From 3d4e6bb44b7d8556fa354613113baf37cf15992a Mon Sep 17 00:00:00 2001
From: kayomn <kayomn@kayomn.net>
Date: Thu, 25 Jul 2024 14:25:55 +0100
Subject: [PATCH] Remove unnecessary delta time arg to fixed-timestep systems

---
 demos/inputs.zig | 14 +++++++-------
 src/ona/ona.zig  | 22 ++++++++++------------
 2 files changed, 17 insertions(+), 19 deletions(-)

diff --git a/demos/inputs.zig b/demos/inputs.zig
index fd3f478..b421a4e 100644
--- a/demos/inputs.zig
+++ b/demos/inputs.zig
@@ -41,9 +41,9 @@ pub const main = ona.App.setup.
 	with_system(.render, ona.system_fn(render), .{.label = "render visuals"}).
 	with_system(.exit, ona.system_fn(cleanup), .{.label = "clean up visuals"}).build();
 
-fn update(visuals: ona.Write(Visuals), app: ona.Read(ona.App), events: ona.Receive(hid.Event), display: ona.Read(gfx.Display)) !void {
-	update_spawned(&visuals.state.spawned_keyboards, @floatCast(app.state.delta_time));
-	update_spawned(&visuals.state.spawned_mouses, @floatCast(app.state.delta_time));
+fn update(visuals: ona.Write(Visuals), events: ona.Receive(hid.Event), display: ona.Read(gfx.Display)) !void {
+	update_spawned(&visuals.state.spawned_keyboards);
+	update_spawned(&visuals.state.spawned_mouses);
 
 	const random = visuals.state.random.random();
 	const width: f32 = @floatFromInt(display.state.width);
@@ -85,11 +85,11 @@ fn update(visuals: ona.Write(Visuals), app: ona.Read(ona.App), events: ona.Recei
 	}
 }
 
-fn update_spawned(spawned: *ona.stack.Parallel(Spawned), delta_time: f32) void {
-	const float_speed = 50;
+fn update_spawned(spawned: *ona.stack.Parallel(Spawned)) void {
+	const float_speed = 6;
 
 	for (spawned.values.slice(.transform)) |*transform| {
-		transform.* = transform.translated(.{0, float_speed * -delta_time});
+		transform.* = transform.translated(.{0, -float_speed});
 	}
 
 	{
@@ -99,7 +99,7 @@ fn update_spawned(spawned: *ona.stack.Parallel(Spawned), delta_time: f32) void {
 		while (index < range) : (index += 1) {
 			const lifetime_seconds = spawned.values.get(.lifetime_seconds, index).?;
 
-			lifetime_seconds.* -= delta_time;
+			lifetime_seconds.* -= 1.0 / 60.0;
 
 			if (lifetime_seconds.* <= 0) {
 				range -= 1;
diff --git a/src/ona/ona.zig b/src/ona/ona.zig
index 386901a..c6fdd0f 100644
--- a/src/ona/ona.zig
+++ b/src/ona/ona.zig
@@ -32,7 +32,6 @@ pub const App = struct {
 	events: *const Events,
 	target_frame_time: f64,
 	elapsed_time: f64,
-	delta_time: f64,
 	is_running: bool,
 
 	pub const Events = struct {
@@ -115,7 +114,6 @@ pub const App = struct {
 						.events = &events,
 						.target_frame_time = 1.0 / 60.0,
 						.elapsed_time = 0,
-						.delta_time = 0,
 						.is_running = true,
 					});
 
@@ -129,11 +127,11 @@ pub const App = struct {
 					while (app.is_running) {
 						const ticks_current = std.time.milliTimestamp();
 						const milliseconds_per_second = 1000.0;
+						const delta_time = @as(f64, @floatFromInt(ticks_current - ticks_previous)) / milliseconds_per_second;
 
-						app.delta_time = @as(f64, @floatFromInt(ticks_current - ticks_previous)) / milliseconds_per_second;
 						app.elapsed_time = @as(f64, @floatFromInt(ticks_current - ticks_initial)) / milliseconds_per_second;
 						ticks_previous = ticks_current;
-						accumulated_time += app.delta_time;
+						accumulated_time += delta_time;
 
 						try world.run_event(events.pre_update);
 
@@ -911,6 +909,14 @@ pub fn system_fn(comptime call: anytype) *const SystemInfo {
 	return system_info;
 }
 
+pub fn thread_restriction(comptime State: type) ThreadRestriction {
+	if (@hasDecl(State, "thread_restriction")) {
+		return State.thread_restriction;
+	}
+
+	return .none;
+}
+
 pub fn type_id(comptime T: type) TypeID {
 	const TypeHandle = struct {
 		comptime {
@@ -922,11 +928,3 @@ pub fn type_id(comptime T: type) TypeID {
 
 	return @enumFromInt(@intFromPtr(&TypeHandle.byte));
 }
-
-pub fn thread_restriction(comptime State: type) ThreadRestriction {
-	if (@hasDecl(State, "thread_restriction")) {
-		return State.thread_restriction;
-	}
-
-	return .none;
-}