Implement opcode-limiting (current: 500 opcodes per second)

.gitignore

@@ -1,3 +1,4 @@
 /target
 /games
 /.vscode
+/.idea

src/main.rs

@@ -2,9 +2,9 @@
 // and https://en.wikipedia.org/wiki/CHIP-8#Opcode_table
 // for information about how to implement a CHIP-8 Emulator
 use chip8::emu::Chip8;
-use std::path::Path;
-
 use pixels::{wgpu::Surface, Pixels, SurfaceTexture};
+use std::path::Path;
+use std::time::{Duration, Instant};
 use winit::dpi::LogicalSize;
 use winit::event::{Event, VirtualKeyCode};
 use winit::event_loop::{ControlFlow, EventLoop};
@@ -13,6 +13,7 @@ use winit_input_helper::WinitInputHelper;
 
 static WIDTH: u32 = 64;
 static HEIGHT: u32 = 32;
+static OPCODES_PER_SECOND: u64 = 500;
 
 fn main() {
     let mut chip8: Chip8 = Default::default();
@@ -24,6 +25,9 @@ fn main() {
     let rom_path = Path::new("./games/c8games/INVADERS");
     chip8.load_rom(rom_path).expect("Unable to load ROM");
 
+    let mut start = Instant::now();
+    let frametime = Duration::from_nanos(1e+9 as u64 / OPCODES_PER_SECOND);
+
     event_loop.run(move |event, _, control_flow| {
         if let Event::RedrawRequested(_) = event {
             draw(&chip8.display.buf, pixels.get_frame());
@@ -44,7 +48,11 @@ fn main() {
                 pixels.resize(size.width, size.height);
             }
 
+            if Instant::now().duration_since(start) > frametime {
                 chip8.execute_cycle();
+                start = Instant::now();
+            }
+
             if chip8.request_redraw {
                 window.request_redraw();
             }