Added more sanity checks to the CGA, EGA, and SVGA polls, fixes #399.

src/video/vid_cga.c

@@ -186,7 +186,7 @@ cga_poll(void *p)
     cga_t *cga = (cga_t *)p;
     uint16_t ca = (cga->crtc[15] | (cga->crtc[14] << 8)) & 0x3fff;
     int drawcursor;
-    int x, c;
+    int x, c, xs_temp, ys_temp;
     int oldvc;
     uint8_t chr, attr;
     uint8_t border;
@@ -438,11 +438,19 @@ cga_poll(void *p)
 				else
 					x = (cga->crtc[1] << 4) + 16;
 				cga->lastline++;
+
+				xs_temp = x;
+				ys_temp = (cga->lastline - cga->firstline) << 1;
+
+				if ((xs_temp > 0) && (ys_temp > 0)) {
+					if (xsize < 64) xs_temp = 656;
+					if (ysize < 32) ys_temp = 400;
+
 					if ((cga->cgamode & 8) && x && (cga->lastline - cga->firstline) &&
-				    ((x != xsize) || (((cga->lastline - cga->firstline) << 1) != ysize) ||
+					    ((xs_temp != xsize) || (ys_temp != ysize) ||
 					    video_force_resize_get())) {
-					xsize = x;
-					ysize = (cga->lastline - cga->firstline) << 1;
+						xsize = xs_temp;
+						ysize = ys_temp;
 						if (xsize < 64) xsize = 656;
 						if (ysize < 32) ysize = 400;
 						set_screen_size(xsize, ysize + 16);
@@ -457,6 +465,8 @@ cga_poll(void *p)
 					else
 						video_blit_memtoscreen_8(0, (cga->firstline - 4) << 1, 0, ((cga->lastline - cga->firstline) + 8) << 1,
 									 xsize, ((cga->lastline - cga->firstline) + 8) << 1);
+				}
+
 				frames++;
 
 				video_res_x = xsize - 16;

src/video/vid_ega.c

@@ -9,14 +9,14 @@
  *		Emulation of the EGA, Chips & Technologies SuperEGA, and
  *		AX JEGA graphics cards.
  *
- * Version:	@(#)vid_ega.c	1.0.19	2018/12/31
+ * Version:	@(#)vid_ega.c	1.0.20	2019/09/26
  *
  * Authors:	Sarah Walker, <http://pcem-emulator.co.uk/>
  *		Miran Grca, <mgrca8@gmail.com>
  *		akm
  *
- *		Copyright 2008-2018 Sarah Walker.
- *		Copyright 2016-2018 Miran Grca.
+ *		Copyright 2008-2019 Sarah Walker.
+ *		Copyright 2016-2019 Miran Grca.
  */
 #include <stdio.h>
 #include <stdint.h>
@@ -413,6 +413,7 @@ void ega_poll(void *p)
 {
         ega_t *ega = (ega_t *)p;
         int x;
+	int xs_temp, ys_temp;
         int drawcursor = 0;
 	int y_add = enable_overscan ? (overscan_y >> 1) : 0;
 	int x_add = enable_overscan ? 8 : 0;
@@ -549,6 +550,10 @@ void ega_poll(void *p)
                         if (ega->interlace && !ega->oddeven) ega->lastline++;
                         if (ega->interlace &&  ega->oddeven) ega->firstline--;
 
+			xs_temp = x;
+			ys_temp = ega->lastline - ega->firstline + 1;
+
+			if ((xs_temp > 0) && (ys_temp > 1)) {
 				x_add = enable_overscan ? 8 : 0;
 				y_add = enable_overscan ? overscan_y : 0;
 				x_add_ex = enable_overscan ? 16 : 0;
@@ -561,14 +566,14 @@ void ega_poll(void *p)
 				} else
 					suppress_overscan = 0;
 
-			if ((x != xsize) || ((ega->lastline - ega->firstline + 1) != ysize) || video_force_resize_get()) {
-                                xsize = x;
-                                ysize = ega->lastline - ega->firstline + 1;
-                                if (xsize < 64)
-					xsize = 640;
-                                if (ysize < 32)
-					ysize = 200;
+				xs_temp = x;
+				ys_temp = ega->lastline - ega->firstline + 1;
+				if (xs_temp < 64)
+					xs_temp = 640;
+				if (ys_temp < 32)
+					ys_temp = 200;
 
+				if ((xs_temp != xsize) || (ys_temp != ysize) || video_force_resize_get()) {
 	                                if (ega->vres)
         	                                set_screen_size(xsize + x_add_ex, (ysize << 1) + y_add_ex);
                 	                else
@@ -608,6 +613,7 @@ void ega_poll(void *p)
 				}
 
 	                        video_blit_memtoscreen(32, 0, ega->firstline, ega->lastline + 1 + y_add_ex, xsize + x_add_ex, ega->lastline - ega->firstline + 1 + y_add_ex);
+			}
 
                         frames++;
                         

src/video/vid_svga.c

@@ -11,13 +11,13 @@
  *		This is intended to be used by another SVGA driver,
  *		and not as a card in it's own right.
  *
- * Version:	@(#)vid_svga.c	1.0.35	2018/10/21
+ * Version:	@(#)vid_svga.c	1.0.36	2019/09/26
  *
  * Authors:	Sarah Walker, <http://pcem-emulator.co.uk/>
  *		Miran Grca, <mgrca8@gmail.com>
  *
- *		Copyright 2008-2018 Sarah Walker.
- *		Copyright 2016-2018 Miran Grca.
+ *		Copyright 2008-2019 Sarah Walker.
+ *		Copyright 2016-2019 Miran Grca.
  */
 #include <inttypes.h>
 #include <stdio.h>
@@ -711,7 +711,7 @@ svga_poll(void *p)
 		wx = x;
 		wy = svga->lastline - svga->firstline;
 
-		if (!svga->override)
+		if (!svga->override && (wx > 0) && (wy > 0))
 			svga_doblit(svga->firstline_draw, svga->lastline_draw + 1, wx, wy, svga);
 
 		svga->firstline = 2000;
@@ -1123,6 +1123,7 @@ svga_doblit(int y1, int y2, int wx, int wy, svga_t *svga)
     int x_add = (enable_overscan) ? 16 : 0;
     uint32_t *p;
     int i, j;
+    int xs_temp, ys_temp;
 
     if ((xsize > 2032) || (ysize > 2032)) {
 	x_add = 0;
@@ -1136,14 +1137,17 @@ svga_doblit(int y1, int y2, int wx, int wy, svga_t *svga)
 	return;
     }
 
-    if ((wx != xsize) || ((wy + 1) != ysize) || video_force_resize_get()) {
+    xs_temp = wx;
+    ys_temp = wy + 1;
+    if (xs_temp < 64)
+	xs_temp = 640;
+    if (ys_temp < 32)
+	ys_temp = 200;
+
+    if ((xs_temp != xsize) || (ys_temp != ysize) || video_force_resize_get()) {
 	/* Screen res has changed.. fix up, and let them know. */
-	xsize = wx;
-	ysize = wy + 1;
-	if (xsize < 64)
-		xsize = 640;
-	if (ysize < 32)
-		ysize = 200;
+	xsize = xs_temp;
+	ysize = ys_temp;
 
 	set_screen_size(xsize+x_add,ysize+y_add);