132 lines
3.0 KiB
C
132 lines
3.0 KiB
C
#include "screen.h"
|
|
|
|
#include "../kernel/ports.h"
|
|
#include "../kernel/util.h"
|
|
|
|
int get_screen_offset(int col, int row) {
|
|
return (row * MAX_COLS + col) * 2;
|
|
}
|
|
|
|
int get_cursor() {
|
|
/*
|
|
* screens use their control register as an index to
|
|
* select their internal registers of which:
|
|
* - 14: high byte of the cursor's offset
|
|
* - 15: low byte of the cursor's offset
|
|
*/
|
|
port_byte_out(REG_SCREEN_CTRL, 14);
|
|
/* get the high byte and shift it a byte */
|
|
int offset = port_byte_in(REG_SCREEN_DATA) << 8;
|
|
port_byte_out(REG_SCREEN_CTRL, 15);
|
|
/* now add the low byte with the free space from before */
|
|
offset += port_byte_in(REG_SCREEN_DATA);
|
|
|
|
/* remember: each cell is two bytes, not one */
|
|
return offset * 2;
|
|
}
|
|
|
|
void set_cursor(int offset) {
|
|
/* convert from cell offset to char offset */
|
|
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);
|
|
}
|
|
|
|
int handle_scrolling(int cursor_offset) {
|
|
/* if within the screen then don't modify */
|
|
if(cursor_offset < MAX_ROWS * MAX_COLS * 2)
|
|
return cursor_offset;
|
|
|
|
/* translate rows back by one */
|
|
unsigned int i;
|
|
for(i = 1; i < MAX_ROWS; ++i)
|
|
{
|
|
memory_copy((char*)get_screen_offset(0, i) + VIDEO_ADDRESS,
|
|
(char*)get_screen_offset(0, i - 1) + VIDEO_ADDRESS,
|
|
MAX_COLS * 2);
|
|
}
|
|
|
|
/* set last line to blank */
|
|
char *last_line = (char*)get_screen_offset(0, MAX_ROWS - 1) + VIDEO_ADDRESS;
|
|
for(i = 0; i < MAX_COLS * 2; ++i)
|
|
last_line[i] = 0;
|
|
|
|
/*
|
|
* move the cursor offset to the last row instead of
|
|
* off the screen
|
|
*/
|
|
cursor_offset -= MAX_COLS * 2;
|
|
|
|
/* updated cursor position */
|
|
return cursor_offset;
|
|
}
|
|
|
|
void print_char(char c, int col, int row, char attr_byte) {
|
|
unsigned char *vidmem = (unsigned char*) VIDEO_ADDRESS;
|
|
|
|
if(!attr_byte)
|
|
attr_byte = WHITE_ON_BLACK;
|
|
|
|
/* get the offset of the screen location specified */
|
|
int offset;
|
|
/*
|
|
* if row & col are non-negative then they can be used
|
|
* as an offset
|
|
*/
|
|
if(col >= 0 && row >= 0)
|
|
offset = get_screen_offset(col, row);
|
|
/* otherwise use the cursor's current location */
|
|
else
|
|
offset = get_cursor();
|
|
|
|
/* handle a newline */
|
|
if(c == '\n')
|
|
{
|
|
int rows = offset / (2 * MAX_COLS);
|
|
offset = get_screen_offset(79,rows);
|
|
}
|
|
/* else set the character */
|
|
else
|
|
{
|
|
vidmem[offset] = c;
|
|
vidmem[offset + 1] = attr_byte;
|
|
}
|
|
|
|
/* update the offset to the next cell */
|
|
offset += 2;
|
|
/* set scrolling adjustment */
|
|
offset = handle_scrolling(offset);
|
|
/* update the cursor position */
|
|
set_cursor(offset);
|
|
}
|
|
|
|
void print_at(const char *msg, int col, int row) {
|
|
if(col >= 0 && row >= 0)
|
|
set_cursor(get_screen_offset(col, row));
|
|
|
|
int i;
|
|
for(i = 0; msg[i] != 0; ++i)
|
|
print_char(msg[i], col, row, WHITE_ON_BLACK);
|
|
}
|
|
|
|
void print(const char *msg) {
|
|
print_at(msg, -1, -1);
|
|
}
|
|
|
|
void clear_screen() {
|
|
int row, col;
|
|
|
|
for(row = 0; row < MAX_ROWS; ++row)
|
|
{
|
|
for(col = 0; col < MAX_COLS; ++col)
|
|
{
|
|
print_char(' ', col, row, WHITE_ON_BLACK);
|
|
}
|
|
}
|
|
|
|
set_cursor(get_screen_offset(0, 0));
|
|
}
|