sms/vdp: highlight cursor with inverted palette

emul/hw/sms/sms.c

@@ -108,6 +108,9 @@ void create_window()
     xcb_map_window(conn, win);
 }
 
+// To make things simple with X11, we only support monochrome display, which is
+// inverted: As soon as the color of the pixel is non-black, we show a black
+// pixel. If the pixel is white, we show black.
 void draw_pixels()
 {
     xcb_get_geometry_reply_t *geom;

emul/hw/sms/vdp.c

@@ -51,6 +51,7 @@ void vdp_data_wr(VDP *vdp, uint8_t val)
     }
 }
 
+// Returns a 8-bit RGB value (0b00bbggrr)
 uint8_t vdp_pixel(VDP *vdp, uint16_t x, uint16_t y)
 {
     if (x >= VDP_SCREENW) {
@@ -63,6 +64,8 @@ uint8_t vdp_pixel(VDP *vdp, uint16_t x, uint16_t y)
     uint16_t offset = 0x3800 + ((y/8) << 6) + ((x/8) << 1);
     uint16_t tableval = vdp->vram[offset] + (vdp->vram[offset+1] << 8);
     uint16_t tilenum = tableval & 0x1ff;
+    // is palette select bit on? if yes, use sprite palette instead
+    uint8_t palettemod = tableval & 0x800 ? 0x10 : 0;
     // tile offset this time. Each tile is 0x20 bytes long.
     offset = tilenum * 0x20;
     // Each 4 byte is a row. Find row first.
@@ -70,8 +73,10 @@ uint8_t vdp_pixel(VDP *vdp, uint16_t x, uint16_t y)
     uint8_t bitnum = 7 - (x%8);
     // Now, let's compose the result by pushing the right bit of our 4 bytes
     // into our result.
-    return ((vdp->vram[offset] >> bitnum) & 1) + \
+    uint8_t palette_id = ((vdp->vram[offset] >> bitnum) & 1) + \
            (((vdp->vram[offset+1] >> bitnum) & 1) << 1) + \
            (((vdp->vram[offset+2] >> bitnum) & 1) << 2) + \
            (((vdp->vram[offset+3] >> bitnum) & 1) << 3);
+    uint8_t rgb = vdp->vram[0x4000+palettemod+palette_id];
+    return rgb;
 }

kernel/grid.asm

@@ -119,7 +119,7 @@ gridPushScr:
 	pop	de
 	ret
 
-; Set character under cursor to A
+; Set character under cursor to A. C is passed to GRID_SETCELL as-is.
 gridSetCur:
 	push	de
 	push	hl
@@ -137,11 +137,27 @@ gridSetCur:
 	pop	de
 	ret
 
+; Call gridSetCur with C = 1.
+gridSetCurH:
+	push	bc
+	ld	c, 1
+	call	gridSetCur
+	pop	bc
+	ret
+
+; Call gridSetCur with C = 0.
+gridSetCurL:
+	push	bc
+	ld	c, 0
+	call	gridSetCur
+	pop	bc
+	ret
+
 ; Clear character under cursor
 gridClrCur:
 	push	af
 	ld	a, ' '
-	call	gridSetCur
+	call	gridSetCurL
 	pop	af
 	ret
 
@@ -210,7 +226,7 @@ gridPutC:
 	cp	' '
 	ret	c		; ignore unhandled control characters
 
-	call	gridSetCur
+	call	gridSetCurL
 	push	af		; --> lvl 1
 	; Move cursor
 	ld	a, (GRID_CURX)

kernel/sms/pad.asm

@@ -181,7 +181,7 @@ padGetC:
 	; no action button pressed, but because our pad status changed, update
 	; VDP before looping.
 	ld	a, (PAD_SELCHR)
-	call	gridSetCur
+	call	gridSetCurH
 	jp	padGetC
 .return:
 	ld	a, LF
@@ -190,7 +190,7 @@ padGetC:
 .advance:
 	ld	a, (PAD_SELCHR)
 	; Z was already set from previous BIT instruction
-	ret
+	jp	gridSetCurL
 .backspace:
 	ld	a, BS
 	; Z was already set from previous BIT instruction

kernel/sms/vdp.asm

@@ -23,8 +23,8 @@
 ; *** Code ***
 
 vdpInit:
-	ld	hl, vdpInitData
-	ld	b, vdpInitDataEnd-vdpInitData
+	ld	hl, .initData
+	ld	b, .initDataEnd-.initData
 	ld	c, VDP_CTLPORT
 	otir
 
@@ -47,10 +47,10 @@ vdpInit:
 	out	(VDP_CTLPORT), a
 	ld	a, 0xc0
 	out	(VDP_CTLPORT), a
-	xor	a			; palette 0: black
-	out	(VDP_DATAPORT), a
-	ld	a, 0x3f			; palette 1: white
-	out	(VDP_DATAPORT), a
+	ld	hl, .paletteData
+	ld	b, .paletteDataEnd-.paletteData
+	ld	c, VDP_DATAPORT
+	otir
 
 	; Define tiles
 	xor	a
@@ -97,6 +97,28 @@ vdpInit:
 	out	(VDP_CTLPORT), a
 	ret
 
+; VDP initialisation data
+.initData:
+; 0x8x == set register X
+.db 0b00000100, 0x80	; Bit 2: Select mode 4
+.db 0b00000000, 0x81
+.db 0b11111111, 0x82	; Name table: 0x3800
+.db 0b11111111, 0x85	; Sprite table: 0x3f00
+.db 0b11111111, 0x86	; sprite use tiles from 0x2000
+.db 0b11111111, 0x87	; Border uses palette 0xf
+.db 0b00000000, 0x88	; BG X scroll
+.db 0b00000000, 0x89	; BG Y scroll
+.db 0b11111111, 0x8a	; Line counter (why have this?)
+.initDataEnd:
+.paletteData:
+; BG palette
+.db 0x00, 0x3f, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
+.db 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
+; Sprite palette (inverted colors)
+.db 0x3f, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
+.db 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
+.paletteDataEnd:
+
 ; Convert ASCII char in A into a tile index corresponding to that character.
 ; When a character is unknown, returns 0x5e (a '~' char).
 vdpConv:
@@ -108,7 +130,8 @@ vdpConv:
 	ld	a, 0x5e
 	ret
 
-; grid routine. Sets cell at row D and column E to character A
+; grid routine. Sets cell at row D and column E to character A. If C is one, we
+; use the sprite palette.
 vdpSetCell:
 	call	vdpConv
 	; store A away
@@ -141,18 +164,11 @@ vdpSetCell:
 	; We're ready to send our data now. Let's go
 	ex	af, af'
 	out	(VDP_DATAPORT), a
+
+	; Palette select is on bit 3 of MSB
+	ld	a, 1
+	and	c
+	rla \ rla \ rla
+	out	(VDP_DATAPORT), a
 	ret
 
-; VDP initialisation data
-vdpInitData:
-; 0x8x == set register X
-.db 0b00000100, 0x80	; Bit 2: Select mode 4
-.db 0b00000000, 0x81
-.db 0b11111111, 0x82	; Name table: 0x3800
-.db 0b11111111, 0x85	; Sprite table: 0x3f00
-.db 0b11111111, 0x86	; sprite use tiles from 0x2000
-.db 0b11111111, 0x87	; Border uses palette 0xf
-.db 0b00000000, 0x88	; BG X scroll
-.db 0b00000000, 0x89	; BG Y scroll
-.db 0b11111111, 0x8a	; Line counter (why have this?)
-vdpInitDataEnd: