From 441c839ba7cf9ca8a6a4b9f79574898a9c0e2b13 Mon Sep 17 00:00:00 2001
From: Gwilym Kuiper <gw@ilym.me>
Date: Thu, 31 Mar 2022 23:58:28 +0100
Subject: [PATCH] Add a slightly crappy dynamic tiles API

---
 agb/examples/dynamic_tiles.rs         | 43 ++++++++++++++++++
 agb/src/display/tiled/vram_manager.rs | 65 ++++++++++++++++++++++++++-
 2 files changed, 107 insertions(+), 1 deletion(-)
 create mode 100644 agb/examples/dynamic_tiles.rs

diff --git a/agb/examples/dynamic_tiles.rs b/agb/examples/dynamic_tiles.rs
new file mode 100644
index 00000000..aa70681b
--- /dev/null
+++ b/agb/examples/dynamic_tiles.rs
@@ -0,0 +1,43 @@
+#![no_std]
+#![no_main]
+
+use agb::display::{palette16::Palette16, tiled::TileSetting, Priority};
+
+#[agb::entry]
+fn main(mut gba: agb::Gba) -> ! {
+    let (gfx, mut vram) = gba.display.video.tiled0();
+    let vblank = agb::interrupt::VBlank::get();
+
+    vram.set_background_palettes(&[Palette16::new([
+        0xff00, 0x0ff0, 0x00ff, 0xf00f, 0xf0f0, 0x0f0f, 0xaaaa, 0x5555, 0x0000, 0x0000, 0x0000,
+        0x0000, 0x0000, 0x0000, 0x0000, 0x0000,
+    ])]);
+
+    let mut bg = gfx.background(Priority::P0);
+
+    for y in 0..20u16 {
+        for x in 0..30u16 {
+            let dynamic_tile = vram.new_dynamic_tile();
+
+            for (i, bit) in dynamic_tile.tile_data.iter_mut().enumerate() {
+                *bit = ((((x + i as u16) % 8) << 4) | ((y + i as u16) % 8)) as u8
+            }
+
+            bg.set_tile(
+                &mut vram,
+                (x, y).into(),
+                &dynamic_tile.tile_set(),
+                TileSetting::from_raw(dynamic_tile.tile_index()),
+            );
+
+            vram.remove_dynamic_tile(dynamic_tile);
+        }
+    }
+
+    bg.commit();
+    bg.show();
+
+    loop {
+        vblank.wait_for_vblank();
+    }
+}
diff --git a/agb/src/display/tiled/vram_manager.rs b/agb/src/display/tiled/vram_manager.rs
index 3fa5689d..acf9d39f 100644
--- a/agb/src/display/tiled/vram_manager.rs
+++ b/agb/src/display/tiled/vram_manager.rs
@@ -1,6 +1,6 @@
 use core::{alloc::Layout, ptr::NonNull};
 
-use alloc::vec::Vec;
+use alloc::{slice, vec::Vec};
 
 use crate::{
     agb_alloc::{block_allocator::BlockAllocator, bump_allocator::StartEnd},
@@ -118,6 +118,29 @@ impl TileReferenceCount {
     }
 }
 
+#[non_exhaustive]
+pub struct DynamicTile<'a> {
+    pub tile_data: &'a mut [u8],
+}
+
+impl DynamicTile<'_> {
+    pub fn tile_set(&self) -> TileSet<'_> {
+        let tiles = unsafe {
+            slice::from_raw_parts_mut(
+                TILE_RAM_START as *mut u8,
+                1024 * TileFormat::FourBpp.tile_size(),
+            )
+        };
+
+        TileSet::new(tiles, TileFormat::FourBpp)
+    }
+
+    pub fn tile_index(&self) -> u16 {
+        let difference = self.tile_data.as_ptr() as usize - TILE_RAM_START;
+        (difference / (8 * 8 / 2)) as u16
+    }
+}
+
 pub struct VRamManager {
     tile_set_to_vram: HashMap<TileInTileSetReference, TileReference>,
     reference_counts: Vec<TileReferenceCount>,
@@ -144,6 +167,46 @@ impl VRamManager {
         TileReference(NonNull::new(ptr as *mut _).unwrap())
     }
 
+    pub fn new_dynamic_tile<'a>(&mut self) -> DynamicTile<'a> {
+        let tile_format = TileFormat::FourBpp;
+        let new_reference: NonNull<u32> =
+            unsafe { TILE_ALLOCATOR.alloc(TILE_LAYOUT) }.unwrap().cast();
+        let tile_reference = TileReference(new_reference);
+
+        let index = Self::index_from_reference(tile_reference);
+
+        let tiles = unsafe {
+            slice::from_raw_parts_mut(TILE_RAM_START as *mut u8, 1024 * tile_format.tile_size())
+        };
+
+        let tile_set = TileSet::new(tiles, tile_format);
+
+        self.tile_set_to_vram.insert(
+            TileInTileSetReference::new(&tile_set, index as u16),
+            tile_reference,
+        );
+
+        self.reference_counts.resize(
+            self.reference_counts.len().max(index + 1),
+            Default::default(),
+        );
+        self.reference_counts[index] =
+            TileReferenceCount::new(TileInTileSetReference::new(&tile_set, index as u16));
+
+        DynamicTile {
+            tile_data: &mut tiles
+                [index * tile_format.tile_size()..(index + 1) * tile_format.tile_size()],
+        }
+    }
+
+    pub fn remove_dynamic_tile(&mut self, dynamic_tile: DynamicTile<'_>) {
+        let pointer = NonNull::new(dynamic_tile.tile_data.as_mut_ptr() as *mut _).unwrap();
+        let tile_reference = TileReference(pointer);
+
+        let tile_index = Self::index_from_reference(tile_reference);
+        self.remove_tile(TileIndex::new(tile_index));
+    }
+
     pub(crate) fn add_tile(&mut self, tile_set: &TileSet<'_>, tile: u16) -> TileIndex {
         let reference = self
             .tile_set_to_vram