From c8584cd8a18667d30c7df19a5864ec274ad37957 Mon Sep 17 00:00:00 2001
From: catfood <protonghost@outlook.com>
Date: Sat, 24 Dec 2022 21:42:44 +0800
Subject: [PATCH] add bottom line

---
 include/tty.h | 3 ++-
 kernel/vga.c  | 9 +++++++--
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/include/tty.h b/include/tty.h
index 81212ce..805238d 100644
--- a/include/tty.h
+++ b/include/tty.h
@@ -68,7 +68,8 @@ typedef struct vga_buf
 	void *buf;		  // 2d array, screen size, for text mode it's [maxline][80]
 	int max_line;	  // to support scroll, max line should be a lot more than screen
 	int scr_top_line; // the index in buf of top line on screen;
-	int scr_cur_line; // the index in buf of the cursor's line
+	int scr_cur_line; // the index in buf of the cursor's line;
+	int scr_bot_line; // the index in buf of the most-bottom printed line
 	int head_line;	  // for circular buffer use
 	int cur_row;
 	int cur_col; // cursor position, on screen
diff --git a/kernel/vga.c b/kernel/vga.c
index 71f7371..3525bf9 100644
--- a/kernel/vga.c
+++ b/kernel/vga.c
@@ -132,7 +132,7 @@ void vga_tty_init(NTTY *tty)
 	// kprintf("malloced %p %p %p\n", vga->buf, &vga->buf, &vga->scr_top_line);
 	vga->cur_col = vga->cur_row = 0;
 	// buf->max_line = SCR_BUFSIZE / SCR_WIDTH;
-	vga->scr_top_line = vga->scr_cur_line = 0;
+	vga->scr_top_line = vga->scr_cur_line = vga->scr_bot_line = 0;
 	vga->head_line = 0;
 	u32 *ptr_buf = (u32 *)vga->buf;
 	for (int i = 0; i < SCR_BUFSIZE * sizeof(u16) / sizeof(u32); ++i)
@@ -551,6 +551,9 @@ void vga_tty_write(NTTY *tty, char ch)
 		}
 	}
 	vga->cur_row = CYCLE_SUB(vga->scr_top_line, vga->scr_cur_line, SCR_MAXLINE);
+	if (CYCLE_SUB(vga->head_line, vga->scr_cur_line, SCR_MAXLINE) >= CYCLE_SUB(vga->head_line, vga->scr_bot_line, SCR_MAXLINE)){
+		vga->scr_bot_line = vga->scr_cur_line;
+	}
 	// kprintf("row: %d; ", vga->cur_row);
 }
 
@@ -577,6 +580,8 @@ void vga_tty_flush(NTTY *tty)
 	u16 *buf = vga->buf;
 	int i, cur_line;
 	vga_set_cursor(INDEX(vga->cur_row, vga->cur_col));
+	vga->cur_row = CYCLE_SUB(vga->scr_top_line, vga->scr_cur_line, SCR_MAXLINE);
+	int bottom = min(max(vga->cur_row, CYCLE_SUB(vga->scr_top_line, vga->scr_bot_line, SCR_MAXLINE)), SCR_HEIGHT);
 	// if (vga->cur_row == SCR_HEIGHT - 1)
 	// {
 	// 	vga_flush_screen(&buf[INDEX(vga->scr_top_line, 0)]);
@@ -585,7 +590,7 @@ void vga_tty_flush(NTTY *tty)
 	// else
 	// {
 		cur_line = vga->scr_top_line;
-		for (i = 0; i <= vga->cur_row; ++i)
+		for (i = 0; i <= bottom; ++i)
 		{
 			vga_flush_line(&buf[INDEX(cur_line, 0)], i);
 			cur_line = NEXTLINE(cur_line);