infinite hardware scrolling

diff --git a/sys1/kern/src/main.c b/sys1/kern/src/main.c
index f0441e5..00d3882 100644 (file)
--- a/sys1/kern/src/main.c
+++ b/sys1/kern/src/main.c
@@ -12,11 +12,31 @@ void drawtext(int x, int y, const char *s)
 
 void kmain(void)
 {
+       int i, row;
+       int line, scroll;
        char buf[64];
+       char twirl[] = "-\\|/";
 
        vga_reset();
-       vga_setcolor(VGA_YELLOW | VGA_BRIGHT, VGA_BLACK);
 
-       sprintf(buf, "kmain addr: %p", (void*)kmain);
-       drawtext(10, 5, buf);
+       line = 0;
+       for(;;) {
+               scroll = line <= 24 ? 0 : line - 24;
+               row = line <= 24 ? line : 24;
+               sprintf(buf, "line %d  (scroll %d [%d])", line, scroll, scroll % 25);
+               vga_scroll(scroll);
+               if(scroll) {
+                       vga_clearline(24);
+               }
+               vga_setcolor(VGA_YELLOW | VGA_BRIGHT, VGA_BLACK);
+               drawtext(line & 7, row, buf);
+
+               for(i=0; i<65536 * 4; i++) {
+                       buf[0] = twirl[(i >> 18) & 3];
+                       buf[1] = 0;
+                       vga_setcolor(VGA_WHITE, VGA_BLACK);
+                       drawtext(50, row, buf);
+               }
+               line++;
+       }
 }

diff --git a/sys1/kern/src/vga.c b/sys1/kern/src/vga.c
index 2967299..ae7c049 100644 (file)
--- a/sys1/kern/src/vga.c
+++ b/sys1/kern/src/vga.c
@@ -28,25 +28,52 @@ void vga_setcursor(int x, int y)
        crtc_write(CRTC_CURPOS_L, loc);
 }
 
-void vga_setstart(int start)
+void vga_scroll(int s)
 {
-       yoffs = start;
-       crtc_write(CRTC_START_H, start >> 8);
-       crtc_write(CRTC_START_L, start);
+       yoffs = s % 25;
+       s = yoffs * 80;
+       crtc_write(CRTC_START_H, s >> 8);
+       crtc_write(CRTC_START_L, s);
 }
 
 void vga_reset(void)
 {
        vga_setcolor(VGA_WHITE, VGA_BLACK);
-       vga_setstart(0);
+       vga_scroll(0);
        vga_setcursor(0, 0);
        memset((void*)0xb8000, 0, 80 * 25 * 2);
 }
 
+void vga_clearline(int row)
+{
+       uint16_t *ptr;
+
+       row += yoffs;
+
+       ptr = (uint16_t*)0xb8000 + row * 80;
+       memset16(ptr, attr, 80);
+
+       if(row - 25 >= 0) {
+               /* write a copy to wrap-around future scrolling */
+               ptr -= 80 * 25;
+               memset16(ptr, attr, 80);
+       }
+}
+
 void vga_drawchar(int x, int y, int c)
 {
-       uint16_t *ptr = (uint16_t*)0xb8000 + (y + yoffs) * 80 + x;
-       *ptr = (c & 0xff) | attr;
+       uint16_t *ptr, val = (c & 0xff) | attr;
+
+       y += yoffs;
+
+       ptr = (uint16_t*)0xb8000 + y * 80 + x;
+       *ptr = val;
+
+       if(y - 25 >= 0) {
+               /* write a copy to wrap-around future scrolling */
+               ptr -= 80 * 25;
+               *ptr = val;
+       }
 }
 
 static void crtc_write(int reg, unsigned char val)

diff --git a/sys1/kern/src/vga.h b/sys1/kern/src/vga.h
index e8be27a..14a91ff 100644 (file)
--- a/sys1/kern/src/vga.h
+++ b/sys1/kern/src/vga.h
@@ -15,10 +15,11 @@ enum {
 
 void vga_setcolor(int fg, int bg);
 void vga_setcursor(int x, int y);
-void vga_setstart(int start);
+void vga_scroll(int s);
 
 void vga_reset(void);
 
+void vga_clearline(int row);
 void vga_drawchar(int x, int y, int c);
 
 #endif /* VGA_H_ */