Implement initial update loop for canvas usage in scripts

.vscode/settings.json

@@ -2,6 +2,7 @@
 	"files.insertFinalNewline": true,
 	"files.trimTrailingWhitespace": true,
 	"zig.initialSetupDone": true,
+	"debug.console.collapseIdenticalLines": false,
 
 	"[zig]": {
 		"editor.formatOnSave": false,

debug/app.ona

@@ -1,19 +1,16 @@
+let ona = @import("ona")
 
-let tool = "wrench"
+var timer = 0
-var test_param = `monkey {tool} {2 + 1 - 1}`
 
-let printer = lambda (pfx):
+ona.on_update(lambda (dt):
-	@print(test_param)
+	timer = timer + dt
 
-	return lambda (msg):
+	if (timer > 1):
-		@print(pfx)
+		@print("test hello world")
-		@print(msg)
+
+		timer = 0
 	end
-end
+end)
-
-let pr = printer("this is a final closure")
-
-pr("goodbye")
 
 return {
 	.title = "Game",

source/coral/io.zig

@@ -178,7 +178,7 @@ pub fn Generator(comptime Output: type, comptime Input: type) type {
 			};
 		}
 
-		pub fn from(comptime invoker: fn (input: Input) Output) Self {
+		pub fn from_fn(comptime invoker: fn (input: Input) Output) Self {
 			const Invoker = struct {
 				fn invoke(_: *const anyopaque, input: Input) Output {
 					return invoker(input);
@@ -358,7 +358,7 @@ pub fn jenkins_hash(comptime int: std.builtin.Type.Int, bytes: []const Byte) mat
     return hash;
 }
 
-pub const null_writer = Writer.from(write_null);
+pub const null_writer = Writer.from_fn(write_null);
 
 pub fn slice_sentineled(comptime sen: anytype, ptr: [*:sen]const @TypeOf(sen)) [:sen]const @TypeOf(sen) {
     var len = @as(usize, 0);

source/coral/map.zig

@@ -23,6 +23,7 @@ pub fn StringTable(comptime Value: type) type {
 pub fn Table(comptime Key: type, comptime Value: type, comptime Traits: type) type {
 	const load_max = 0.75;
 	const max_int = math.max_int(@typeInfo(usize).Int);
+	const has_traits = @sizeOf(Traits) != 0;
 
 	return struct {
 		allocator: io.Allocator,
@@ -89,7 +90,7 @@ pub fn Table(comptime Key: type, comptime Value: type, comptime Traits: type) ty
 		}
 
 		fn hash_key(self: Self, key: Key) usize {
-			return if (@sizeOf(Traits) == 0) Traits.hash(key) else self.traits.hash(key);
+			return if (has_traits) self.traits.hash(key) else Traits.hash(key);
 		}
 
 		pub fn remove(self: *Self, key: Key) ?Entry {
@@ -119,7 +120,7 @@ pub fn Table(comptime Key: type, comptime Value: type, comptime Traits: type) ty
 			{
 				const hash_max = @min(max_int, self.entries.len);
 				const has_context = @sizeOf(Traits) != 0;
-				var hashed_key = (if (has_context) self.traits.hash(key) else Traits.hash(key)) % hash_max;
+				var hashed_key = self.hash_key(key) % hash_max;
 
 				while (true) {
 					const entry = &(self.entries[hashed_key] orelse {
@@ -222,7 +223,7 @@ pub fn Table(comptime Key: type, comptime Value: type, comptime Traits: type) ty
 
 			const hash_max = @min(max_int, self.entries.len);
 			const has_context = @sizeOf(Traits) != 0;
-			var hashed_key = (if (has_context) self.traits.hash(key) else Traits.hash(key)) % hash_max;
+			var hashed_key = self.hash_key(key) % hash_max;
 			var iterations = @as(usize, 0);
 
 			while (iterations < self.count) : (iterations += 1) {

source/coral/utf8.zig

@@ -201,6 +201,36 @@ pub const HexadecimalFormat = struct {
 	}
 };
 
+pub const SmallString = extern struct {
+	data: [256]u8 = [_]u8{0} ** 256,
+
+	pub const FromError = error {
+		InvalidUtf8,
+		TooBig,
+	};
+
+	pub fn from_units(units: []const u8) FromError!SmallString {
+		var self = SmallString{};
+		const units_range = self.data.len - 1;
+
+		if (units.len > units_range) {
+			return error.TooBig;
+		}
+
+		io.copy(self.data[0 .. units_range], units);
+
+		self.data[units_range] = @intCast(units_range - units.len);
+
+		return self;
+	}
+
+	pub fn to_units(self: *const SmallString) [:0]const u8 {
+		const units_range = self.data.len - 1;
+
+		return @ptrCast(self.data[0 .. units_range - self.data[units_range]]);
+	}
+};
+
 pub fn alloc_formatted(allocator: io.Allocator, comptime format: []const u8, args: anytype) io.AllocationError![]io.Byte {
 	const formatted_len = print_formatted(io.null_writer, format, args);
 

source/ona/app.zig

@@ -1,101 +0,0 @@
-const coral = @import("coral");
-
-const ext = @import("./ext.zig");
-
-const file = @import("./file.zig");
-
-const kym = @import("./kym.zig");
-
-pub const Manifest = struct {
-	title: [255:0]coral.io.Byte = [_:0]coral.io.Byte{0} ** 255,
-	width: u16 = 640,
-	height: u16 = 480,
-	tick_rate: f32 = 60.0,
-
-	pub fn load(self: *Manifest, env: *kym.RuntimeEnv) kym.RuntimeError!void {
-		const manifest = (try env.import(file.Path.from(&.{"app.ona"}))).pop() orelse return;
-
-		defer env.release(manifest);
-
-		const width = @as(u16, get: {
-			if (try kym.get_field(env, manifest, "width")) |ref| {
-				defer env.release(ref);
-
-				const fixed = try env.expect_fixed(ref);
-
-				if (fixed > 0 and fixed < coral.math.max_int(@typeInfo(@TypeOf(self.width)).Int)) {
-					break: get @intCast(fixed);
-				}
-			}
-
-			break: get self.width;
-		});
-
-		const height = @as(u16, get: {
-			if (try kym.get_field(env, manifest, "height")) |ref| {
-				defer env.release(ref);
-
-				const fixed = try env.expect_fixed(ref);
-
-				if (fixed > 0 and fixed < coral.math.max_int(@typeInfo(@TypeOf(self.height)).Int)) {
-					break: get @intCast(fixed);
-				}
-			}
-
-			break: get self.height;
-		});
-
-		const tick_rate = @as(f32, get: {
-			if (try kym.get_field(env, manifest, "tick_rate")) |ref| {
-				defer env.release(ref);
-
-				break: get @floatCast(try env.expect_float(ref));
-			}
-
-			break: get self.tick_rate;
-		});
-
-		if (try kym.get_field(env, manifest, "title")) |ref| {
-			defer env.release(ref);
-
-			const title_string = try env.expect_string(ref);
-			const limited_title_len = @min(title_string.len, self.title.len);
-
-			coral.io.copy(&self.title, title_string[0 .. limited_title_len]);
-			coral.io.zero(self.title[limited_title_len .. self.title.len]);
-		} else {
-			coral.io.zero(&self.title);
-		}
-
-		self.tick_rate = tick_rate;
-		self.width = width;
-		self.height = height;
-	}
-};
-
-pub fn log_info(message: []const coral.io.Byte) void {
-	ext.SDL_LogInfo(
-		ext.SDL_LOG_CATEGORY_APPLICATION,
-		"%.*s",
-		coral.math.clamped_cast(@typeInfo(c_int).Int, message.len),
-		message.ptr,
-	);
-}
-
-pub fn log_warn(message: []const coral.io.Byte) void {
-	ext.SDL_LogWarn(
-		ext.SDL_LOG_CATEGORY_APPLICATION,
-		"%.*s",
-		coral.math.clamped_cast(@typeInfo(c_int).Int, message.len),
-		message.ptr,
-	);
-}
-
-pub fn log_fail(message: []const coral.io.Byte) void {
-	ext.SDL_LogError(
-		ext.SDL_LOG_CATEGORY_APPLICATION,
-		"%.*s",
-		coral.math.clamped_cast(@typeInfo(c_int).Int, message.len),
-		message.ptr,
-	);
-}

source/ona/file.zig

@@ -11,9 +11,9 @@ pub const Access = union (enum) {
 			.null => return null,
 
 			.sandboxed_path => |sandboxed_path| {
-				const path_string = sandboxed_path.joined(readable_path).get_string();
+				const path_bytes = sandboxed_path.joined(readable_path).to_bytes();
 
-				return @ptrCast(ext.SDL_RWFromFile(path_string.ptr, "rb"));
+				return @ptrCast(ext.SDL_RWFromFile(path_bytes.ptr, "rb"));
 			},
 		}
 	}
@@ -23,8 +23,7 @@ pub const Access = union (enum) {
 			.null => return null,
 
 			.sandboxed_path => |sandboxed_path| {
-				const path_string = sandboxed_path.joined(path).get_string();
+				const rw_ops = ext.SDL_RWFromFile(sandboxed_path.joined(path).to_bytes(), "rb") orelse return null;
-				const rw_ops = ext.SDL_RWFromFile(path_string, "rb") orelse return null;
 				const file_size = ext.SDL_RWseek(rw_ops, 0, ext.RW_SEEK_END);
 
 				if (ext.SDL_RWclose(rw_ops) != 0 or file_size < 0) {
@@ -43,26 +42,26 @@ pub const Info = struct {
 	size: u64,
 };
 
-pub const Path = extern struct {
+pub const Path = struct {
 	data: [4096]coral.io.Byte = [_]coral.io.Byte{0} ** 4096,
 
-	pub const cwd = Path.from(&.{"./"});
+	pub const cwd = Path.of(&.{"./"});
 
-	pub fn from(components: []const []const u8) Path {
+	pub const FromError = error {
-		// TODO: Implement proper parsing / removal of duplicate path delimiters.
+		InvalidPath,
-		var path = Path{};
+		TooBig,
+	};
 
-		{
+	pub fn from_bytes(bytes: []const coral.io.Byte) FromError!Path {
-			var writable_slice = coral.io.FixedBuffer{.bytes = &path.data};
+		var self = Path{};
 
-			for (components) |component| {
+		if (bytes.len >= self.data.len) {
-				if (writable_slice.write(component) != component.len) {
+			return error.TooBig;
-					break;
-				}
-			}
 		}
 
-		return path;
+		coral.io.copy(&self.data, bytes);
+
+		return self;
 	}
 
 	pub fn joined(self: Path, other: Path) Path {
@@ -96,7 +95,24 @@ pub const Path = extern struct {
 		return path;
 	}
 
-	pub fn get_string(self: Path) [:0]const coral.io.Byte {
+	pub fn of(components: []const []const u8) Path {
+		// TODO: Implement proper parsing / removal of duplicate path delimiters.
+		var path = Path{};
+
+		{
+			var writable_slice = coral.io.FixedBuffer{.bytes = &path.data};
+
+			for (components) |component| {
+				if (writable_slice.write(component) != component.len) {
+					break;
+				}
+			}
+		}
+
+		return path;
+	}
+
+	pub fn to_bytes(self: Path) [:0]const coral.io.Byte {
 		coral.debug.assert(self.data[self.data.len - 1] == 0);
 
 		return coral.io.slice_sentineled(@as(coral.io.Byte, 0), @as([*:0]const coral.io.Byte, @ptrCast(&self.data)));

source/ona/kym.zig

@@ -22,6 +22,16 @@ pub const Fixed = i32;
 ///
 pub const Float = f64;
 
+///
+/// Specialized import logic hook type for exposing native logic to scripts.
+///
+pub const Importer = coral.io.Generator(RuntimeError!?*RuntimeObj, *RuntimeEnv);
+
+///
+/// Byte string printing function.
+///
+pub const Print = fn ([]const coral.io.Byte) void;
+
 ///
 /// Supertype for all numeric types.
 ///
@@ -47,11 +57,13 @@ pub const RuntimeEnv = struct {
 	allocator: coral.io.Allocator,
 	options: Options,
 	interned_symbols: SymbolSet,
+	importer_overrides: ImporterTable,
 	locals: LocalList,
 	frames: FrameList,
 
 	const FrameList = coral.list.Stack(struct {
 		callable: *RuntimeObj,
+		caller: ?*RuntimeObj,
 		locals_top: usize,
 		arg_count: u8,
 
@@ -66,6 +78,16 @@ pub const RuntimeEnv = struct {
 		}
 	});
 
+	const ImporterTable = coral.map.Table(file.Path, Importer, struct {
+		pub fn hash(file_path: file.Path) usize {
+			return coral.io.djb2_hash(@typeInfo(usize).Int, file_path.to_bytes());
+		}
+
+		pub fn equals(a: file.Path, b: file.Path) bool {
+			return coral.io.are_equal(a.to_bytes(), b.to_bytes());
+		}
+	});
+
 	const LocalList = coral.list.Stack(?*RuntimeObj);
 
 	///
@@ -73,13 +95,8 @@ pub const RuntimeEnv = struct {
 	///
 	pub const Options = struct {
 		import_access: file.Access = .null,
-		print: ?*const Printer = null,
+		print_out: ?*const Print = null,
-		print_error: ?*const Printer = null,
+		print_err: ?*const Print = null,
-
-		///
-		/// Byte string printing function.
-		///
-		pub const Printer = fn ([]const coral.io.Byte) void;
 	};
 
 	const SymbolSet = coral.map.StringTable([:0]coral.io.Byte);
@@ -95,7 +112,7 @@ pub const RuntimeEnv = struct {
 	///
 	/// `self` is returned for function chaining.
 	///
-	pub fn arg_get(self: *RuntimeEnv, arg_index: Local) RuntimeError!*RuntimeEnv {
+	pub fn arg(self: *RuntimeEnv, arg_index: Local) RuntimeError!*RuntimeEnv {
 		const frame = self.frames.peek() orelse {
 			return self.raise(error.IllegalState, "cannot get args outside of a call frame", .{});
 		};
@@ -112,11 +129,13 @@ pub const RuntimeEnv = struct {
 	}
 
 	///
-	/// Attempts to pop the top-most value of `self` and call it with `local_arg_count` as the number of locals prior to
+	/// Attempts to pop the top-most value of `self` and call it with `arg_count` as the number of values prior to it in
-	/// it in `self` that are intended to be arguments to it. Once the callable returns, the locals marked as arguments
+	/// `self` that are intended to be arguments to it. Once the callable returns, the locals marked as arguments are
-	/// are popped as well.
+	/// popped as well.
 	///
-	/// A `local_arg_count` of `0` will call the function with no arguments and pop nothing other than the callable from
+	/// An optional `caller` may be specified for attaching an owning object to the call frame.
+	///
+	/// A `arg_count` value of `0` will call the function with no arguments and pop nothing other than the callable from
 	/// `self` during invocation.
 	///
 	/// A [RuntimeError] is returned if `self` is out of memory, the top-most local is nil or not callable, or the
@@ -124,16 +143,17 @@ pub const RuntimeEnv = struct {
 	///
 	/// `self` is returned for function chaining.
 	///
-	pub fn call(self: *RuntimeEnv, local_arg_count: Local) RuntimeError!*RuntimeEnv {
+	pub fn call(self: *RuntimeEnv, arg_count: Local, caller: ?*RuntimeObj) RuntimeError!*RuntimeEnv {
 		const callable = try self.expect_object(self.pop());
 
 		defer self.release(callable);
 
 		const result = get_result: {
 			try self.frames.push_one(.{
-				.locals_top = self.locals.values.len - local_arg_count,
+				.locals_top = self.locals.values.len - arg_count,
 				.callable = callable.internal().acquire(),
-				.arg_count = local_arg_count,
+				.caller = caller,
+				.arg_count = arg_count,
 			});
 
 			defer {
@@ -707,6 +727,27 @@ pub const RuntimeEnv = struct {
 		};
 	}
 
+	///
+	/// Attempts to return the caller of the current call frame, if one exists, otherwise returning `null`.
+	///
+	/// A [RuntimeError] is returned if `self` is out of memory or the virtual machine is not inside a managed call
+	/// frame.
+	///
+	/// *Note* any returned non-null pointer must be released via [RuntimeEnv.release] or else the resources belonging
+	/// to the objects will never be freed by the runtime.
+	///
+	pub fn get_caller(self: *RuntimeEnv) RuntimeError!?*RuntimeObj {
+		const frame = self.frames.peek() orelse {
+			return self.raise(error.IllegalState, "cannot get caller outside of a call frame", .{});
+		};
+
+		if (frame.caller) |object| {
+			return object.internal().acquire();
+		}
+
+		return null;
+	}
+
 	///
 	/// Attempts to pop the top-most value and index into it with `index`, pushing the retrieved value.
 	///
@@ -846,27 +887,30 @@ pub const RuntimeEnv = struct {
 	}
 
 	///
-	/// Attempts to import a script from the import [file.Access] (specified during [RuntimeEnv.init]) from `file_path`.
+	/// Attempts to import a script from the the [Importer] (specified during [RuntimeEnv.init]) from `path`.
 	///
-	/// If the loaded script is a plain text file, it will be read, parsed, and compiled into an optimized format before
+	/// After loading, the result of the import is returned.
-	/// being executed.
 	///
-	/// If the loaded script is already compiled, it is immediately executed.
+	/// A [RuntimeError] is returned if `self` is out of memory, no import at `path` could be found by the runtime,
-	///
+	/// import raised an error during execution.
-	/// After completing execution, the return value is pushed to the top of `self`.
-	///
-	/// A [RuntimeError] is returned if `self` is out of memory, no file at `file_path` could be found by the runtime,
-	/// the script is a source file and contains invalid syntax, or the imported script raised an error during
-	/// execution.
-	///
-	/// Any syntax errors are reported using [print_error] prior to raising a runtime error.
 	///
 	/// `self` is returned for function chaining.
 	///
 	pub fn import(self: *RuntimeEnv, file_path: file.Path) RuntimeError!*RuntimeEnv {
-		{
+		if (self.importer_overrides.lookup(file_path)) |importer| {
-			var callable = new_chunk: {
+			if (try importer.invoke(self)) |object| {
-				const file_name = file_path.get_string();
+				errdefer self.release(object);
+
+				try self.locals.push_one(object);
+			} else {
+				try self.locals.push_one(null);
+			}
+
+			return self;
+		}
+
+		const callable = new_chunk: {
+			const file_name = file_path.to_bytes();
 
 			const file_data =
 				(try file.allocate_and_load(self.allocator, self.options.import_access, file_path)) orelse {
@@ -886,7 +930,7 @@ pub const RuntimeEnv = struct {
 
 				root.parse(&stream) catch |parse_error| {
 					for (root.error_messages.values) |error_message| {
-							self.print_error(error_message);
+						self.print_err(error_message);
 					}
 
 					return self.raise(parse_error, "failed to parse `{name}`", .{.name = file_name});
@@ -897,15 +941,12 @@ pub const RuntimeEnv = struct {
 
 			errdefer chunk.deinit(self);
 
-				break: new_chunk (try self.new_dynamic(coral.io.bytes_of(&chunk), Chunk.typeinfo)).pop().?;
+			break: new_chunk (try self.new_dynamic(Chunk.typeinfo, chunk)).pop().?;
 		};
 
-			errdefer self.release(callable);
+		defer self.release(callable);
 
-			try self.locals.push_one(callable);
+		return (try self.push(callable)).call(0, null);
-		}
-
-		return self.call(0);
 	}
 
 	///
@@ -929,6 +970,7 @@ pub const RuntimeEnv = struct {
 
 		return .{
 			.interned_symbols = SymbolSet.init(allocator, .{}),
+			.importer_overrides = ImporterTable.init(allocator, .{}),
 			.locals = locals,
 			.frames = frames,
 			.allocator = allocator,
@@ -1083,14 +1125,14 @@ pub const RuntimeEnv = struct {
 	///
 	/// Attempts to create a new dynamic object from `userdata` and `typeinfo`, pushing it to the top of `self`.
 	///
-	/// *Note* that the number of bytes in `userdata` must match the size described in `typeinfo` exactly.
+	/// *Note* the size of the type specified in `userdata` must match the size described in `typeinfo` exactly.
 	///
 	/// A [RuntimeError] is returned if `self` is out of memory.
 	///
 	/// `self` is returned for function chaining.
 	///
-	pub fn new_dynamic(self: *RuntimeEnv, userdata: []const coral.io.Byte, typeinfo: *const Typeinfo) RuntimeError!*RuntimeEnv {
+	pub fn new_dynamic(self: *RuntimeEnv, typeinfo: *const Typeinfo, userdata: anytype) RuntimeError!*RuntimeEnv {
-		coral.debug.assert(userdata.len == typeinfo.size);
+		coral.debug.assert(@sizeOf(@TypeOf(userdata)) == typeinfo.size);
 
 		const dynamic = new: {
 			const dynamic = try self.allocator.reallocate(null, @sizeOf(usize) + typeinfo.size);
@@ -1098,7 +1140,7 @@ pub const RuntimeEnv = struct {
 			errdefer self.allocator.deallocate(dynamic);
 
 			coral.io.copy(dynamic, coral.io.bytes_of(&typeinfo));
-			coral.io.copy(dynamic[@sizeOf(usize) ..], userdata[0 .. typeinfo.size]);
+			coral.io.copy(dynamic[@sizeOf(usize) ..], coral.io.bytes_of(&userdata));
 
 			break: new try RuntimeObj.allocate(self.allocator, .{
 				.ref_count = 1,
@@ -1221,7 +1263,7 @@ pub const RuntimeEnv = struct {
 
 		errdefer table.deinit(self);
 
-		return self.new_dynamic(coral.io.bytes_of(&table), Table.typeinfo);
+		return self.new_dynamic(Table.typeinfo, table);
 	}
 
 	///
@@ -1295,6 +1337,16 @@ pub const RuntimeEnv = struct {
 		return self;
 	}
 
+	///
+	/// Attempst to override the behavior of all imports at `path` to execute the import logic specified in `importer`
+	/// instead for `self`.
+	///
+	/// A [RuntimeError] is returned if `self` is out of memory.
+	///
+	pub fn override_import(self: *RuntimeEnv, path: file.Path, importer: Importer) RuntimeError!void {
+		_ = try self.importer_overrides.replace(path, importer);
+	}
+
 	///
 	/// Pops the top-most value of `self`, returning the value.
 	///
@@ -1310,20 +1362,20 @@ pub const RuntimeEnv = struct {
 	}
 
 	///
-	/// Prints `buffer` to the printing operation specified in the options of `self`.
+	/// Prints `buffer` to the error printing operation specified in the options of `self.
 	///
-	pub fn print(self: *RuntimeEnv, buffer: []const coral.io.Byte) void {
+	pub fn print_err(self: *RuntimeEnv, buffer: []const coral.io.Byte) void {
-		if (self.options.print) |op| {
+		if (self.options.print_err) |print| {
-			op(buffer);
+			print(buffer);
 		}
 	}
 
 	///
-	/// Prints `buffer` to the error printing operation specified in the options of `self.
+	/// Prints `buffer` to the printing operation specified in the options of `self`.
 	///
-	pub fn print_error(self: *RuntimeEnv, buffer: []const coral.io.Byte) void {
+	pub fn print_out(self: *RuntimeEnv, buffer: []const coral.io.Byte) void {
-		if (self.options.print_error) |op| {
+		if (self.options.print_out) |print| {
-			op(buffer);
+			print(buffer);
 		}
 	}
 
@@ -1359,10 +1411,10 @@ pub const RuntimeEnv = struct {
 
 		defer self.allocator.deallocate(formatted_message);
 
-		self.print_error(formatted_message);
+		self.print_err(formatted_message);
 
 		if (!self.frames.is_empty()) {
-			self.print_error("stack trace:");
+			self.print_err("stack trace:");
 
 			var remaining_frames = self.frames.values.len;
 
@@ -1392,9 +1444,9 @@ pub const RuntimeEnv = struct {
 
 					defer self.allocator.deallocate(chunk_name);
 
-					self.print_error(chunk_name);
+					self.print_err(chunk_name);
 				} else {
-					self.print_error(get_name: {
+					self.print_err(get_name: {
 						const string = name.is_string();
 
 						coral.debug.assert(string != null);
@@ -2083,10 +2135,10 @@ pub const Typeinfo = struct {
 		///
 		/// The [RuntimeEnv] is returned for function chaining.
 		///
-		pub fn push_index(self: *const GetContext) RuntimeError!*RuntimeEnv {
+		pub fn get_index(self: *const GetContext) *RuntimeObj {
 			coral.debug.assert(self.env.locals.values.len > 0);
 
-			return self.env.push(self.env.locals.values[self.env.locals.values.len - 1]);
+			return self.env.locals.values[self.env.locals.values.len - 1].?.internal().acquire();
 		}
 	};
 
@@ -2106,10 +2158,10 @@ pub const Typeinfo = struct {
 		///
 		/// The [RuntimeEnv] is returned for function chaining.
 		///
-		pub fn push_index(self: *const SetContext) RuntimeError!*RuntimeEnv {
+		pub fn get_index(self: *const SetContext) *RuntimeObj {
 			coral.debug.assert(self.env.locals.values.len > 0);
 
-			return self.env.push(self.env.locals.values[self.env.locals.values.len - 1]);
+			return self.env.locals.values[self.env.locals.values.len - 1].?.internal().acquire();
 		}
 
 		///
@@ -2119,10 +2171,10 @@ pub const Typeinfo = struct {
 		///
 		/// The [RuntimeEnv] is returned for function chaining.
 		///
-		pub fn push_value(self: *const SetContext) RuntimeError!*RuntimeEnv {
+		pub fn get_value(self: *const SetContext) ?*RuntimeObj {
 			coral.debug.assert(self.env.locals.values.len > 1);
 
-			return self.env.push(self.env.locals.values[self.env.locals.values.len - 2]);
+			return if (self.env.locals.values[self.env.locals.values.len - 2]) |object| object.internal().acquire() else null;
 		}
 	};
 

source/ona/kym/Chunk.zig

@@ -1,5 +1,3 @@
-const app = @import("../app.zig");
-
 const coral = @import("coral");
 
 const file = @import("../file.zig");
@@ -221,8 +219,8 @@ const Compiler = struct {
 				}
 
 				if (try get_binding_index(environment, declaration_set.declaration)) |index| {
-					try self.compile_expression(environment, declaration_set.assign, null);
 					try self.chunk.write(expression.line, .{.push_binding = index});
+					try self.compile_expression(environment, declaration_set.assign, null);
 
 					if (is_declaration_boxed(declaration_set.declaration)) {
 						try self.chunk.write(expression.line, .set_box);
@@ -247,6 +245,16 @@ const Compiler = struct {
 				try self.chunk.write(expression.line, .set_dynamic);
 			},
 
+			.field_invoke => |field_invoke| {
+				const argument_count = try self.compile_argument(environment, field_invoke.argument);
+
+				try self.compile_expression(environment, field_invoke.object, null);
+				try self.chunk.write(expression.line, .{.push_const = try self.declare_symbol(field_invoke.identifier)});
+				try self.chunk.write(expression.line, .get_dynamic);
+				try self.compile_expression(environment, field_invoke.object, null);
+				try self.chunk.write(expression.line, .{.call_from = argument_count});
+			},
+
 			.subscript_get => |subscript_get| {
 				try self.compile_expression(environment, subscript_get.object, null);
 				try self.compile_expression(environment, subscript_get.index, null);
@@ -345,7 +353,7 @@ const Compiler = struct {
 			});
 		}
 
-		const constant = (try self.env.new_dynamic(coral.io.bytes_of(&chunk), typeinfo)).pop().?;
+		const constant = (try self.env.new_dynamic(typeinfo, chunk)).pop().?;
 
 		errdefer self.env.release(constant);
 
@@ -483,6 +491,7 @@ pub const Opcode = union (enum) {
 	get_box,
 	set_box,
 	call: u8,
+	call_from: u8,
 	bind: u8,
 
 	not,
@@ -747,7 +756,15 @@ pub fn execute(self: *Self, env: *kym.RuntimeEnv) kym.RuntimeError!?*kym.Runtime
 				try env.index_set(index, value);
 			},
 
-			.call => |call| _ = try env.call(call),
+			.call => |call| _ = try env.call(call, null),
+
+			.call_from => |call_from| {
+				const caller = try env.expect_object(env.pop());
+
+				defer env.release(caller);
+
+				_ = try env.call(call_from, caller);
+			},
 
 			.not => {
 				const object = try env.expect_object(env.pop());
@@ -918,28 +935,28 @@ pub fn init(env: *kym.RuntimeEnv, name: []const coral.io.Byte, environment: *con
 }
 
 fn syscall_import(env: *kym.RuntimeEnv) kym.RuntimeError!?*kym.RuntimeObj {
-	const arg = (try env.arg_get(0)).pop() orelse {
+	const arg = (try env.arg(0)).pop() orelse {
 		return env.raise(error.BadOperation, "`@import` requires one argument to be a valid import path", .{});
 	};
 
 	defer env.release(arg);
 
-	return (try env.import(file.Path.from(&.{try env.expect_string(arg)}))).pop();
+	return (try env.import(file.Path.of(&.{try env.expect_string(arg)}))).pop();
 }
 
 fn syscall_print(env: *kym.RuntimeEnv) kym.RuntimeError!?*kym.RuntimeObj {
-	const string = (try (try env.arg_get(0)).to_string()).pop().?;
+	const string = (try (try env.arg(0)).to_string()).pop().?;
 
 	defer env.release(string);
 
-	env.print(string.is_string().?);
+	env.print_out(string.is_string().?);
 
 	return null;
 }
 
 fn syscall_vec2(env: *kym.RuntimeEnv) kym.RuntimeError!?*kym.RuntimeObj {
 	const x = @as(f32, get_x: {
-		const x = (try env.arg_get(0)).pop() orelse {
+		const x = (try env.arg(0)).pop() orelse {
 			return env.raise(error.BadOperation, "a first argument is required to create a vector", .{});
 		};
 
@@ -948,7 +965,7 @@ fn syscall_vec2(env: *kym.RuntimeEnv) kym.RuntimeError!?*kym.RuntimeObj {
 		break: get_x @floatCast(try env.expect_float(x));
 	});
 
-	if ((try env.arg_get(1)).pop()) |y| {
+	if ((try env.arg(1)).pop()) |y| {
 		defer env.release(y);
 
 		return (try env.new_vector2(.{
@@ -962,7 +979,7 @@ fn syscall_vec2(env: *kym.RuntimeEnv) kym.RuntimeError!?*kym.RuntimeObj {
 
 fn syscall_vec3(env: *kym.RuntimeEnv) kym.RuntimeError!?*kym.RuntimeObj {
 	const x = @as(f32, get_x: {
-		const x = (try env.arg_get(0)).pop() orelse {
+		const x = (try env.arg(0)).pop() orelse {
 			return env.raise(error.BadOperation, "a first argument is required to create a vector", .{});
 		};
 
@@ -971,12 +988,12 @@ fn syscall_vec3(env: *kym.RuntimeEnv) kym.RuntimeError!?*kym.RuntimeObj {
 		break: get_x @floatCast(try env.expect_float(x));
 	});
 
-	if ((try env.arg_get(1)).pop()) |y| {
+	if ((try env.arg(1)).pop()) |y| {
 		defer env.release(y);
 
 		return (try env.new_vector3(.{
 			.z = @as(f32, get_z: {
-				const z = (try env.arg_get(0)).pop() orelse {
+				const z = (try env.arg(0)).pop() orelse {
 					return env.raise(error.BadOperation,
 						"a third argument is required to create a vector if a first and second exist", .{});
 				};

source/ona/kym/Table.zig

@@ -57,7 +57,7 @@ fn typeinfo_destruct(context: kym.Typeinfo.DestructContext) void {
 
 fn typeinfo_get(context: kym.Typeinfo.GetContext) kym.RuntimeError!?*kym.RuntimeObj {
 	const table = @as(*Self, @ptrCast(@alignCast(context.userdata)));
-	const index = (try context.push_index()).pop().?;
+	const index = context.get_index();
 
 	defer context.env.release(index);
 
@@ -81,7 +81,7 @@ fn typeinfo_get(context: kym.Typeinfo.GetContext) kym.RuntimeError!?*kym.Runtime
 
 fn typeinfo_set(context: kym.Typeinfo.SetContext) kym.RuntimeError!void {
 	const table = @as(*Self, @ptrCast(@alignCast(context.userdata)));
-	const index = (try context.push_index()).pop().?;
+	const index = context.get_index();
 
 	errdefer context.env.release(index);
 
@@ -98,7 +98,7 @@ fn typeinfo_set(context: kym.Typeinfo.SetContext) kym.RuntimeError!void {
 				context.env.release(replacing);
 			}
 
-			if ((try context.push_value()).pop()) |value| {
+			if (context.get_value()) |value| {
 				errdefer context.env.release(value);
 
 				maybe_replacing.* = value;
@@ -110,7 +110,7 @@ fn typeinfo_set(context: kym.Typeinfo.SetContext) kym.RuntimeError!void {
 		}
 	}
 
-	const value = (try context.push_value()).pop() orelse {
+	const value = context.get_value() orelse {
 		if (table.associative.remove(index)) |removed| {
 			context.env.release(removed.key);
 			context.env.release(removed.value);

source/ona/kym/tree/Expr.zig

@@ -25,6 +25,7 @@ kind: union (enum) {
 	declaration_set: DeclarationSet,
 	field_get: FieldGet,
 	field_set: FieldSet,
+	field_invoke: FieldInvoke,
 	subscript_get: SubscriptGet,
 	subscript_set: SubscriptSet,
 	binary_op: BinaryOp,
@@ -112,6 +113,12 @@ pub const DeclarationSet = struct {
 	assign: *const Self,
 };
 
+pub const FieldInvoke = struct {
+	argument: ?*const Self,
+	identifier: []const coral.io.Byte,
+	object: *const Self,
+};
+
 pub const FieldGet = struct {
 	identifier: []const coral.io.Byte,
 	object: *const Self,
@@ -364,7 +371,7 @@ fn parse_factor(root: *tree.Root, stream: *tokens.Stream, environment: *tree.Env
 						switch (stream.token) {
 							.symbol_comma => stream.skip_newlines(),
 							.symbol_paren_right => break,
-							else => return root.report_error(stream.line, "expected `,` or `)` after lambda argument", .{}),
+							else => return root.report_error(stream.line, "expected `,` or `)` after argument", .{}),
 						}
 
 						const next_argument = try parse(root, stream, environment);
@@ -382,12 +389,22 @@ fn parse_factor(root: *tree.Root, stream: *tokens.Stream, environment: *tree.Env
 				expression = try root.create_expr(.{
 					.line = lines_stepped,
 
-					.kind = .{
+					.kind = switch (expression.kind) {
+						.field_get => |field_get| .{
+							.field_invoke = .{
+								.identifier = field_get.identifier,
+								.argument = first_argument,
+								.object = field_get.object,
+							},
+						},
+
+						else => .{
 							.invoke = .{
 								.argument = first_argument,
 								.object = unnecessary_temp,
 							},
 						},
+					}
 				});
 			},
 

source/ona/ona.zig

@@ -1,5 +1,3 @@
-const app = @import("./app.zig");
-
 const coral = @import("coral");
 
 const ext = @import("./ext.zig");
@@ -10,84 +8,306 @@ const heap = @import("./heap.zig");
 
 const kym = @import("./kym.zig");
 
-fn last_sdl_error() [:0]const u8 {
+const App = struct {
-	return coral.io.slice_sentineled(@as(u8, 0), @as([*:0]const u8, @ptrCast(ext.SDL_GetError())));
+	renderer: *ext.SDL_Renderer,
+	window: *ext.SDL_Window,
+	systems: Systems,
+	target_frame_time: f64,
+
+	keys: struct {
+		pressed: [ext.SDL_NUM_SCANCODES]bool = [_]bool{false} ** ext.SDL_NUM_SCANCODES,
+		released: [ext.SDL_NUM_SCANCODES]bool = [_]bool{false} ** ext.SDL_NUM_SCANCODES,
+		held: [ext.SDL_NUM_SCANCODES]bool = [_]bool{false} ** ext.SDL_NUM_SCANCODES,
+	},
+
+	const DynamicObject = struct {
+		self: *App,
+
+		fn get(context: kym.Typeinfo.GetContext) kym.RuntimeError!?*kym.RuntimeObj {
+			const index = context.get_index();
+
+			defer context.env.release(index);
+
+			const on_update_symbol = (try context.env.new_symbol("on_update")).pop().?;
+
+			defer context.env.release(on_update_symbol);
+
+			if (index.equals(on_update_symbol)) {
+				return (try context.env.new_syscall(on_update)).pop();
 			}
 
-pub fn run_app(file_access: file.Access) void {
+			return null;
-	defer heap.trace_leaks();
-
-	if (ext.SDL_Init(ext.SDL_INIT_EVERYTHING) != 0) {
-		return app.log_fail(last_sdl_error());
 		}
 
-	defer ext.SDL_Quit();
+		fn on_update(env: *kym.RuntimeEnv) kym.RuntimeError!?*kym.RuntimeObj {
+			const caller_object = try env.expect_object(try env.get_caller());
 
-	var script_env = kym.RuntimeEnv.init(heap.allocator, 255, .{
+			defer env.release(caller_object);
-		.print = app.log_info,
+
-		.print_error = app.log_fail,
+			const app = @as(*DynamicObject, @ptrCast(@alignCast(try env.expect_dynamic(caller_object, typeinfo))));
-		.import_access = file_access,
+
-	}) catch {
+			const callable = try env.expect_object((try env.arg(0)).pop());
-		return app.log_fail("failed to initialize script runtime");
+
+			errdefer env.release(callable);
+
+			try app.self.systems.push_one(callable);
+
+			return null;
+		}
+
+		const typeinfo = &kym.Typeinfo{
+			.name = "ona",
+			.size = @sizeOf(DynamicObject),
+			.get = get,
+		};
 	};
 
-	defer script_env.deinit();
+	pub const InitError = error {
+		RendererUnavailable,
+		WindowUnavailable,
+	};
 
-	var manifest = app.Manifest{};
+	const Systems = coral.list.Stack(*kym.RuntimeObj);
 
-	manifest.load(&script_env) catch return;
+	pub fn as_importer(self: *App) kym.Importer {
+		return kym.Importer.bind(App, self, import);
+	}
 
+	pub fn deinit(self: *App) void {
+		ext.SDL_DestroyWindow(self.window);
+		ext.SDL_DestroyRenderer(self.renderer);
+		self.systems.deinit();
+	}
+
+	fn import(self: *App, env: *kym.RuntimeEnv) kym.RuntimeError!?*kym.RuntimeObj {
+		return (try env.new_dynamic(DynamicObject.typeinfo, DynamicObject{.self = self})).pop();
+	}
+
+	pub fn init() InitError!App {
 		const window = create: {
+			const height = 480;
+			const width = 640;
 			const pos = ext.SDL_WINDOWPOS_CENTERED;
-		const flags = 0;
+			const flags = ext.SDL_WINDOW_HIDDEN;
 
-		break: create ext.SDL_CreateWindow(&manifest.title, pos, pos, manifest.width, manifest.height, flags) orelse {
+			break: create ext.SDL_CreateWindow("", pos, pos, width, height, flags) orelse {
-			return app.log_fail(last_sdl_error());
+				return error.WindowUnavailable;
 			};
 		};
 
-	defer ext.SDL_DestroyWindow(window);
+		errdefer ext.SDL_DestroyWindow(window);
 
 		const renderer = create: {
 			const default_driver_index = -1;
 			const flags = ext.SDL_RENDERER_ACCELERATED;
 
 			break: create ext.SDL_CreateRenderer(window, default_driver_index, flags) orelse {
-			return app.log_fail(last_sdl_error());
+				return error.RendererUnavailable;
 			};
 		};
 
-	defer ext.SDL_DestroyRenderer(renderer);
+		errdefer ext.SDL_DestroyRenderer(renderer);
 
-	{
+		return .{
-		var previous_ticks = ext.SDL_GetTicks64();
+			.systems = Systems.init(heap.allocator),
+			.target_frame_time = 1.0 / 60.0,
+			.renderer = renderer,
+			.window = window,
+			.keys = .{},
+		};
+	}
 
-		while (true) {
+	pub fn load(self: *App, env: *kym.RuntimeEnv) kym.RuntimeError!void {
-			{
+		var previous_width = @as(c_int, 0);
+		var previous_height = @as(c_int, 0);
+
+		ext.SDL_GetWindowSize(self.window, &previous_width, &previous_height);
+
+		var width = previous_width;
+		var height = previous_height;
+
+		defer {
+			const pos = ext.SDL_WINDOWPOS_CENTERED;
+
+			ext.SDL_SetWindowSize(self.window, width, height);
+			ext.SDL_SetWindowPosition(self.window, pos, pos);
+			ext.SDL_ShowWindow(self.window);
+		}
+
+		if ((try env.import(file.Path.of(&.{"app.ona"}))).pop()) |manifest| {
+			defer env.release(manifest);
+
+			if (try kym.get_field(env, manifest, "width")) |object| {
+				defer env.release(object);
+
+				const fixed = try env.expect_fixed(object);
+
+				if (fixed > 0 and fixed < coral.math.max_int(@typeInfo(@TypeOf(width)).Int)) {
+					width = @intCast(fixed);
+				}
+			}
+
+			if (try kym.get_field(env, manifest, "height")) |object| {
+				defer env.release(object);
+
+				const fixed = try env.expect_fixed(object);
+
+				if (fixed > 0 and fixed < coral.math.max_int(@typeInfo(@TypeOf(height)).Int)) {
+					height = @intCast(fixed);
+				}
+			}
+
+			if (try kym.get_field(env, manifest, "tick_rate")) |object| {
+				defer env.release(object);
+
+				self.target_frame_time = 1.0 / try env.expect_float(object);
+			}
+
+			if (try kym.get_field(env, manifest, "title")) |object| {
+				defer env.release(object);
+
+				const title = coral.utf8.SmallString.from_units(try env.expect_string(object)) catch |from_error| {
+					return switch (from_error) {
+						error.InvalidUtf8 => env.raise(error.TypeMismatch, "`title` cannot contain invalid utf8", .{}),
+						error.TooBig => env.raise(error.TypeMismatch, "`title` is too long", .{}),
+					};
+				};
+
+				ext.SDL_SetWindowTitle(self.window, title.to_units());
+			} else {
+				ext.SDL_SetWindowTitle(self.window, "Ona");
+			}
+		}
+	}
+
+	pub fn poll(self: *App) bool {
 		var event = @as(ext.SDL_Event, undefined);
 
+		coral.io.zero(@ptrCast(&self.keys.pressed));
+		coral.io.zero(@ptrCast(&self.keys.released));
+
 		while (ext.SDL_PollEvent(&event) != 0) {
 			switch (event.type) {
-						ext.SDL_QUIT => return,
+				ext.SDL_QUIT => return false,
+
+				ext.SDL_KEYDOWN => {
+					self.keys.pressed[event.key.keysym.scancode] = true;
+					self.keys.held[event.key.keysym.scancode] = true;
+				},
+
+				ext.SDL_KEYUP => {
+					self.keys.released[event.key.keysym.scancode] = true;
+					self.keys.held[event.key.keysym.scancode] = false;
+				},
+
 				else => {},
 			}
 		}
+
+		return true;
 	}
 
-			{
+	pub fn render(self: *App) void {
-				// Based on https://fabiensanglard.net/timer_and_framerate/index.php.
+		_ = ext.SDL_SetRenderDrawColor(self.renderer, 0, 0, 0, 255);
-				const current_ticks = ext.SDL_GetTicks64();
+		_ = ext.SDL_RenderClear(self.renderer);
-				const milliseconds_per_second = 1000.0;
+		_ = ext.SDL_RenderPresent(self.renderer);
-				const tick_frequency = @as(u64, @intFromFloat(milliseconds_per_second / manifest.tick_rate));
-
-				while (previous_ticks < current_ticks) {
-					previous_ticks += tick_frequency;
-				}
 	}
 
-			_ = ext.SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255);
+	pub fn update(self: *App, env: *kym.RuntimeEnv, time_delta: f32) kym.RuntimeError!void {
-			_ = ext.SDL_RenderClear(renderer);
+		for (self.systems.values) |system| {
-			_ = ext.SDL_RenderPresent(renderer);
+			(try (try (try env.new_float(time_delta)).push(system)).call(1, null)).discard();
 		}
 	}
+};
+
+fn last_sdl_error() [:0]const u8 {
+	return coral.io.slice_sentineled(@as(u8, 0), @as([*:0]const u8, @ptrCast(ext.SDL_GetError())));
+}
+
+fn load_prompt() void {
+
+}
+
+pub fn log_info(message: []const coral.io.Byte) void {
+	ext.SDL_LogInfo(
+		ext.SDL_LOG_CATEGORY_APPLICATION,
+		"%.*s",
+		coral.math.clamped_cast(@typeInfo(c_int).Int, message.len),
+		message.ptr,
+	);
+}
+
+pub fn log_warn(message: []const coral.io.Byte) void {
+	ext.SDL_LogWarn(
+		ext.SDL_LOG_CATEGORY_APPLICATION,
+		"%.*s",
+		coral.math.clamped_cast(@typeInfo(c_int).Int, message.len),
+		message.ptr,
+	);
+}
+
+pub fn log_fail(message: []const coral.io.Byte) void {
+	ext.SDL_LogError(
+		ext.SDL_LOG_CATEGORY_APPLICATION,
+		"%.*s",
+		coral.math.clamped_cast(@typeInfo(c_int).Int, message.len),
+		message.ptr,
+	);
+}
+
+const milliseconds_per_second = 1000;
+
+pub fn run_app(file_access: file.Access) void {
+	defer heap.trace_leaks();
+
+	if (ext.SDL_Init(ext.SDL_INIT_EVERYTHING) != 0) {
+		return log_fail(last_sdl_error());
+	}
+
+	defer ext.SDL_Quit();
+
+	var app = App.init() catch |init_error| {
+		return log_fail(switch (init_error) {
+			error.WindowUnavailable => "unable to acquire window",
+			error.RendererUnavailable => "unable to acquire renderer",
+		});
+	};
+
+	defer app.deinit();
+
+	var script_env = kym.RuntimeEnv.init(heap.allocator, 255, .{
+		.import_access = file_access,
+		.print_out = log_info,
+		.print_err = log_fail,
+	}) catch {
+		return log_fail("failed to initialize script runtime");
+	};
+
+	defer script_env.deinit();
+
+	script_env.override_import(file.Path.of(&.{"ona"}), app.as_importer()) catch return;
+
+	app.load(&script_env) catch load_prompt();
+
+	var ticks_previous = ext.SDL_GetTicks64();
+	var accumulated_time = @as(f64, 0);
+
+	running_loop: while (true) {
+		const ticks_current = ext.SDL_GetTicks64();
+		const delta_time = @as(f64, @floatFromInt(ticks_current - ticks_previous)) / milliseconds_per_second;
+
+		ticks_previous = ticks_current;
+		accumulated_time += delta_time;
+
+		while (accumulated_time >= app.target_frame_time) : (accumulated_time -= app.target_frame_time) {
+			if (!app.poll()) {
+				break: running_loop;
+			}
+
+			app.update(&script_env, @floatCast(app.target_frame_time)) catch return;
+		}
+
+		app.render();
+		ext.SDL_Delay(1);
+	}
 }