# HG changeset patch
# User Michael Pavone <pavone@retrodev.com>
# Date 1496290249 25200
# Node ID 1eded4f19910ecbf37bd41b7ae05cb23beebfc6f
# Parent  1df16f5985f3b8f638e176b4f08d4c83eba1f3e5
Prevent emulated screen from "rolling" when the vertical resolution is changed at an inopportune time

diff -r 1df16f5985f3 -r 1eded4f19910 vdp.c
--- a/vdp.c	Wed May 31 09:45:37 2017 -0700
+++ b/vdp.c	Wed May 31 21:10:49 2017 -0700
@@ -1738,6 +1738,11 @@
 		if (output_line < context->inactive_start + context->border_bot && context->output_lines > 0) {
 			output_line = context->output_lines++;//context->border_top + context->vcounter;
 		} else if (output_line >= 0x200 - context->border_top) {
+			if (output_line == 0x200 - context->border_top) {
+				//We're at the top of the display, force context->output_lines to be zero to avoid
+				//potential screen rolling if the mode is changed at an inopportune time
+				context->output_lines = 0;
+			}
 			output_line = context->output_lines++;//context->vcounter - (0x200 - context->border_top);
 		} else {
 			output_line = INVALID_LINE;