ona/demos/effects.zig

const gfx = @import("gfx");

const ona = @import("ona");

const std = @import("std");

const CRT = extern struct {
	width: f32,
	height: f32,
	time: f32,
	padding: [4]u8 = undefined,
};

const Effects = struct {
	render_texture: gfx.Texture = .default,
	image_textures: [2]gfx.Texture = [_]gfx.Texture{.default} ** 2,
	last_time: f64 = 0,
	image_index: usize = 0,
	crt_effect: gfx.Effect = .default,
};

fn load(display: ona.Write(gfx.Display), effects: ona.Write(Effects), assets: ona.Write(gfx.Assets)) !void {
	display.state.width, display.state.height = .{1280, 720};

	effects.state.render_texture = try assets.state.load_texture(.{
		.format = .rgba8,

		.access = .{
			.render = .{
				.width = display.state.width,
				.height = display.state.height,
			},
		},
	});

	effects.state.crt_effect = try assets.state.load_effect_file(ona.files.bundle, "./crt.frag.spv");

	var descs = gfx.Descs.init(ona.heap.allocator);

	defer {
		descs.deinit();
	}

	effects.state.image_textures = .{
		try assets.state.load_texture(try descs.checker_texture(.{
			.colors = .{gfx.colors.black, gfx.colors.purple},
			.width = 8,
			.height = 8,
		})),

		try assets.state.load_texture(try descs.checker_texture(.{
			.colors = .{gfx.colors.black, gfx.colors.grey},
			.width = 8,
			.height = 8,
		}))
	};
}

pub const main = ona.App.game
	.with_module(gfx)
	.with_state(Effects{})
	.with_system(.load, ona.system_fn(load), .{.label = "load effects"})
	.with_system(.update, ona.system_fn(update), .{.label = "update effects"})
	.with_system(.render, ona.system_fn(render), .{.label = "render effects"}).build();

fn update(effects: ona.Write(Effects), loop: ona.Read(ona.Loop)) void {
	const update_seconds = 5;

	if ((loop.state.elapsed_time - effects.state.last_time) > update_seconds) {
		effects.state.image_index = (effects.state.image_index + 1) % effects.state.image_textures.len;
		effects.state.last_time = loop.state.elapsed_time;
	}
}

fn render(commands: gfx.Commands, effects: ona.Write(Effects), loop: ona.Read(ona.Loop), display: ona.Write(gfx.Display)) !void {
	try commands.set_target(.{
		.texture = effects.state.render_texture,
		.clear_color = gfx.colors.black,
		.clear_depth = 0,
		.clear_stencil = 0,
	});

	const width: f32 = @floatFromInt(display.state.width);
	const height: f32 = @floatFromInt(display.state.height);

	try commands.draw_texture(.{
		.texture = effects.state.image_textures[effects.state.image_index],
		.size = .{width, height},
	});

	try commands.set_effect(.{
		.effect = effects.state.crt_effect,

		.properties = std.mem.asBytes(&CRT{
			.width = width,
			.height = height,
			.time = @floatCast(loop.state.elapsed_time),
		}),
	});

	try commands.set_target(.{
		.clear_color = null,
		.clear_depth = null,
		.clear_stencil = null,
	});

	try commands.draw_texture(.{
		.texture = effects.state.render_texture,
		.size = .{width, height},
	});
}