Function evaluate

example/color_node_editor.cpp:48–121

static bool  emulate_three_button_mouse = false;

ImU32 evaluate(const Graph<Node>& graph, const int root_node)
{
    std::stack<int> postorder;
    dfs_traverse(
        graph, root_node, [&postorder](const int node_id) -> void { postorder.push(node_id); });

    std::stack<float> value_stack;
    while (!postorder.empty())
    {
        const int id = postorder.top();
        postorder.pop();
        const Node node = graph.node(id);

        switch (node.type)
        {
        case NodeType::add:
        {
            const float rhs = value_stack.top();
            value_stack.pop();
            const float lhs = value_stack.top();
            value_stack.pop();
            value_stack.push(lhs + rhs);
        }
        break;
        case NodeType::multiply:
        {
            const float rhs = value_stack.top();
            value_stack.pop();
            const float lhs = value_stack.top();
            value_stack.pop();
            value_stack.push(rhs * lhs);
        }
        break;
        case NodeType::sine:
        {
            const float x = value_stack.top();
            value_stack.pop();
            const float res = std::abs(std::sin(x));
            value_stack.push(res);
        }
        break;
        case NodeType::time:
        {
            value_stack.push(current_time_seconds);
        }
        break;
        case NodeType::value:
        {
            // If the edge does not have an edge connecting to another node, then just use the value
            // at this node. It means the node's input pin has not been connected to anything and
            // the value comes from the node's UI.
            if (graph.num_edges_from_node(id) == 0ull)
            {
                value_stack.push(node.value);
            }
        }
        break;
        default: