From 22a8f67d816426ba92e59d9ac71fbe5d8844cd32 Mon Sep 17 00:00:00 2001
From: Rekai Musuka <rekai@musuka.dev>
Date: Fri, 21 Oct 2022 05:12:29 -0300
Subject: [PATCH] fix: speed percentage in title is now accurate

We now properly account for full speed being 59.97Hz not, 59Hz or 60Hz
---
 src/emu.zig  | 30 ++++++++++++++++--------------
 src/main.zig |  9 +++++----
 src/util.zig |  4 ++--
 3 files changed, 23 insertions(+), 20 deletions(-)

diff --git a/src/emu.zig b/src/emu.zig
index fbe9a93..b5b5b61 100644
--- a/src/emu.zig
+++ b/src/emu.zig
@@ -9,12 +9,19 @@ const Timer = std.time.Timer;
 const Thread = std.Thread;
 const Atomic = std.atomic.Atomic;
 
-// One frame operates at 59.7275005696Hz
-const cycles_per_frame: u64 = 228 * (308 * 4);
-const clock_rate: u64 = 1 << 24;
+// 228 Lines which consist of 308 dots (which are 4 cycles long)
+const cycles_per_frame: u64 = 228 * (308 * 4); //280896
+const clock_rate: u64 = 1 << 24; // 16.78MHz 
+
+// TODO: Don't truncate this, be more accurate w/ timing
+// 59.6046447754ns (truncated to just 59ns)
 const clock_period: u64 = std.time.ns_per_s / clock_rate;
 const frame_period = (clock_period * cycles_per_frame);
 
+// 59.7275005696Hz
+pub const frame_rate = @intToFloat(f64, std.time.ns_per_s) / 
+    ((@intToFloat(f64, std.time.ns_per_s) / @intToFloat(f64, clock_rate)) * @intToFloat(f64, cycles_per_frame));
+
 const log = std.log.scoped(.Emulation);
 
 const RunKind = enum {
@@ -27,9 +34,9 @@ const RunKind = enum {
 
 pub fn run(kind: RunKind, quit: *Atomic(bool), fps: *FpsAverage, sched: *Scheduler, cpu: *Arm7tdmi, bus: *Bus) void {
     switch (kind) {
-        .Unlimited => runUnSync(quit, sched, cpu, bus),
+        .Unlimited => runUnsync(quit, sched, cpu, bus),
         .Limited => runSync(quit, sched, cpu, bus),
-        .UnlimitedFPS => runUnSyncFps(quit, fps, sched, cpu, bus),
+        .UnlimitedFPS => runUnsyncFps(quit, fps, sched, cpu, bus),
         .LimitedFPS => runSyncFps(quit, fps, sched, cpu, bus),
         .LimitedBusy => runBusyLoop(quit, sched, cpu, bus),
     }
@@ -47,7 +54,7 @@ pub fn runFrame(sched: *Scheduler, cpu: *Arm7tdmi, bus: *Bus) void {
     }
 }
 
-pub fn runUnSync(quit: *Atomic(bool), sched: *Scheduler, cpu: *Arm7tdmi, bus: *Bus) void {
+pub fn runUnsync(quit: *Atomic(bool), sched: *Scheduler, cpu: *Arm7tdmi, bus: *Bus) void {
     log.info("Unsynchronized EmuThread has begun", .{});
     while (!quit.load(.Unordered)) runFrame(sched, cpu, bus);
 }
@@ -69,13 +76,13 @@ pub fn runSync(quit: *Atomic(bool), sched: *Scheduler, cpu: *Arm7tdmi, bus: *Bus
     }
 }
 
-pub fn runUnSyncFps(quit: *Atomic(bool), fps: *FpsAverage, sched: *Scheduler, cpu: *Arm7tdmi, bus: *Bus) void {
+pub fn runUnsyncFps(quit: *Atomic(bool), fps: *FpsAverage, sched: *Scheduler, cpu: *Arm7tdmi, bus: *Bus) void {
     log.info("Unsynchronized EmuThread with FPS Tracking has begun", .{});
     var fps_timer = Timer.start() catch unreachable;
 
     while (!quit.load(.Unordered)) {
         runFrame(sched, cpu, bus);
-        fps.add(emuFps(fps_timer.lap()));
+        fps.add(fps_timer.lap());
     }
 }
 
@@ -93,7 +100,7 @@ pub fn runSyncFps(quit: *Atomic(bool), fps: *FpsAverage, sched: *Scheduler, cpu:
         sleep(&timer, &wake_time);
 
         // Determine FPS
-        fps.add(emuFps(fps_timer.lap()));
+        fps.add(fps_timer.lap());
 
         // Update to the new wake time
         wake_time += frame_period;
@@ -149,8 +156,3 @@ fn sleep(timer: *Timer, wake_time: *u64) void {
 fn spinLoop(timer: *Timer, wake_time: u64) void {
     while (true) if (timer.read() > wake_time) break;
 }
-
-inline fn emuFps(left: u64) u64 {
-    @setRuntimeSafety(false);
-    return @floatToInt(u64, @intToFloat(f64, std.time.ns_per_s) / @intToFloat(f64, left));
-}
diff --git a/src/main.zig b/src/main.zig
index 7c4bb15..8a723f6 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -17,6 +17,7 @@ const window_scale = 3;
 const gba_width = @import("ppu.zig").width;
 const gba_height = @import("ppu.zig").height;
 const framebuf_pitch = @import("ppu.zig").framebuf_pitch;
+const expected_rate = @import("emu.zig").frame_rate;
 
 pub const enable_logging: bool = false;
 const is_binary: bool = false;
@@ -76,10 +77,10 @@ pub fn main() anyerror!void {
 
     // Init Atomics
     var quit = Atomic(bool).init(false);
-    var emu_fps = FpsAverage.init();
+    var emu_rate = FpsAverage.init();
 
     // Create Emulator Thread
-    const emu_thread = try Thread.spawn(.{}, emu.run, .{ .UnlimitedFPS, &quit, &emu_fps, &scheduler, &cpu, &bus });
+    const emu_thread = try Thread.spawn(.{}, emu.run, .{ .LimitedFPS, &quit, &emu_rate, &scheduler, &cpu, &bus });
     defer emu_thread.join();
 
     // Initialize SDL
@@ -161,8 +162,8 @@ pub fn main() anyerror!void {
         _ = SDL.SDL_RenderCopy(renderer, texture, null, null);
         SDL.SDL_RenderPresent(renderer);
 
-        const avg = emu_fps.calc();
-        const dyn_title = std.fmt.bufPrint(&dyn_title_buf, "{s} [Emu: {d:0>3}fps, {d:0>3}%] ", .{ title, avg, (avg * 100 / 59) }) catch unreachable;
+        const actual = emu_rate.calc();
+        const dyn_title = std.fmt.bufPrint(&dyn_title_buf, "{s} [Emu: {d:0>3.2}fps, {d:0>3.2}%] ", .{ title, actual, actual * 100 / expected_rate }) catch unreachable;
         SDL.SDL_SetWindowTitle(window, dyn_title.ptr);
     }
 
diff --git a/src/util.zig b/src/util.zig
index 7880a5a..1f3e260 100644
--- a/src/util.zig
+++ b/src/util.zig
@@ -33,8 +33,8 @@ pub const FpsAverage = struct {
         self.sample_count += 1;
     }
 
-    pub fn calc(self: *const Self) u64 {
-        return self.total / self.sample_count;
+    pub fn calc(self: *const Self) f64 {
+        return @intToFloat(f64, std.time.ns_per_s) / (@intToFloat(f64, self.total) / @intToFloat(f64, self.sample_count));
     }
 
     fn reset(self: *Self, sample: u64) void {