CGA and Tandy 1000 HX/SX: Properly implement the light pen strobe. Jungle Hunt's palette changed area still moves, that's a PIT bug, I'm going to look into that again in 5.0 when I go back to porting 808x etc. from MartyPC.

src/include/86box/vid_cga.h

@@ -31,6 +31,8 @@ typedef struct cga_t {
     uint8_t cgamode;
     uint8_t cgacol;
 
+    uint8_t lp_strobe;
+
     int      fontbase;
     int      linepos;
     int      displine;

src/machine/m_tandy.c

@@ -84,6 +84,7 @@ typedef struct t1kvid_t {
     uint32_t b8000_mask;
     uint32_t b8000_limit;
     uint8_t  planar_ctrl;
+    uint8_t  lp_strobe;
 
     int      linepos;
     int      displine;
@@ -770,6 +771,15 @@ recalc_address_sl(tandy_t *dev)
     }
 }
 
+static void
+vid_update_latch(t1kvid_t *vid)
+{
+    uint32_t lp_latch = vid->displine * vid->crtc[1];
+
+    vid->crtc[0x10] = (lp_latch >> 8) & 0x3f;
+    vid->crtc[0x11] = lp_latch & 0xff;
+}
+
 static void
 vid_out(uint16_t addr, uint8_t val, void *priv)
 {
@@ -816,6 +826,18 @@ vid_out(uint16_t addr, uint8_t val, void *priv)
             vid->array_index = val & 0x1f;
             break;
 
+        case 0x3db:
+            if (dev->is_sl2 && (vid->lp_strobe == 1))
+                vid->lp_strobe = 0;
+            break;
+
+        case 0x3dc:
+            if (dev->is_sl2 && (vid->lp_strobe == 0)) {
+                vid->lp_strobe = 1;
+                vid_update_latch(vid);
+            }
+            break;
+
         case 0x03de:
             if (vid->array_index & 16)
                 val &= 0xf;
@@ -852,7 +874,7 @@ static uint8_t
 vid_in(uint16_t addr, void *priv)
 {
     const tandy_t  *dev = (tandy_t *) priv;
-    const t1kvid_t *vid = dev->vid;
+    t1kvid_t       *vid = dev->vid;
     uint8_t         ret = 0xff;
 
     if ((addr >= 0x3d0) && (addr <= 0x3d7))
@@ -864,29 +886,25 @@ vid_in(uint16_t addr, void *priv)
             break;
 
         case 0x03d5:
-            switch (vid->crtcreg) {
-                default:
             ret = vid->crtc[vid->crtcreg];
             break;
-                case 0x10:
-                    if (dev->is_sl2)
-                        ret = vid->crtc[vid->crtcreg];
-                    else
-                        ret = 0x0f;
-                    break;
-                case 0x11:
-                    if (dev->is_sl2)
-                        ret = vid->crtc[vid->crtcreg];
-                    else
-                        ret = 0x78;
-                    break;
-            }
-            break;
 
         case 0x03da:
             ret = vid->stat;
             break;
 
+        case 0x3db:
+            if (dev->is_sl2 && (vid->lp_strobe == 1))
+                vid->lp_strobe = 0;
+            break;
+
+        case 0x3dc:
+            if (dev->is_sl2 && (vid->lp_strobe == 0)) {
+                vid->lp_strobe = 1;
+                vid_update_latch(vid);
+            }
+            break;
+
         default:
             break;
     }

src/video/vid_cga.c

@@ -70,6 +70,15 @@ static video_timings_t timing_cga = { .type = VIDEO_ISA, .write_b = 8, .write_w
 
 void cga_recalctimings(cga_t *cga);
 
+static void
+cga_update_latch(cga_t *cga)
+{
+    uint32_t lp_latch = cga->displine * cga->crtc[1];
+
+    cga->crtc[0x10] = (lp_latch >> 8) & 0x3f;
+    cga->crtc[0x11] = lp_latch & 0xff;
+}
+
 void
 cga_out(uint16_t addr, uint8_t val, void *priv)
 {
@@ -87,7 +96,7 @@ cga_out(uint16_t addr, uint8_t val, void *priv)
             old                     = cga->crtc[cga->crtcreg];
             cga->crtc[cga->crtcreg] = val & crtcmask[cga->crtcreg];
             if (old != val) {
-                if ((cga->crtcreg < 0xe) || (cga->crtcreg > 0x10)) {
+                if ((cga->crtcreg < 0xe) || (cga->crtcreg > 0x11)) {
                     cga->fullchange = changeframecount;
                     cga_recalctimings(cga);
                 }
@@ -111,6 +120,17 @@ cga_out(uint16_t addr, uint8_t val, void *priv)
                 cga_recalctimings(cga);
             return;
 
+        case 0x3DB:
+            if (cga->lp_strobe == 1)
+                cga->lp_strobe = 0;
+            return;
+        case 0x3DC:
+            if (cga->lp_strobe == 0) {
+                cga->lp_strobe = 1;
+                cga_update_latch(cga);
+            }
+            return;
+
         default:
             break;
     }
@@ -119,8 +139,7 @@ cga_out(uint16_t addr, uint8_t val, void *priv)
 uint8_t
 cga_in(uint16_t addr, void *priv)
 {
-    const cga_t *cga = (cga_t *) priv;
+    cga_t  *cga = (cga_t *) priv;
-
     uint8_t ret = 0xff;
 
     if ((addr >= 0x3d0) && (addr <= 0x3d7))
@@ -131,22 +150,23 @@ cga_in(uint16_t addr, void *priv)
             ret = cga->crtcreg;
             break;
         case 0x3D5:
-            switch (cga->crtcreg) {
-                default:
             ret = cga->crtc[cga->crtcreg];
             break;
-                case 0x10:
-                    ret = 0x0f;
-                    break;
-                case 0x11:
-                    ret = 0x78;
-                    break;
-            }
-            break;
         case 0x3DA:
             ret = cga->cgastat;
             break;
 
+        case 0x3DB:
+            if (cga->lp_strobe == 1)
+                cga->lp_strobe = 0;
+            break;
+        case 0x3DC:
+            if (cga->lp_strobe == 0) {
+                cga->lp_strobe = 1;
+                cga_update_latch(cga);
+            }
+            break;
+
         default:
             break;
     }