folder_tree_std.cpp

#include <nana/deploy.hpp>
#include <nana/gui.hpp>
#include <nana/gui/widgets/treebox.hpp>
#include <nana/filesystem/filesystem_ext.hpp>

int main()
{
        using namespace nana;
        namespace fs = std::filesystem;
        namespace fs_ext = nana::filesystem_ext;
        using SubDirectories = fs::directory_iterator;


        form fm{ API::make_center(400, 500), appear::decorate<appear::taskbar>() };
        fm.caption("Nana C++ Library - Treebox-nana::experimental::filesystem example.");

        nana::treebox tree{ fm,{ 10, 10, 380, 480 } };

        auto node = tree.insert(fs_ext::def_root, fs_ext::def_rootname);

        // Boost can throw an exception "Access is denied"
        // when accessing some system paths, like "C:\Config.Msi"
        try {
        for (const auto& dir : SubDirectories{ fs_ext::def_rootstr })
        {
                if (! fs::is_directory(dir) ) continue;
                tree.insert(node, dir.path().filename().generic_string(), dir.path().filename().generic_string());
                break;
        }
        } catch (...) {}

        tree.events().expanded([&tree](const arg_treebox& arg)
        {
                if (!arg.operated) return; //If this is contracted.

                //Windows supports the path separator '/'
                auto Path = tree.make_key_path(arg.item, "/") + "/";

                //avoids frequent useless refreshing
                tree.auto_draw(false);

                try {
                //Walk in the path directory for sub directories.
                for (const auto& dir : SubDirectories{ Path })
                {
                        if (!fs::is_directory(dir)) continue; //If it is not a directory.

                        auto child = tree.insert(arg.item, dir.path().filename().generic_string(),
                                                               dir.path().filename().generic_string());
                        if (child.empty()) continue;

                        //Find a directory in child directory, if there is a directory,
                        //insert it into the child, just insert one node to indicate the
                        //node has a child and an arrow symbol will be?displayed in the
                        //front of the node.
                        try {
                        for (const auto& dr : SubDirectories{ dir.path() })
                        {
                                if (!fs::is_directory(dr)) continue; //If it is not a directory.
                                tree.insert(child, dr.path().filename().generic_string(),
                                                       dr.path().filename().generic_string());
                                break;
                        }
                        } catch (...) {}
                }
                } catch (...) {}
                tree.auto_draw(true);
        });

        fm.show();
        exec(

#ifdef NANA_AUTOMATIC_GUI_TESTING
                2, 1, [&node]()
        {
                node.expand(true);
        }
#endif

        );
}