feat: new game boy API

examples/sdl/src/main.rs

@@ -5,7 +5,14 @@ fn main() {
     game_boy.load_boot_default();
 
     for i in 0..37000 {
-        game_boy.clock();
+        // runs the CPU clock and determines the number of
+        // cycles that have advanced for that clock tick
+        let cycles = game_boy.clock();
+
+        // calls the clock in the PPU to update its own
+        // execution lifecycle by one set of ticks
+        game_boy.ppu_clock(cycles);
+
         if game_boy.cpu().pc() >= 0x6032 {
             println!("{}", i);
             break;

src/cpu.rs

@@ -506,7 +506,7 @@ impl Cpu {
         }
     }
 
-    pub fn clock(&mut self) {
+    pub fn clock(&mut self) -> u8 {
         let pc = self.pc;
 
         // fetches the current instruction and increments
@@ -535,9 +535,9 @@ impl Cpu {
         instruction_fn(self);
         self.ticks = self.ticks.wrapping_add(*instruction_time as u32);
 
-        // calls the clock in the PPU to update its own
-        // execution lifecycle by one set of ticks
-        self.ppu().clock(*instruction_time);
+        // returns the number of cycles that the operation
+        // that has been executed has taken
+        *instruction_time
     }
 
     #[inline(always)]

src/gb.rs

@@ -12,10 +12,14 @@ impl GameBoy {
         GameBoy { cpu: cpu }
     }
 
-    pub fn clock(&mut self) {
+    pub fn clock(&mut self) -> u8 {
         self.cpu.clock()
     }
 
+    pub fn ppu_clock(&mut self, cycles: u8) {
+        self.ppu().clock(cycles)
+    }
+
     pub fn cpu(&mut self) -> &mut Cpu {
         &mut self.cpu
     }

src/ppu.rs

@@ -88,8 +88,8 @@ impl Ppu {
         }
     }
 
-    pub fn clock(&mut self, ticks: u8) {
-        self.mode_clock += ticks as u16;
+    pub fn clock(&mut self, cycles: u8) {
+        self.mode_clock += cycles as u16;
         match self.mode {
             PpuMode::OamRead => {
                 if self.mode_clock >= 204 {