From b43c8ac7c9fce26e63d666c5d735056d0efc84ab Mon Sep 17 00:00:00 2001
From: Rekai Musuka <rekai@musuka.dev>
Date: Wed, 14 Apr 2021 01:21:45 -0500
Subject: [PATCH] feat(cartridge): grab title from the ROM

---
 src/bus.rs       |  4 ++++
 src/cartridge.rs | 17 +++++++++++++++++
 src/cpu.rs       |  4 ++++
 src/main.rs      | 11 +++++++----
 src/ppu.rs       | 12 +++++++-----
 5 files changed, 39 insertions(+), 9 deletions(-)

diff --git a/src/bus.rs b/src/bus.rs
index 4d7d676..4181683 100644
--- a/src/bus.rs
+++ b/src/bus.rs
@@ -63,6 +63,10 @@ impl Bus {
         Ok(())
     }
 
+    pub fn rom_title(&self) -> Option<&str> {
+        self.cartridge.as_ref()?.title()
+    }
+
     pub fn step(&mut self, cycles: Cycle) {
         self.ppu.step(cycles);
         self.timer.step(cycles);
diff --git a/src/cartridge.rs b/src/cartridge.rs
index 4f66dd5..6d78c0e 100644
--- a/src/cartridge.rs
+++ b/src/cartridge.rs
@@ -9,6 +9,7 @@ const MBC_TYPE_ADDRESS: usize = 0x0147;
 #[derive(Debug, Clone, Default)]
 pub struct Cartridge {
     memory: Vec<u8>,
+    title: Option<String>,
     mbc: Box<dyn MemoryBankController>,
 }
 
@@ -20,6 +21,7 @@ impl Cartridge {
 
         Ok(Self {
             mbc: Self::detect_mbc(&memory),
+            title: Self::find_title(&memory),
             memory,
         })
     }
@@ -46,6 +48,21 @@ impl Cartridge {
         }
     }
 
+    fn find_title(memory: &[u8]) -> Option<String> {
+        // FIXME: Get rid of magic values and handle cases
+        // where 0x134..0x143 reads past the length of the
+        // string
+
+        let slice = &memory[0x134..0x143];
+
+        let str_with_nulls = std::str::from_utf8(slice).ok();
+        str_with_nulls.map(|s| s.trim_matches('\0').to_string())
+    }
+
+    pub fn title(&self) -> Option<&str> {
+        self.title.as_deref()
+    }
+
     fn find_ram_size(memory: &[u8]) -> RamSize {
         let id = memory[RAM_SIZE_ADDRESS];
         id.into()
diff --git a/src/cpu.rs b/src/cpu.rs
index 7dafb42..28281c9 100644
--- a/src/cpu.rs
+++ b/src/cpu.rs
@@ -68,6 +68,10 @@ impl Cpu {
     pub fn load_cartridge(&mut self, path: &str) -> std::io::Result<()> {
         self.bus.load_cartridge(path)
     }
+
+    pub fn rom_title(&self) -> Option<&str> {
+        self.bus.rom_title()
+    }
 }
 
 impl Cpu {
diff --git a/src/main.rs b/src/main.rs
index f7be0e6..506ed42 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -31,7 +31,7 @@ fn main() -> Result<()> {
                 .takes_value(true)
                 .required(true)
                 .index(1)
-                .help("The ROM that the emulator will run"),
+                .help("Path to the Game ROM"),
         )
         .arg(
             Arg::with_name("boot")
@@ -58,10 +58,13 @@ fn main() -> Result<()> {
         .load_cartridge(rom_path)
         .expect("Failed to load ROM");
 
+    let default_title = "DMG-01 Emulator";
+    let cartridge_title = game_boy.rom_title().unwrap_or(&default_title);
+
     // Initialize GUI
     let event_loop = EventLoop::new();
     let mut input = WinitInputHelper::new();
-    let window = create_window(&event_loop)?;
+    let window = create_window(&event_loop, cartridge_title)?;
     let mut pixels = create_pixels(&window)?;
 
     let mut now = Instant::now();
@@ -114,10 +117,10 @@ fn main() -> Result<()> {
     });
 }
 
-fn create_window(event_loop: &EventLoop<()>) -> Result<Window> {
+fn create_window(event_loop: &EventLoop<()>, title: &str) -> Result<Window> {
     let size = LogicalSize::new((GB_WIDTH as f64) * SCALE, (GB_HEIGHT as f64) * SCALE);
     Ok(WindowBuilder::new()
-        .with_title("DMG-1 Emulator")
+        .with_title(title)
         .with_inner_size(size)
         .with_min_inner_size(size)
         .build(&event_loop)?)
diff --git a/src/ppu.rs b/src/ppu.rs
index ea369c4..c1be252 100644
--- a/src/ppu.rs
+++ b/src/ppu.rs
@@ -49,7 +49,7 @@ impl Ppu {
         let start: u32 = self.cycles.into();
         let end: u32 = cycles.into();
 
-        for cycle in start..(start + end).into() {
+        for _ in start..(start + end) {
             self.cycles += 1;
 
             match self.stat.mode() {
@@ -155,10 +155,12 @@ impl Ppu {
             let attr = self.oam.attribute((cycle / 2) as usize);
             let line_y = self.pos.line_y + 16;
 
-            if attr.x > 0 && line_y >= attr.y && line_y < (attr.y + sprite_height) {
-                if !self.sprite_buffer.full() {
-                    self.sprite_buffer.add(attr);
-                }
+            if attr.x > 0
+                && line_y >= attr.y
+                && line_y < (attr.y + sprite_height)
+                && !self.sprite_buffer.full()
+            {
+                self.sprite_buffer.add(attr);
             }
         }
     }