sms: add cursor indicator to text mode

I do this by adding an inverted version of all glyphs in the upper
range of the pattern memory. This is a big waste of the pattern
space (only one inverted character is needed at once), but it's the
simplest way to proceed. I'll change this if I ever need more
pattern space.

Also, remove _blank. It was wastefully blanking the whole memory.
Only the name table needs to be blanked on initialization.

arch/z80/sms/blk.fs

@@ -16,8 +16,6 @@ CREATE _idat
 0b00000000 C, 0x89 C, ( BG Y scroll )
 0b11111111 C, 0x8a C, ( Line counter (why have this?) )
 ( ----- 603 )
-: _zero ( x -- send 0 _data x times )
-    ( x ) 0 DO 0 _data LOOP ;
 ( Each row in ~FNT is a row of the glyph and there is 7 of
 them.  We insert a blank one at the end of those 7. For each
 row we set, we need to send 3 zero-bytes because each pixel in
@@ -37,7 +35,8 @@ always stay zero. )
     ( set palette bit for at specified pos )
     2 * 1+ 0x7800 OR _ctl 0x8 _data ;
 : VDP$
-    9 0 DO _idat I 2 * + @ _ctl LOOP _blank
+    9 0 DO _idat I 2 * + @ _ctl LOOP
+    ( blank screen ) 0x7800 _ctl COLS LINES * 2 * _zero
     ( palettes )
     0xc000 _ctl
     ( BG ) 1 _zero 0x3f _data 14 _zero

arch/z80/sms/xcomptextmode.fs

@@ -29,7 +29,7 @@ CURRENT @ XCURRENT !
 283 335 LOADR ( boot.z80 )
 353 LOAD  ( xcomp core low )
 CREATE ~FNT CPFNT5x7
-470 472 LOADR ( VDP )
+470 472 LOADR ( TMS9918 )
 402 404 LOADR ( Grid )
 625 626 LOADR ( SMS ports )
 620 LOAD ( PAD ) : (ps2kc) (ps2kcA) ; 411 414 LOADR

blk.fs

@@ -2780,28 +2780,31 @@ CODE _data
     A L LDrr, TMS_DATAPORT OUTiA,
 ;CODE
 ( ----- 471 )
-CODE _blank ( this is way too slow in Forth )
-    A XORr, TMS_CTLPORT OUTiA,
-    A 0x40 LDri, TMS_CTLPORT OUTiA,
-    HL 0x4000 LDdi,
-    BEGIN,
-        A XORr, TMS_DATAPORT OUTiA,
-        HL DECd, HLZ,
-    JRNZ, AGAIN,
-;CODE
-( ----- 472 )
+: _zero ( x -- send 0 _data x times )
+    ( x ) 0 DO 0 _data LOOP ;
 ( Each row in ~FNT is a row of the glyph and there is 7 of
 them.  We insert a blank one at the end of those 7. )
 : _sfont ( a -- Send font to TMS )
     7 0 DO C@+ _data LOOP DROP
     ( blank row ) 0 _data ;
+: _sfont^ ( a -- Send inverted font to TMS )
+    7 0 DO C@+ 0xff XOR _data LOOP DROP
+    ( blank row ) 0xff _data ;
 : CELL! ( c pos )
     0x7800 OR _ctl ( tilenum )
     0x20 - ( glyph ) 0x5e MOD _data ;
+( ----- 472 )
+: CURSOR! ( new old -- )
+    0x7800 OR DUP _ctl [ TMS_DATAPORT LITN ] PC@
+        0x7f AND ( new cmd glyph ) SWAP _ctl _data
+    0x7800 OR DUP _ctl [ TMS_DATAPORT LITN ] PC@
+        0x80 OR ( cmd glyph ) SWAP _ctl _data ;
 : COLS 40 ; : LINES 24 ;
 : TMS$
-    0x8100 _ctl ( blank screen ) _blank
+    0x8100 _ctl ( blank screen )
+    0x7800 _ctl COLS LINES * _zero
     0x4000 _ctl 0x5e 0 DO ~FNT I 7 * + _sfont LOOP
+    0x4400 _ctl 0x5e 0 DO ~FNT I 7 * + _sfont^ LOOP
     0x820e _ctl ( name table 0x3800 )
     0x8400 _ctl ( pattern table 0x0000 )
     0x87f0 _ctl ( colors 0 and 1 )