feat: pause emu when UI reads emu state

src/core/emu.zig

@@ -4,7 +4,7 @@ const config = @import("../config.zig");
 
 const Scheduler = @import("scheduler.zig").Scheduler;
 const Arm7tdmi = @import("cpu.zig").Arm7tdmi;
-const FpsTracker = @import("../util.zig").FpsTracker;
+const Tracker = @import("../util.zig").FpsTracker;
 
 const Timer = std.time.Timer;
 const Atomic = std.atomic.Atomic;
@@ -35,18 +35,18 @@ const RunKind = enum {
     LimitedFPS,
 };
 
-pub fn run(quit: *Atomic(bool), scheduler: *Scheduler, cpu: *Arm7tdmi, tracker: *FpsTracker) void {
+pub fn run(quit: *Atomic(bool), pause: *Atomic(bool), cpu: *Arm7tdmi, scheduler: *Scheduler, tracker: *Tracker) void {
     const audio_sync = config.config().guest.audio_sync and !config.config().host.mute;
     if (audio_sync) log.info("Audio sync enabled", .{});
 
     if (config.config().guest.video_sync) {
-        inner(.LimitedFPS, audio_sync, quit, scheduler, cpu, tracker);
+        inner(.LimitedFPS, audio_sync, quit, pause, cpu, scheduler, tracker);
     } else {
-        inner(.UnlimitedFPS, audio_sync, quit, scheduler, cpu, tracker);
+        inner(.UnlimitedFPS, audio_sync, quit, pause, cpu, scheduler, tracker);
     }
 }
 
-fn inner(comptime kind: RunKind, audio_sync: bool, quit: *Atomic(bool), scheduler: *Scheduler, cpu: *Arm7tdmi, tracker: ?*FpsTracker) void {
+fn inner(comptime kind: RunKind, audio_sync: bool, quit: *Atomic(bool), pause: *Atomic(bool), cpu: *Arm7tdmi, scheduler: *Scheduler, tracker: ?*Tracker) void {
     if (kind == .UnlimitedFPS or kind == .LimitedFPS) {
         std.debug.assert(tracker != null);
         log.info("FPS tracking enabled", .{});
@@ -57,6 +57,8 @@ fn inner(comptime kind: RunKind, audio_sync: bool, quit: *Atomic(bool), schedule
             log.info("Emulation w/out video sync", .{});
 
             while (!quit.load(.Monotonic)) {
+                if (pause.load(.Monotonic)) continue;
+
                 runFrame(scheduler, cpu);
                 audioSync(audio_sync, cpu.bus.apu.stream, &cpu.bus.apu.is_buffer_full);
 
@@ -69,6 +71,8 @@ fn inner(comptime kind: RunKind, audio_sync: bool, quit: *Atomic(bool), schedule
             var wake_time: u64 = frame_period;
 
             while (!quit.load(.Monotonic)) {
+                if (pause.load(.Monotonic)) continue;
+
                 runFrame(scheduler, cpu);
                 const new_wake_time = videoSync(&timer, wake_time);
 

src/platform.zig

@@ -389,8 +389,9 @@ pub const Gui = struct {
         const fbo_id = try Self.genFrameBufObject(out_tex);
         defer gl.deleteFramebuffers(1, &fbo_id);
 
-        var quit = std.atomic.Atomic(bool).init(false);
         var tracker = FpsTracker.init();
+        var quit = std.atomic.Atomic(bool).init(false);
+        var pause = std.atomic.Atomic(bool).init(false);
 
         var title_buf: [0x100]u8 = undefined;
 
@@ -441,12 +442,6 @@ pub const Gui = struct {
                             SDL.SDLK_s => keyinput.shoulder_r.set(),
                             SDL.SDLK_RETURN => keyinput.start.set(),
                             SDL.SDLK_RSHIFT => keyinput.select.set(),
-                            SDL.SDLK_i => {
-                                comptime std.debug.assert(sample_format == SDL.AUDIO_U16);
-                                log.err("Sample Count: {}", .{@intCast(u32, SDL.SDL_AudioStreamAvailable(cpu.bus.apu.stream)) / (2 * @sizeOf(u16))});
-                            },
-                            // SDL.SDLK_j => log.err("Scheduler Capacity: {} | Scheduler Event Count: {}", .{ scheduler.queue.capacity(), scheduler.queue.count() }),
-                            SDL.SDLK_k => {},
                             else => {},
                         }
 
@@ -456,6 +451,14 @@ pub const Gui = struct {
                 }
             }
 
+            // We Access non-atomic parts of the Emulator here
+            {
+                pause.store(true, .Monotonic);
+                defer pause.store(false, .Monotonic);
+
+                self.state.fps_hist.push(tracker.value()) catch {};
+
+                // Draw GBA Screen to Texture
                 {
                     gl.bindFramebuffer(gl.FRAMEBUFFER, fbo_id);
                     defer gl.bindFramebuffer(gl.FRAMEBUFFER, 0);
@@ -465,18 +468,12 @@ pub const Gui = struct {
                     self.drawGbaTexture(obj_ids, emu_tex, buf);
                 }
 
-            // Background
+                // Background Colour
                 const size = zgui.io.getDisplaySize();
                 gl.viewport(0, 0, @floatToInt(c_int, size[0]), @floatToInt(c_int, size[1]));
                 gl.clearColor(0, 0, 0, 1.0);
                 gl.clear(gl.COLOR_BUFFER_BIT);
 
-            zgui.backend.newFrame(width, height);
-            self.draw(out_tex, cpu);
-            zgui.backend.draw();
-
-            SDL.SDL_GL_SwapWindow(self.window);
-
                 if (tracker) |t| {
                     const emu_fps = t.value();
                     self.state.fps_hist.push(emu_fps) catch {};
@@ -484,9 +481,14 @@ pub const Gui = struct {
                     const dyn_title = std.fmt.bufPrintZ(&title_buf, "ZBA | {s} [Emu: {}fps] ", .{ self.title, emu_fps }) catch unreachable;
                     SDL.SDL_SetWindowTitle(self.window, dyn_title.ptr);
                 }
+
+                zgui.backend.newFrame(width, height);
+                self.draw(out_tex, cpu);
+                zgui.backend.draw();
             }
 
-        quit.store(true, .Monotonic); // Terminate Emulator Thread
+            SDL.SDL_GL_SwapWindow(self.window);
+        }
     }
 
     fn glGetProcAddress(ctx: SDL.SDL_GLContext, proc: [:0]const u8) ?*anyopaque {