From d294fb6d09da8e862c3a70aeaaa2e1cfd377a76a Mon Sep 17 00:00:00 2001
From: Wayne Warthen <wwarthen@gmail.com>
Date: Wed, 3 Apr 2024 11:52:18 -0700
Subject: [PATCH] Reset Video Hardware on OS Reset

- When an OS performs a reset operation, the HBIOS hook has been extended to automatically reset the video hardware of the CRT device (if it exists).
- This should go a long way toward fixing corrupt video after an application is run that reprograms the video hardware.
- An OS reset may or may not be performed when an application exits depending on the behavior of the application.  So, if an application exits without initiating a reset, then the video will not be reset.  Most applications that muck with the video chip directly will perform the reset at exit, so this is not normally an issue.
- If the OS encounters an error (such as drive not ready when doing a DIR), the error message may be erased by this new behavior depending on the specific scenario.
---
 Source/HBIOS/hbios.asm |  5 +++++
 Source/HBIOS/term.asm  | 38 ++++++++++++++++++++++++++++++++++++--
 Source/ver.inc         |  2 +-
 Source/ver.lib         |  2 +-
 4 files changed, 43 insertions(+), 4 deletions(-)

diff --git a/Source/HBIOS/hbios.asm b/Source/HBIOS/hbios.asm
index 279e3110..4dee78c9 100644
--- a/Source/HBIOS/hbios.asm
+++ b/Source/HBIOS/hbios.asm
@@ -4269,6 +4269,8 @@ SYS_RESCOLD:
 SYS_RESUSER:
 ;
 #IF (CPUFAM == CPU_Z180)
+;
+; IF Z180 CPU, CHECK FOR INVALID OPCODE FLAG AND HANDLE IF SO
 ;
 	IN0	A,(Z180_ITC)		; GET ITC REGISTER
 	XOR	$80			; PRECLEAR TRAP BIT
@@ -4305,6 +4307,9 @@ SYS_RESUSER2:
 	JP	NEWLINE			; FORMATTING & EXIT
 ;
 #ENDIF
+;
+	; RESET ACTIVE VIDEO DISPLAY ATTACHED TO EMULATOR
+	CALL	TERM_RESET
 ;
 	RET				; ELSE RETURN WITH USER RESET VECTOR IN HL
 ;
diff --git a/Source/HBIOS/term.asm b/Source/HBIOS/term.asm
index 5e569516..dae95e44 100644
--- a/Source/HBIOS/term.asm
+++ b/Source/HBIOS/term.asm
@@ -31,6 +31,8 @@ TERM_PREINIT:
 	XOR	A			; SIGNAL SUCCESS
 	RET				; DONE
 ;
+#IF (TERMENABLE)
+;
 ;======================================================================
 ; TERMINAL DRIVER - ATTACH
 ;======================================================================
@@ -47,8 +49,6 @@ TERM_PREINIT:
 ;   DE: VDA DRIVER'S DISPATCH ADDRESS
 ;   HL: VDA DRIVER'S INSTANCE DATA
 ;
-#IF (TERMENABLE)
-;
 TERM_ATTACH:
 ;
 	LD	A,(TERM_DEVCNT)		; GET NEXT DEVICE NUMBER TO USE
@@ -83,6 +83,34 @@ TERM_ATTACH:
 	RET				; RETURN
 ;
 ;======================================================================
+; TERMINAL DRIVER - RESET
+;======================================================================
+;
+; RESET THE FULL EMULATION STACK INCLUDING THE UNDERLYING VDA.
+; THIS IS USED TO RECOVER FROM APPLICATIONS THAT REPROGRAM THE
+; VIDEO CHIP.
+;
+TERM_RESET:
+	; ABORT IF NOTHING ATTACHED
+	LD	A,(TERM_DEVCNT)
+	OR	A
+	JR	NZ,TERM_RESET1
+	OR	$FF
+	RET
+;
+TERM_RESET1:
+	; CALL EMULATOR INITDEV FUNCTION
+  #IF (VDAEMU == EMUTYP_TTY)
+	CALL	TTY_INITDEV
+  #ENDIF
+  #IF (VDAEMU == EMUTYP_ANSI)
+	CALL	ANSI_INITDEV
+  #ENDIF
+;
+	XOR	A
+	RET
+;
+;======================================================================
 ; TERMINAL DRIVER PRIVATE DATA
 ;======================================================================
 ;
@@ -95,4 +123,10 @@ TERM_DEVCNT	.DB	0		; TERMINAL DEVICE COUNT
   #INCLUDE "tty.asm"
   #INCLUDE "ansi.asm"
 ;
+#ELSE
+;
+TERM_RESET:
+	XOR	A
+	RET
+;
 #ENDIF
\ No newline at end of file
diff --git a/Source/ver.inc b/Source/ver.inc
index 79ccbb29..84a9fb0e 100644
--- a/Source/ver.inc
+++ b/Source/ver.inc
@@ -2,7 +2,7 @@
 #DEFINE	RMN	5
 #DEFINE	RUP	0
 #DEFINE	RTP	0
-#DEFINE BIOSVER	"3.5.0-dev.22"
+#DEFINE BIOSVER	"3.5.0-dev.23"
 #define rmj	RMJ
 #define rmn	RMN
 #define rup	RUP
diff --git a/Source/ver.lib b/Source/ver.lib
index 9d5a054e..fdf43c6a 100644
--- a/Source/ver.lib
+++ b/Source/ver.lib
@@ -3,5 +3,5 @@ rmn	equ	5
 rup	equ	0
 rtp	equ	0
 biosver	macro
-	db	"3.5.0-dev.22"
+	db	"3.5.0-dev.23"
 	endm