Object based font rendering (#450)

* Pulled out of something else I was working on.

- [x] Changelog updated / no changelog update needed

CHANGELOG.md

@@ -8,10 +8,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 - New `include_palette` macro for including every colour in an image as a `u16` slice.
+- New object based text renderer.
 
 ### Changed
 - Changed the default template game.
-- `DynamicSprite` has a new API which changes the constructor and adds a `set_pixel` method.
+- `DynamicSprite` has a new API which changes the constructor and adds a `set_pixel` and `clear` methods.
 - You no longer need to install arm-none-eabi-binutils. In order to write games using `agb`, you now only need to install rust nightly.
 - 10% performance improvement with the software mixer.
 

agb-image-converter/src/font_loader.rs

@@ -25,9 +25,9 @@ pub fn load_font(font_data: &[u8], pixels_per_em: f32) -> TokenStream {
     let line_metrics = font.horizontal_line_metrics(pixels_per_em).unwrap();
 
     let line_height = line_metrics.new_line_size as i32;
-    let ascent = line_metrics.ascent as i32;
+    let mut ascent = line_metrics.ascent as i32;
 
-    let font = (0..128)
+    let letters: Vec<_> = (0..128)
         .map(|i| font.rasterize(char::from_u32(i).unwrap(), pixels_per_em))
         .map(|(metrics, bitmap)| {
             let width = metrics.width;
@@ -56,25 +56,37 @@ pub fn load_font(font_data: &[u8], pixels_per_em: f32) -> TokenStream {
                 advance_width: metrics.advance_width,
             }
         })
-        .map(|letter_data| {
-            let data_raw = ByteString(&letter_data.rendered);
-            let height = letter_data.height as u8;
-            let width = letter_data.width as u8;
-            let xmin = letter_data.xmin as i8;
-            let ymin = letter_data.ymin as i8;
-            let advance_width = letter_data.advance_width.ceil() as u8;
+        .collect();
 
-            quote!(
-                display::FontLetter::new(
-                    #width,
-                    #height,
-                    #data_raw,
-                    #xmin,
-                    #ymin,
-                    #advance_width,
-                )
+    let maximum_above_line = letters
+        .iter()
+        .map(|x| (x.height as i32 + x.ymin))
+        .max()
+        .unwrap();
+
+    if (ascent - maximum_above_line) < 0 {
+        ascent = maximum_above_line;
+    }
+
+    let font = letters.iter().map(|letter_data| {
+        let data_raw = ByteString(&letter_data.rendered);
+        let height = letter_data.height as u8;
+        let width = letter_data.width as u8;
+        let xmin = letter_data.xmin as i8;
+        let ymin = letter_data.ymin as i8;
+        let advance_width = letter_data.advance_width.ceil() as u8;
+
+        quote!(
+            display::FontLetter::new(
+                #width,
+                #height,
+                #data_raw,
+                #xmin,
+                #ymin,
+                #advance_width,
             )
-        });
+        )
+    });
 
     quote![
         display::Font::new(&[#(#font),*], #line_height, #ascent)

agb/examples/object_text_render.rs

@@ -0,0 +1,99 @@
+#![no_std]
+#![no_main]
+
+use agb::{
+    display::{
+        object::{ChangeColour, ObjectTextRender, PaletteVram, Size, TextAlignment},
+        palette16::Palette16,
+        Font, HEIGHT, WIDTH,
+    },
+    include_font,
+    input::Button,
+};
+
+extern crate alloc;
+
+use core::fmt::Write;
+
+const FONT: Font = include_font!("examples/font/yoster.ttf", 12);
+#[agb::entry]
+fn entry(gba: agb::Gba) -> ! {
+    main(gba);
+}
+
+fn main(mut gba: agb::Gba) -> ! {
+    let (mut unmanaged, _sprites) = gba.display.object.get_unmanaged();
+
+    loop {
+        let mut palette = [0x0; 16];
+        palette[1] = 0xFF_FF;
+        palette[2] = 0x00_FF;
+        let palette = Palette16::new(palette);
+        let palette = PaletteVram::new(&palette).unwrap();
+
+        let timer = gba.timers.timers();
+        let mut timer: agb::timer::Timer = timer.timer2;
+
+        timer.set_enabled(true);
+        timer.set_divider(agb::timer::Divider::Divider256);
+
+        let mut wr = ObjectTextRender::new(&FONT, Size::S16x16, palette);
+        let start = timer.value();
+
+        let player_name = "You";
+        let _ = writeln!(
+            wr,
+            "Woah!{change2} {player_name}! {change1}Hey there! I have a bunch of text I want to show you. However, you will find that the amount of text I can display is limited. Who'd have thought! Good thing that my text system supports scrolling! It only took around 20 jank versions to get here!",
+            change2 = ChangeColour::new(2),
+            change1 = ChangeColour::new(1),
+        );
+        let end = timer.value();
+
+        agb::println!(
+            "Write took {} cycles",
+            256 * (end.wrapping_sub(start) as u32)
+        );
+
+        let vblank = agb::interrupt::VBlank::get();
+        let mut input = agb::input::ButtonController::new();
+
+        let start = timer.value();
+
+        wr.layout((WIDTH, 40).into(), TextAlignment::Justify, 2);
+        let end = timer.value();
+
+        agb::println!(
+            "Layout took {} cycles",
+            256 * (end.wrapping_sub(start) as u32)
+        );
+
+        let mut line_done = false;
+        let mut frame = 0;
+
+        loop {
+            vblank.wait_for_vblank();
+            input.update();
+            let oam = &mut unmanaged.iter();
+            wr.commit(oam);
+
+            let start = timer.value();
+            if frame % 4 == 0 {
+                line_done = !wr.next_letter_group();
+            }
+            if line_done && input.is_just_pressed(Button::A) {
+                line_done = false;
+                wr.pop_line();
+            }
+            wr.update((0, HEIGHT - 40).into());
+            let end = timer.value();
+
+            frame += 1;
+
+            agb::println!(
+                "Took {} cycles, line done {}",
+                256 * (end.wrapping_sub(start) as u32),
+                line_done
+            );
+        }
+    }
+}

agb/src/agb_alloc/mod.rs

@@ -1,4 +1,3 @@
-use core::alloc::{Allocator, Layout};
 use core::ops::{Deref, DerefMut};
 use core::ptr::NonNull;
 
@@ -45,18 +44,23 @@ static GLOBAL_ALLOC: BlockAllocator = unsafe {
 
 macro_rules! impl_zst_allocator {
     ($name_of_struct: ty, $name_of_static: ident) => {
-        unsafe impl Allocator for $name_of_struct {
-            fn allocate(&self, layout: Layout) -> Result<NonNull<[u8]>, core::alloc::AllocError> {
+        unsafe impl core::alloc::Allocator for $name_of_struct {
+            fn allocate(
+                &self,
+                layout: core::alloc::Layout,
+            ) -> Result<core::ptr::NonNull<[u8]>, core::alloc::AllocError> {
                 $name_of_static.allocate(layout)
             }
 
-            unsafe fn deallocate(&self, ptr: NonNull<u8>, layout: Layout) {
+            unsafe fn deallocate(&self, ptr: core::ptr::NonNull<u8>, layout: core::alloc::Layout) {
                 $name_of_static.deallocate(ptr, layout)
             }
         }
     };
 }
 
+pub(crate) use impl_zst_allocator;
+
 /// This is the allocator for the External Working Ram. This is currently
 /// equivalent to the Global Allocator (where things are allocated if no allocator is provided). This implements the allocator trait, so
 /// is meant to be used in specifying where certain structures should be

agb/src/display/bitmap3.rs

@@ -30,4 +30,19 @@ impl Bitmap3<'_> {
         let y = y.try_into().unwrap();
         BITMAP_MODE_3.set(x, y, colour);
     }
+
+    #[must_use]
+    pub fn read_point(&self, x: i32, y: i32) -> u16 {
+        let x = x.try_into().unwrap();
+        let y = y.try_into().unwrap();
+        BITMAP_MODE_3.get(x, y)
+    }
+
+    pub fn clear(&mut self, colour: u16) {
+        for y in 0..(HEIGHT as usize) {
+            for x in 0..(WIDTH as usize) {
+                BITMAP_MODE_3.set(x, y, colour);
+            }
+        }
+    }
 }

agb/src/display/font.rs

@@ -10,12 +10,12 @@ use super::tiled::{DynamicTile, RegularMap, TileSetting, VRamManager};
 /// Does not support any unicode features.
 /// For usage see the `text_render.rs` example
 pub struct FontLetter {
-    width: u8,
-    height: u8,
-    data: &'static [u8],
-    xmin: i8,
-    ymin: i8,
-    advance_width: u8,
+    pub(crate) width: u8,
+    pub(crate) height: u8,
+    pub(crate) data: &'static [u8],
+    pub(crate) xmin: i8,
+    pub(crate) ymin: i8,
+    pub(crate) advance_width: u8,
 }
 
 impl FontLetter {
@@ -37,17 +37,24 @@ impl FontLetter {
             advance_width,
         }
     }
+
+    pub(crate) const fn bit_absolute(&self, x: usize, y: usize) -> bool {
+        let position = x + y * self.width as usize;
+        let byte = self.data[position / 8];
+        let bit = position % 8;
+        ((byte >> bit) & 1) != 0
+    }
 }
 
 pub struct Font {
-    letters: &'static [FontLetter],
+    letters: &'static [FontLetter; 128],
     line_height: i32,
     ascent: i32,
 }
 
 impl Font {
     #[must_use]
-    pub const fn new(letters: &'static [FontLetter], line_height: i32, ascent: i32) -> Self {
+    pub const fn new(letters: &'static [FontLetter; 128], line_height: i32, ascent: i32) -> Self {
         Self {
             letters,
             line_height,
@@ -55,8 +62,16 @@ impl Font {
         }
     }
 
-    fn letter(&self, letter: char) -> &'static FontLetter {
-        &self.letters[letter as usize]
+    pub(crate) fn letter(&self, letter: char) -> &'static FontLetter {
+        &self.letters[letter as usize & (128 - 1)]
+    }
+
+    pub(crate) fn ascent(&self) -> i32 {
+        self.ascent
+    }
+
+    pub(crate) fn line_height(&self) -> i32 {
+        self.line_height
     }
 }
 

agb/src/display/object.rs

@@ -9,6 +9,7 @@
 //! harder to integrate into your games depending on how they are architectured.
 
 mod affine;
+mod font;
 mod managed;
 mod sprites;
 mod unmanaged;
@@ -22,6 +23,8 @@ pub use affine::AffineMatrixInstance;
 pub use managed::{OamManaged, Object};
 pub use unmanaged::{AffineMode, OamIterator, OamSlot, OamUnmanaged, ObjectUnmanaged};
 
+pub use font::{ChangeColour, ObjectTextRender, TextAlignment};
+
 use super::DISPLAY_CONTROL;
 
 const OBJECT_ATTRIBUTE_MEMORY: *mut u16 = 0x0700_0000 as *mut u16;

agb/src/display/object/font.rs

@@ -0,0 +1,511 @@
+use core::fmt::{Display, Write};
+
+use agb_fixnum::{Num, Vector2D};
+use alloc::{collections::VecDeque, vec::Vec};
+
+use crate::display::Font;
+
+use self::{
+    preprocess::{Line, Preprocessed, PreprocessedElement},
+    renderer::{Configuration, WordRender},
+};
+
+use super::{OamIterator, ObjectUnmanaged, PaletteVram, Size, SpriteVram};
+
+mod preprocess;
+mod renderer;
+
+#[derive(Debug, PartialEq, Eq, Clone, Copy)]
+#[non_exhaustive]
+pub(crate) enum WhiteSpace {
+    NewLine,
+    Space,
+}
+
+impl WhiteSpace {
+    pub(crate) fn from_char(c: char) -> Self {
+        match c {
+            ' ' => WhiteSpace::Space,
+            '\n' => WhiteSpace::NewLine,
+            _ => panic!("char not supported whitespace"),
+        }
+    }
+}
+
+struct BufferedRender<'font> {
+    char_render: WordRender,
+    preprocessor: Preprocessed,
+    buffered_chars: VecDeque<char>,
+    letters: Letters,
+    font: &'font Font,
+}
+
+#[derive(Debug, Default)]
+struct Letters {
+    letters: VecDeque<SpriteVram>,
+    number_of_groups: usize,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]
+#[non_exhaustive]
+/// The text alignment of the layout
+pub enum TextAlignment {
+    #[default]
+    /// Left aligned, the left edge of the text lines up
+    Left,
+    /// Right aligned, the right edge of the text lines up
+    Right,
+    /// Center aligned, the center of the text lines up
+    Center,
+    /// Justified, both the left and right edges line up with space width adapted to make it so.
+    Justify,
+}
+
+struct TextAlignmentSettings {
+    space_width: Num<i32, 10>,
+    start_x: i32,
+}
+
+impl TextAlignment {
+    fn settings(self, line: &Line, minimum_space_width: i32, width: i32) -> TextAlignmentSettings {
+        match self {
+            TextAlignment::Left => TextAlignmentSettings {
+                space_width: minimum_space_width.into(),
+                start_x: 0,
+            },
+            TextAlignment::Right => TextAlignmentSettings {
+                space_width: minimum_space_width.into(),
+                start_x: width - line.width(),
+            },
+            TextAlignment::Center => TextAlignmentSettings {
+                space_width: minimum_space_width.into(),
+                start_x: (width - line.width()) / 2,
+            },
+            TextAlignment::Justify => {
+                let space_width = if line.number_of_spaces() != 0 {
+                    Num::new(
+                        width - line.width() + line.number_of_spaces() as i32 * minimum_space_width,
+                    ) / line.number_of_spaces() as i32
+                } else {
+                    minimum_space_width.into()
+                };
+                TextAlignmentSettings {
+                    space_width,
+                    start_x: 0,
+                }
+            }
+        }
+    }
+}
+
+impl<'font> BufferedRender<'font> {
+    #[must_use]
+    fn new(font: &'font Font, sprite_size: Size, palette: PaletteVram) -> Self {
+        let config = Configuration::new(sprite_size, palette);
+        BufferedRender {
+            char_render: WordRender::new(config),
+            preprocessor: Preprocessed::new(),
+            buffered_chars: VecDeque::new(),
+            letters: Default::default(),
+            font,
+        }
+    }
+}
+
+fn is_private_use(c: char) -> bool {
+    ('\u{E000}'..'\u{F8FF}').contains(&c)
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+/// Changes the palette to use to draw characters.
+/// ```rust,no_run
+/// # #![no_std]
+/// # #![no_main]
+/// use agb::display::object::{ObjectTextRender, PaletteVram, ChangeColour, Size};
+/// use agb::display::palette16::Palette16;
+/// use agb::display::Font;
+///
+/// use core::fmt::Write;
+///
+/// const EXAMPLE_FONT: Font = agb::include_font!("examples/font/yoster.ttf", 12);
+///
+/// # fn foo() {
+/// let mut palette = [0x0; 16];
+/// palette[1] = 0xFF_FF;
+/// palette[2] = 0x00_FF;
+/// let palette = Palette16::new(palette);
+/// let palette = PaletteVram::new(&palette).unwrap();
+/// let mut writer = ObjectTextRender::new(&EXAMPLE_FONT, Size::S16x16, palette);
+///
+/// let _ = writeln!(writer, "Hello, {}World{}!", ChangeColour::new(2), ChangeColour::new(1));
+/// # }
+/// ```
+pub struct ChangeColour(u8);
+
+impl ChangeColour {
+    #[must_use]
+    /// Creates the colour changer. Colour is a palette index and must be in the range 0..16.
+    pub fn new(colour: usize) -> Self {
+        assert!(colour < 16, "paletted colour must be valid (0..=15)");
+
+        Self(colour as u8)
+    }
+
+    fn try_from_char(c: char) -> Option<Self> {
+        let c = c as u32 as usize;
+        if (0xE000..0xE000 + 16).contains(&c) {
+            Some(ChangeColour::new(c - 0xE000))
+        } else {
+            None
+        }
+    }
+
+    fn to_char(self) -> char {
+        char::from_u32(self.0 as u32 + 0xE000).unwrap()
+    }
+}
+
+impl Display for ChangeColour {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        f.write_char(self.to_char())
+    }
+}
+
+impl BufferedRender<'_> {
+    fn input_character(&mut self, character: char) {
+        if !is_private_use(character) {
+            self.preprocessor
+                .add_character(self.font, character, self.char_render.sprite_width());
+        }
+        self.buffered_chars.push_back(character);
+    }
+
+    fn process(&mut self) {
+        let Some(c) = self.buffered_chars.pop_front() else {
+            return;
+        };
+        match c {
+            ' ' | '\n' => {
+                if let Some(group) = self.char_render.finalise_letter() {
+                    self.letters.letters.push_back(group);
+                    self.letters.number_of_groups += 1;
+                }
+
+                self.letters.number_of_groups += 1;
+            }
+            letter => {
+                if let Some(group) = self.char_render.render_char(self.font, letter) {
+                    self.letters.letters.push_back(group);
+                    self.letters.number_of_groups += 1;
+                }
+            }
+        }
+    }
+}
+
+/// The object text renderer. Uses objects to render and layout text. It's use is non trivial.
+/// Changes the palette to use to draw characters.
+/// ```rust,no_run
+/// #![no_std]
+/// #![no_main]
+/// use agb::display::object::{ObjectTextRender, PaletteVram, TextAlignment, Size};
+/// use agb::display::palette16::Palette16;
+/// use agb::display::{Font, WIDTH};
+///
+/// use core::fmt::Write;
+///
+/// const EXAMPLE_FONT: Font = agb::include_font!("examples/font/yoster.ttf", 12);
+///
+/// #[agb::entry]
+/// fn main(gba: &mut agb::Gba) -> ! {
+///     let (mut unmanaged, _) = gba.display.object.get_unmanaged();
+///     let vblank = agb::interrupt::VBlank::get();
+///
+///     let mut palette = [0x0; 16];
+///     palette[1] = 0xFF_FF;
+///     let palette = Palette16::new(palette);
+///     let palette = PaletteVram::new(&palette).unwrap();
+///
+///     let mut writer = ObjectTextRender::new(&EXAMPLE_FONT, Size::S16x16, palette);
+///
+///     let _ = writeln!(writer, "Hello, World!");
+///     writer.layout((WIDTH, 40).into(), TextAlignment::Left, 2);
+///
+///     loop {
+///         writer.next_letter_group();
+///         writer.update((0, 0).into());
+///         vblank.wait_for_vblank();
+///         let oam = &mut unmanaged.iter();
+///         writer.commit(oam);
+///     }
+/// }
+/// ```
+pub struct ObjectTextRender<'font> {
+    buffer: BufferedRender<'font>,
+    layout: LayoutCache,
+    number_of_objects: usize,
+}
+
+impl<'font> ObjectTextRender<'font> {
+    #[must_use]
+    /// Creates a new text renderer with a given font, sprite size, and palette.
+    /// You must ensure that the sprite size can accomodate the letters from the
+    /// font otherwise it will panic at render time.
+    pub fn new(font: &'font Font, sprite_size: Size, palette: PaletteVram) -> Self {
+        Self {
+            buffer: BufferedRender::new(font, sprite_size, palette),
+            number_of_objects: 0,
+            layout: LayoutCache {
+                positions: VecDeque::new(),
+                line_capacity: VecDeque::new(),
+                objects: Vec::new(),
+                objects_are_at_origin: (0, 0).into(),
+                area: (0, 0).into(),
+            },
+        }
+    }
+}
+
+impl Write for ObjectTextRender<'_> {
+    fn write_str(&mut self, s: &str) -> core::fmt::Result {
+        for c in s.chars() {
+            self.buffer.input_character(c);
+        }
+
+        Ok(())
+    }
+}
+
+impl ObjectTextRender<'_> {
+    /// Commits work already done to screen. You can commit to multiple places in the same frame.
+    pub fn commit(&mut self, oam: &mut OamIterator) {
+        for (object, slot) in self.layout.objects.iter().zip(oam) {
+            slot.set(object);
+        }
+    }
+
+    /// Force a relayout, must be called after writing.
+    pub fn layout(
+        &mut self,
+        area: Vector2D<i32>,
+        alignment: TextAlignment,
+        paragraph_spacing: i32,
+    ) {
+        self.layout.create_positions(
+            self.buffer.font,
+            &self.buffer.preprocessor,
+            &LayoutSettings {
+                area,
+                alignment,
+                paragraph_spacing,
+            },
+        );
+    }
+
+    /// Removes one complete line. Returns whether a line could be removed. You must call [`update`][ObjectTextRender::update] after this
+    pub fn pop_line(&mut self) -> bool {
+        let width = self.layout.area.x;
+        let space = self.buffer.font.letter(' ').advance_width as i32;
+        let line_height = self.buffer.font.line_height();
+        if let Some(line) = self.buffer.preprocessor.lines(width, space).next() {
+            // there is a line
+            if self.layout.objects.len() >= line.number_of_letter_groups() {
+                // we have enough rendered letter groups to count
+                self.number_of_objects -= line.number_of_letter_groups();
+                for _ in 0..line.number_of_letter_groups() {
+                    self.buffer.letters.letters.pop_front();
+                    self.layout.positions.pop_front();
+                }
+                self.layout.line_capacity.pop_front();
+                self.layout.objects.clear();
+                self.buffer.preprocessor.pop(&line);
+                for position in self.layout.positions.iter_mut() {
+                    position.y -= line_height as i16;
+                }
+                return true;
+            }
+        }
+        false
+    }
+
+    /// Updates the internal state of the number of letters to write and popped
+    /// line. Should be called in the same frame as and after
+    /// [`next_letter_group`][ObjectTextRender::next_letter_group], [`next_line`][ObjectTextRender::next_line], and [`pop_line`][ObjectTextRender::pop_line].
+    pub fn update(&mut self, position: Vector2D<i32>) {
+        if !self.buffer.buffered_chars.is_empty()
+            && self.buffer.letters.letters.len() <= self.number_of_objects + 5
+        {
+            self.buffer.process();
+        }
+
+        self.layout.update_objects_to_display_at_position(
+            position,
+            self.buffer.letters.letters.iter(),
+            self.number_of_objects,
+        );
+    }
+
+    /// Causes the next letter group to be shown on the next update. Returns
+    /// whether another letter could be added in the space given.
+    pub fn next_letter_group(&mut self) -> bool {
+        if !self.can_render_another_element() {
+            return false;
+        }
+        self.number_of_objects += 1;
+        self.at_least_n_letter_groups(self.number_of_objects);
+
+        true
+    }
+
+    fn can_render_another_element(&self) -> bool {
+        let max_number_of_lines = (self.layout.area.y / self.buffer.font.line_height()) as usize;
+
+        let max_number_of_objects = self
+            .layout
+            .line_capacity
+            .iter()
+            .take(max_number_of_lines)
+            .sum::<usize>();
+
+        max_number_of_objects > self.number_of_objects
+    }
+
+    /// Causes the next line to be shown on the next update. Returns
+    /// whether another line could be added in the space given.
+    pub fn next_line(&mut self) -> bool {
+        let max_number_of_lines = (self.layout.area.y / self.buffer.font.line_height()) as usize;
+
+        // find current line
+
+        for (start, end) in self
+            .layout
+            .line_capacity
+            .iter()
+            .scan(0, |count, line_size| {
+                let start = *count;
+                *count += line_size;
+                Some((start, *count))
+            })
+            .take(max_number_of_lines)
+        {
+            if self.number_of_objects >= start && self.number_of_objects < end {
+                self.number_of_objects = end;
+                self.at_least_n_letter_groups(end);
+                return true;
+            }
+        }
+
+        false
+    }
+
+    fn at_least_n_letter_groups(&mut self, n: usize) {
+        while !self.buffer.buffered_chars.is_empty() && self.buffer.letters.letters.len() <= n {
+            self.buffer.process();
+        }
+    }
+}
+
+struct LayoutCache {
+    positions: VecDeque<Vector2D<i16>>,
+    line_capacity: VecDeque<usize>,
+    objects: Vec<ObjectUnmanaged>,
+    objects_are_at_origin: Vector2D<i32>,
+    area: Vector2D<i32>,
+}
+
+impl LayoutCache {
+    fn update_objects_to_display_at_position<'a>(
+        &mut self,
+        position: Vector2D<i32>,
+        letters: impl Iterator<Item = &'a SpriteVram>,
+        number_of_objects: usize,
+    ) {
+        let already_done = if position == self.objects_are_at_origin {
+            self.objects.len()
+        } else {
+            self.objects.clear();
+            0
+        };
+        self.objects.extend(
+            self.positions
+                .iter()
+                .zip(letters)
+                .take(number_of_objects)
+                .skip(already_done)
+                .map(|(offset, letter)| {
+                    let position = offset.change_base() + position;
+                    let mut object = ObjectUnmanaged::new(letter.clone());
+                    object.show().set_position(position);
+                    object
+                }),
+        );
+        self.objects.truncate(number_of_objects);
+        self.objects_are_at_origin = position;
+    }
+
+    fn create_positions(
+        &mut self,
+        font: &Font,
+        preprocessed: &Preprocessed,
+        settings: &LayoutSettings,
+    ) {
+        self.area = settings.area;
+        self.line_capacity.clear();
+        self.positions.clear();
+        for (line, line_positions) in Self::create_layout(font, preprocessed, settings) {
+            self.line_capacity.push_back(line.number_of_letter_groups());
+            self.positions
+                .extend(line_positions.map(|x| Vector2D::new(x.x as i16, x.y as i16)));
+        }
+    }
+
+    fn create_layout<'a>(
+        font: &Font,
+        preprocessed: &'a Preprocessed,
+        settings: &'a LayoutSettings,
+    ) -> impl Iterator<Item = (Line, impl Iterator<Item = Vector2D<i32>> + 'a)> + 'a {
+        let minimum_space_width = font.letter(' ').advance_width as i32;
+        let width = settings.area.x;
+        let line_height = font.line_height();
+
+        let mut head_position: Vector2D<Num<i32, 10>> = (0, -line_height).into();
+
+        preprocessed
+            .lines_element(width, minimum_space_width)
+            .map(move |(line, line_elements)| {
+                let line_settings = settings
+                    .alignment
+                    .settings(&line, minimum_space_width, width);
+
+                head_position.y += line_height;
+                head_position.x = line_settings.start_x.into();
+
+                (
+                    line,
+                    line_elements.filter_map(move |element| match element.decode() {
+                        PreprocessedElement::LetterGroup { width } => {
+                            let this_position = head_position;
+                            head_position.x += width as i32;
+                            Some(this_position.floor())
+                        }
+                        PreprocessedElement::WhiteSpace(space) => {
+                            match space {
+                                WhiteSpace::NewLine => {
+                                    head_position.y += settings.paragraph_spacing;
+                                }
+                                WhiteSpace::Space => head_position.x += line_settings.space_width,
+                            }
+                            None
+                        }
+                    }),
+                )
+            })
+    }
+}
+
+#[derive(PartialEq, Eq, Default)]
+struct LayoutSettings {
+    area: Vector2D<i32>,
+    alignment: TextAlignment,
+    paragraph_spacing: i32,
+}

agb/src/display/object/font/preprocess.rs

@@ -0,0 +1,241 @@
+use alloc::collections::VecDeque;
+
+use crate::display::Font;
+
+use super::WhiteSpace;
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub(crate) struct PreprocessedElementEncoded(u8);
+
+impl PreprocessedElementEncoded {
+    pub(crate) fn decode(self) -> PreprocessedElement {
+        match self.0 {
+            255 => PreprocessedElement::WhiteSpace(WhiteSpace::NewLine),
+            254 => PreprocessedElement::WhiteSpace(WhiteSpace::Space),
+            width => PreprocessedElement::LetterGroup { width },
+        }
+    }
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+
+pub(crate) enum PreprocessedElement {
+    LetterGroup { width: u8 },
+    WhiteSpace(WhiteSpace),
+}
+
+impl PreprocessedElement {
+    fn encode(self) -> PreprocessedElementEncoded {
+        PreprocessedElementEncoded(match self {
+            PreprocessedElement::LetterGroup { width } => width,
+            PreprocessedElement::WhiteSpace(space) => match space {
+                WhiteSpace::NewLine => 255,
+                WhiteSpace::Space => 254,
+            },
+        })
+    }
+}
+
+#[derive(Default, Debug)]
+pub(crate) struct Preprocessed {
+    widths: VecDeque<PreprocessedElementEncoded>,
+    preprocessor: Preprocessor,
+}
+
+#[derive(Debug, Default)]
+struct Preprocessor {
+    width_in_sprite: i32,
+}
+
+impl Preprocessor {
+    fn add_character(
+        &mut self,
+        font: &Font,
+        character: char,
+        sprite_width: i32,
+        widths: &mut VecDeque<PreprocessedElementEncoded>,
+    ) {
+        match character {
+            space @ (' ' | '\n') => {
+                if self.width_in_sprite != 0 {
+                    widths.push_back(
+                        PreprocessedElement::LetterGroup {
+                            width: self.width_in_sprite as u8,
+                        }
+                        .encode(),
+                    );
+                    self.width_in_sprite = 0;
+                }
+                widths.push_back(
+                    PreprocessedElement::WhiteSpace(WhiteSpace::from_char(space)).encode(),
+                );
+            }
+            letter => {
+                let letter = font.letter(letter);
+                if self.width_in_sprite + letter.width as i32 > sprite_width {
+                    widths.push_back(
+                        PreprocessedElement::LetterGroup {
+                            width: self.width_in_sprite as u8,
+                        }
+                        .encode(),
+                    );
+                    self.width_in_sprite = 0;
+                }
+                if self.width_in_sprite != 0 {
+                    self.width_in_sprite += letter.xmin as i32;
+                }
+                self.width_in_sprite += letter.advance_width as i32;
+            }
+        }
+    }
+}
+
+pub(crate) struct Lines<'preprocess> {
+    minimum_space_width: i32,
+    layout_width: i32,
+    data: &'preprocess VecDeque<PreprocessedElementEncoded>,
+    current_start_idx: usize,
+}
+
+pub(crate) struct Line {
+    width: i32,
+    number_of_text_elements: usize,
+    number_of_spaces: usize,
+    number_of_letter_groups: usize,
+}
+
+impl Line {
+    #[inline(always)]
+    pub(crate) fn width(&self) -> i32 {
+        self.width
+    }
+    #[inline(always)]
+    pub(crate) fn number_of_text_elements(&self) -> usize {
+        self.number_of_text_elements
+    }
+    #[inline(always)]
+    pub(crate) fn number_of_spaces(&self) -> usize {
+        self.number_of_spaces
+    }
+    #[inline(always)]
+    pub(crate) fn number_of_letter_groups(&self) -> usize {
+        self.number_of_letter_groups
+    }
+}
+
+impl<'pre> Iterator for Lines<'pre> {
+    type Item = Line;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        if self.current_start_idx >= self.data.len() {
+            return None;
+        }
+
+        let mut line_idx_length = 0;
+        let mut current_line_width_pixels = 0;
+        let mut spaces_after_last_word_count = 0usize;
+        let mut start_of_current_word = usize::MAX;
+        let mut length_of_current_word_pixels = 0;
+        let mut length_of_current_word = 0;
+        let mut number_of_spaces = 0;
+        let mut number_of_letter_groups = 0;
+
+        while let Some(next) = self.data.get(self.current_start_idx + line_idx_length) {
+            match next.decode() {
+                PreprocessedElement::LetterGroup { width } => {
+                    if start_of_current_word == usize::MAX {
+                        start_of_current_word = line_idx_length;
+                    }
+                    length_of_current_word_pixels += width as i32;
+                    length_of_current_word += 1;
+                    if current_line_width_pixels
+                        + length_of_current_word_pixels
+                        + spaces_after_last_word_count as i32 * self.minimum_space_width
+                        >= self.layout_width
+                    {
+                        line_idx_length = start_of_current_word;
+                        break;
+                    }
+                }
+                PreprocessedElement::WhiteSpace(space) => {
+                    if start_of_current_word != usize::MAX {
+                        // flush word
+                        current_line_width_pixels += length_of_current_word_pixels
+                            + spaces_after_last_word_count as i32 * self.minimum_space_width;
+                        number_of_spaces += spaces_after_last_word_count;
+                        number_of_letter_groups += length_of_current_word;
+
+                        // reset parser
+                        length_of_current_word_pixels = 0;
+                        length_of_current_word = 0;
+                        start_of_current_word = usize::MAX;
+                        spaces_after_last_word_count = 0;
+                    }
+
+                    match space {
+                        WhiteSpace::NewLine => {
+                            line_idx_length += 1;
+                            break;
+                        }
+                        WhiteSpace::Space => {
+                            spaces_after_last_word_count += 1;
+                        }
+                    }
+                }
+            };
+
+            line_idx_length += 1;
+        }
+
+        self.current_start_idx += line_idx_length;
+
+        Some(Line {
+            width: current_line_width_pixels,
+            number_of_text_elements: line_idx_length,
+            number_of_spaces,
+            number_of_letter_groups,
+        })
+    }
+}
+
+impl Preprocessed {
+    pub(crate) fn new() -> Self {
+        Default::default()
+    }
+
+    pub(crate) fn add_character(&mut self, font: &Font, c: char, sprite_width: i32) {
+        self.preprocessor
+            .add_character(font, c, sprite_width, &mut self.widths);
+    }
+
+    pub(crate) fn pop(&mut self, line: &Line) {
+        let elements = line.number_of_text_elements();
+        for _ in 0..elements {
+            self.widths.pop_front();
+        }
+    }
+
+    pub(crate) fn lines(&self, layout_width: i32, minimum_space_width: i32) -> Lines<'_> {
+        Lines {
+            minimum_space_width,
+            layout_width,
+            data: &self.widths,
+            current_start_idx: 0,
+        }
+    }
+
+    pub(crate) fn lines_element(
+        &self,
+        layout_width: i32,
+        minimum_space_width: i32,
+    ) -> impl Iterator<Item = (Line, impl Iterator<Item = PreprocessedElementEncoded> + '_)> {
+        let mut idx = 0;
+        self.lines(layout_width, minimum_space_width).map(move |x| {
+            let length = x.number_of_text_elements;
+
+            let d = self.widths.range(idx..(idx + length)).copied();
+            idx += length;
+            (x, d)
+        })
+    }
+}

agb/src/display/object/font/renderer.rs

@@ -0,0 +1,117 @@
+use crate::display::{
+    object::{DynamicSprite, PaletteVram, Size, SpriteVram},
+    Font,
+};
+
+use super::ChangeColour;
+
+struct WorkingLetter {
+    dynamic: DynamicSprite,
+    // where to render the letter from x_min to x_max
+    x_offset: i32,
+}
+
+impl WorkingLetter {
+    fn new(size: Size) -> Self {
+        Self {
+            dynamic: DynamicSprite::new(size),
+            x_offset: 0,
+        }
+    }
+
+    fn reset(&mut self) {
+        self.x_offset = 0;
+    }
+}
+
+pub struct Configuration {
+    sprite_size: Size,
+    palette: PaletteVram,
+}
+
+impl Configuration {
+    #[must_use]
+    pub fn new(sprite_size: Size, palette: PaletteVram) -> Self {
+        Self {
+            sprite_size,
+            palette,
+        }
+    }
+}
+
+pub(crate) struct WordRender {
+    working: WorkingLetter,
+    config: Configuration,
+    colour: usize,
+}
+
+impl WordRender {
+    pub(crate) fn sprite_width(&self) -> i32 {
+        self.config.sprite_size.to_width_height().0 as i32
+    }
+
+    #[must_use]
+    pub(crate) fn new(config: Configuration) -> Self {
+        WordRender {
+            working: WorkingLetter::new(config.sprite_size),
+            config,
+            colour: 1,
+        }
+    }
+
+    #[must_use]
+    pub(crate) fn finalise_letter(&mut self) -> Option<SpriteVram> {
+        if self.working.x_offset == 0 {
+            return None;
+        }
+
+        let mut new_sprite = DynamicSprite::new(self.config.sprite_size);
+        core::mem::swap(&mut self.working.dynamic, &mut new_sprite);
+        let sprite = new_sprite.to_vram(self.config.palette.clone());
+        self.working.reset();
+
+        Some(sprite)
+    }
+
+    #[must_use]
+    pub(crate) fn render_char(&mut self, font: &Font, c: char) -> Option<SpriteVram> {
+        if let Some(next_colour) = ChangeColour::try_from_char(c) {
+            self.colour = next_colour.0 as usize;
+            return None;
+        }
+
+        let font_letter: &crate::display::FontLetter = font.letter(c);
+
+        // uses more than the sprite can hold
+        let group = if self.working.x_offset + font_letter.width as i32
+            > self.config.sprite_size.to_width_height().0 as i32
+        {
+            self.finalise_letter()
+        } else {
+            None
+        };
+
+        if self.working.x_offset != 0 {
+            self.working.x_offset += font_letter.xmin as i32;
+        }
+
+        let y_position = font.ascent() - font_letter.height as i32 - font_letter.ymin as i32;
+
+        for y in 0..font_letter.height as usize {
+            for x in 0..font_letter.width as usize {
+                let rendered = font_letter.bit_absolute(x, y);
+                if rendered {
+                    self.working.dynamic.set_pixel(
+                        x + self.working.x_offset as usize,
+                        (y_position + y as i32) as usize,
+                        self.colour,
+                    );
+                }
+            }
+        }
+
+        self.working.x_offset += font_letter.advance_width as i32;
+
+        group
+    }
+}

agb/src/display/object/sprites/sprite_allocator.rs

@@ -1,14 +1,12 @@
 use core::{alloc::Allocator, ptr::NonNull};
 
 use alloc::{
-    alloc::Global,
     boxed::Box,
     rc::{Rc, Weak},
-    vec::Vec,
 };
 
 use crate::{
-    agb_alloc::{block_allocator::BlockAllocator, bump_allocator::StartEnd},
+    agb_alloc::{block_allocator::BlockAllocator, bump_allocator::StartEnd, impl_zst_allocator},
     display::palette16::Palette16,
     hash_map::HashMap,
 };
@@ -18,8 +16,8 @@ use super::{
     BYTES_PER_TILE_4BPP,
 };
 
-const PALETTE_SPRITE: usize = 0x0500_0200;
-const TILE_SPRITE: usize = 0x06010000;
+pub const PALETTE_SPRITE: usize = 0x0500_0200;
+pub const TILE_SPRITE: usize = 0x06010000;
 
 static SPRITE_ALLOCATOR: BlockAllocator = unsafe {
     BlockAllocator::new(StartEnd {
@@ -28,6 +26,10 @@ static SPRITE_ALLOCATOR: BlockAllocator = unsafe {
     })
 };
 
+pub struct SpriteAllocator;
+
+impl_zst_allocator!(SpriteAllocator, SPRITE_ALLOCATOR);
+
 static PALETTE_ALLOCATOR: BlockAllocator = unsafe {
     BlockAllocator::new(StartEnd {
         start: || PALETTE_SPRITE,
@@ -35,6 +37,10 @@ static PALETTE_ALLOCATOR: BlockAllocator = unsafe {
     })
 };
 
+pub struct PaletteAllocator;
+
+impl_zst_allocator!(PaletteAllocator, PALETTE_ALLOCATOR);
+
 /// The Sprite Id is a thin wrapper around the pointer to the sprite in
 /// rom and is therefore a unique identifier to a sprite
 #[derive(Clone, Copy, PartialEq, Eq, Hash)]
@@ -162,13 +168,21 @@ impl SpriteVram {
                 .as_ptr()
                 .copy_from_nonoverlapping(data.as_ptr(), data.len());
         }
-        Ok(SpriteVram {
+        Ok(unsafe { Self::from_location_size(allocated, size, palette) })
+    }
+
+    unsafe fn from_location_size(
+        data: NonNull<u8>,
+        size: Size,
+        palette: PaletteVram,
+    ) -> SpriteVram {
+        SpriteVram {
             data: Rc::new(SpriteVramData {
-                location: Location::from_sprite_ptr(allocated),
+                location: Location::from_sprite_ptr(data),
                 size,
                 palette,
             }),
-        })
+        }
     }
 
     pub(crate) fn location(&self) -> u16 {
@@ -290,31 +304,54 @@ impl Default for SpriteLoader {
 }
 
 /// Sprite data that can be used to create sprites in vram.
-pub struct DynamicSprite<A: Allocator = Global> {
-    data: Box<[u8], A>,
+pub struct DynamicSprite {
+    data: Box<[u16], SpriteAllocator>,
     size: Size,
 }
 
-impl DynamicSprite {
-    #[must_use]
-    /// Creates a new dynamic sprite.
-    pub fn new(size: Size) -> Self {
-        Self::new_in(size, Global)
+impl Clone for DynamicSprite {
+    fn clone(&self) -> Self {
+        let allocation = SpriteAllocator
+            .allocate(self.size.layout())
+            .expect("cannot allocate dynamic sprite");
+
+        let allocation = core::ptr::slice_from_raw_parts_mut(
+            allocation.as_ptr() as *mut _,
+            allocation.len() / 2,
+        );
+
+        let mut data = unsafe { Box::from_raw_in(allocation, SpriteAllocator) };
+
+        data.clone_from_slice(&self.data);
+
+        Self {
+            data,
+            size: self.size,
+        }
     }
 }
 
-impl<A: Allocator> DynamicSprite<A> {
+impl DynamicSprite {
+    /// Creates a new dynamic sprite of a given size
+    pub fn try_new(size: Size) -> Result<Self, LoaderError> {
+        let allocation = SpriteAllocator
+            .allocate_zeroed(size.layout())
+            .map_err(|_| LoaderError::SpriteFull)?;
+
+        let allocation = core::ptr::slice_from_raw_parts_mut(
+            allocation.as_ptr() as *mut _,
+            allocation.len() / 2,
+        );
+
+        let data = unsafe { Box::from_raw_in(allocation, SpriteAllocator) };
+
+        Ok(DynamicSprite { data, size })
+    }
+
     #[must_use]
-    /// Creates a new dynamic sprite of a given size in a given allocator.
-    pub fn new_in(size: Size, allocator: A) -> Self {
-        let num_bytes = size.number_of_tiles() * BYTES_PER_TILE_4BPP;
-        let mut data = Vec::with_capacity_in(num_bytes, allocator);
-
-        data.resize(num_bytes, 0);
-
-        let data = data.into_boxed_slice();
-
-        DynamicSprite { data, size }
+    /// Creates a new dynamic sprite of a given size
+    pub fn new(size: Size) -> Self {
+        Self::try_new(size).expect("couldn't allocate dynamic sprite")
     }
 
     /// Set the pixel of a sprite to a given paletted pixel. Panics if the
@@ -333,24 +370,36 @@ impl<A: Allocator> DynamicSprite<A> {
 
         let tile_number_to_modify = adjust_tile_x + adjust_tile_y * sprite_tile_x;
 
-        let byte_to_modify_in_tile = x / 2 + y * 4;
-        let byte_to_modify = tile_number_to_modify * BYTES_PER_TILE_4BPP + byte_to_modify_in_tile;
-        let mut byte = self.data[byte_to_modify];
-        let parity = (x & 0b1) * 4;
+        let (x_in_tile, y_in_tile) = (x % 8, y % 8);
 
-        byte = (byte & !(0b1111 << parity)) | ((paletted_pixel as u8) << parity);
-        self.data[byte_to_modify] = byte;
+        let half_word_to_modify_in_tile = x_in_tile / 4 + y_in_tile * 2;
+
+        let half_word_to_modify =
+            tile_number_to_modify * BYTES_PER_TILE_4BPP / 2 + half_word_to_modify_in_tile;
+        let mut half_word = self.data[half_word_to_modify];
+
+        let nibble_to_modify = (x % 4) * 4;
+
+        half_word = (half_word & !(0b1111 << nibble_to_modify))
+            | ((paletted_pixel as u16) << nibble_to_modify);
+        self.data[half_word_to_modify] = half_word;
     }
 
-    /// Tries to copy the sprite to vram to be used to set object sprites.
-    pub fn try_vram(&self, palette: PaletteVram) -> Result<SpriteVram, LoaderError> {
-        SpriteVram::new(&self.data, self.size, palette)
+    /// Wipes the sprite
+    pub fn clear(&mut self, paletted_pixel: usize) {
+        assert!(paletted_pixel < 0x10);
+        let reset =
+            (paletted_pixel | paletted_pixel << 4 | paletted_pixel << 8 | paletted_pixel << 12)
+                as u16;
+        self.data.fill(reset);
     }
 
     #[must_use]
     /// Tries to copy the sprite to vram to be used to set object sprites.
     /// Panics if it cannot be allocated.
-    pub fn to_vram(&self, palette: PaletteVram) -> SpriteVram {
-        self.try_vram(palette).expect("cannot create sprite")
+    pub fn to_vram(self, palette: PaletteVram) -> SpriteVram {
+        let data = unsafe { NonNull::new_unchecked(Box::leak(self.data).as_mut_ptr()) };
+
+        unsafe { SpriteVram::from_location_size(data.cast(), self.size, palette) }
     }
 }

agb/src/display/object/unmanaged/object.rs

@@ -101,7 +101,6 @@ impl OamSlot<'_> {
     /// By writing these as two separate functions, one inlined and one not, the
     /// compiler doesn't have to copy around the slot structure while still
     /// keeping move semantics. This is slightly faster in benchmarks.
-    #[inline(never)]
     fn set_inner(&self, object: &ObjectUnmanaged) {
         let mut attributes = object.attributes;
         // SAFETY: This function is not reentrant and we currently hold a mutable borrow of the [UnmanagedOAM].

agb/src/no_game.rs

@@ -129,13 +129,10 @@ fn generate_sprites() -> Box<[SpriteVram]> {
         .collect();
 
     // generate sprites
-    let mut sprite = DynamicSprite::new(Size::S8x8);
+
     for (palette, colour) in (0..PALETTE.len()).map(|x| (x / 15, x % 15)) {
-        for y in 0..8 {
-            for x in 0..8 {
-                sprite.set_pixel(x, y, colour + 1);
-            }
-        }
+        let mut sprite = DynamicSprite::new(Size::S8x8);
+        sprite.clear(colour + 1);
         sprites.push(sprite.to_vram(palettes[palette].clone()));
     }