From fd386888f47b150ced84db8acb24cdc6fea757a4 Mon Sep 17 00:00:00 2001
From: Marto <marto@marto.si>
Date: Sat, 26 Apr 2025 00:05:11 +0200
Subject: [PATCH] fixes

---
 src/main.zig | 53 ++++++++++++++++++++++++++--------------------------
 1 file changed, 26 insertions(+), 27 deletions(-)

diff --git a/src/main.zig b/src/main.zig
index 8b5a929..45c735e 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -4,7 +4,7 @@ const rl = @import("raylib");
 const WIDTH = 64;
 const HEIGHT = 32;
 const SCALE = 15;
-const FREQUENCY = 30;
+const FREQUENCY = 60;
 
 const MEMORY_SIZE = 4096;
 const FONT_START = 0x050;
@@ -27,7 +27,7 @@ const Emulator = struct {
     prng: std.Random.Xoshiro256,
 
     pub fn init(allocator: std.mem.Allocator) !Emulator {
-        return Emulator{ .screen = clearScreen(), .memory = try initMemory(allocator), .stack = std.ArrayList(u16).init(allocator), .v = std.mem.zeroes([16]u8), .i = 0, .key_pressed = 0, .pc = PROGRAM_START, .delay_timer = FREQUENCY, .sound_timer = 0, .legacy = true, .legacy_memory = false, .add_index_exception = false, .prng = std.Random.DefaultPrng.init(blk: {
+        return Emulator{ .screen = clearScreen(), .memory = try initMemory(allocator), .stack = std.ArrayList(u16).init(allocator), .v = std.mem.zeroes([16]u8), .i = 0, .key_pressed = 0, .pc = PROGRAM_START, .delay_timer = 0, .sound_timer = 0, .legacy = true, .legacy_memory = false, .add_index_exception = false, .prng = std.Random.DefaultPrng.init(blk: {
             var seed: u64 = undefined;
             try std.posix.getrandom(std.mem.asBytes(&seed));
             break :blk seed;
@@ -40,9 +40,8 @@ const Emulator = struct {
 
     pub fn instructionCycle(self: *Emulator) !void {
         const instruction: u16 = @as(u16, self.memory[self.pc]) << 8 | @as(u16, self.memory[self.pc + 1]);
-        var bd: [10]u8 = undefined;
-        _ = try std.fmt.bufPrint(&bd, "{X:0>4}", .{instruction});
-        std.debug.print("Instruction: {s}\n\n", .{bd});
+        // var bd: [10]u8 = undefined;
+        // _ = try std.fmt.bufPrint(&bd, "{X:0>4}", .{instruction});
         const first: u8 = @truncate(instruction >> 12);
 
         const x: u8 = @truncate((instruction >> 8) & 0xF);
@@ -126,9 +125,9 @@ const Emulator = struct {
                     },
                     0x6 => {
                         // shifting v[x] right and saving the dropped bit into V[0xF]
-                        // if (self.legacy) {
-                        //     self.v[x] = self.v[y];
-                        // }
+                        if (self.legacy) {
+                            self.v[x] = self.v[y];
+                        }
 
                         self.v[0xF] = self.v[x] & 0x1;
                         self.v[x] >>= 1;
@@ -141,11 +140,11 @@ const Emulator = struct {
                     },
                     0xE => {
                         // shifting v[x] left and saving the dropped bit into V[0xF]
-                        // if (self.legacy) {
-                        //     self.v[x] = self.v[y];
-                        // }
+                        if (self.legacy) {
+                            self.v[x] = self.v[y];
+                        }
 
-                        self.v[0xF] = (self.v[x] & 0x80) >> 7;
+                        self.v[0xF] = self.v[x] >> 7;
                         self.v[x] <<= 1;
                     },
                     else => {},
@@ -195,12 +194,12 @@ const Emulator = struct {
                                 self.v[0xF] = 1;
                         }
 
-                        x_coord += 1;
-                        if (x_coord >= WIDTH) break;
+                        x_coord = (x_coord + 1) % WIDTH;
+                        // if (x_coord >= WIDTH) break;
                     }
                     x_coord = self.v[x] % WIDTH;
-                    y_coord += 1;
-                    if (y_coord >= HEIGHT) break;
+                    y_coord = (y_coord + 1) % HEIGHT;
+                    // if (y_coord >= HEIGHT) break;
                 }
             },
             0xE => {
@@ -217,13 +216,10 @@ const Emulator = struct {
             },
             0xF => {
                 switch (nn) {
-                    // set delay
+                    // set vx to delay
                     0x07 => self.v[x] = self.delay_timer,
-                    0x15 => {
-                        // set delay, adjust fps
-                        self.delay_timer = self.v[x];
-                        rl.setTargetFPS(self.delay_timer);
-                    },
+                    // set delay
+                    0x15 => self.delay_timer = self.v[x],
                     // set sound timer
                     0x18 => self.sound_timer = self.v[x],
                     0x1E => {
@@ -399,16 +395,19 @@ pub fn main() !void {
     rl.initWindow(WIDTH * SCALE, HEIGHT * SCALE, "CHIP-8 Emulator");
     defer rl.closeWindow();
 
-    rl.setTargetFPS(chip8.delay_timer);
-    var cycle_count: usize = 0;
+    rl.setTargetFPS(FREQUENCY);
 
     while (!rl.windowShouldClose()) {
-        cycle_count += 1;
-        std.debug.print("Cycle count: {d}\n", .{cycle_count});
         chip8.getInput();
         try chip8.instructionCycle();
+
         chip8.draw();
-        // todo sound timer decrease i guess
+
+        if (chip8.delay_timer > 0) chip8.delay_timer -= 1;
+        if (chip8.sound_timer > 0) {
+            // todo sound implementation
+            chip8.sound_timer -= 1;
+        }
     }
 }