more writing, but the demo just shows white

book/src/ch03/gba_prng.md

@@ -297,7 +297,7 @@ do this as our first thing at startup, but we might show the title and like a
 
 ```rust
 /// Mucks with the settings of Timers 0 and 1.
-fn u32_from_user_wait() -> u32 {
+unsafe fn u32_from_user_wait() -> u32 {
   let mut t = TimerControl::default();
   t.set_enabled(true);
   t.set_cascading(true);

book/src/ch03/memory_game.md

@@ -1,2 +1,212 @@
 # memory_game
+
+For this example to show off our new skills we'll make a "memory" game. The idea
+is that there's some face down cards and you pick one, it flips, you pick a
+second, if they match they both go away, if they don't match they both turn back
+face down. The player keeps going until all the cards are gone, then we'll deal
+the cards again.
+
+For this example, I started with the `light_cycle.rs` example and then just
+copied it into a new file, `memory_game.rs`. Then I added most all the code from
+the previous sections right into that file, so we'll assume that all those
+definitions are in scope.
+
+## Getting Some Images
+
+First we need some images to show! Let's have one for our little selector thingy
+that we'll move around to pick cards with. How about some little triangles at
+the corner of a square like on a picture frame.
+
+```rust
+#[rustfmt::skip]
+pub const CARD_SELECTOR: Tile4bpp = Tile4bpp {
+  data : [
+    0x44400444,
+    0x44000044,
+    0x40000004,
+    0x00000000,
+    0x00000000,
+    0x40000004,
+    0x44000044,
+    0x44400444
+  ]
+};
+```
+
+That weird looking attribute keeps rustfmt from spreading out the values, so
+that we can see it as an ASCII art. Now that we understand what an individual
+tile looks like, let's add some mono-color squares.
+
+```rust
+#[rustfmt::skip]
+pub const FULL_ONE: Tile4bpp = Tile4bpp {
+  data : [
+    0x11111111,
+    0x11111111,
+    0x11111111,
+    0x11111111,
+    0x11111111,
+    0x11111111,
+    0x11111111,
+    0x11111111,
+  ]
+};
+
+#[rustfmt::skip]
+pub const FULL_TWO: Tile4bpp = Tile4bpp {
+  data : [
+    0x22222222,
+    0x22222222,
+    0x22222222,
+    0x22222222,
+    0x22222222,
+    0x22222222,
+    0x22222222,
+    0x22222222
+  ]
+};
+
+#[rustfmt::skip]
+pub const FULL_THREE: Tile4bpp = Tile4bpp {
+  data : [
+    0x33333333,
+    0x33333333,
+    0x33333333,
+    0x33333333,
+    0x33333333,
+    0x33333333,
+    0x33333333,
+    0x33333333
+  ]
+};
+```
+
+We can control the rest with palbank selection. Since there's 16 palbanks,
+that's 48 little colored squares we can make, and 16 different selector colors,
+which should be plenty in both cases.
+
+## Setup The Images
+
+### Arrange the PALRAM
+
+Alright, so, as we went over, the first step is to make sure that we've got our
+palette data in order. We'll be using this to set our palette values.
+
+```rust
+pub fn set_bg_palette(slot: usize, color: u16) {
+  assert!(slot < 256);
+  unsafe { PALRAM_BG_BASE.offset(slot as isize).write(color) }
+}
+```
+
+Should the type of `slot` be changed to `u8` instead of `usize`? Well, maybe.
+Let's not worry about it at the moment.
+
+Of course, we don't need to set the color black, all the values start as black.
+We just need to set the other colors we'll be wanting. For this demo, we'll just
+use the same basic colors for both the BG and Object stuff.
+
+```rust
+pub fn init_palette() {
+  // palbank 0: black/white/gray
+  set_bg_palette(2, rgb16(31, 31, 31));
+  set_bg_palette(3, rgb16(15, 15, 15));
+  // palbank 1 is reds
+  set_bg_palette(1 * 16 + 1, rgb16(31, 0, 0));
+  set_bg_palette(1 * 16 + 2, rgb16(22, 0, 0));
+  set_bg_palette(1 * 16 + 3, rgb16(10, 0, 0));
+  // palbank 2 is greens
+  set_bg_palette(2 * 16 + 1, rgb16(0, 31, 0));
+  set_bg_palette(2 * 16 + 2, rgb16(0, 22, 0));
+  set_bg_palette(2 * 16 + 3, rgb16(0, 10, 0));
+  // palbank 2 is blues
+  set_bg_palette(3 * 16 + 1, rgb16(0, 0, 31));
+  set_bg_palette(3 * 16 + 2, rgb16(0, 0, 22));
+  set_bg_palette(3 * 16 + 3, rgb16(0, 0, 10));
+
+  // Direct copy all BG selections into OBJ palette too
+  let mut bgp = PALRAM_BG_BASE;
+  let mut objp = PALRAM_OBJECT_BASE;
+  for _ in 0..(4 * 16) {
+    objp.write(bgp.read());
+    bgp = bgp.offset(1);
+    objp = objp.offset(1);
+  }
+}
+```
+
+### Arrange the Objects
+
+So, time to think about objects. I'm thinking we'll have 13 objects in use. One
+for the selector, and then 12 for the cards (a simple grid that's 4 wide and 3
+tall).
+
+We want a way to easily clear away all the objects that we're not using, which
+is all the slots starting at some index and then going to the end.
+
+```rust
+pub fn clear_objects_starting_with(base_slot: usize) {
+  let mut obj = ObjectAttributes::default();
+  obj.set_rendering(ObjectRenderMode::Disabled);
+  for s in base_slot..128 {
+    set_object_attributes(s, obj);
+  }
+}
+```
+
+Next we set out the positions of our cards. We set the tile data we need, and
+then assign the object attributes to go with it. For this, we'll make the
+position finder function be its own thing since we'll also need it for the card
+selector to move around. Finally, we set our selector as being at position 0,0
+of the card grid.
+
+```rust
+pub fn position_of_card(card_col: usize, card_row: usize) -> (u16, u16) {
+  (10 + card_col as u16 * 17, 5 + card_row as u16 * 15)
+}
+
+pub fn arrange_cards() {
+  set_obj_tile_4bpp(1, FULL_ONE);
+  set_obj_tile_4bpp(2, FULL_TWO);
+  set_obj_tile_4bpp(3, FULL_THREE);
+  let mut obj = ObjectAttributes::default();
+  obj.set_tile_index(2); // along with palbank0, this is a white card
+  for card_row in 0..3 {
+    for card_col in 0..4 {
+      let (col, row) = position_of_card(card_col, card_row);
+      obj.set_column(col);
+      obj.set_row(row);
+      set_object_attributes(1 + card_col as usize + (card_row as usize * 3), obj);
+    }
+  }
+}
+
+pub fn init_selector() {
+  set_obj_tile_4bpp(0, CARD_SELECTOR);
+  let mut obj = ObjectAttributes::default();
+  let (col, row) = position_of_card(0, 0);
+  obj.set_column(col);
+  obj.set_row(row);
+  set_object_attributes(0, obj);
+}
+```
+
+### Arrange the Background
+
+TODO
+
+## Shuffling The Cards
+
+TODO
+
+## Picking One Card
+
+TODO
+
+## Picking The Second Card
+
+TODO
+
+## Resetting The Game
+
 TODO

book/src/ch03/regular_backgrounds.md

@@ -76,28 +76,28 @@ within, and then you add the index of the tile slot you're placing it into times
 the size of that type of tile. Like this:
 
 ```rust
-pub fn bg_tile_4pp(base_block: usize, tile_index: usize) -> Tile4bpp {
+pub fn bg_tile_4bpp(base_block: usize, tile_index: usize) -> Tile4bpp {
   assert!(base_block < 4);
   assert!(tile_index < 512);
   let address = VRAM + size_of::<Charblock4bpp>() * base_block + size_of::<Tile4bpp>() * tile_index;
   unsafe { VolatilePtr(address as *mut Tile4bpp).read() }
 }
 
-pub fn set_bg_tile_4pp(base_block: usize, tile_index: usize, tile: Tile4bpp) {
+pub fn set_bg_tile_4bpp(base_block: usize, tile_index: usize, tile: Tile4bpp) {
   assert!(base_block < 4);
   assert!(tile_index < 512);
   let address = VRAM + size_of::<Charblock4bpp>() * base_block + size_of::<Tile4bpp>() * tile_index;
   unsafe { VolatilePtr(address as *mut Tile4bpp).write(tile) }
 }
 
-pub fn bg_tile_8pp(base_block: usize, tile_index: usize) -> Tile8bpp {
+pub fn bg_tile_8bpp(base_block: usize, tile_index: usize) -> Tile8bpp {
   assert!(base_block < 4);
   assert!(tile_index < 256);
   let address = VRAM + size_of::<Charblock8bpp>() * base_block + size_of::<Tile8bpp>() * tile_index;
   unsafe { VolatilePtr(address as *mut Tile8bpp).read() }
 }
 
-pub fn set_bg_tile_8pp(base_block: usize, tile_index: usize, tile: Tile8bpp) {
+pub fn set_bg_tile_8bpp(base_block: usize, tile_index: usize, tile: Tile8bpp) {
   assert!(base_block < 4);
   assert!(tile_index < 256);
   let address = VRAM + size_of::<Charblock8bpp>() * base_block + size_of::<Tile8bpp>() * tile_index;
@@ -154,7 +154,7 @@ appropriately.
 #[derive(Clone, Copy)]
 #[repr(transparent)]
 pub struct RegularScreenblock {
-  data: [RegularScreenblockEntry; 32 * 32],
+  pub data: [RegularScreenblockEntry; 32 * 32],
 }
 
 #[derive(Debug, Clone, Copy, Default)]
@@ -207,7 +207,7 @@ impl RegularScreenblockEntry {
   }
   pub fn set_palbank_index(&mut self, palbank_index: u16) {
     self.0 &= 0b1111_1111_1111;
-    self.0 |= palbank_index;
+    self.0 |= palbank_index << 12;
   }
 }
 ```

book/src/ch03/regular_objects.md

@@ -67,6 +67,32 @@ two object charblocks. However, in video modes 3, 4, and 5 the space for the
 background cuts into the lower charblock, so you can only safely use the upper
 charblock.
 
+```rust
+pub fn obj_tile_4bpp(tile_index: usize) -> Tile4bpp {
+  assert!(tile_index < 512);
+  let address = VRAM + size_of::<Charblock4bpp>() * 4 + 32 * tile_index;
+  unsafe { VolatilePtr(address as *mut Tile4bpp).read() }
+}
+
+pub fn set_obj_tile_4bpp(tile_index: usize, tile: Tile4bpp) {
+  assert!(tile_index < 512);
+  let address = VRAM + size_of::<Charblock4bpp>() * 4 + 32 * tile_index;
+  unsafe { VolatilePtr(address as *mut Tile4bpp).write(tile) }
+}
+
+pub fn obj_tile_8bpp(tile_index: usize) -> Tile8bpp {
+  assert!(tile_index < 512);
+  let address = VRAM + size_of::<Charblock8bpp>() * 4 + 32 * tile_index;
+  unsafe { VolatilePtr(address as *mut Tile8bpp).read() }
+}
+
+pub fn set_obj_tile_8bpp(tile_index: usize, tile: Tile8bpp) {
+  assert!(tile_index < 512);
+  let address = VRAM + size_of::<Charblock8bpp>() * 4 + 32 * tile_index;
+  unsafe { VolatilePtr(address as *mut Tile8bpp).write(tile) }
+}
+```
+
 With backgrounds you picked every single tile individually with a bunch of
 screen entry values. Objects don't do that at all. Instead you pick a base tile,
 size, and shape, then it figures out the rest from there. However, you may

book/src/ch03/tile_data.md

@@ -26,13 +26,13 @@ Knowing this, we can write the following definitions:
 #[derive(Debug, Clone, Copy, Default)]
 #[repr(transparent)]
 pub struct Tile4bpp {
-  data: [u32; 8]
+  pub data: [u32; 8]
 }
 
 #[derive(Debug, Clone, Copy, Default)]
 #[repr(transparent)]
 pub struct Tile8bpp {
-  data: [u32; 16]
+  pub data: [u32; 16]
 }
 ```
 
@@ -65,13 +65,13 @@ tiles, and with 8bpp there's 256 tiles. So they'd be something like this:
 #[derive(Clone, Copy)]
 #[repr(transparent)]
 pub struct Charblock4bpp {
-  data: [Tile4bpp; 512],
+  pub data: [Tile4bpp; 512],
 }
 
 #[derive(Clone, Copy)]
 #[repr(transparent)]
 pub struct Charblock8bpp {
-  data: [Tile8bpp; 256],
+  pub data: [Tile8bpp; 256],
 }
 ```
 

examples/memory_game.rs

@@ -12,48 +12,16 @@ fn panic(_info: &core::panic::PanicInfo) -> ! {
 #[start]
 fn main(_argc: isize, _argv: *const *const u8) -> isize {
   unsafe {
-    DISPCNT.write(MODE3 | BG2);
+    init_palette();
-  }
+    init_background();
-
+    clear_objects_starting_with(13);
-  let mut px = SCREEN_WIDTH / 2;
+    arrange_cards();
-  let mut py = SCREEN_HEIGHT / 2;
+    init_selector();
-  let mut color = rgb16(31, 0, 0);
-
     loop {
-    // read the input for this frame
+      // TODO the game
-    let this_frame_keys = key_input();
-
-    // adjust game state and wait for vblank
-    px += 2 * this_frame_keys.column_direction() as isize;
-    py += 2 * this_frame_keys.row_direction() as isize;
-    wait_until_vblank();
-
-    // draw the new game and wait until the next frame starts.
-    unsafe {
-      if px < 0 || py < 0 || px == SCREEN_WIDTH || py == SCREEN_HEIGHT {
-        // out of bounds, reset the screen and position.
-        mode3_clear_screen(0);
-        color = color.rotate_left(5);
-        px = SCREEN_WIDTH / 2;
-        py = SCREEN_HEIGHT / 2;
-      } else {
-        let color_here = mode3_read_pixel(px, py);
-        if color_here != 0 {
-          // crashed into our own line, reset the screen
-          mode3_clear_screen(0);
-          color = color.rotate_left(5);
-        } else {
-          // draw the new part of the line
-          mode3_draw_pixel(px, py, color);
-          mode3_draw_pixel(px, py + 1, color);
-          mode3_draw_pixel(px + 1, py, color);
-          mode3_draw_pixel(px + 1, py + 1, color);
     }
   }
 }
-    wait_until_vdraw();
-  }
-}
 
 #[derive(Debug, Clone, Copy, Hash, PartialEq, Eq, PartialOrd, Ord)]
 #[repr(transparent)]
@@ -180,25 +148,25 @@ pub fn wait_until_vdraw() {
 #[derive(Debug, Clone, Copy, Default, PartialEq, Eq)]
 #[repr(transparent)]
 pub struct Tile4bpp {
-  data: [u32; 8],
+  pub data: [u32; 8],
 }
 
 #[derive(Debug, Clone, Copy, Default, PartialEq, Eq)]
 #[repr(transparent)]
 pub struct Tile8bpp {
-  data: [u32; 16],
+  pub data: [u32; 16],
 }
 
 #[derive(Clone, Copy)]
 #[repr(transparent)]
 pub struct Charblock4bpp {
-  data: [Tile4bpp; 512],
+  pub data: [Tile4bpp; 512],
 }
 
 #[derive(Clone, Copy)]
 #[repr(transparent)]
 pub struct Charblock8bpp {
-  data: [Tile8bpp; 256],
+  pub data: [Tile8bpp; 256],
 }
 
 pub const PALRAM_BG_BASE: VolatilePtr<u16> = VolatilePtr(0x500_0000 as *mut u16);
@@ -213,34 +181,87 @@ pub fn set_bg_palette(slot: usize, color: u16) {
   unsafe { PALRAM_BG_BASE.offset(slot as isize).write(color) }
 }
 
-pub fn bg_tile_4pp(base_block: usize, tile_index: usize) -> Tile4bpp {
+pub unsafe fn init_palette() {
+  // palbank 0: black/white/gray
+  set_bg_palette(2, rgb16(31, 31, 31));
+  set_bg_palette(3, rgb16(15, 15, 15));
+  // palbank 1 is reds
+  set_bg_palette(1 * 16 + 1, rgb16(31, 0, 0));
+  set_bg_palette(1 * 16 + 2, rgb16(22, 0, 0));
+  set_bg_palette(1 * 16 + 3, rgb16(10, 0, 0));
+  // palbank 2 is greens
+  set_bg_palette(2 * 16 + 1, rgb16(0, 31, 0));
+  set_bg_palette(2 * 16 + 2, rgb16(0, 22, 0));
+  set_bg_palette(2 * 16 + 3, rgb16(0, 10, 0));
+  // palbank 2 is blues
+  set_bg_palette(3 * 16 + 1, rgb16(0, 0, 31));
+  set_bg_palette(3 * 16 + 2, rgb16(0, 0, 22));
+  set_bg_palette(3 * 16 + 3, rgb16(0, 0, 10));
+
+  // Direct copy all BG selections into OBJ palette too
+  let mut bgp = PALRAM_BG_BASE;
+  let mut objp = PALRAM_OBJECT_BASE;
+  for _ in 0..(4 * 16) {
+    objp.write(bgp.read());
+    bgp = bgp.offset(1);
+    objp = objp.offset(1);
+  }
+}
+
+pub fn bg_tile_4bpp(base_block: usize, tile_index: usize) -> Tile4bpp {
   assert!(base_block < 4);
   assert!(tile_index < 512);
   let address = VRAM + size_of::<Charblock4bpp>() * base_block + size_of::<Tile4bpp>() * tile_index;
   unsafe { VolatilePtr(address as *mut Tile4bpp).read() }
 }
 
-pub fn set_bg_tile_4pp(base_block: usize, tile_index: usize, tile: Tile4bpp) {
+pub fn set_bg_tile_4bpp(base_block: usize, tile_index: usize, tile: Tile4bpp) {
   assert!(base_block < 4);
   assert!(tile_index < 512);
   let address = VRAM + size_of::<Charblock4bpp>() * base_block + size_of::<Tile4bpp>() * tile_index;
   unsafe { VolatilePtr(address as *mut Tile4bpp).write(tile) }
 }
 
-pub fn bg_tile_8pp(base_block: usize, tile_index: usize) -> Tile8bpp {
+pub fn bg_tile_8bpp(base_block: usize, tile_index: usize) -> Tile8bpp {
   assert!(base_block < 4);
   assert!(tile_index < 256);
   let address = VRAM + size_of::<Charblock8bpp>() * base_block + size_of::<Tile8bpp>() * tile_index;
   unsafe { VolatilePtr(address as *mut Tile8bpp).read() }
 }
 
-pub fn set_bg_tile_8pp(base_block: usize, tile_index: usize, tile: Tile8bpp) {
+pub fn set_bg_tile_8bpp(base_block: usize, tile_index: usize, tile: Tile8bpp) {
   assert!(base_block < 4);
   assert!(tile_index < 256);
   let address = VRAM + size_of::<Charblock8bpp>() * base_block + size_of::<Tile8bpp>() * tile_index;
   unsafe { VolatilePtr(address as *mut Tile8bpp).write(tile) }
 }
 
+//
+
+pub fn obj_tile_4bpp(tile_index: usize) -> Tile4bpp {
+  assert!(tile_index < 512);
+  let address = VRAM + size_of::<Charblock4bpp>() * 4 + 32 * tile_index;
+  unsafe { VolatilePtr(address as *mut Tile4bpp).read() }
+}
+
+pub fn set_obj_tile_4bpp(tile_index: usize, tile: Tile4bpp) {
+  assert!(tile_index < 512);
+  let address = VRAM + size_of::<Charblock4bpp>() * 4 + 32 * tile_index;
+  unsafe { VolatilePtr(address as *mut Tile4bpp).write(tile) }
+}
+
+pub fn obj_tile_8bpp(tile_index: usize) -> Tile8bpp {
+  assert!(tile_index < 512);
+  let address = VRAM + size_of::<Charblock8bpp>() * 4 + 32 * tile_index;
+  unsafe { VolatilePtr(address as *mut Tile8bpp).read() }
+}
+
+pub fn set_obj_tile_8bpp(tile_index: usize, tile: Tile8bpp) {
+  assert!(tile_index < 512);
+  let address = VRAM + size_of::<Charblock8bpp>() * 4 + 32 * tile_index;
+  unsafe { VolatilePtr(address as *mut Tile8bpp).write(tile) }
+}
+
 #[derive(Clone, Copy)]
 #[repr(transparent)]
 pub struct RegularScreenblock {
@@ -284,7 +305,7 @@ impl RegularScreenblockEntry {
   }
   pub fn set_palbank_index(&mut self, palbank_index: u16) {
     self.0 &= 0b1111_1111_1111;
-    self.0 |= palbank_index;
+    self.0 |= palbank_index << 12;
   }
 }
 
@@ -324,6 +345,69 @@ pub fn set_object_attributes(slot: usize, obj: ObjectAttributes) {
   }
 }
 
+pub fn clear_objects_starting_with(base_slot: usize) {
+  let mut obj = ObjectAttributes::default();
+  obj.set_rendering(ObjectRenderMode::Disabled);
+  for s in base_slot..128 {
+    set_object_attributes(s, obj);
+  }
+}
+
+pub fn position_of_card(card_col: usize, card_row: usize) -> (u16, u16) {
+  (10 + card_col as u16 * 17, 5 + card_row as u16 * 15)
+}
+
+pub fn arrange_cards() {
+  set_obj_tile_4bpp(1, FULL_ONE);
+  set_obj_tile_4bpp(2, FULL_TWO);
+  set_obj_tile_4bpp(3, FULL_THREE);
+  let mut obj = ObjectAttributes::default();
+  obj.set_tile_index(2); // along with palbank0, this is a white card
+  for card_row in 0..3 {
+    for card_col in 0..4 {
+      let (col, row) = position_of_card(card_col, card_row);
+      obj.set_column(col);
+      obj.set_row(row);
+      set_object_attributes(1 + card_col as usize + (card_row as usize * 3), obj);
+    }
+  }
+}
+
+pub fn init_selector() {
+  set_obj_tile_4bpp(0, CARD_SELECTOR);
+  let mut obj = ObjectAttributes::default();
+  let (col, row) = position_of_card(0, 0);
+  obj.set_column(col);
+  obj.set_row(row);
+  set_object_attributes(0, obj);
+}
+
+/// BG2 Control
+pub const BG2CNT: VolatilePtr<u16> = VolatilePtr(0x400_000C as *mut u16);
+
+pub unsafe fn init_background() {
+  // put the bg tiles in charblock 0
+  set_bg_tile_4bpp(0, 0, FULL_ONE);
+  set_bg_tile_4bpp(0, 1, FULL_THREE);
+  // make a checker pattern, place at screenblock 8 (aka the start of charblock 1)
+  let entry_black = RegularScreenblockEntry::default();
+  let mut entry_gray = RegularScreenblockEntry::default();
+  entry_gray.set_tile_id(1);
+  let mut using_black = true;
+  let mut screenblock: RegularScreenblock = core::mem::zeroed();
+  for entry_mut in screenblock.data.iter_mut() {
+    *entry_mut = if using_black { entry_black } else { entry_gray };
+    using_black = !using_black;
+  }
+  let p: VolatilePtr<RegularScreenblock> = VolatilePtr((VRAM + size_of::<Charblock8bpp>()) as *mut RegularScreenblock);
+  p.write(screenblock);
+  // turn on bg2 and configure it
+  let display_control_value = DISPCNT.read();
+  DISPCNT.write(display_control_value | BG2);
+  const SCREEN_BASE_BLOCK_FIRST_BIT: u32 = 8;
+  BG2CNT.write(8 << SCREEN_BASE_BLOCK_FIRST_BIT);
+}
+
 #[derive(Debug, Clone, Copy, Default, PartialEq, Eq)]
 pub struct ObjectAttributes {
   attr0: u16,
@@ -634,7 +718,7 @@ impl TimerControl {
 }
 
 /// Mucks with the settings of Timers 0 and 1.
-fn u32_from_user_wait() -> u32 {
+unsafe fn u32_from_user_wait() -> u32 {
   let mut t = TimerControl::default();
   t.set_enabled(true);
   t.set_cascading(true);
@@ -649,3 +733,60 @@ fn u32_from_user_wait() -> u32 {
   let high = TM1D.read() as u32;
   (high << 32) | low
 }
+
+/// For the user's "cursor" to select a card
+#[rustfmt::skip]
+pub const CARD_SELECTOR: Tile4bpp = Tile4bpp {
+  data : [
+    0x11100111,
+    0x11000011,
+    0x10000001,
+    0x00000000,
+    0x00000000,
+    0x10000001,
+    0x11000011,
+    0x11100111
+  ]
+};
+
+#[rustfmt::skip]
+pub const FULL_ONE: Tile4bpp = Tile4bpp {
+  data : [
+    0x11111111,
+    0x11111111,
+    0x11111111,
+    0x11111111,
+    0x11111111,
+    0x11111111,
+    0x11111111,
+    0x11111111,
+  ]
+};
+
+#[rustfmt::skip]
+pub const FULL_TWO: Tile4bpp = Tile4bpp {
+  data : [
+    0x22222222,
+    0x22222222,
+    0x22222222,
+    0x22222222,
+    0x22222222,
+    0x22222222,
+    0x22222222,
+    0x22222222
+  ]
+};
+
+#[rustfmt::skip]
+pub const FULL_THREE: Tile4bpp = Tile4bpp {
+  data : [
+    0x33333333,
+    0x33333333,
+    0x33333333,
+    0x33333333,
+    0x33333333,
+    0x33333333,
+    0x33333333,
+    0x33333333
+  ]
+};

src/core_extras.rs

@@ -5,9 +5,6 @@
 /// Read and Write are made to be volatile. Offset is made to be
 /// wrapping_offset. This makes it much easier to correctly work with IO
 /// Registers and all display related memory on the GBA.
-///
-/// As a bonus, use of this type is mostly `cargo test` safe. Reads will return
-/// a `zeroed()` value instead, and writes will do nothing.
 #[derive(Debug, Clone, Copy, Hash, PartialEq, Eq, PartialOrd, Ord)]
 #[repr(transparent)]
 pub struct VolatilePtr<T>(pub *mut T);
@@ -20,47 +17,23 @@ impl<T> core::fmt::Pointer for VolatilePtr<T> {
 }
 
 impl<T> VolatilePtr<T> {
-  /// Performs a volatile read.
+  /// Performs a `read_volatile`.
-  ///
-  /// # Safety
-  ///
-  /// This method adds absolutely no additional safety, so all safety concerns
-  /// for a normal raw pointer volatile read apply.
   pub unsafe fn read(&self) -> T {
-    #[cfg(not(test))]
+    self.0.read_volatile()
-    {
-      core::ptr::read_volatile(self.0)
-    }
-    #[cfg(test)]
-    {
-      core::mem::zeroed::<T>()
-    }
   }
 
-  /// Performs a volatile write.
+  /// Performs a `write_volatile`.
-  ///
-  /// # Safety
-  ///
-  /// This method adds absolutely no additional safety, so all safety concerns
-  /// for a normal raw pointer volatile write apply.
   pub unsafe fn write(&self, data: T) {
-    #[cfg(not(test))]
+    self.0.write_volatile(data);
-    {
-      core::ptr::write_volatile(self.0, data);
-    }
-    #[cfg(test)]
-    {
-      drop(data)
-    }
   }
 
-  /// Performs a wrapping_offset by the number of slots given to a new position.
+  /// Performs a `wrapping_offset`.
-  ///
+  pub fn offset(self, count: isize) -> Self {
-  /// # Safety
-  ///
-  /// This is a wrapping_offset, so all safety concerns of a normal raw pointer
-  /// wrapping_offset apply.
-  pub unsafe fn offset(self, count: isize) -> Self {
     VolatilePtr(self.0.wrapping_offset(count))
   }
+
+  /// Performs a cast into some new pointer type.
+  pub fn cast<Z>(self) -> VolatilePtr<Z> {
+    VolatilePtr(self.0 as *mut Z)
+  }
 }