From c5cebb9520fcb6325a97b62233035d488a581ad1 Mon Sep 17 00:00:00 2001
From: Gwilym Kuiper <gw@ilym.me>
Date: Mon, 4 Apr 2022 22:06:08 +0100
Subject: [PATCH] Theory a font renderer

---
 agb-image-converter/Cargo.toml         |  1 +
 agb-image-converter/src/font_loader.rs | 36 +++++++++++++++++
 agb-image-converter/src/lib.rs         | 55 ++++++++++++++++++++++++++
 3 files changed, 92 insertions(+)
 create mode 100644 agb-image-converter/src/font_loader.rs

diff --git a/agb-image-converter/Cargo.toml b/agb-image-converter/Cargo.toml
index 850090a..6f845b2 100644
--- a/agb-image-converter/Cargo.toml
+++ b/agb-image-converter/Cargo.toml
@@ -17,3 +17,4 @@ syn = "1"
 proc-macro2 = "1"
 quote = "1"
 asefile = "0.3.4"
+fontdue = "0.7"
diff --git a/agb-image-converter/src/font_loader.rs b/agb-image-converter/src/font_loader.rs
new file mode 100644
index 0000000..f3b5047
--- /dev/null
+++ b/agb-image-converter/src/font_loader.rs
@@ -0,0 +1,36 @@
+use crate::ByteString;
+use quote::quote;
+
+use proc_macro2::TokenStream;
+
+struct LetterData {
+    width: usize,
+    rendered: Vec<u8>,
+}
+
+pub fn load_font(font_data: &[u8], pixels_per_em: f32) -> TokenStream {
+    let font = fontdue::Font::from_bytes(font_data, Default::default()).expect("Invalid font data");
+
+    let font = (0..128)
+        .map(|i| font.rasterize(char::from_u32(i).unwrap(), pixels_per_em))
+        .map(|(metrics, bitmap)| {
+            let width = metrics.width;
+            LetterData {
+                width,
+                rendered: bitmap,
+            }
+        })
+        .map(|letter_data| {
+            let data_raw = ByteString(&letter_data.rendered);
+            let width = letter_data.width as u8;
+
+            quote!(agb::display::FontLetter {
+                width: #width,
+                data: #data_raw,
+            })
+        });
+
+    quote![
+        #(#font),*
+    ]
+}
diff --git a/agb-image-converter/src/lib.rs b/agb-image-converter/src/lib.rs
index e4d8e95..0d45a06 100644
--- a/agb-image-converter/src/lib.rs
+++ b/agb-image-converter/src/lib.rs
@@ -3,7 +3,9 @@ use proc_macro::TokenStream;
 use proc_macro2::Literal;
 use syn::parse::Parser;
 use syn::{parse_macro_input, punctuated::Punctuated, LitStr};
+use syn::{Expr, ExprLit, Lit};
 
+use std::fs::File;
 use std::path::PathBuf;
 use std::{iter, path::Path, str};
 
@@ -12,6 +14,7 @@ use quote::{format_ident, quote, ToTokens};
 mod aseprite;
 mod colour;
 mod config;
+mod font_loader;
 mod image_loader;
 mod palette16;
 mod rust_generator;
@@ -309,6 +312,58 @@ fn palete_tile_data(
     (palette_data, tile_data, assignments)
 }
 
+#[proc_macro]
+pub fn include_font(input: TokenStream) -> TokenStream {
+    let parser = Punctuated::<Expr, syn::Token![,]>::parse_separated_nonempty;
+    let parsed = match parser.parse(input) {
+        Ok(e) => e,
+        Err(e) => return e.to_compile_error().into(),
+    };
+
+    let all_args: Vec<_> = parsed.into_iter().collect();
+    if all_args.len() != 2 {
+        panic!("Include_font requires 2 arguments, got {}", all_args.len());
+    }
+
+    let filename = match &all_args[0] {
+        Expr::Lit(ExprLit {
+            lit: Lit::Str(str_lit),
+            ..
+        }) => str_lit.value(),
+        _ => panic!("Expected literal string as first argument to include_font"),
+    };
+
+    let font_size = match &all_args[1] {
+        Expr::Lit(ExprLit {
+            lit: Lit::Float(value),
+            ..
+        }) => value.base10_parse::<f32>().expect("Invalid float literal"),
+        Expr::Lit(ExprLit {
+            lit: Lit::Int(value),
+            ..
+        }) => value
+            .base10_parse::<i32>()
+            .expect("Invalid integer literal") as f32,
+        _ => panic!("Expected literal float or integer as second argument to include_font"),
+    };
+
+    let root = std::env::var("CARGO_MANIFEST_DIR").expect("Failed to get cargo manifest dir");
+    let path = Path::new(&root).join(&*filename);
+
+    let file_content = std::fs::read(&path).expect("Failed to read ttf file");
+
+    let rendered = font_loader::load_font(&file_content, font_size);
+
+    let include_path = path.to_string_lossy();
+
+    quote!({
+        let _ = include_bytes!(#include_path);
+
+        #rendered
+    })
+    .into()
+}
+
 #[cfg(test)]
 mod tests {
     use asefile::AnimationDirection;