feat(display): DrawText with built-in Spleen 8x16 font (BSD-2)

crates/libkos/src/display.rs

@@ -37,3 +37,16 @@ pub fn get_dimensions(ep: CapSlot) -> (Dimension, Dimension) {
         (Dimension::new(0), Dimension::new(0))
     }
 }
+
+/// Draws `s` (up to `TEXT_BYTES` per call, more in several) from `(x, y)`.
+pub fn draw_text(ep: CapSlot, x: ScreenCoord, y: ScreenCoord, fg: Color, bg: Color, s: &[u8]) {
+    use types::display::text::{TEXT_BYTES, Text};
+    for (i, chunk) in s.chunks(TEXT_BYTES).enumerate() {
+        let x = ScreenCoord::new(x.raw().saturating_add((i * TEXT_BYTES * CELL_WIDTH) as u16));
+        let _ = syscall::request(ep, Text::new(x, y, fg, bg, chunk).words());
+    }
+}
+
+/// The display server's character cell, in pixels.
+pub const CELL_WIDTH: usize = 8;
+pub const CELL_HEIGHT: usize = 16;

crates/servers/display-server/src/font/LICENSE-spleen

@@ -0,0 +1,24 @@
+Copyright (c) 2018-2024, Frederic Cambus
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+  * Redistributions of source code must retain the above copyright
+    notice, this list of conditions and the following disclaimer.
+
+  * Redistributions in binary form must reproduce the above copyright
+    notice, this list of conditions and the following disclaimer in the
+    documentation and/or other materials provided with the distribution.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS
+BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+POSSIBILITY OF SUCH DAMAGE.

crates/servers/display-server/src/font/mod.rs

@@ -0,0 +1,114 @@
+//! The display server's one font: Spleen 8x16 (BSD-2-Clause, Frederic
+//! Cambus; see LICENSE-spleen), printable ASCII only. Generated from
+//! spleen-8x16.bdf; each glyph is 16 rows, bit 7 the leftmost pixel.
+
+pub const WIDTH: u16 = 8;
+pub const HEIGHT: u16 = 16;
+
+const FIRST: u8 = b' ';
+const LAST: u8 = b'~';
+
+/// The glyph for `c`; anything unprintable shows as `?`.
+pub fn glyph(c: u8) -> &'static [u8; 16] {
+    let c = if (FIRST..=LAST).contains(&c) { c } else { b'?' };
+    &GLYPHS[usize::from(c - FIRST)]
+}
+
+#[rustfmt::skip]
+static GLYPHS: [[u8; 16]; 95] = [
+    [0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00], // ' '
+    [0x00, 0x00, 0x18, 0x18, 0x18, 0x18, 0x18, 0x18, 0x18, 0x00, 0x18, 0x18, 0x00, 0x00, 0x00, 0x00], // '!'
+    [0x00, 0x66, 0x66, 0x66, 0x66, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00], // '"'
+    [0x00, 0x00, 0x6c, 0x6c, 0xfe, 0x6c, 0x6c, 0x6c, 0x6c, 0xfe, 0x6c, 0x6c, 0x00, 0x00, 0x00, 0x00], // '#'
+    [0x00, 0x10, 0x7e, 0xd0, 0xd0, 0xd0, 0x7c, 0x16, 0x16, 0x16, 0x16, 0xfc, 0x10, 0x00, 0x00, 0x00], // '$'
+    [0x00, 0x00, 0x06, 0x66, 0x6c, 0x0c, 0x18, 0x18, 0x30, 0x36, 0x66, 0x60, 0x00, 0x00, 0x00, 0x00], // '%'
+    [0x00, 0x00, 0x38, 0x6c, 0x6c, 0x6c, 0x38, 0x70, 0xda, 0xcc, 0xcc, 0x7a, 0x00, 0x00, 0x00, 0x00], // '&'
+    [0x00, 0x18, 0x18, 0x18, 0x18, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00], // "'"
+    [0x00, 0x0e, 0x18, 0x30, 0x30, 0x60, 0x60, 0x60, 0x60, 0x30, 0x30, 0x18, 0x0e, 0x00, 0x00, 0x00], // '('
+    [0x00, 0x70, 0x18, 0x0c, 0x0c, 0x06, 0x06, 0x06, 0x06, 0x0c, 0x0c, 0x18, 0x70, 0x00, 0x00, 0x00], // ')'
+    [0x00, 0x00, 0x00, 0x00, 0x66, 0x3c, 0x18, 0xff, 0x18, 0x3c, 0x66, 0x00, 0x00, 0x00, 0x00, 0x00], // '*'
+    [0x00, 0x00, 0x00, 0x00, 0x00, 0x18, 0x18, 0x7e, 0x18, 0x18, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00], // '+'
+    [0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x18, 0x18, 0x30, 0x00, 0x00, 0x00], // ','
+    [0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x7e, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00], // '-'
+    [0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x18, 0x18, 0x00, 0x00, 0x00, 0x00], // '.'
+    [0x00, 0x06, 0x06, 0x0c, 0x0c, 0x18, 0x18, 0x30, 0x30, 0x60, 0x60, 0xc0, 0xc0, 0x00, 0x00, 0x00], // '/'
+    [0x00, 0x00, 0x7c, 0xc6, 0xc6, 0xce, 0xde, 0xf6, 0xe6, 0xc6, 0xc6, 0x7c, 0x00, 0x00, 0x00, 0x00], // '0'
+    [0x00, 0x00, 0x18, 0x38, 0x78, 0x58, 0x18, 0x18, 0x18, 0x18, 0x18, 0x7e, 0x00, 0x00, 0x00, 0x00], // '1'
+    [0x00, 0x00, 0x7c, 0xc6, 0x06, 0x06, 0x0c, 0x18, 0x30, 0x60, 0xc6, 0xfe, 0x00, 0x00, 0x00, 0x00], // '2'
+    [0x00, 0x00, 0x7c, 0xc6, 0x06, 0x06, 0x3c, 0x06, 0x06, 0x06, 0xc6, 0x7c, 0x00, 0x00, 0x00, 0x00], // '3'
+    [0x00, 0x00, 0xc0, 0xc0, 0xcc, 0xcc, 0xcc, 0xcc, 0xfe, 0x0c, 0x0c, 0x0c, 0x00, 0x00, 0x00, 0x00], // '4'
+    [0x00, 0x00, 0xfe, 0xc6, 0xc0, 0xc0, 0xfc, 0x06, 0x06, 0x06, 0xc6, 0x7c, 0x00, 0x00, 0x00, 0x00], // '5'
+    [0x00, 0x00, 0x7c, 0xc6, 0xc0, 0xc0, 0xfc, 0xc6, 0xc6, 0xc6, 0xc6, 0x7c, 0x00, 0x00, 0x00, 0x00], // '6'
+    [0x00, 0x00, 0xfe, 0xc6, 0x06, 0x06, 0x0c, 0x18, 0x30, 0x30, 0x30, 0x30, 0x00, 0x00, 0x00, 0x00], // '7'
+    [0x00, 0x00, 0x7c, 0xc6, 0xc6, 0xc6, 0x7c, 0xc6, 0xc6, 0xc6, 0xc6, 0x7c, 0x00, 0x00, 0x00, 0x00], // '8'
+    [0x00, 0x00, 0x7c, 0xc6, 0xc6, 0xc6, 0xc6, 0x7e, 0x06, 0x06, 0xc6, 0x7c, 0x00, 0x00, 0x00, 0x00], // '9'
+    [0x00, 0x00, 0x00, 0x00, 0x00, 0x18, 0x18, 0x00, 0x00, 0x00, 0x18, 0x18, 0x00, 0x00, 0x00, 0x00], // ':'
+    [0x00, 0x00, 0x00, 0x00, 0x00, 0x18, 0x18, 0x00, 0x00, 0x00, 0x18, 0x18, 0x30, 0x00, 0x00, 0x00], // ';'
+    [0x00, 0x00, 0x06, 0x0c, 0x18, 0x30, 0x60, 0x60, 0x30, 0x18, 0x0c, 0x06, 0x00, 0x00, 0x00, 0x00], // '<'
+    [0x00, 0x00, 0x00, 0x00, 0x00, 0x7e, 0x00, 0x00, 0x7e, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00], // '='
+    [0x00, 0x00, 0x60, 0x30, 0x18, 0x0c, 0x06, 0x06, 0x0c, 0x18, 0x30, 0x60, 0x00, 0x00, 0x00, 0x00], // '>'
+    [0x00, 0x00, 0x7c, 0xc6, 0x06, 0x0c, 0x18, 0x30, 0x30, 0x00, 0x30, 0x30, 0x00, 0x00, 0x00, 0x00], // '?'
+    [0x00, 0x00, 0x00, 0x7c, 0xc2, 0xda, 0xda, 0xda, 0xda, 0xde, 0xc0, 0x7c, 0x00, 0x00, 0x00, 0x00], // '@'
+    [0x00, 0x00, 0x7c, 0xc6, 0xc6, 0xc6, 0xfe, 0xc6, 0xc6, 0xc6, 0xc6, 0xc6, 0x00, 0x00, 0x00, 0x00], // 'A'
+    [0x00, 0x00, 0xfc, 0xc6, 0xc6, 0xc6, 0xfc, 0xc6, 0xc6, 0xc6, 0xc6, 0xfc, 0x00, 0x00, 0x00, 0x00], // 'B'
+    [0x00, 0x00, 0x7e, 0xc0, 0xc0, 0xc0, 0xc0, 0xc0, 0xc0, 0xc0, 0xc0, 0x7e, 0x00, 0x00, 0x00, 0x00], // 'C'
+    [0x00, 0x00, 0xfc, 0xc6, 0xc6, 0xc6, 0xc6, 0xc6, 0xc6, 0xc6, 0xc6, 0xfc, 0x00, 0x00, 0x00, 0x00], // 'D'
+    [0x00, 0x00, 0x7e, 0xc0, 0xc0, 0xc0, 0xf8, 0xc0, 0xc0, 0xc0, 0xc0, 0x7e, 0x00, 0x00, 0x00, 0x00], // 'E'
+    [0x00, 0x00, 0x7e, 0xc0, 0xc0, 0xc0, 0xf8, 0xc0, 0xc0, 0xc0, 0xc0, 0xc0, 0x00, 0x00, 0x00, 0x00], // 'F'
+    [0x00, 0x00, 0x7e, 0xc0, 0xc0, 0xc0, 0xde, 0xc6, 0xc6, 0xc6, 0xc6, 0x7e, 0x00, 0x00, 0x00, 0x00], // 'G'
+    [0x00, 0x00, 0xc6, 0xc6, 0xc6, 0xc6, 0xfe, 0xc6, 0xc6, 0xc6, 0xc6, 0xc6, 0x00, 0x00, 0x00, 0x00], // 'H'
+    [0x00, 0x00, 0x7e, 0x18, 0x18, 0x18, 0x18, 0x18, 0x18, 0x18, 0x18, 0x7e, 0x00, 0x00, 0x00, 0x00], // 'I'
+    [0x00, 0x00, 0x7e, 0x18, 0x18, 0x18, 0x18, 0x18, 0x18, 0x18, 0x18, 0xf0, 0x00, 0x00, 0x00, 0x00], // 'J'
+    [0x00, 0x00, 0xc6, 0xc6, 0xc6, 0xcc, 0xf8, 0xcc, 0xc6, 0xc6, 0xc6, 0xc6, 0x00, 0x00, 0x00, 0x00], // 'K'
+    [0x00, 0x00, 0xc0, 0xc0, 0xc0, 0xc0, 0xc0, 0xc0, 0xc0, 0xc0, 0xc0, 0x7e, 0x00, 0x00, 0x00, 0x00], // 'L'
+    [0x00, 0x00, 0xc6, 0xee, 0xfe, 0xd6, 0xc6, 0xc6, 0xc6, 0xc6, 0xc6, 0xc6, 0x00, 0x00, 0x00, 0x00], // 'M'
+    [0x00, 0x00, 0xc6, 0xc6, 0xe6, 0xe6, 0xd6, 0xd6, 0xce, 0xce, 0xc6, 0xc6, 0x00, 0x00, 0x00, 0x00], // 'N'
+    [0x00, 0x00, 0x7c, 0xc6, 0xc6, 0xc6, 0xc6, 0xc6, 0xc6, 0xc6, 0xc6, 0x7c, 0x00, 0x00, 0x00, 0x00], // 'O'
+    [0x00, 0x00, 0xfc, 0xc6, 0xc6, 0xc6, 0xfc, 0xc0, 0xc0, 0xc0, 0xc0, 0xc0, 0x00, 0x00, 0x00, 0x00], // 'P'
+    [0x00, 0x00, 0x7c, 0xc6, 0xc6, 0xc6, 0xc6, 0xc6, 0xc6, 0xd6, 0xd6, 0x7c, 0x18, 0x0c, 0x00, 0x00], // 'Q'
+    [0x00, 0x00, 0xfc, 0xc6, 0xc6, 0xc6, 0xfc, 0xc6, 0xc6, 0xc6, 0xc6, 0xc6, 0x00, 0x00, 0x00, 0x00], // 'R'
+    [0x00, 0x00, 0x7e, 0xc0, 0xc0, 0xc0, 0x7c, 0x06, 0x06, 0x06, 0x06, 0xfc, 0x00, 0x00, 0x00, 0x00], // 'S'
+    [0x00, 0x00, 0xff, 0x18, 0x18, 0x18, 0x18, 0x18, 0x18, 0x18, 0x18, 0x18, 0x00, 0x00, 0x00, 0x00], // 'T'
+    [0x00, 0x00, 0xc6, 0xc6, 0xc6, 0xc6, 0xc6, 0xc6, 0xc6, 0xc6, 0xc6, 0x7e, 0x00, 0x00, 0x00, 0x00], // 'U'
+    [0x00, 0x00, 0xc6, 0xc6, 0xc6, 0xc6, 0xc6, 0xc6, 0xc6, 0x6c, 0x38, 0x10, 0x00, 0x00, 0x00, 0x00], // 'V'
+    [0x00, 0x00, 0xc6, 0xc6, 0xc6, 0xc6, 0xc6, 0xc6, 0xd6, 0xfe, 0xee, 0xc6, 0x00, 0x00, 0x00, 0x00], // 'W'
+    [0x00, 0x00, 0xc6, 0xc6, 0xc6, 0x6c, 0x38, 0x6c, 0xc6, 0xc6, 0xc6, 0xc6, 0x00, 0x00, 0x00, 0x00], // 'X'
+    [0x00, 0x00, 0xc6, 0xc6, 0xc6, 0xc6, 0x7e, 0x06, 0x06, 0x06, 0x06, 0xfc, 0x00, 0x00, 0x00, 0x00], // 'Y'
+    [0x00, 0x00, 0xfe, 0x06, 0x06, 0x0c, 0x18, 0x30, 0x60, 0xc0, 0xc0, 0xfe, 0x00, 0x00, 0x00, 0x00], // 'Z'
+    [0x00, 0x3e, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x3e, 0x00, 0x00, 0x00], // '['
+    [0x00, 0xc0, 0xc0, 0x60, 0x60, 0x30, 0x30, 0x18, 0x18, 0x0c, 0x0c, 0x06, 0x06, 0x00, 0x00, 0x00], // '\\'
+    [0x00, 0x7c, 0x0c, 0x0c, 0x0c, 0x0c, 0x0c, 0x0c, 0x0c, 0x0c, 0x0c, 0x0c, 0x7c, 0x00, 0x00, 0x00], // ']'
+    [0x00, 0x10, 0x38, 0x6c, 0xc6, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00], // '^'
+    [0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xfe, 0x00], // '_'
+    [0x00, 0x30, 0x18, 0x0c, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00], // '`'
+    [0x00, 0x00, 0x00, 0x00, 0x00, 0x7c, 0x06, 0x7e, 0xc6, 0xc6, 0xc6, 0x7e, 0x00, 0x00, 0x00, 0x00], // 'a'
+    [0x00, 0x00, 0xc0, 0xc0, 0xc0, 0xfc, 0xc6, 0xc6, 0xc6, 0xc6, 0xc6, 0xfc, 0x00, 0x00, 0x00, 0x00], // 'b'
+    [0x00, 0x00, 0x00, 0x00, 0x00, 0x7e, 0xc0, 0xc0, 0xc0, 0xc0, 0xc0, 0x7e, 0x00, 0x00, 0x00, 0x00], // 'c'
+    [0x00, 0x00, 0x06, 0x06, 0x06, 0x7e, 0xc6, 0xc6, 0xc6, 0xc6, 0xc6, 0x7e, 0x00, 0x00, 0x00, 0x00], // 'd'
+    [0x00, 0x00, 0x00, 0x00, 0x00, 0x7e, 0xc6, 0xc6, 0xfe, 0xc0, 0xc0, 0x7e, 0x00, 0x00, 0x00, 0x00], // 'e'
+    [0x00, 0x00, 0x1e, 0x30, 0x30, 0x30, 0x7c, 0x30, 0x30, 0x30, 0x30, 0x30, 0x00, 0x00, 0x00, 0x00], // 'f'
+    [0x00, 0x00, 0x00, 0x00, 0x00, 0x7e, 0xc6, 0xc6, 0xc6, 0xc6, 0xc6, 0x7c, 0x06, 0x06, 0xfc, 0x00], // 'g'
+    [0x00, 0x00, 0xc0, 0xc0, 0xc0, 0xfc, 0xc6, 0xc6, 0xc6, 0xc6, 0xc6, 0xc6, 0x00, 0x00, 0x00, 0x00], // 'h'
+    [0x00, 0x00, 0x18, 0x18, 0x00, 0x38, 0x18, 0x18, 0x18, 0x18, 0x18, 0x1c, 0x00, 0x00, 0x00, 0x00], // 'i'
+    [0x00, 0x00, 0x18, 0x18, 0x00, 0x18, 0x18, 0x18, 0x18, 0x18, 0x18, 0x18, 0x18, 0x18, 0x70, 0x00], // 'j'
+    [0x00, 0x00, 0xc0, 0xc0, 0xc0, 0xcc, 0xd8, 0xf0, 0xf0, 0xd8, 0xcc, 0xc6, 0x00, 0x00, 0x00, 0x00], // 'k'
+    [0x00, 0x00, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x1c, 0x00, 0x00, 0x00, 0x00], // 'l'
+    [0x00, 0x00, 0x00, 0x00, 0x00, 0xec, 0xd6, 0xd6, 0xd6, 0xd6, 0xc6, 0xc6, 0x00, 0x00, 0x00, 0x00], // 'm'
+    [0x00, 0x00, 0x00, 0x00, 0x00, 0xfc, 0xc6, 0xc6, 0xc6, 0xc6, 0xc6, 0xc6, 0x00, 0x00, 0x00, 0x00], // 'n'
+    [0x00, 0x00, 0x00, 0x00, 0x00, 0x7c, 0xc6, 0xc6, 0xc6, 0xc6, 0xc6, 0x7c, 0x00, 0x00, 0x00, 0x00], // 'o'
+    [0x00, 0x00, 0x00, 0x00, 0x00, 0xfc, 0xc6, 0xc6, 0xc6, 0xc6, 0xc6, 0xfc, 0xc0, 0xc0, 0xc0, 0x00], // 'p'
+    [0x00, 0x00, 0x00, 0x00, 0x00, 0x7e, 0xc6, 0xc6, 0xc6, 0xc6, 0xc6, 0x7e, 0x06, 0x06, 0x06, 0x00], // 'q'
+    [0x00, 0x00, 0x00, 0x00, 0x00, 0x7e, 0xc6, 0xc0, 0xc0, 0xc0, 0xc0, 0xc0, 0x00, 0x00, 0x00, 0x00], // 'r'
+    [0x00, 0x00, 0x00, 0x00, 0x00, 0x7e, 0xc0, 0xc0, 0x7c, 0x06, 0x06, 0xfc, 0x00, 0x00, 0x00, 0x00], // 's'
+    [0x00, 0x00, 0x30, 0x30, 0x30, 0x7c, 0x30, 0x30, 0x30, 0x30, 0x30, 0x1e, 0x00, 0x00, 0x00, 0x00], // 't'
+    [0x00, 0x00, 0x00, 0x00, 0x00, 0xc6, 0xc6, 0xc6, 0xc6, 0xc6, 0xc6, 0x7e, 0x00, 0x00, 0x00, 0x00], // 'u'
+    [0x00, 0x00, 0x00, 0x00, 0x00, 0xc6, 0xc6, 0xc6, 0xc6, 0x6c, 0x38, 0x10, 0x00, 0x00, 0x00, 0x00], // 'v'
+    [0x00, 0x00, 0x00, 0x00, 0x00, 0xc6, 0xc6, 0xd6, 0xd6, 0xd6, 0xd6, 0x6e, 0x00, 0x00, 0x00, 0x00], // 'w'
+    [0x00, 0x00, 0x00, 0x00, 0x00, 0xc6, 0x6c, 0x38, 0x38, 0x6c, 0xc6, 0xc6, 0x00, 0x00, 0x00, 0x00], // 'x'
+    [0x00, 0x00, 0x00, 0x00, 0x00, 0xc6, 0xc6, 0xc6, 0xc6, 0xc6, 0xc6, 0x7e, 0x06, 0x06, 0xfc, 0x00], // 'y'
+    [0x00, 0x00, 0x00, 0x00, 0x00, 0xfe, 0x06, 0x0c, 0x18, 0x30, 0x60, 0xfe, 0x00, 0x00, 0x00, 0x00], // 'z'
+    [0x00, 0x0e, 0x18, 0x18, 0x18, 0x18, 0x70, 0x70, 0x18, 0x18, 0x18, 0x18, 0x0e, 0x00, 0x00, 0x00], // '{'
+    [0x00, 0x18, 0x18, 0x18, 0x18, 0x18, 0x18, 0x18, 0x18, 0x18, 0x18, 0x18, 0x18, 0x00, 0x00, 0x00], // '|'
+    [0x00, 0x70, 0x18, 0x18, 0x18, 0x18, 0x0e, 0x0e, 0x18, 0x18, 0x18, 0x18, 0x70, 0x00, 0x00, 0x00], // '}'
+    [0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x32, 0x7e, 0x4c, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00], // '~'
+];

crates/servers/display-server/src/lib.rs

@@ -1,5 +1,6 @@
 #![no_std]
 
+pub mod font;
 pub mod protocol;
 pub mod server;
 

crates/servers/display-server/src/protocol.rs

@@ -1,4 +1,5 @@
 use server_framework::{Decode, Encode};
+use types::display::text::Text;
 use types::display::{Color, Dimension, ScreenCoord};
 
 #[derive(Debug, PartialEq)]
@@ -7,6 +8,7 @@ pub enum DisplayRequest {
     Clear { color: Color },
     Flush,
     GetDimensions,
+    DrawText(Text),
 }
 
 #[derive(Debug, PartialEq)]
@@ -27,6 +29,7 @@ impl Encode for DisplayRequest {
             DisplayRequest::Clear { color } => [1, color.raw() as usize, 0, 0],
             DisplayRequest::Flush => [2, 0, 0, 0],
             DisplayRequest::GetDimensions => [3, 0, 0, 0],
+            DisplayRequest::DrawText(t) => t.words(),
         }
     }
 }
@@ -45,7 +48,7 @@ impl Decode for DisplayRequest {
             1 => Some(DisplayRequest::Clear { color: Color::from_raw(words[1] as u32) }),
             2 => Some(DisplayRequest::Flush),
             3 => Some(DisplayRequest::GetDimensions),
-            _ => None,
+            _ => Text::from_words(words).map(DisplayRequest::DrawText),
         }
     }
 }

crates/servers/display-server/src/server.rs

@@ -2,7 +2,10 @@ use server_framework::Server;
 
 use crate::protocol::{DisplayRequest, DisplayResponse};
 use port_framebuffer::Framebuffer;
-use types::display::Dimension;
+use types::display::text::Text;
+use types::display::{Dimension, ScreenCoord};
+
+use crate::font;
 
 pub struct DisplayServer<F: Framebuffer> {
     fb: F,
@@ -16,6 +19,28 @@ impl<F: Framebuffer> DisplayServer<F> {
     pub fn framebuffer(&self) -> &F {
         &self.fb
     }
+
+    /// Draws each cell whole, background too, so text overwrites what was
+    /// there; cells past the screen edge are skipped.
+    fn draw_text(&mut self, t: &Text) {
+        let (fw, fh) = (self.fb.width().raw(), self.fb.height().raw());
+        let (x0, y0) = (t.x.raw(), t.y.raw());
+        if y0.saturating_add(font::HEIGHT) > fh {
+            return;
+        }
+        for (i, c) in t.chars().iter().enumerate() {
+            let Some(cx) = x0.checked_add(i as u16 * font::WIDTH).filter(|cx| cx + font::WIDTH <= fw) else {
+                return;
+            };
+            for (row, bits) in font::glyph(*c).iter().enumerate() {
+                for col in 0..font::WIDTH {
+                    let on = bits & (0x80 >> col) != 0;
+                    let (x, y) = (ScreenCoord::new(cx + col), ScreenCoord::new(y0 + row as u16));
+                    self.fb.write_pixel(x, y, if on { t.fg } else { t.bg });
+                }
+            }
+        }
+    }
 }
 
 impl<F: Framebuffer> Server for DisplayServer<F> {
@@ -44,6 +69,10 @@ impl<F: Framebuffer> Server for DisplayServer<F> {
                 self.fb.flush();
                 DisplayResponse::Ok
             }
+            DisplayRequest::DrawText(t) => {
+                self.draw_text(&t);
+                DisplayResponse::Ok
+            }
             DisplayRequest::GetDimensions => DisplayResponse::Dimensions {
                 width: self.fb.width(),
                 height: self.fb.height(),

crates/servers/display-server/src/tests/server.rs

@@ -138,3 +138,32 @@ fn an_off_screen_rect_draws_nothing() {
     }
     assert_eq!(server.framebuffer().pixel_count(), 0);
 }
+
+#[test]
+fn text_draws_whole_glyph_cells() {
+    use types::display::text::Text;
+    let mut server = test_server();
+    let (fg, bg) = (Color::rgb(255, 255, 255), Color::rgb(0, 0, 0));
+    let t = Text::new(ScreenCoord::new(8), ScreenCoord::new(16), fg, bg, b"A");
+    assert_eq!(server.handle(DisplayRequest::DrawText(t)), DisplayResponse::Ok);
+    // One 8x16 cell, written row by row.
+    assert_eq!(server.framebuffer().pixel_count(), 128);
+    // 'A' row 2 is 0x7c: column 0 off, column 1 on.
+    let at = |i: usize| server.framebuffer().pixel_at(i);
+    assert_eq!(at(16), (ScreenCoord::new(8), ScreenCoord::new(18), bg));
+    assert_eq!(at(17), (ScreenCoord::new(9), ScreenCoord::new(18), fg));
+}
+
+#[test]
+fn text_past_the_edge_is_cut_not_wrapped() {
+    use types::display::text::Text;
+    let mut server = test_server();
+    let c = Color::rgb(1, 1, 1);
+    // 320 wide: from x=304 only two cells fit.
+    let t = Text::new(ScreenCoord::new(304), ScreenCoord::new(0), c, c, b"abc");
+    server.handle(DisplayRequest::DrawText(t));
+    assert_eq!(server.framebuffer().pixel_count(), 256);
+    let low = Text::new(ScreenCoord::new(0), ScreenCoord::new(230), c, c, b"a");
+    server.handle(DisplayRequest::DrawText(low));
+    assert_eq!(server.framebuffer().pixel_count(), 256);
+}

crates/types/src/display.rs

@@ -48,3 +48,78 @@ impl Dimension {
         self.0
     }
 }
+
+/// `DrawText`, shared by the display server and `libkos::display`: up to
+/// `TEXT_BYTES` characters at a pixel position, each cell `fg` on `bg`.
+/// Words: `[TEXT | len << 8 | fg << 16, x | y << 16 | bg << 32, bytes 0..8, 8..16]`.
+pub mod text {
+    use super::{Color, ScreenCoord};
+
+    pub const TEXT: usize = 4;
+    pub const TEXT_BYTES: usize = 16;
+
+    #[derive(Debug, Clone, Copy, PartialEq, Eq)]
+    pub struct Text {
+        pub x: ScreenCoord,
+        pub y: ScreenCoord,
+        pub fg: Color,
+        pub bg: Color,
+        pub bytes: [u8; TEXT_BYTES],
+        pub len: usize,
+    }
+
+    impl Text {
+        /// `s` past `TEXT_BYTES` is cut off.
+        pub fn new(x: ScreenCoord, y: ScreenCoord, fg: Color, bg: Color, s: &[u8]) -> Self {
+            let len = s.len().min(TEXT_BYTES);
+            let mut bytes = [0u8; TEXT_BYTES];
+            bytes[..len].copy_from_slice(&s[..len]);
+            Self { x, y, fg, bg, bytes, len }
+        }
+
+        pub fn chars(&self) -> &[u8] {
+            &self.bytes[..self.len.min(TEXT_BYTES)]
+        }
+
+        pub fn words(&self) -> [usize; 4] {
+            let (lo, hi) = self.bytes.as_chunks::<8>().0.split_at(1);
+            [
+                TEXT | self.len << 8 | (self.fg.raw() as usize) << 16,
+                self.x.raw() as usize | (self.y.raw() as usize) << 16 | (self.bg.raw() as usize) << 32,
+                u64::from_le_bytes(lo[0]) as usize,
+                u64::from_le_bytes(hi[0]) as usize,
+            ]
+        }
+
+        pub fn from_words(w: [usize; 4]) -> Option<Self> {
+            let len = (w[0] >> 8) & 0xFF;
+            if w[0] & 0xFF != TEXT || len > TEXT_BYTES {
+                return None;
+            }
+            let mut bytes = [0u8; TEXT_BYTES];
+            for (b, word) in bytes.as_chunks_mut::<8>().0.iter_mut().zip(&w[2..]) {
+                *b = (*word as u64).to_le_bytes();
+            }
+            Some(Self {
+                x: ScreenCoord::new((w[1] & 0xFFFF) as u16),
+                y: ScreenCoord::new(((w[1] >> 16) & 0xFFFF) as u16),
+                fg: Color::from_raw((w[0] >> 16) as u32),
+                bg: Color::from_raw((w[1] >> 32) as u32),
+                bytes,
+                len,
+            })
+        }
+    }
+
+    #[cfg(test)]
+    mod tests {
+        use super::*;
+
+        #[test]
+        fn text_round_trips() {
+            let t = Text::new(ScreenCoord::new(1272), ScreenCoord::new(784), Color::rgb(1, 2, 3), Color::rgb(4, 5, 6), b"$ ls -la /home/x");
+            assert_eq!(Text::from_words(t.words()), Some(t));
+            assert_eq!(Text::new(t.x, t.y, t.fg, t.bg, &[b'a'; 40]).len, TEXT_BYTES);
+        }
+    }
+}