a800xl-utils 0.1.4

misc utilities for mos-a800xl-none target (Atari 800XL/XE)
Documentation 
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use crate::cio::{Cmd, IOCB};
use crate::consts;
use ufmt_write::uWrite;

/// show / hide text cursor
pub fn show_cursor(visible: bool) {
    unsafe {
        *crate::consts::CRSINH = !visible as u8;
    }
}

/// reset ATRACT (screen saver counter)
pub fn clear_atract() {
    unsafe { *consts::ATRACT = 0 }
}

/// move text cursor to specified position
pub fn gotoxy(x: i16, y: i16) {
    unsafe {
        **consts::OLDADR = *consts::OLDCHR;
        *consts::OLDADR = (*consts::SAVMSC).add(40 * y as usize + x as usize);
        let c = **consts::OLDADR;
        *consts::OLDCHR = c;
        if *consts::CRSINH == 0 {
            **consts::OLDADR |= 0x80;
        }
        set_pos(x, y);
    }
}

/// set current cursor position
pub fn set_pos(x: i16, y: i16) {
    unsafe {
        *consts::COLCRS = x as u16;
        *consts::ROWCRS = y as u8;
    }
}

/// set old cursor position (starting point for drawto)

pub fn set_start_pos(x: i16, y: i16) {
    unsafe {
        *consts::OLDCOL = x as u16;
        *consts::OLDROW = y as u8;
    }
}

/// initialize BASIC-like graphics mode
/// by opening 'S:' device on #6 CIO channel

pub fn init_graphics(mode: u8, open_mode: u8) {
    IOCB::new(6)
        .cmd(Cmd::Open as u8)
        .buffer(b"S:\x9b")
        .icax1(open_mode)
        .icax2(mode)
        .call();
}

/// close #6 CIO channel
pub fn close_graphics() {
    IOCB::new(6).cmd(Cmd::Close as u8).call();
}

/// draw line from (x, y) to (dx, dy)
pub fn draw_line(x: i16, y: i16, dx: i16, dy: i16) {
    set_start_pos(x, y);
    draw_to(dx, dy);
}

/// draw line from last position to (dx, dy)
pub fn draw_to(dx: i16, dy: i16) {
    set_pos(dx, dy);
    IOCB::new(6).cmd(17).icax1(12).icax2(0).call();
}

/// set color for next plot / draw operation
pub fn set_color(color: u8) {
    unsafe {
        *consts::ATACHR = color;
    }
}

pub fn plot(x: i16, y: i16) {
    set_pos(x, y);
    let color = unsafe { *consts::ATACHR };
    IOCB::new(6)
        .cmd(Cmd::PutBytes as u8)
        .buffer(&[])
        .call_with_a(color);
}

/// clear screen (for now only text gr0 mode)
pub fn clrscr() {
    // TODO: support other graphics modes
    let scr_slice = unsafe {
        let scr_addr = *consts::SAVMSC;
        core::slice::from_raw_parts_mut(scr_addr, 40 * 24)
    };
    scr_slice.fill(0);
}

/// convert atascii code to screen code
pub fn atascii_to_screen(b: u8) -> u8 {
    (match b & 0x7f {
        0..=31 => b + 64,
        32..=95 => b - 32,
        _ => b,
    }) | (b & 128)
}

/// [ufmt::uWrite] implementation for writing directly to screen memory
/// (it converts atascii text to screen codes)
pub struct ScreenMemoryWriter<'a> {
    buffer: &'a mut [u8],
    written: usize,
}

impl<'a> ScreenMemoryWriter<'a> {
    pub fn new(buffer: &'a mut [u8]) -> ScreenMemoryWriter<'a> {
        ScreenMemoryWriter { buffer, written: 0 }
    }
}

impl<'a> uWrite for ScreenMemoryWriter<'a> {
    type Error = ();

    fn write_str(&mut self, s: &str) -> Result<(), Self::Error> {
        for b in s.bytes().map(atascii_to_screen) {
            if self.written >= self.buffer.len() {
                return Err(());
            }
            self.buffer[self.written] = b;
            self.written += 1;
        }
        Ok(())
    }
}