node: child_at function

headers/enduro2d/high/node.hpp

@@ -125,6 +125,9 @@ namespace e2d
 
         node_iptr next_sibling() noexcept;
         const_node_iptr next_sibling() const noexcept;
+
+        node_iptr child_at(std::size_t index) noexcept;
+        const_node_iptr child_at(std::size_t index) const noexcept;
     protected:
         node() = default;
         node(gobject owner);

samples/bin/library/scripts/emmy/high/node.lua

@@ -140,5 +140,10 @@ function node.send_forward(self) end
 ---@return boolean
 function node.bring_to_front(self) end
 
+---@param self node
+---@param index integer
+---@return node
+function node.child_at(self, index) end
+
 ---@type node
 _G.node = _G.node or node

sources/enduro2d/high/bindings/high_binds/node_binds.cpp

@@ -141,7 +141,13 @@ namespace e2d::bindings::high
                 [](node& n) -> node_iptr { return n.prev_sibling(); }),
 
             "next_sibling", sol::property(
-                [](node& n) -> node_iptr { return n.next_sibling(); })
+                [](node& n) -> node_iptr { return n.next_sibling(); }),
+
+            "child_at", [](node& n, i32 index) -> node_iptr {
+                return index >= 0
+                    ? n.child_at(math::numeric_cast<std::size_t>(index))
+                    : node_iptr();
+            }
         );
     }
 }

sources/enduro2d/high/node.cpp

@@ -414,6 +414,22 @@ namespace e2d
         }
         return const_node_iptr(&*iter);
     }
+
+    node_iptr node::child_at(std::size_t index) noexcept {
+        node_iptr child = first_child();
+        for ( std::size_t i = 0; i < index && child; ++i ) {
+            child = child->next_sibling();
+        }
+        return child;
+    }
+
+    const_node_iptr node::child_at(std::size_t index) const noexcept {
+        const_node_iptr child = first_child();
+        for ( std::size_t i = 0; i < index && child; ++i ) {
+            child = child->next_sibling();
+        }
+        return child;
+    }
 }
 
 namespace e2d

untests/sources/untests_high/node.cpp

@@ -429,6 +429,27 @@ TEST_CASE("node") {
             REQUIRE_FALSE(cn4->next_sibling());
         }
     }
+    SECTION("child_at") {
+        auto p = node::create();
+
+        auto n1 = node::create(p);
+        auto n2 = node::create(p);
+        auto n3 = node::create(p);
+
+        REQUIRE(p->child_at(0) == n1);
+        REQUIRE(p->child_at(1) == n2);
+        REQUIRE(p->child_at(2) == n3);
+        REQUIRE_FALSE(p->child_at(3));
+
+        {
+            const_node_iptr cp = p;
+
+            REQUIRE(cp->child_at(0) == n1);
+            REQUIRE(cp->child_at(1) == n2);
+            REQUIRE(cp->child_at(2) == n3);
+            REQUIRE_FALSE(cp->child_at(3));
+        }
+    }
     SECTION("add_child_to_back/add_child_to_front") {
         auto p = node::create();
         auto n1 = node::create();