From be650779e645913f37105528179a1b13bd0a7793 Mon Sep 17 00:00:00 2001
From: Gwilym Kuiper <gw@ilym.me>
Date: Tue, 3 May 2022 23:23:25 +0100
Subject: [PATCH] Correctly allocate screenblocks

---
 agb/src/display/tiled/map.rs                  | 15 ++++++
 agb/src/display/tiled/mod.rs                  |  4 ++
 agb/src/display/tiled/tiled0.rs               | 47 ++++++++++++++++---
 .../the-hat-chooses-the-wizard/src/main.rs    |  4 +-
 4 files changed, 61 insertions(+), 9 deletions(-)

diff --git a/agb/src/display/tiled/map.rs b/agb/src/display/tiled/map.rs
index c42cbeda..568091f6 100644
--- a/agb/src/display/tiled/map.rs
+++ b/agb/src/display/tiled/map.rs
@@ -164,7 +164,10 @@ impl RegularMap {
 pub struct MapLoan<'a, T> {
     map: T,
     background_id: u8,
+    screenblock_id: u8,
+    screenblock_length: u8,
     regular_map_list: &'a RefCell<Bitarray<1>>,
+    screenblock_list: &'a RefCell<Bitarray<1>>,
 }
 
 impl<'a, T> Deref for MapLoan<'a, T> {
@@ -185,12 +188,18 @@ impl<'a, T> MapLoan<'a, T> {
     pub(crate) fn new(
         map: T,
         background_id: u8,
+        screenblock_id: u8,
+        screenblock_length: u8,
         regular_map_list: &'a RefCell<Bitarray<1>>,
+        screenblock_list: &'a RefCell<Bitarray<1>>,
     ) -> Self {
         MapLoan {
             map,
             background_id,
+            screenblock_id,
+            screenblock_length,
             regular_map_list,
+            screenblock_list,
         }
     }
 }
@@ -200,5 +209,11 @@ impl<'a, T> Drop for MapLoan<'a, T> {
         self.regular_map_list
             .borrow_mut()
             .set(self.background_id as usize, false);
+
+        let mut screenblock_list = self.screenblock_list.borrow_mut();
+
+        for i in self.screenblock_id..self.screenblock_id + self.screenblock_length {
+            screenblock_list.set(i as usize, false);
+        }
     }
 }
diff --git a/agb/src/display/tiled/mod.rs b/agb/src/display/tiled/mod.rs
index b09f3e6e..5a53cad6 100644
--- a/agb/src/display/tiled/mod.rs
+++ b/agb/src/display/tiled/mod.rs
@@ -48,6 +48,10 @@ impl RegularBackgroundSize {
         (self.width() * self.height()) as usize
     }
 
+    pub(crate) fn num_screen_blocks(&self) -> usize {
+        self.num_tiles() / (32 * 32)
+    }
+
     pub(crate) fn rem_euclid_width(&self, x: i32) -> u16 {
         ((x as u32) & (self.width() - 1)) as u16
     }
diff --git a/agb/src/display/tiled/tiled0.rs b/agb/src/display/tiled/tiled0.rs
index f6c20db8..fbc523e2 100644
--- a/agb/src/display/tiled/tiled0.rs
+++ b/agb/src/display/tiled/tiled0.rs
@@ -9,6 +9,7 @@ use super::{MapLoan, RegularBackgroundSize, RegularMap};
 
 pub struct Tiled0 {
     regular: RefCell<Bitarray<1>>,
+    screenblocks: RefCell<Bitarray<1>>,
 }
 
 impl Tiled0 {
@@ -17,6 +18,7 @@ impl Tiled0 {
 
         Self {
             regular: Default::default(),
+            screenblocks: Default::default(),
         }
     }
 
@@ -31,15 +33,46 @@ impl Tiled0 {
             panic!("can only have 4 active backgrounds");
         }
 
-        let bg = RegularMap::new(
-            new_background as u8,
-            (new_background + 16) as u8,
-            priority,
-            size,
-        );
+        let num_screenblocks = size.num_screen_blocks();
+        let mut screenblocks = self.screenblocks.borrow_mut();
+
+        let screenblock = find_screenblock_gap(&screenblocks, num_screenblocks);
+        for id in screenblock..(screenblock + num_screenblocks) {
+            screenblocks.set(id, true);
+        }
+
+        let bg = RegularMap::new(new_background as u8, screenblock as u8 + 16, priority, size);
 
         regular.set(new_background, true);
 
-        MapLoan::new(bg, new_background as u8, &self.regular)
+        MapLoan::new(
+            bg,
+            new_background as u8,
+            screenblock as u8,
+            num_screenblocks as u8,
+            &self.regular,
+            &self.screenblocks,
+        )
     }
 }
+
+fn find_screenblock_gap(screenblocks: &Bitarray<1>, gap: usize) -> usize {
+    let mut candidate = 0;
+
+    'outer: while candidate < 16 - gap {
+        let starting_point = candidate;
+        for attempt in starting_point..(starting_point + gap) {
+            if screenblocks.get(attempt) == Some(true) {
+                candidate = attempt + 1;
+                continue 'outer;
+            }
+        }
+
+        return candidate;
+    }
+
+    panic!(
+        "Failed to find screenblock gap of at least {} elements",
+        gap
+    );
+}
diff --git a/examples/the-hat-chooses-the-wizard/src/main.rs b/examples/the-hat-chooses-the-wizard/src/main.rs
index 57ab5ec2..cf5524dd 100644
--- a/examples/the-hat-chooses-the-wizard/src/main.rs
+++ b/examples/the-hat-chooses-the-wizard/src/main.rs
@@ -846,7 +846,7 @@ fn main(mut agb: agb::Gba) -> ! {
 
             let map_current_level = current_level;
             let mut background = InfiniteScrolledMap::new(
-                tiled.background(Priority::P2, RegularBackgroundSize::Background32x32),
+                tiled.background(Priority::P2, RegularBackgroundSize::Background64x64),
                 Box::new(|pos: Vector2D<i32>| {
                     let level = &map_tiles::LEVELS[map_current_level as usize];
                     (
@@ -861,7 +861,7 @@ fn main(mut agb: agb::Gba) -> ! {
                 }),
             );
             let mut foreground = InfiniteScrolledMap::new(
-                tiled.background(Priority::P0, RegularBackgroundSize::Background32x32),
+                tiled.background(Priority::P0, RegularBackgroundSize::Background64x64),
                 Box::new(|pos: Vector2D<i32>| {
                     let level = &map_tiles::LEVELS[map_current_level as usize];
                     (