module: injected mach.Entity.Mod for global entity operations

Signed-off-by: Stephen Gutekanst <stephen@hexops.com>

src/Core.zig

@@ -106,7 +106,7 @@ fn start(core: *Mod) !void {
     core.state().run_state = .running;
 }
 
-fn init(core: *Mod) !void {
+fn init(entity: *mach.Entity.Mod, core: *Mod) !void {
     mach.core.allocator = gpa.allocator(); // TODO: banish this global allocator
 
     // Initialize GPU implementation
@@ -116,7 +116,7 @@ fn init(core: *Mod) !void {
     try mach.core.init(.{});
 
     // TODO(important): update this information upon framebuffer resize events
-    const main_window = try core.newEntity();
+    const main_window = try entity.new();
     try core.set(main_window, .framebuffer_format, mach.core.descriptor.format);
     try core.set(main_window, .framebuffer_width, mach.core.descriptor.width);
     try core.set(main_window, .framebuffer_height, mach.core.descriptor.height);

src/main.zig

@@ -40,7 +40,7 @@ pub const EventID = @import("module/main.zig").EventID;
 pub const AnyEvent = @import("module/main.zig").AnyEvent;
 pub const merge = @import("module/main.zig").merge;
 pub const builtin_modules = @import("module/main.zig").builtin_modules;
-pub const EntityModule = @import("module/main.zig").EntityModule;
+pub const Entity = @import("module/main.zig").Entity;
 
 /// To use experimental sysgpu graphics API, you can write this in your main.zig:
 ///

src/module/entities.zig

@@ -9,7 +9,7 @@ const StringTable = @import("StringTable.zig");
 const ComponentTypesByName = @import("module.zig").ComponentTypesByName;
 const merge = @import("main.zig").merge;
 const builtin_modules = @import("main.zig").builtin_modules;
-const EntityModule = @import("main.zig").EntityModule;
+const Entity = @import("main.zig").Entity;
 const ModuleName = @import("module.zig").ModuleName;
 const ComponentNameM = @import("module.zig").ComponentNameM;
 const ComponentName = @import("module.zig").ComponentName;
@@ -130,7 +130,7 @@ pub fn Entities(comptime modules: anytype) type {
                 .component_names = component_names,
                 .buckets = buckets,
             };
-            entities.id_name = entities.componentName(EntityModule.name, .id);
+            entities.id_name = entities.componentName(Entity.name, .id);
 
             const columns = try allocator.alloc(Archetype.Column, 1);
             columns[0] = .{
@@ -1076,7 +1076,7 @@ test "example" {
     // Query for all entities that have all of the given components
     const W = @TypeOf(world);
     var q = try world.query(.{
-        .ids = W.ComponentQuery{ .read = W.ModuleComponentName{ .module = EntityModule.name, .component = .id } },
+        .ids = W.ComponentQuery{ .read = W.ModuleComponentName{ .module = Entity.name, .component = .id } },
         .rotations = W.ComponentQuery{ .write = W.ModuleComponentName{ .module = Game.name, .component = .rotation } },
     });
     while (q.next()) |v| {
@@ -1090,7 +1090,7 @@ test "example" {
     // Dynamic queries (e.g. issued from another programming language without comptime)
     var q2 = try world.queryDynamic(.{
         .op_and = &.{
-            .{ .read = world.componentName(EntityModule.name, .id) },
+            .{ .read = world.componentName(Entity.name, .id) },
             .{ .read = world.componentName(Game.name, .rotation) },
         },
     });

src/module/main.zig

@@ -13,10 +13,10 @@ pub const AnyEvent = @import("module.zig").AnyEvent;
 pub const Merge = @import("module.zig").Merge;
 pub const merge = @import("module.zig").merge;
 
-pub const builtin_modules = .{EntityModule};
+pub const builtin_modules = .{Entity};
 
 /// Builtin .entity module
-pub const EntityModule = struct {
+pub const Entity = struct {
     pub const name = .entity;
 
     pub const Mod = mach.Mod(@This());
@@ -82,14 +82,15 @@ test "entities DB" {
     defer world.deinit(allocator);
 
     // Initialize module state.
+    var entity = &world.mod.entity;
     var physics = &world.mod.physics;
     var renderer = &world.mod.renderer;
     physics.init(.{ .pointer = 123 });
     _ = physics.state().pointer; // == 123
 
-    const player1 = try physics.newEntity();
-    const player2 = try physics.newEntity();
-    const player3 = try physics.newEntity();
+    const player1 = try entity.new();
+    const player2 = try entity.new();
+    const player3 = try entity.new();
     try physics.set(player1, .id, 1001);
     try renderer.set(player1, .id, 1001);
 

src/module/module.zig

@@ -574,6 +574,36 @@ pub fn ModSet(comptime modules: anytype) type {
         pub fn Mod(comptime M: anytype) type {
             const module_tag = M.name;
             const components = ComponentTypesM(M){};
+
+            if (M.name == .entity) {
+                // The .entity module is a special builtin module, with its own unique API.
+                return struct {
+                    /// Private/internal fields
+                    __entities: *Entities(modules),
+                    __is_initialized: bool,
+                    __state: void,
+
+                    pub const IsInjectedArgument = void;
+
+                    pub inline fn read(comptime component_name: ComponentNameM(M)) Entities(modules).ComponentQuery {
+                        return .{ .read = .{
+                            .module = M.name,
+                            .component = comptime stringToEnum(ComponentName(modules), @tagName(component_name)).?,
+                        } };
+                    }
+
+                    /// Returns a new entity.
+                    pub inline fn new(m: *@This()) !EntityID {
+                        return m.__entities.new();
+                    }
+
+                    /// Removes an entity.
+                    pub inline fn remove(m: *@This(), entity: EntityID) !void {
+                        try m.__entities.remove(entity);
+                    }
+                };
+            }
+
             return struct {
                 /// Private/internal fields
                 __entities: *Entities(modules),
@@ -622,16 +652,6 @@ pub fn ModSet(comptime modules: anytype) type {
                     return &m.__state;
                 }
 
-                /// Returns a new entity.
-                pub inline fn newEntity(m: *@This()) !EntityID {
-                    return m.__entities.new();
-                }
-
-                /// Removes an entity.
-                pub inline fn removeEntity(m: *@This(), entity: EntityID) !void {
-                    try m.__entities.remove(entity);
-                }
-
                 /// Sets the named component to the specified value for the given entity,
                 /// moving the entity from it's current archetype table to the new archetype
                 /// table if required.