Remove pop while loading a level

agb/src/display/background.rs

@@ -458,6 +458,14 @@ pub struct InfiniteScrolledMap<'a> {
 
     current_pos: Vector2D<i32>,
     offset: Vector2D<i32>,
+
+    copied_up_to: i32,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum PartialUpdateStatus {
+    Done,
+    Continue,
 }
 
 impl<'a> InfiniteScrolledMap<'a> {
@@ -470,10 +478,26 @@ impl<'a> InfiniteScrolledMap<'a> {
             get_tile,
             current_pos: (0, 0).into(),
             offset: (0, 0).into(),
+            copied_up_to: 0,
         }
     }
 
-    pub fn init(&mut self, vram: &mut VRamManager, pos: Vector2D<i32>) {
+    pub fn init(
+        &mut self,
+        vram: &mut VRamManager,
+        pos: Vector2D<i32>,
+        between_updates: Box<dyn Fn()>,
+    ) {
+        while self.init_partial(vram, pos) != PartialUpdateStatus::Done {
+            between_updates();
+        }
+    }
+
+    pub fn init_partial(
+        &mut self,
+        vram: &mut VRamManager,
+        pos: Vector2D<i32>,
+    ) -> PartialUpdateStatus {
         self.current_pos = pos;
 
         let x_start = div_floor(self.current_pos.x, 8);
@@ -492,29 +516,45 @@ impl<'a> InfiniteScrolledMap<'a> {
         self.map.set_scroll_pos(offset_scroll);
         self.offset = (x_start, y_start).into();
 
-        for (y_idx, y) in (y_start..y_end).enumerate() {
+        let copy_from = self.copied_up_to;
+        const ROWS_TO_COPY: i32 = 2;
+
+        for (y_idx, y) in
+            ((y_start + copy_from)..(y_end.min(y_start + copy_from + ROWS_TO_COPY))).enumerate()
+        {
             for (x_idx, x) in (x_start..x_end).enumerate() {
                 let pos = (x, y).into();
                 let (tile_set_ref, tile_setting) = (self.get_tile)(pos);
 
                 self.map.set_tile(
                     vram,
-                    (x_idx as u16, y_idx as u16).into(),
+                    (x_idx as u16, (y_idx + copy_from as usize) as u16).into(),
                     tile_set_ref,
                     tile_setting,
                 );
             }
         }
+
+        if copy_from + ROWS_TO_COPY >= y_end - y_start {
+            self.copied_up_to = 0;
+            PartialUpdateStatus::Done
+        } else {
+            self.copied_up_to = copy_from + ROWS_TO_COPY;
+            PartialUpdateStatus::Continue
+        }
     }
 
-    pub fn set_pos(&mut self, vram: &mut VRamManager, new_pos: Vector2D<i32>) {
+    pub fn set_pos(
+        &mut self,
+        vram: &mut VRamManager,
+        new_pos: Vector2D<i32>,
+    ) -> PartialUpdateStatus {
         let old_pos = self.current_pos;
 
         let difference = new_pos - old_pos;
 
         if difference.x.abs() > 10 * 8 || difference.y.abs() > 10 * 8 {
-            self.init(vram, new_pos);
-            return;
+            return self.init_partial(vram, new_pos);
         }
 
         self.current_pos = new_pos;
@@ -599,6 +639,8 @@ impl<'a> InfiniteScrolledMap<'a> {
             .into();
 
         self.map.set_scroll_pos(new_scroll);
+
+        PartialUpdateStatus::Done
     }
 
     pub fn show(&mut self) {

examples/the-hat-chooses-the-wizard/src/main.rs

@@ -5,7 +5,9 @@ extern crate alloc;
 
 use agb::{
     display::{
-        background::{InfiniteScrolledMap, TileFormat, TileSet, TileSetting, VRamManager},
+        background::{
+            InfiniteScrolledMap, PartialUpdateStatus, TileFormat, TileSet, TileSetting, VRamManager,
+        },
         object::{ObjectControl, ObjectStandard, Size},
         Priority, HEIGHT, WIDTH,
     },
@@ -285,12 +287,12 @@ impl<'a, 'b> Map<'a, 'b> {
         self.foreground.commit();
     }
 
-    pub fn init_background(&mut self, vram: &mut VRamManager) {
-        self.background.init(vram, self.position.floor());
+    pub fn init_background(&mut self, vram: &mut VRamManager) -> PartialUpdateStatus {
+        self.background.init_partial(vram, self.position.floor())
     }
 
-    pub fn init_foreground(&mut self, vram: &mut VRamManager) {
-        self.foreground.init(vram, self.position.floor());
+    pub fn init_foreground(&mut self, vram: &mut VRamManager) -> PartialUpdateStatus {
+        self.foreground.init_partial(vram, self.position.floor())
     }
 }
 
@@ -885,32 +887,21 @@ fn main(mut agb: agb::Gba) -> ! {
                 agb::input::ButtonController::new(),
             );
 
+            while level.background.init_background(&mut vram) != PartialUpdateStatus::Done {
                 music_box.before_frame(&mut mixer);
                 mixer.frame();
                 vblank.wait_for_vblank();
                 mixer.after_vblank();
-            let (before_init_cycles, before_init_cycles_2) =
-                (timer.get_value(), timer_cascade.get_value());
-
-            level.background.init_background(&mut vram);
-
-            let (after_init_cycles, after_init_cycles_2) =
-                (timer.get_value(), timer_cascade.get_value());
-            let after_init_cycles =
-                (after_init_cycles as u32) | ((after_init_cycles_2 as u32) << 16);
-            let before_init_cycles =
-                (before_init_cycles as u32) | ((before_init_cycles_2 as u32) << 16);
+            }
 
+            while level.background.init_foreground(&mut vram) != PartialUpdateStatus::Done {
                 music_box.before_frame(&mut mixer);
                 mixer.frame();
-            agb::println!("cycles for init {}", after_init_cycles - before_init_cycles);
                 vblank.wait_for_vblank();
-
                 mixer.after_vblank();
+            }
 
-            level.background.init_foreground(&mut vram);
-
-            for _ in 0..60 {
+            for _ in 0..20 {
                 music_box.before_frame(&mut mixer);
                 mixer.frame();
                 vblank.wait_for_vblank();