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

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);
+}