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;