fix: title offset calculation

To avoid 0x0 characters in ROM title.

CHANGELOG.md

@@ -17,7 +17,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
-*
+* Bug with ROM title that included 0x0 characters in it
 
 ## [0.6.7] - 2023-02-13
 

frontends/sdl/src/main.rs

@@ -57,6 +57,10 @@ impl Emulator {
             "========= Cartridge =========\n{}\n=============================\n",
             rom
         );
+        self.graphics
+            .window_mut()
+            .set_title(format!("{} - {}", TITLE, rom.title()).as_str())
+            .unwrap();
     }
 
     pub fn run(&mut self) {
@@ -189,6 +193,8 @@ fn main() {
     let mut game_boy = GameBoy::new();
     game_boy.load_boot_default();
 
+    // creates a new generic emulator structure loads the default
+    // ROM file and starts running it
     let mut emulator = Emulator::new(game_boy, SCREEN_SCALE);
     emulator.load_rom("../../res/roms/pocket.gb");
     emulator.run();

frontends/sdl/src/util.rs

@@ -3,7 +3,7 @@ use sdl2::{
     AudioSubsystem, EventPump, TimerSubsystem, VideoSubsystem,
 };
 
-/// Structure that provide the complete set of Graphics
+/// Structure that provides the complete set of Graphics
 /// and Sound syb-system ready to be used by the overall
 /// emulator infrastructure.
 pub struct Graphics {
@@ -67,6 +67,8 @@ impl Graphics {
     }
 }
 
+/// Creates an SDL2 Surface structure from the provided
+/// bytes that represent an image (eg: an PNG image buffer).
 pub fn surface_from_bytes(bytes: &[u8]) -> Surface {
     unsafe {
         let rw_ops = RWops::from_bytes(bytes).unwrap();

src/rom.rs

@@ -222,6 +222,11 @@ pub struct Cartridge {
     /// If the RAM access ia enabled, this flag allows
     /// control of memory access to avoid corruption.
     ram_enabled: bool,
+
+    // The final offset of the last character of the title
+    // that is considered to be non zero (0x0) so that a
+    // proper safe conversion to UTF-8 string can be done.
+    title_offset: usize,
 }
 
 impl Cartridge {
@@ -235,6 +240,7 @@ impl Cartridge {
             rom_offset: 0x4000,
             ram_offset: 0x0000,
             ram_enabled: false,
+            title_offset: 0x0143,
         }
     }
 
@@ -312,6 +318,7 @@ impl Cartridge {
         self.ram_offset = 0x0000;
         self.set_mbc();
         self.set_computed();
+        self.set_title_offset();
         self.allocate_ram();
         self.set_rom_bank(1);
         self.set_ram_bank(0);
@@ -326,6 +333,18 @@ impl Cartridge {
         self.ram_bank_count = self.ram_size().ram_banks();
     }
 
+    pub fn set_title_offset(&mut self) {
+        let mut offset: usize = 0;
+        for byte in &self.rom_data[0x0134..0x0143] {
+            if *byte != 0u8 {
+                offset += 1;
+                continue;
+            }
+            break;
+        }
+        self.title_offset = 0x0134 + offset;
+    }
+
     fn allocate_ram(&mut self) {
         let ram_banks = max(self.ram_size().ram_banks(), 1);
         self.ram_data = vec![0u8; ram_banks as usize * RAM_BANK_SIZE];
@@ -335,7 +354,7 @@ impl Cartridge {
 #[cfg_attr(feature = "wasm", wasm_bindgen)]
 impl Cartridge {
     pub fn title(&self) -> String {
-        String::from(std::str::from_utf8(&self.rom_data[0x0134..0x0143]).unwrap())
+        String::from(std::str::from_utf8(&self.rom_data[0x0134..self.title_offset]).unwrap())
     }
 
     pub fn rom_type(&self) -> RomType {