SpaceAnalyzer: Do not reset the path to '/' after a refresh

Clicking analyze or deleting a file would always cause the tree view in
the widget to reset back to viewing the root. This was changed to stay
in the directory currently being viewed

Userland/Applications/SpaceAnalyzer/TreeMapWidget.cpp

@@ -357,11 +357,27 @@ void TreeMapWidget::context_menu_event(GUI::ContextMenuEvent& context_menu_event
         on_context_menu_request(context_menu_event);
 }
 
+void TreeMapWidget::recalculate_path_for_new_tree()
+{
+    TreeNode const* current = &m_tree->root();
+    size_t new_path_length = 0;
+    for (auto& segment : m_path) {
+        auto maybe_child = current->child_with_name(segment);
+        if (!maybe_child.has_value())
+            break;
+        new_path_length++;
+        current = &maybe_child.release_value();
+    }
+    m_path.shrink(new_path_length);
+    if (new_path_length < m_viewpoint)
+        m_viewpoint = new_path_length - 1;
+}
+
 void TreeMapWidget::set_tree(RefPtr<Tree> tree)
 {
     m_tree = tree;
-    m_path.clear();
-    m_viewpoint = 0;
+    recalculate_path_for_new_tree();
+
     if (on_path_change) {
         on_path_change();
     }

Userland/Applications/SpaceAnalyzer/TreeMapWidget.h

@@ -51,6 +51,7 @@ private:
     void lay_out_children(TreeNode const&, Gfx::IntRect const&, int depth, Function);
     void paint_cell_frame(GUI::Painter&, TreeNode const&, Gfx::IntRect const&, Gfx::IntRect const&, int depth, HasLabel has_label) const;
     Vector<DeprecatedString> path_to_position(Gfx::IntPoint);
+    void recalculate_path_for_new_tree();
 
     RefPtr<Tree> m_tree;
     Vector<DeprecatedString> m_path;

Userland/Applications/SpaceAnalyzer/main.cpp

@@ -183,7 +183,10 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
 
     auto& file_menu = window->add_menu("&File");
     file_menu.add_action(GUI::Action::create("&Analyze", [&](auto&) {
-        if (auto result = analyze(tree, treemapwidget, statusbar); result.is_error()) {
+        // FIXME: Just modify the tree in memory instead of traversing the entire file system
+        // FIXME: Dispose of the old tree
+        auto new_tree = adopt_ref(*new Tree(""));
+        if (auto result = analyze(new_tree, treemapwidget, statusbar); result.is_error()) {
             GUI::MessageBox::show_error(window, DeprecatedString::formatted("{}", result.error()));
         }
     }));
@@ -237,9 +240,9 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
             }
         }
 
-        // TODO: Refreshing data always causes resetting the viewport back to "/".
-        // It would be great if we found a way to preserve viewport across refreshes.
-        if (auto result = analyze(tree, treemapwidget, statusbar); result.is_error()) {
+        // FIXME: Dispose of the old tree
+        auto new_tree = adopt_ref(*new Tree(""));
+        if (auto result = analyze(new_tree, treemapwidget, statusbar); result.is_error()) {
             GUI::MessageBox::show_error(window, DeprecatedString::formatted("{}", result.error()));
         }
     });