Simplify tiled0-2

agb/src/display/tiled/mod.rs

@@ -210,15 +210,21 @@ pub(self) fn find_screenblock_gap(screenblocks: &Bitarray<1>, gap: usize) -> usi
     );
 }
 
-pub(self) trait TiledMode {
+trait TiledMode {
-    const REGULAR_BACKGROUNDS: usize;
-    const AFFINE_BACKGROUNDS: usize;
     fn screenblocks(&self) -> &RefCell<Bitarray<1>>;
+}
+
+trait CreatableRegularTiledMode: TiledMode {
+    const REGULAR_BACKGROUNDS: usize;
     fn regular(&self) -> &RefCell<Bitarray<1>>;
+}
+
+trait CreatableAffineTiledMode: TiledMode {
+    const AFFINE_BACKGROUNDS: usize;
     fn affine(&self) -> &RefCell<Bitarray<1>>;
 }
 
-pub trait RegularTiledMode {
+trait RegularTiledMode {
     fn regular_background(
         &self,
         priority: Priority,
@@ -226,7 +232,7 @@ pub trait RegularTiledMode {
     ) -> MapLoan<'_, RegularMap>;
 }
 
-pub trait AffineTiledMode {
+trait AffineTiledMode {
     fn affine_background(
         &self,
         priority: Priority,
@@ -234,15 +240,9 @@ pub trait AffineTiledMode {
     ) -> MapLoan<'_, AffineMap>;
 }
 
-// withoutboats: https://internals.rust-lang.org/t/const-generics-where-restrictions/12742/6
-pub struct If<const B: bool>;
-pub trait True {}
-impl True for If<true> {}
-
 impl<T> RegularTiledMode for T
 where
-    T: TiledMode,
+    T: CreatableRegularTiledMode,
-    If<{ T::REGULAR_BACKGROUNDS > 0 }>: True,
 {
     fn regular_background(
         &self,
@@ -283,8 +283,7 @@ where
 
 impl<T> AffineTiledMode for T
 where
-    T: TiledMode,
+    T: CreatableAffineTiledMode,
-    If<{ T::AFFINE_BACKGROUNDS > 0 }>: True,
 {
     fn affine_background(
         &self,

agb/src/display/tiled/tiled0.rs

@@ -1,6 +1,9 @@
 use core::cell::RefCell;
 
-use super::{MapLoan, RegularBackgroundSize, RegularMap, RegularTiledMode, TiledMode};
+use super::{
+    CreatableRegularTiledMode, MapLoan, RegularBackgroundSize, RegularMap, RegularTiledMode,
+    TiledMode,
+};
 use crate::{
     bitarray::Bitarray,
     display::{set_graphics_mode, DisplayMode, Priority},
@@ -31,18 +34,15 @@ impl Tiled0 {
 }
 
 impl TiledMode for Tiled0 {
-    const REGULAR_BACKGROUNDS: usize = 4;
-    const AFFINE_BACKGROUNDS: usize = 0;
-
     fn screenblocks(&self) -> &RefCell<Bitarray<1>> {
         &self.screenblocks
     }
+}
+
+impl CreatableRegularTiledMode for Tiled0 {
+    const REGULAR_BACKGROUNDS: usize = 4;
 
     fn regular(&self) -> &RefCell<Bitarray<1>> {
         &self.regular
     }
-
-    fn affine(&self) -> &RefCell<Bitarray<1>> {
-        unimplemented!()
-    }
 }

agb/src/display/tiled/tiled1.rs

@@ -1,6 +1,6 @@
 use core::cell::RefCell;
 
-use super::TiledMode;
+use super::{CreatableAffineTiledMode, CreatableRegularTiledMode, TiledMode};
 use crate::{
     bitarray::Bitarray,
     display::{set_graphics_mode, tiled::AFFINE_BG_ID_OFFSET, DisplayMode},
@@ -30,16 +30,21 @@ impl Tiled1 {
 }
 
 impl TiledMode for Tiled1 {
-    const REGULAR_BACKGROUNDS: usize = 2;
-    const AFFINE_BACKGROUNDS: usize = 1;
-
     fn screenblocks(&self) -> &RefCell<Bitarray<1>> {
         &self.screenblocks
     }
+}
+
+impl CreatableRegularTiledMode for Tiled1 {
+    const REGULAR_BACKGROUNDS: usize = 2;
 
     fn regular(&self) -> &RefCell<Bitarray<1>> {
         &self.regular
     }
+}
+
+impl CreatableAffineTiledMode for Tiled1 {
+    const AFFINE_BACKGROUNDS: usize = 1;
 
     fn affine(&self) -> &RefCell<Bitarray<1>> {
         &self.affine

agb/src/display/tiled/tiled2.rs

@@ -1,6 +1,8 @@
 use core::cell::RefCell;
 
-use super::{AffineBackgroundSize, AffineMap, AffineTiledMode, MapLoan, TiledMode};
+use super::{
+    AffineBackgroundSize, AffineMap, AffineTiledMode, CreatableAffineTiledMode, MapLoan, TiledMode,
+};
 use crate::{
     bitarray::Bitarray,
     display::{set_graphics_mode, tiled::AFFINE_BG_ID_OFFSET, DisplayMode, Priority},
@@ -36,16 +38,13 @@ impl Tiled2 {
 }
 
 impl TiledMode for Tiled2 {
-    const REGULAR_BACKGROUNDS: usize = 0;
-    const AFFINE_BACKGROUNDS: usize = 2;
-
     fn screenblocks(&self) -> &RefCell<Bitarray<1>> {
         &self.screenblocks
     }
+}
 
-    fn regular(&self) -> &RefCell<Bitarray<1>> {
+impl CreatableAffineTiledMode for Tiled2 {
-        unimplemented!()
+    const AFFINE_BACKGROUNDS: usize = 2;
-    }
 
     fn affine(&self) -> &RefCell<Bitarray<1>> {
         &self.affine