Further ECS-ification, use systems

src/main.zig

@@ -5,20 +5,23 @@ const core = @import("mach").core;
 const Renderer = @import("./renderer.zig");
 
 const flecszigble = @import("flecs-zig-ble");
-const World = flecszigble.World(void);
+const Context = flecszigble.Context(void);
+const World = Context.World;
+const Iter = Context.Iter;
+
+const flecs = flecszigble.flecs;
+const OnLoad = flecs.pipeline.OnLoad;
+const OnUpdate = flecs.pipeline.OnUpdate;
+const OnStore = flecs.pipeline.OnStore;
 
 pub const App = @This();
 
 gpa: GeneralPurposeAllocator,
 allocator: std.mem.Allocator,
+random: std.Random,
 world: *World,
-random: std.rand.Random,
-
 renderer: *Renderer,
 
-app_timer: core.Timer,
-title_timer: core.Timer,
-
 pub fn init(app: *App) !void {
     try core.init(.{
         // Request high performance = prefer dedicated GPU when available.
@@ -35,6 +38,11 @@ pub fn init(app: *App) !void {
     app.gpa = GeneralPurposeAllocator{};
     app.allocator = app.gpa.allocator();
 
+    // Create a pseudo-random number generator, but initialize it with
+    // a constant seed so we always get the same result when launching.
+    var prng = std.Random.DefaultPrng.init(0);
+    app.random = prng.random();
+
     // Initialize flecs-zig-ble and create a new Flecs world.
     //
     // Flecs is a library for using Entity Component System (ECS) design
@@ -45,32 +53,43 @@ pub fn init(app: *App) !void {
     // and modified. For example by using systems, you are able to get
     // entities that match a set of components, and modify their values.
     flecszigble.init(app.allocator);
-    app.world = try World.init();
+    const world = try World.init();
+    app.world = world;
 
-    // Create a pseudo-random number generator, but initialize it with
-    // a constant seed so we always get the same result when launching.
-    var prng = std.rand.DefaultPrng.init(0);
-    app.random = prng.random();
+    // Create a singleton component for accessing the `App` from ECS.
+    _ = try world.singleton("App", *App, app);
 
-    app.renderer = try Renderer.init(app);
+    // TODO: The way we register systems using flecs-zig-ble is still very WIP.
+    _ = try world.system("PollEvents", pollEvents, OnLoad, "App");
+
+    const s = try world.system("UpdateWindowTitle", updateWindowTitle, OnStore, "");
+    // Set the update interval of the `UpdateWindowTitle` system to 1 second.
+    _ = flecszigble.c.ecs_set_interval(world.raw, s.raw, 1.0);
 
-    app.app_timer = try core.Timer.start();
-    app.title_timer = try core.Timer.start();
+    app.renderer = try Renderer.init(app);
 }
 
 pub fn deinit(app: *App) void {
     // Using `defer` here, so we can specify them
     // in the order they were created in `init`.
     defer core.deinit();
-    defer _ = app.gpa.deinit(); // TODO: Check for memory leaks?
+    defer _ = app.gpa.deinit();
     defer app.world.deinit();
     defer app.renderer.deinit();
 }
 
+/// Update function called by Mach Core, which we'll just use to update Flecs.
+/// This will then process all the systems we've registered in our pipeline.
 pub fn update(app: *App) !bool {
-    // Read events from the OS such as input.
-    var iter = core.pollEvents();
-    while (iter.next()) |event| {
+    return !app.world.progress(0.0);
+}
+
+/// Read events from the OS such as input.
+pub fn pollEvents(it: Iter) void {
+    const app = it.field(*App, 1)[0];
+
+    var pollIter = core.pollEvents();
+    while (pollIter.next()) |event| {
         switch (event) {
             // Allow the renderer to act on the window being resized.
             // This is required so we can resize necessary buffers.
@@ -78,19 +97,17 @@ pub fn update(app: *App) !bool {
 
             // Close the window when requested, such as when
             // pressing the X button in the window title bar.
-            .close => return true,
+            .close => it.world.quit(),
 
             else => {},
         }
     }
+}
 
-    app.renderer.update();
-
-    // Update the window title to show FPS and input frequency.
-    if (app.title_timer.read() >= 1.0) {
-        app.title_timer.reset();
-        try core.printTitle("Triangle [ {d}fps ] [ Input {d}hz ]", .{ core.frameRate(), core.inputRate() });
-    }
-
-    return false;
+/// Update the window title to show FPS and input frequency.
+pub fn updateWindowTitle(_: Iter) void {
+    core.printTitle(
+        "Triangle [ {d}fps ] [ Input {d}hz ]",
+        .{ core.frameRate(), core.inputRate() },
+    ) catch @panic("Title too long!");
 }

src/renderer.zig

@@ -18,7 +18,12 @@ const VertexData = primitives.VertexData;
 const PrimitiveData = primitives.PrimitiveData;
 
 const flecszigble = @import("flecs-zig-ble");
-const Entity = flecszigble.Entity(void);
+const Context = flecszigble.Context(void);
+const Entity = Context.Entity;
+const Iter = Context.Iter;
+
+const flecs = flecszigble.flecs;
+const OnStore = flecs.pipeline.OnStore;
 
 const Transform = struct { value: Mat };
 const CameraPerspective = struct {
@@ -46,6 +51,7 @@ const ObjectData = struct {
 const Renderer = @This();
 
 app: *App,
+time: f32 = 0.0,
 
 pipeline: *gpu.RenderPipeline,
 view_proj_buffer: *gpu.Buffer,
@@ -56,7 +62,6 @@ depth_texture_view: ?*gpu.TextureView = null,
 
 primitive_data: []PrimitiveData,
 object_data: []ObjectData,
-camera_entity: Entity,
 
 pub fn init(app: *App) !*Renderer {
     // A string buffer used to format objects' labels.
@@ -225,11 +230,22 @@ pub fn init(app: *App) !*Renderer {
         };
     }
 
-    _ = try app.world.component(Transform);
-    _ = try app.world.component(CameraPerspective);
+    // Register components necessary for the camera.
+    _ = try app.world.component("Transform", Transform);
+    _ = try app.world.component("CameraPerspective", CameraPerspective);
+
+    const camera_entity = try app.world.entity(
+        .{ .name = "Camera", .symbol = "Camera" },
+        .{ Transform, CameraPerspective },
+    );
+    camera_entity.set(CameraPerspective, .{
+        .field_of_view = 45.0,
+        .near_plane = 0.05,
+        .far_plane = 80.0,
+    });
 
-    const camera_entity = try app.world.entity(.{ .name = "Camera" }, .{ Transform, CameraPerspective });
-    camera_entity.set(CameraPerspective, .{ .field_of_view = 45.0, .near_plane = 0.05, .far_plane = 80.0 });
+    const render_expr = "App, [in] CameraPerspective(Camera), [out] Transform(Camera)";
+    _ = try app.world.system("Render", render, OnStore, render_expr);
 
     const result = try app.allocator.create(Renderer);
     result.* = .{
@@ -239,7 +255,6 @@ pub fn init(app: *App) !*Renderer {
         .camera_bind_group = camera_bind_group,
         .primitive_data = primitive_data,
         .object_data = object_data,
-        .camera_entity = camera_entity,
     };
 
     // Initialize the depth texture.
@@ -250,8 +265,8 @@ pub fn init(app: *App) !*Renderer {
 }
 
 pub fn deinit(self: *Renderer) void {
-    // Using `defer` here, so we can specify them
-    // in the order they were created in `init`.
+    // Using `defer` here, so we can specify resources we
+    // want to free in the order they were created in `init`.
     defer self.app.allocator.destroy(self);
 
     defer self.pipeline.release();
@@ -278,34 +293,39 @@ pub fn resize(self: *Renderer) void {
     self.recreateDepthTexture();
 }
 
-pub fn update(self: *Renderer) void {
+pub fn render(it: Iter) void {
+    const app = it.field(*App, 1)[0];
+    const camera_perspective = it.field(CameraPerspective, 2)[0];
+    const camera_transform = &it.field(Transform, 3)[0];
+
+    const self = app.renderer;
+    self.time += it.deltaTime();
+
     // Set up a view matrix from the camera transform.
     // This moves everything to be relative to the camera.
     // TODO: Actually implement camera transform instead of hardcoding a look-at matrix.
     // const view_matrix = zm.inverse(app.camera_transform);
-    const time = self.app.app_timer.read();
     const camera_distance = 8.0;
-    const x = @cos(time * std.math.tau / 20) * camera_distance;
-    const z = @sin(time * std.math.tau / 20) * camera_distance;
+    const x = @cos(self.time * std.math.tau / 20) * camera_distance;
+    const z = @sin(self.time * std.math.tau / 20) * camera_distance;
     const camera_pos = vec(x, 2.0, z, 1.0);
     const view_matrix = zm.lookAtLh(camera_pos, vec(0, 0, 0, 1), vec(0, 1, 0, 1));
 
     // Setting the transform here doesn't do anything because it's not used
     // anywhere. In the future we would want to set the camera transform
     // outside of the rendering step, and then get and use it here, instead.
-    self.camera_entity.set(Transform, .{ .value = view_matrix });
+    camera_transform.* = .{ .value = view_matrix };
     // TODO: Not sure if this is the proper transform, or actually inverted.
 
     // Set up a projection matrix using the size of the window.
     // The perspective projection will make things further away appear smaller.
     const width: f32 = @floatFromInt(core.descriptor.width);
     const height: f32 = @floatFromInt(core.descriptor.height);
-    const perspective = self.camera_entity.get(CameraPerspective).?;
     const proj_matrix = zm.perspectiveFovLh(
-        std.math.degreesToRadians(f32, perspective.field_of_view),
+        std.math.degreesToRadians(f32, camera_perspective.field_of_view),
         width / height,
-        perspective.near_plane,
-        perspective.far_plane,
+        camera_perspective.near_plane,
+        camera_perspective.far_plane,
     );
 
     const view_proj_matrix = zm.mul(view_matrix, proj_matrix);