From 273639bd795633fd5e4bb8cef142c90079d1efc0 Mon Sep 17 00:00:00 2001
From: TomW <TomW@localhost>
Date: Sat, 7 Dec 2013 14:02:03 +0000
Subject: [PATCH] Implemented VGA colour plane mask, 640x200x2 (eg Windows 2.x
 startup screen) now displayed correctly.

---
 src/vid_svga.c        |  6 ++++++
 src/vid_svga.h        |  2 ++
 src/vid_svga_render.c | 32 ++++++++++++++++----------------
 3 files changed, 24 insertions(+), 16 deletions(-)

diff --git a/src/vid_svga.c b/src/vid_svga.c
index 741cc9d..d27d635 100644
--- a/src/vid_svga.c
+++ b/src/vid_svga.c
@@ -44,6 +44,12 @@ void svga_out(uint16_t addr, uint8_t val, void *p)
                         }
                         if (svga->attraddr == 0x10) 
                                 svga_recalctimings(svga);
+                        if (svga->attraddr == 0x12)
+                        {
+                                if ((val & 0xf) != svga->plane_mask)
+                                        svga->fullchange = changeframecount;
+                                svga->plane_mask = val & 0xf;
+                        }
                 }
                 svga->attrff ^= 1;
                 break;
diff --git a/src/vid_svga.h b/src/vid_svga.h
index 630dfa9..f969abd 100644
--- a/src/vid_svga.h
+++ b/src/vid_svga.h
@@ -23,6 +23,8 @@ typedef struct svga_t
         
         uint8_t cgastat;
         
+        uint8_t plane_mask;
+        
         int fast;
         uint8_t colourcompare, colournocare;
         int readmode, writemode, readplane;
diff --git a/src/vid_svga_render.c b/src/vid_svga_render.c
index d0b76d0..19850f3 100644
--- a/src/vid_svga_render.c
+++ b/src/vid_svga_render.c
@@ -280,17 +280,17 @@ void svga_render_4bpp_lowres(svga_t *svga)
                         svga->ma &= svga->vrammask;
 
                         dat = edatlookup[edat[0] >> 6][edat[1] >> 6] | (edatlookup[edat[2] >> 6][edat[3] >> 6] << 2);
-                        p[0]  = p[1]  = svga->pallook[svga->egapal[dat >> 4]];
-                        p[2]  = p[3]  = svga->pallook[svga->egapal[dat & 0xf]];
+                        p[0]  = p[1]  = svga->pallook[svga->egapal[(dat >> 4) & svga->plane_mask]];
+                        p[2]  = p[3]  = svga->pallook[svga->egapal[dat & svga->plane_mask]];
                         dat = edatlookup[(edat[0] >> 4) & 3][(edat[1] >> 4) & 3] | (edatlookup[(edat[2] >> 4) & 3][(edat[3] >> 4) & 3] << 2);
-                        p[4]  = p[5]  = svga->pallook[svga->egapal[dat >> 4]];
-                        p[6]  = p[7]  = svga->pallook[svga->egapal[dat & 0xf]];
+                        p[4]  = p[5]  = svga->pallook[svga->egapal[(dat >> 4) & svga->plane_mask]];
+                        p[6]  = p[7]  = svga->pallook[svga->egapal[dat & svga->plane_mask]];
                         dat = edatlookup[(edat[0] >> 2) & 3][(edat[1] >> 2) & 3] | (edatlookup[(edat[2] >> 2) & 3][(edat[3] >> 2) & 3] << 2);
-                        p[8]  = p[9]  = svga->pallook[svga->egapal[dat >> 4]];
-                        p[10] = p[11] = svga->pallook[svga->egapal[dat & 0xf]];
+                        p[8]  = p[9]  = svga->pallook[svga->egapal[(dat >> 4) & svga->plane_mask]];
+                        p[10] = p[11] = svga->pallook[svga->egapal[dat & svga->plane_mask]];
                         dat = edatlookup[edat[0] & 3][edat[1] & 3] | (edatlookup[edat[2] & 3][edat[3] & 3] << 2);
-                        p[12] = p[13] = svga->pallook[svga->egapal[dat >> 4]];
-                        p[14] = p[15] = svga->pallook[svga->egapal[dat & 0xf]];
+                        p[12] = p[13] = svga->pallook[svga->egapal[(dat >> 4) & svga->plane_mask]];
+                        p[14] = p[15] = svga->pallook[svga->egapal[dat & svga->plane_mask]];
                                                 
                         p += 16;
                 }
@@ -329,17 +329,17 @@ void svga_render_4bpp_highres(svga_t *svga)
                         svga->ma &= svga->vrammask;
 
                         dat = edatlookup[edat[0] >> 6][edat[1] >> 6] | (edatlookup[edat[2] >> 6][edat[3] >> 6] << 2);
-                        p[0] = svga->pallook[svga->egapal[dat >> 4]];
-                        p[1] = svga->pallook[svga->egapal[dat & 0xf]];
+                        p[0] = svga->pallook[svga->egapal[(dat >> 4) & svga->plane_mask]];
+                        p[1] = svga->pallook[svga->egapal[dat & svga->plane_mask]];
                         dat = edatlookup[(edat[0] >> 4) & 3][(edat[1] >> 4) & 3] | (edatlookup[(edat[2] >> 4) & 3][(edat[3] >> 4) & 3] << 2);
-                        p[2] = svga->pallook[svga->egapal[dat >> 4]];
-                        p[3] = svga->pallook[svga->egapal[dat & 0xf]];
+                        p[2] = svga->pallook[svga->egapal[(dat >> 4) & svga->plane_mask]];
+                        p[3] = svga->pallook[svga->egapal[dat & svga->plane_mask]];
                         dat = edatlookup[(edat[0] >> 2) & 3][(edat[1] >> 2) & 3] | (edatlookup[(edat[2] >> 2) & 3][(edat[3] >> 2) & 3] << 2);
-                        p[4] = svga->pallook[svga->egapal[dat >> 4]];
-                        p[5] = svga->pallook[svga->egapal[dat & 0xf]];
+                        p[4] = svga->pallook[svga->egapal[(dat >> 4) & svga->plane_mask]];
+                        p[5] = svga->pallook[svga->egapal[dat & svga->plane_mask]];
                         dat = edatlookup[edat[0] & 3][edat[1] & 3] | (edatlookup[edat[2] & 3][edat[3] & 3] << 2);
-                        p[6] = svga->pallook[svga->egapal[dat >> 4]];
-                        p[7] = svga->pallook[svga->egapal[dat & 0xf]];
+                        p[6] = svga->pallook[svga->egapal[(dat >> 4) & svga->plane_mask]];
+                        p[7] = svga->pallook[svga->egapal[dat & svga->plane_mask]];
                         
                         p += 8;
                 }