Add types for tile data.

examples/mode0.rs

@@ -3,8 +3,8 @@
 
 use gba::{
   bios::VBlankIntrWait,
-  mmio::{BG_PALRAM, DISPCNT, DISPSTAT, IE, IME},
-  sample_art::decompress_sample_font_to_vram_4bpp,
+  mmio::{BG_PALRAM, DISPCNT, DISPSTAT, IE, IME, VRAM_BG_TILE4},
+  sample_art::decompress_cga_face_to_vram_4bpp,
   video::{Color, DisplayControl, DisplayStatus},
   IrqBits,
 };
@@ -13,7 +13,8 @@ gba::panic_handler!(empty_loop);
 
 #[no_mangle]
 pub extern "C" fn main() -> ! {
-  decompress_sample_font_to_vram_4bpp();
+  decompress_cga_face_to_vram_4bpp(VRAM_BG_TILE4.as_region());
+
   BG_PALRAM.index(1).write(Color::WHITE);
   // TODO: set up the tilemap to look like something interesting
 

src/mmio.rs

@@ -6,7 +6,7 @@ use voladdress::VolAddress;
 use voladdress::{VolBlock, VolGrid2d, VolGrid2dStrided};
 
 use crate::{
-  video::{Color, DisplayControl, DisplayStatus},
+  video::{Color, DisplayControl, DisplayStatus, Tile4bpp},
   IrqBits, KeyInput,
 };
 
@@ -88,6 +88,14 @@ pub const BG_PALRAM: VolBlock<Color, SOGBA, SOGBA, 256> =
 pub const OBJ_PALRAM: VolBlock<Color, SOGBA, SOGBA, 256> =
   unsafe { VolBlock::new(0x0500_0000) };
 
+/// The VRAM's background tile view, using 4bpp tiles.
+pub const VRAM_BG_TILE4: VolBlock<Tile4bpp, SOGBA, SOGBA, 2048> =
+  unsafe { VolBlock::new(0x0600_0000) };
+
+/// The VRAM's background tile view, using 8bpp tiles.
+pub const VRAM_BG_TILE8: VolBlock<Tile4bpp, SOGBA, SOGBA, 1024> =
+  unsafe { VolBlock::new(0x0600_0000) };
+
 /// The VRAM's view in Video Mode 3.
 ///
 /// Each location is a direct color value.

src/sample_art.rs

@@ -1,13 +1,25 @@
-use crate::{bios::LZ77UnCompReadNormalWrite16bit, mmio::MODE3_VRAM};
+//! Sample art data that the crate uses in examples.
+//!
+//! You can also use this if you think it looks cool.
 
-/// Decompresses the sample font (256 tiles) into VRAM.
-pub fn decompress_sample_font_to_vram_4bpp() {
+use voladdress::{Safe, VolRegion};
+
+use crate::{bios::LZ77UnCompReadNormalWrite16bit, video::Tile4bpp};
+
+/// Decompresses the sample CGA font face into VRAM.
+///
+/// The decompressed data will be 4bpp.
+///
+/// ## Panics
+/// The provided destination needs to be at least 256 tiles, or this will panic.
+pub fn decompress_cga_face_to_vram_4bpp(dest: VolRegion<Tile4bpp, Safe, Safe>) {
+  assert!(dest.len() >= 256);
   // TODO: we should allow inputting *where* in VRAM the tiles go, instead of
   // always using the VRAM base address.
   unsafe {
     LZ77UnCompReadNormalWrite16bit(
       CGA_8X8_THICK_LZ77.as_ptr(),
-      MODE3_VRAM.as_usize() as *mut u16,
+      dest.as_mut_ptr().cast(),
     )
   }
 }

src/video.rs

@@ -210,3 +210,33 @@ impl DisplayStatus {
     Self(u16_with_value(8, 15, self.0, line as u16))
   }
 }
+
+/// Data for a 4-bit-per-pixel tile.
+///
+/// The tile is 8 pixels wide and 8 pixels tall. Each pixel is 4 bits, giving an
+/// index within the palbank for this tile's visual element. An index of 0 is a
+/// "transparent" pixel. For alignment purposes, all the data is bit packed as
+/// `u32` values.
+///
+/// Generally, you are expected to make tile art on your development machine in
+/// some way, and then pack it into your ROM as a static value. The data is then
+/// copied from ROM into the correct VRAM location at runtime. You are not
+/// expected to manipulate particular pixels within a tile at runtime.
+#[derive(Clone, Copy)]
+#[repr(transparent)]
+pub struct Tile4bpp(pub [u32; 8]);
+
+/// Data for a 8-bit-per-pixel tile.
+///
+/// The tile is 8 pixels wide and 8 pixels tall. Each pixel is 8 bits, giving an
+/// index within the full palette for this tile's visual element. An index of 0
+/// is a "transparent" pixel. For alignment purposes, all the data is bit packed
+/// as `u32` values.
+///
+/// Generally, you are expected to make tile art on your development machine in
+/// some way, and then pack it into your ROM as a static value. The data is then
+/// copied from ROM into the correct VRAM location at runtime. You are not
+/// expected to manipulate particular pixels within a tile at runtime.
+#[derive(Clone, Copy)]
+#[repr(transparent)]
+pub struct Tile8bpp(pub [u32; 16]);