From: John Tsiombikas <nuclear@member.fsf.org>
Date: Wed, 9 Jun 2021 15:24:22 +0000 (+0300)
Subject: changed the scroll repeat window to a power of two (25 -> 32 lines)
X-Git-Url: http://git.mutantstargoat.com/user/nuclear/?p=3sys;a=commitdiff_plain;h=6ccd3a47d05be145256a79a1de100f01ebd16a79

changed the scroll repeat window to a power of two (25 -> 32 lines)
---

diff --git a/sys1/kern/src/main.c b/sys1/kern/src/main.c
index 44acf3c..2e7a280 100644
--- a/sys1/kern/src/main.c
+++ b/sys1/kern/src/main.c
@@ -31,7 +31,7 @@ void kmain(void)
 		vga_setcolor(VGA_YELLOW | VGA_BRIGHT, VGA_BLACK);
 		drawtext(line & 7, row, buf);
 
-		for(i=0; i<65536 * 4; i++) {
+		for(i=0; i<65536 * 16; i++) {
 			buf[0] = twirl[(i >> 15) & 3];
 			buf[1] = 0;
 			vga_setcolor(VGA_WHITE, VGA_BLACK);
diff --git a/sys1/kern/src/vga.c b/sys1/kern/src/vga.c
index ae7c049..c1edd9a 100644
--- a/sys1/kern/src/vga.c
+++ b/sys1/kern/src/vga.c
@@ -30,7 +30,7 @@ void vga_setcursor(int x, int y)
 
 void vga_scroll(int s)
 {
-	yoffs = s % 25;
+	yoffs = s & 0x1f;
 	s = yoffs * 80;
 	crtc_write(CRTC_START_H, s >> 8);
 	crtc_write(CRTC_START_L, s);
@@ -53,9 +53,9 @@ void vga_clearline(int row)
 	ptr = (uint16_t*)0xb8000 + row * 80;
 	memset16(ptr, attr, 80);
 
-	if(row - 25 >= 0) {
+	if(row - 32 >= 0) {
 		/* write a copy to wrap-around future scrolling */
-		ptr -= 80 * 25;
+		ptr -= 80 * 32;
 		memset16(ptr, attr, 80);
 	}
 }
@@ -69,9 +69,9 @@ void vga_drawchar(int x, int y, int c)
 	ptr = (uint16_t*)0xb8000 + y * 80 + x;
 	*ptr = val;
 
-	if(y - 25 >= 0) {
+	if(y - 32 >= 0) {
 		/* write a copy to wrap-around future scrolling */
-		ptr -= 80 * 25;
+		ptr -= 80 * 32;
 		*ptr = val;
 	}
 }