tty - VGA text terminal driver

Header: kernel/include/kernel/tty.h
Source: kernel/arch/i386/tty.c

Provides a simple 80×25 VGA text-mode terminal. Each write is mirrored to the VESA TTY renderer when it is available, so the same text appears on both outputs.

The driver maintains a per-row fill counter (t_line_fill) so that backspace can retreat to the correct column even after a line wrap.

Functions

terminal_initialize

void terminal_initialize(void);

Clear the VGA text buffer, reset the cursor to position (0, 0), and set the default colour to white-on-black. Must be called before any other t_ function.

t_putchar

void t_putchar(char c);

Write a single character to the terminal at the current cursor position and advance the cursor. A newline ('\n') moves to the start of the next row. If the cursor reaches the bottom of the screen, t_scroll() is called to shift all rows up by one. Also forwards c to vesa_tty_putchar().

t_backspace

void t_backspace(void);

Erase the character to the left of the cursor and move the cursor back one position. Handles the case where the cursor is at the start of a row by retreating to the end of the previous row using the saved t_line_fill value.

t_write

void t_write(const char *data, size_t size);

Write size bytes from data to the terminal by calling t_putchar() for each byte.

t_writestring

void t_writestring(const char *data);

Write the null-terminated string data to the terminal. Equivalent to t_write(data, strlen(data)).

t_hex

void t_hex(uint32_t num);

Print num as an unsigned hexadecimal integer (no 0x prefix).

t_dec

void t_dec(uint32_t num);

Print num as an unsigned decimal integer.

t_spinner_tick

void t_spinner_tick(uint32_t tick);

Render one frame of a four-character spinner (|, /, -, \) in the top-right corner of the VGA buffer. The frame is chosen from tick so the animation advances roughly every 12 timer ticks. Also calls vesa_tty_spinner_tick() to update the VESA display.

Called from the PIT timer callback on every tick to give a live visual indication that the kernel has not stalled.