sms: add cursor visual indicator in VDP mode 4

This required the change of CURSOR! signature: we now supply it
with both old and new cursor positions.

Also, fix broken _bs in Grid subsystem.

arch/z80/sms/blk.fs

@@ -29,8 +29,13 @@ always stay zero. )
     ( blank row ) 4 _zero ;
 : CELL! ( c pos )
     2 * 0x7800 OR _ctl ( c )
-    0x20 - ( glyph ) 0x5e MOD _data 0 _data ;
+    0x20 - ( glyph ) 0x5e MOD _data ;
 ( ----- 604 )
+: CURSOR! ( new old -- )
+    ( unset palette bit in old tile )
+    2 * 1+ 0x7800 OR _ctl 0 _data
+    ( set palette bit for at specified pos )
+    2 * 1+ 0x7800 OR _ctl 0x8 _data ;
 : VDP$
     9 0 DO _idat I 2 * + @ _ctl LOOP _blank
     ( palettes )
@@ -40,8 +45,7 @@ always stay zero. )
     0x4000 _ctl 0x5e 0 DO ~FNT I 7 * + _sfont LOOP
     ( bit 6, enable display, bit 7, ?? ) 0x81c0 _ctl ;
 
-: COLS 32 ;
-: LINES 24 ;
+: COLS 32 ; : LINES 24 ;
 ( ----- 610 )
 Pad driver - read input from MD controller
 

blk.fs

@@ -2214,8 +2214,8 @@ See doc/grid.txt.
 Load range: B402-B403
 ( ----- 402 )
 : XYPOS [ GRID_MEM LITN ] ; : XYMODE [ GRID_MEM LITN ] 2+ ;
-'? CURSOR! NIP NOT [IF] : CURSOR! DROP ; [THEN]
-: XYPOS! COLS LINES * MOD DUP CURSOR! XYPOS ! ;
+'? CURSOR! NIP NOT [IF] : CURSOR! 2DROP ; [THEN]
+: XYPOS! COLS LINES * MOD DUP XYPOS @ CURSOR! XYPOS ! ;
 : AT-XY ( x y -- ) COLS * + XYPOS! ;
 '? NEWLN NIP NOT [IF]
 : NEWLN ( ln -- ) COLS * DUP COLS + SWAP DO 0x20 I CELL! LOOP ;
@@ -2223,7 +2223,7 @@ Load range: B402-B403
 : _lf XYMODE C@ IF EXIT THEN
     XYPOS @ COLS / 1+ LINES MOD DUP NEWLN
     COLS * XYPOS! ;
-: _bs 0 ( blank ) XYPOS @ TUCK CELL! ( pos ) 1- XYPOS! ;
+: _bs 0x20 ( blank ) XYPOS @ TUCK CELL! ( pos ) 1- XYPOS! ;
 ( ----- 403 )
 : (emit)
     DUP 0x08 = IF DROP _bs EXIT THEN
@@ -2231,7 +2231,7 @@ Load range: B402-B403
     DUP 0x20 < IF DROP EXIT THEN
     XYPOS @ CELL!
     XYPOS @ 1+ DUP COLS MOD IF XYPOS! ELSE _lf THEN ;
-: GRID$ 0 XYPOS! 0 XYMODE C! ;
+: GRID$ 0 XYPOS ! 0 XYMODE C! ;
 ( ----- 410 )
 PS/2 keyboard subsystem
 

cvm/forth.fs

@@ -1,6 +1,7 @@
 : COLS 80 ; : LINES 32 ;
-: CURSOR! ( pos -- ) COLS /MOD 6 PC! ( y ) 5 PC! ( x ) ;
-: CELL! ( c pos -- ) CURSOR! 0 PC! ;
+: CURSOR! ( new old -- )
+    DROP COLS /MOD 6 PC! ( y ) 5 PC! ( x ) ;
+: CELL! ( c pos -- ) 0 CURSOR! 0 PC! ;
 : NEWLN ( ln -- ) DROP 0xa 0 PC! ;
 
 SYSVARS 0x70 + CONSTANT GRID_MEM

doc/protocol.txt

@@ -42,13 +42,13 @@ previously enabled one.
 A grid is a device that shows as a grid of ASCII characters and
 allows random access to it.
 
-COLS      -- n     Number of columns in the device
-LINES     -- n     Number of lines in the device
-CELL!     c pos -- Set character at pos
+COLS      -- n       Number of columns in the device
+LINES     -- n       Number of lines in the device
+CELL!     c pos --   Set character at pos
 
 Optional:
-NEWLN     ln --    "Enter" line ln
-CURSOR!   pos --   Set cursor's position
+NEWLN     ln --      "Enter" line ln
+CURSOR!   new old -- Move cursor from old pos to new pos
 
 "pos" is a simple number (y * cols) + x. For example, if we
 have 40 columns per line, the position (x, y) (12, 10) is 412.