gpt4 book ai didi

gcc - OSDev:为什么我的 VGA 终端滚动不起作用?

转载 作者:行者123 更新时间:2023-12-04 15:27:57 30 4
gpt4 key购买 nike

我正在开发操作系统作为个人爱好,以便我可以学习软件工程和计算机体系结构。

当文本到达底部或 VGA_HEIGHT 时,我试图让 VGA 终端“滚动”。我将 OSDev wiki 中的代码与我自己的代码混合使用。

我的目标是复制每一行,然后将其写入其正上方的行。

这是我正在使用的代码:

void terminal_putentryat(unsigned char c, uint8_t color, size_t x, size_t y) {
const size_t index = y * VGA_WIDTH + x;
terminal_buffer[index] = vga_entry(c, color);
}

void terminal_putchar(char c) {
unsigned char uc = c;

switch(c) {
case NEWLINE:
terminal_row++;
terminal_column = 0;
terminal_putentryat(' ', terminal_color, terminal_column, terminal_row);
update_cursor(terminal_column + 1, terminal_row);
break;

case '\t':
/* TODO: Implement tab */
terminal_column += 4;
break;

default:
terminal_putentryat(uc, terminal_color, terminal_column, terminal_row);
update_cursor(terminal_column + 1, terminal_row);
if (++terminal_column == VGA_WIDTH) {
terminal_column = 0;
if (++terminal_row == VGA_HEIGHT)
terminal_row = 0;
}
}
if(terminal_row >= VGA_HEIGHT) {
terminal_print_error();
terminal_buffer[(15 * VGA_WIDTH) + 15] = terminal_buffer[(0 * VGA_WIDTH) + 4];
size_t i, j;
for(i = 0; i < VGA_WIDTH-1; i++) {
for(j = VGA_HEIGHT-2; j > 0; j--)
terminal_buffer[(j * VGA_WIDTH) + i] = terminal_buffer[((j+1) * VGA_WIDTH) + i];
}
}
}

但是这个功能只能部分工作。具体来说,本节:
if(terminal_row >= VGA_HEIGHT) {
terminal_print_error();
terminal_buffer[(15 * VGA_WIDTH) + 15] = terminal_buffer[(0 * VGA_WIDTH) + 4];
size_t i, j;
for(i = 0; i < VGA_WIDTH-1; i++) {
for(j = VGA_HEIGHT-2; j > 0; j--)
terminal_buffer[(j * VGA_WIDTH) + i] = terminal_buffer[((j+1) * VGA_WIDTH) + i];
}
}

它仅部分复制数据。例如,当我使用“printf()”写入终端时,如果字符串比正在滚动的数据长,则不会滚动。
/*
* This is the screen driver. It contains functions which print
* characters and colors to the screen
* using the VGA controller.
*/

#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include <string.h>

#include <kernel/tty.h>

#include "vga.h"

#define REG_SCREEN_CTRL 0x3D4
#define REG_SCREEN_DATA 0x3D5

#define NEWLINE 0x0A
#define TAB 0x09

static const size_t VGA_WIDTH = 80;
static const size_t VGA_HEIGHT = 25;
static uint16_t *const VGA_MEMORY = (uint16_t *)0xC03FF000;

static size_t terminal_row;
static size_t terminal_column;
static uint8_t terminal_color;
static uint16_t *terminal_buffer;

int get_offset(int col, int row) {
return 2 * (row * VGA_WIDTH + col);
}

int get_offset_row(int offset) {
return offset / (2 * VGA_WIDTH);
}

int get_offset_col(int offset) {
return (offset - (get_offset_row(offset) * 2 * VGA_WIDTH)) / 2;
}

static void scroll() {
if(terminal_row >= VGA_HEIGHT) {

}
}
void terminal_print_error(void) {
if(terminal_row >= VGA_HEIGHT) {
terminal_row = 0;
/* print white/red E to bottom right corner of screen */
terminal_putentryat('E', vga_entry_color(VGA_COLOR_RED, VGA_COLOR_WHITE),
VGA_WIDTH - 1, VGA_HEIGHT - 1);
}
}

void terminal_initialize(void) {
terminal_row = 0;
terminal_column = 0;
terminal_color = vga_entry_color(VGA_COLOR_BLACK, VGA_COLOR_CYAN);
terminal_buffer = VGA_MEMORY;
for (size_t y = 0; y < VGA_HEIGHT; y++) {
for (size_t x = 0; x < VGA_WIDTH; x++) {
const size_t index = y * VGA_WIDTH + x;
terminal_buffer[index] = vga_entry(' ', terminal_color);
}
}
}

void terminal_setcolor(uint8_t color) {
terminal_color = color;
}

void terminal_putentryat(unsigned char c, uint8_t color, size_t x, size_t y) {
const size_t index = y * VGA_WIDTH + x;
terminal_buffer[index] = vga_entry(c, color);
}

void terminal_putchar(char c) {
unsigned char uc = c;

switch(c) {
case NEWLINE:
terminal_row++;
terminal_column = 0;
terminal_putentryat(' ', terminal_color, terminal_column, terminal_row);
update_cursor(terminal_column + 1, terminal_row);
break;

case '\t':
/* TODO: Implement tab */
terminal_column += 4;
break;

default:
terminal_putentryat(uc, terminal_color, terminal_column, terminal_row);
update_cursor(terminal_column + 1, terminal_row);
if (++terminal_column == VGA_WIDTH) {
terminal_column = 0;
if (++terminal_row == VGA_HEIGHT)
terminal_row = 0;
}
}
if(terminal_row >= VGA_HEIGHT) {
terminal_print_error();
terminal_buffer[(15 * VGA_WIDTH) + 15] = terminal_buffer[(0 * VGA_WIDTH) + 4];
size_t i, j;
for(i = 0; i < VGA_WIDTH-1; i++) {
for(j = VGA_HEIGHT-2; j > 0; j--)
terminal_buffer[(j * VGA_WIDTH) + i] = terminal_buffer[((j+1) * VGA_WIDTH) + i];
}
}
}

void terminal_write(const char *data, size_t size) {
for (size_t i = 0; i < size; i++)
terminal_putchar(data[i]);
}

void terminal_writestring(const char *data) {
terminal_write(data, strlen(data));
}

/* inb */
unsigned char port_byte_in(unsigned short port) {
unsigned char result;
asm ("in %%dx, %%al" : "=a" (result) : "d" (port));
return result;
}

void port_byte_out(unsigned short port, unsigned char data) {
asm ("out %%al, %%dx" : : "a" (data), "d" (port));
}

int get_cursor_offset() {
/* Use the VGA ports to get the current cursor position
* 1. Ask for high byte of the cursor offset (data 14)
* 2. Ask for low byte (data 15)
*/
port_byte_out(REG_SCREEN_CTRL, 14);
int offset = port_byte_in(REG_SCREEN_DATA) << 8; /* High byte: << 8 */
port_byte_out(REG_SCREEN_CTRL, 15);
offset += port_byte_in(REG_SCREEN_DATA);
return offset * 2; /* Position * size of character cell */
}

void set_cursor_offset(int offset) {
/* Similar to get_cursor_offset, but instead of reading we write data */
offset /= 2;
port_byte_out(REG_SCREEN_CTRL, 14);
port_byte_out(REG_SCREEN_DATA, (unsigned char)(offset >> 8));
port_byte_out(REG_SCREEN_CTRL, 15);
port_byte_out(REG_SCREEN_DATA, (unsigned char)(offset & 0xff));
}

void update_cursor(int x, int y) {
uint16_t pos = y * VGA_WIDTH + x;

port_byte_out(REG_SCREEN_CTRL, 15);
port_byte_out(REG_SCREEN_DATA, (uint8_t)(pos & 0xFF));
port_byte_out(REG_SCREEN_CTRL, 14);
port_byte_out(REG_SCREEN_DATA, (uint8_t)(pos >> 8) & 0xFF);
}

/*
void enable_cursor(uint8_t cursor_start, uint8_t cursor_end) {
outb(0x3D4, 0x0A);
outb(0x3D, (inb(0x3D5) & 0xC0) | cursor_start);

outb(0x3D4, 0x0B);
outb(0x3D5, (inb(0x3D5) & 0xE0) | cursor_end);
}
*/

最佳答案

我相信循环滚动的工作大部分是正确的,但是在它导致您遇到的一些错误之前有很多代码。

当光标宽度超过屏幕右边缘时,switch 语句中的默认情况是增加光标行。 if (++terminal_row == VGA_HEIGHT)如果行增量超过屏幕的底部边缘,则将光标行重置为 0。这可以防止滚动代码永远运行。您应该删除 if (++terminal_row == VGA_HEIGHT) terminal_row = 0;并替换为 terminal_row++;因为紧跟在 switch 之后的逻辑处理终端行变量。

我建议分离修改 terminal_row 的逻辑和 terminal_column来自验证、重置和滚动这些变量的逻辑。例如,您对 '\t' 字符的处理,如果放在一行的最后 3 个字符内,会将字符溢出到下一行而不更新 terminal_rowterminal_column vars 到他们应该在的地方。

  • 你的换行符总是在行的开头留下一个空白字符,因为你这样做 terminal_putentryat在将光标修改为换行符之后,而不是之前。事实上,你不应该这样做terminal_putentryat对于任何换行符,因为明显没有字符改变,只有光标位置。
  • 您可能需要修改 \t 的处理方式调用 terminal_write(' ');而不是直接修改列变量。这简化了实际更新终端的逻辑。上面的第二段详细介绍了此更改解决的一些问题。
  • update_cursor()应该只调用一次,在 terminal_putchar() 结束时因为你输入的每个字符都应该更新游标。如果您愿意,这可能会改变 terminal_putchar()处理 0 宽度的字符,但这对我来说似乎违反直觉,因为此函数专门用于处理显示的字符。
  • 向上修改终端缓冲区以滚动的循环永远不会清除底行字符
  • 函数底部的逻辑处理 terminal_row >= VGA_HEIGHT从不将 terminal_row 重置为有效值。它确实调用了 terminal_print_error()但是当您想将行保留在底部时,此函数会将您的行重置为 0。
    void terminal_putchar(char c) {
    unsigned char uc = c;

    // Handle character output and terminal_row/column modification
    switch(c) {
    case NEWLINE:
    terminal_row++;
    terminal_column = 0;
    break;

    case '\t':
    terminal_write(' ');
    break;

    default:
    terminal_putentryat(uc, terminal_color, terminal_column, terminal_row);
    terminal_column++;
    }

    // Handle validation on terminal_column before terminal_row, since the logic in terminal_column can update terminal_row
    if(terminal_column >= VGA_WIDTH) {
    terminal_column = 0;
    terminal_row++;
    }

    // Handle validating terminal_row, and scrolling the screen upwards if necessary.
    if(terminal_row >= VGA_HEIGHT) {
    // You shouldn't need terminal_print_error() since you are handling the case where terminal_row >= VGA_HEIGHT
    // terminal_print_error();

    // What does this line do? Appears to set the 16th character of the 16th row to the same value as the 5th character of the 1st row.
    // terminal_buffer[(15 * VGA_WIDTH) + 15] = terminal_buffer[(0 * VGA_WIDTH) + 4];

    size_t i, j;
    for(i = 0; i < VGA_WIDTH-1; i++) {
    for(j = VGA_HEIGHT-2; j > 0; j--) {
    terminal_buffer[(j * VGA_WIDTH) + i] = terminal_buffer[((j+1) * VGA_WIDTH) + i];
    }
    }

    // Also clear out the bottom row
    for(i = 0; i < VGA_WIDTH-1; i++) {
    terminal_putentryat(' ', terminal_color, i, VGA_HEIGHT-1);
    }

    terminal_row = VGA_HEIGHT-1;
    }

    update_cursor(terminal_column, terminal_row);
    }
  • 关于gcc - OSDev:为什么我的 VGA 终端滚动不起作用?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/53128322/

    30 4 0
    Copyright 2021 - 2024 cfsdn All Rights Reserved 蜀ICP备2022000587号
    广告合作:1813099741@qq.com 6ren.com