; NOTE: WHEN WE GO TO RESTORE THE USER SPACE BANK, WE DON'T
+	; REALLY HAVE A GOOD SOURCE OF WHAT BANK ID TO RESTORE IT TO.
+	; IN THEORY, WE ARE BEING INVOKED EITHER DURING SYSTEM BOOT OR
+	; VIA HB_INVOKE.  DURING SYSTEM BOOT, THE USER BANK IS NOT
+	; RELEVANT.  FOR HB_INVOKE, THE PREVIOUS USER BANK WILL BE
+	; RECORDED IN HB_INVBNK.  SO, WE BLINDLY USE HB_INVBNK.  THIS
+	; WILL BE CORRECT WHEN INVOKED VIA HB_INVOKE AND SHOULD DO NO
+	; HARM WHEN INVOKED DURING SYSTEM BOOT.  THIS REALLY NEEDS TO
+	; BE REVIEWED.
+	;
+	LD	A,(FNT_BID)		; GET THE FONT BANK ID
+	PUSH	BC			; SAVE BC
+	PUSH	HL			; SAVE HL
+	LD	B,$00			; POINT TO USER PDRS
+	CALL	Z280_BNKSEL		; SELECT Z280 USER BANK
+	POP	HL			; RECOVER HL
+	PUSH	HL			; AND RESAVE IT
+	LDUP	A,(HL)			; GET THE BYTE FROM USER SPACE
+	PUSH	AF			; SAVE THE BYTE
+	LD	A,(HB_INVBNK)		; GET PRIOR BANK (SEE NOTE ABOVE)
+	LD	B,$00			; POINT TO USER PDRS
+	CALL	Z280_BNKSEL		; SELECT IT
+	POP	AF			; RECOVER VALUE
+	POP	HL			; RECOVER HL
+	POP	BC			; RECOVER BC
+	RET				; DONE
 #ELSE
 	PUSH	DE
 	LD	A,(FNT_BID)
@@ -9689,6 +9718,7 @@ FNT_CMPMASK	.EQU	$00
 ; FONT LOCATION MAP
 ;
 FNT_MAP:
+	.DB	'F','M'		; TABLE SIGNATURE
   #IFDEF USEFONT6X8
 	; FOR NOW, WE NEVER COMPRESS THE 6X8 FONT.  SEE TMS DRIVER.
 ;;;	.DB	FONTID_6X8 | FNT_CMPMASK

Source/HBIOS/romfonts.asm

@@ -35,6 +35,7 @@ FMT_8X16	.EQU	COMP
 ;
 ; FONT LOCATION MAP
 ;
+	.DB	'F','M'		; TABLE SIGNATURE
 #IF USEFONT6X8
 	.DB	FONTID_6X8 | FMT_6X8
 	.DW	FONT6X8

Source/HBIOS/vrc.asm

@@ -23,9 +23,11 @@ VRC_COLS	.EQU	64
 ;
 #DEFINE USEFONT8X8
 #DEFINE	VRC_FONT FONT8X8
-;
 VRC_FONTID	.EQU	FONTID_8X8
-;VRC_FONTID	.EQU	FONTID_6X8
+;
+;;;#DEFINE USEFONT6X8
+;;;#DEFINE VRC_FONT FONT6X8
+;;;VRC_FONTID	.EQU	FONTID_6X8
 ;
 TERMENABLE	.SET	TRUE		; INCLUDE TERMINAL PSEUDODEVICE DRIVER
 KBDENABLE	.SET	TRUE		; INCLUDE KBD KEYBOARD SUPPORT