VT/ANSI Terminal Core

ANSI/VT100 escape sequence parser and VGA-backed terminal renderer. More...

Functions
void	vt_init (void)
	Clears the VGA framebuffer, resets cursor position to (0,0), sets default attribute (light gray on black), and initialises the ANSI escape parser state machine. Called once during kernel boot before any console output.
void	vt_clear (void)
	Fills all 80x25 VGA cells with space characters using the current default attribute, resets the cursor position to row 0 column 0, and updates the hardware cursor via VGA CRT registers.
void	vt_write_byte (char c)
	If inside an ANSI escape sequence, feeds to the CSI parser and applies the completed command (cursor movement, erase, SGR color). Otherwise:
void	vt_write (const char *buf, size_t len)
	Calls vt_write_byte() for each byte in [buf, buf+len). Efficient for bulk output from tty_write() or printk().
void	vt_set_cursor_visible (bool visible)
	Writes to VGA CRT registers VGA_CUR_START_REG (index 0x0A): sets VGA_CUR_DISABLE bit to hide, clears it and sets scanline range to show.
void	vt_get_winsize (uint16_t *rows, uint16_t *cols)
	Used by tty_ioctl TIOCGWINSZ to fill struct minios_winsize.ws_row/ws_col.
uint8_t	vt_current_attr (void)
	The attribute byte encodes foreground color (bits 3:0), background color (bits 6:4), and blink (bit 7) as set by the most recent SGR sequence.

Detailed Description

ANSI/VT100 escape sequence parser and VGA-backed terminal renderer.

The VT core parses ANSI escape sequences (CSI cursor movement, SGR color, erase commands) and renders output to the VGA 80x25 text-mode framebuffer. It implements a software cursor, 256-color SGR mapped to the nearest VGA 16-color palette entry, and hardware cursor sync via the VGA CRT registers.

Function Documentation

vt_clear()

void vt_clear

(

void

)

Fills all 80x25 VGA cells with space characters using the current default attribute, resets the cursor position to row 0 column 0, and updates the hardware cursor via VGA CRT registers.

vt_clear() - Clear the terminal screen and reset cursor to (0,0).

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vt_current_attr()

uint8_t vt_current_attr

(

void

)

The attribute byte encodes foreground color (bits 3:0), background color (bits 6:4), and blink (bit 7) as set by the most recent SGR sequence.

vt_current_attr() - Return the current VGA text attribute byte.

Returns

Current VGA attribute byte (e.g. 0x07 = light gray on black).

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vt_get_winsize()

void vt_get_winsize	(	uint16_t *	rows,
		uint16_t *	cols )

Used by tty_ioctl TIOCGWINSZ to fill struct minios_winsize.ws_row/ws_col.

vt_get_winsize() - Query the terminal dimensions.

Parameters

rows	Output; set to SCREEN_ROWS (25).
cols	Output; set to SCREEN_COLS (80).

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vt_init()

void vt_init

(

void

)

Clears the VGA framebuffer, resets cursor position to (0,0), sets default attribute (light gray on black), and initialises the ANSI escape parser state machine. Called once during kernel boot before any console output.

vt_init() - Initialise the VT terminal state.

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vt_set_cursor_visible()

void vt_set_cursor_visible

(

bool

visible

)

Writes to VGA CRT registers VGA_CUR_START_REG (index 0x0A): sets VGA_CUR_DISABLE bit to hide, clears it and sets scanline range to show.

vt_set_cursor_visible() - Show or hide the hardware VGA text cursor.

Parameters

visible

true to enable the underline hardware cursor, false to hide it.

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vt_write()

void vt_write	(	const char *	buf,
		size_t	len )

Calls vt_write_byte() for each byte in [buf, buf+len). Efficient for bulk output from tty_write() or printk().

vt_write() - Write a buffer of bytes through the VT state machine.

Parameters

buf	Pointer to the bytes to write.
len	Number of bytes in @buf.

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vt_write_byte()

void vt_write_byte

(

char

c

)

If inside an ANSI escape sequence, feeds to the CSI parser and applies the completed command (cursor movement, erase, SGR color). Otherwise:

vt_write_byte() - Process one output byte through the VT state machine.

Parameters

c	Byte to process.

• ESC (0x1B): begins escape sequence.
• '\n': advances row, scrolls if at bottom.
• '\r': resets column to 0.
• '\b': moves cursor left one cell (backspace).
• Other printable bytes: writes to the VGA cell at the current cursor position with the current attribute, then advances the cursor.

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