magic colour changing

agb/examples/object_text_render.rs

@@ -4,7 +4,7 @@
 use agb::{
     display::{
         object::{
-            font::{ObjectTextRender, TextAlignment},
+            font::{ChangeColour, ObjectTextRender, TextAlignment},
             PaletteVram, Size,
         },
         palette16::Palette16,
@@ -30,14 +30,17 @@ fn main(mut gba: agb::Gba) -> ! {
     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 mut wr = ObjectTextRender::new(&FONT, Size::S16x16, palette);
+        let player_name = "You";
         let _ = writeln!(
             wr,
-            "Woah! 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!"
-        
+            "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 vblank = agb::interrupt::VBlank::get();
@@ -64,9 +67,7 @@ fn main(mut gba: agb::Gba) -> ! {
             if frame % 4 == 0 {
                 line_done = !wr.next_letter_group();
             }
-            if line_done
-            && input.is_just_pressed(Button::A)
-            {
+            if line_done && input.is_just_pressed(Button::A) {
                 line_done = false;
                 wr.pop_line();
             }

agb/src/display/object/font.rs

@@ -1,4 +1,4 @@
-use core::fmt::Write;
+use core::fmt::{Display, Write};
 
 use agb_fixnum::Vector2D;
 use alloc::{collections::VecDeque, vec::Vec};
@@ -97,6 +97,37 @@ fn is_private_use(c: char) -> bool {
     ('\u{E000}'..'\u{F8FF}').contains(&c)
 }
 
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct ChangeColour(u8);
+
+impl ChangeColour {
+    #[must_use]
+    pub fn new(colour: u32) -> 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;
+        if c >= 0xE000 && c < 0xE000 + 16 {
+            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) {

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

@@ -1,6 +1,4 @@
-use core::num::NonZeroU8;
-
-use alloc::{collections::VecDeque, vec::Vec};
+use alloc::collections::VecDeque;
 
 use crate::display::Font;
 

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

@@ -3,6 +3,8 @@ use crate::display::{
     Font,
 };
 
+use super::ChangeColour;
+
 struct WorkingLetter {
     dynamic: DynamicSprite,
     // where to render the letter from x_min to x_max
@@ -73,6 +75,11 @@ impl WordRender {
 
     #[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