Properly link flecs library

engine/libs/flecs/examples/cpp/queries/hierarchy/.gitignore

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+.bake_cache
+.DS_Store
+.vscode
+gcov
+bin

engine/libs/flecs/examples/cpp/queries/hierarchy/include/hierarchy.h

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+#ifndef HIERARCHY_H
+#define HIERARCHY_H
+
+/* This generated file contains includes for project dependencies */
+#include "hierarchy/bake_config.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
+

engine/libs/flecs/examples/cpp/queries/hierarchy/include/hierarchy/bake_config.h

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+/*
+                                   )
+                                  (.)
+                                  .|.
+                                  | |
+                              _.--| |--._
+                           .-';  ;`-'& ; `&.
+                          \   &  ;    &   &_/
+                           |"""---...---"""|
+                           \ | | | | | | | /
+                            `---.|.|.|.---'
+
+ * This file is generated by bake.lang.c for your convenience. Headers of
+ * dependencies will automatically show up in this file. Include bake_config.h
+ * in your main project file. Do not edit! */
+
+#ifndef HIERARCHY_BAKE_CONFIG_H
+#define HIERARCHY_BAKE_CONFIG_H
+
+/* Headers of public dependencies */
+#include <flecs.h>
+
+#endif
+

engine/libs/flecs/examples/cpp/queries/hierarchy/project.json

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+{
+    "id": "hierarchy",
+    "type": "application",
+    "value": {
+        "author": "Jane Doe",
+        "description": "A simple hello world flecs application",
+        "use": [
+            "flecs"
+        ],
+        "language": "c++"
+    }
+}

engine/libs/flecs/examples/cpp/queries/hierarchy/src/main.cpp

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+#include <hierarchy.h>
+#include <iostream>
+
+struct Position {
+    double x, y;
+};
+
+// Tags for local/world position
+struct Local { };
+struct World { };
+
+int main(int, char *[]) {
+    flecs::world ecs;
+
+    // Create a hierarchy. For an explanation see the entities/hierarchy example
+    flecs::entity sun = ecs.entity("Sun")
+        .add<Position, World>()
+        .set<Position, Local>({1, 1});
+
+        ecs.entity("Mercury")
+            .child_of(sun)
+            .add<Position, World>()
+            .set<Position, Local>({1, 1});
+
+        ecs.entity("Venus")
+            .child_of(sun)
+            .add<Position, World>()
+            .set<Position, Local>({2, 2});
+
+        flecs::entity earth = ecs.entity("Earth")
+            .child_of(sun)
+            .add<Position, World>()
+            .set<Position, Local>({3, 3});
+
+            ecs.entity("Moon")
+                .child_of(earth)
+                .add<Position, World>()
+                .set<Position, Local>({0.1, 0.1});
+
+    // Create a hierarchical query to compute the global position from the
+    // local position and the parent position.
+    flecs::query<const Position, const Position, Position> q = 
+        ecs.query_builder<const Position, const Position, Position>()
+            // Modify terms from template to make sure the query selects the
+            // local, world and parent position components.
+            .term_at(1).second<Local>()
+            .term_at(2).second<World>()
+            .term_at(3).second<World>()
+
+            // Extend the 2nd query argument to select it from the parent
+            .term_at(2)
+                // Get from the parent, in breadth-first order (cascade)
+                .parent().cascade()
+                // Make term component optional so we also match the root (sun)
+                .optional()
+            // Finalize the query
+            .build();
+
+    // Do the transform
+    q.iter([](flecs::iter& it, 
+        const Position *p, const Position *p_parent, Position *p_out) 
+    {
+        for (auto i : it) {
+            p_out[i].x = p[i].x;
+            p_out[i].y = p[i].y;
+            if (p_parent) {
+                p_out[i].x += p_parent->x;
+                p_out[i].y += p_parent->y;
+            }
+        }
+    });
+
+    // Print world positions
+    ecs.each([](flecs::entity e, flecs::pair<Position, World> p) {
+        std::cout << e.name() << ": {" << p->x << ", " << p->y << "}\n";
+    });
+}