[PATCH yew-widget-toolkit v2 1/3] widget: navigation drawer: fix first open for default collapsed menus

[Dominik Csapak <d.csapak@proxmox.com>]

A menu item can have it's default expanded state have set to collapsed.
This was correctly displayed when the menu was created, but the first
toggle falsely relied on the fact that non-existent entries in the
`menu_states` HashMap should be interpreted as expanded.

Fix this by introducing a `NavigationDrawerState` struct that saves
which items where changed from the default. The default states for all
entries is collected on creation or when the menu changes.

This eliminates the multiple hardcoded default values and it keeps the
saved data minimal, by only saving the keys of menus and only keeping
the state of the ones that changed.

It also prepares us to save the data later, when we want to have the
collapsed/expanded state persistent.

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
---
 src/widget/nav/navigation_drawer.rs | 97 ++++++++++++++++++++++-------
 1 file changed, 76 insertions(+), 21 deletions(-)

diff --git a/src/widget/nav/navigation_drawer.rs b/src/widget/nav/navigation_drawer.rs
index 87f0743..eae2ca4 100644
--- a/src/widget/nav/navigation_drawer.rs
+++ b/src/widget/nav/navigation_drawer.rs
@@ -1,4 +1,4 @@
-use std::collections::HashMap;
+use std::collections::{HashMap, HashSet};
 use std::rc::Rc;
 
 use yew::html::{IntoEventCallback, IntoPropValue};
@@ -146,6 +146,12 @@ impl NavigationDrawer {
     }
 }
 
+/// A struct that holds the current state that can get saved to local storage
+#[derive(Default, Clone, PartialEq)]
+struct NavigationDrawerState {
+    changed_expanded: HashSet<String>, // contains all keys that deviate from their default
+}
+
 pub enum Msg {
     Select(Option<Key>, bool, bool),
     SelectionChange(Selection),
@@ -154,12 +160,31 @@ pub enum Msg {
     MenuOpen(Key),
 }
 
+// iterates over a menu and saves all submenus that are collapsed by default
+fn collect_default_collapse_states(menu: &Menu) -> HashMap<Key, bool> {
+    let mut defaults = HashMap::new();
+    collect_default_collapsed_impl(&mut defaults, menu);
+    defaults
+}
+
+fn collect_default_collapsed_impl(defaults: &mut HashMap<Key, bool>, menu: &Menu) {
+    for entry in menu.children.iter() {
+        if let MenuEntry::Item(item) = entry
+            && let (Some(key), Some(submenu)) = (&item.key, &item.submenu)
+        {
+            defaults.insert(key.clone(), item.default_collapsed);
+            collect_default_collapsed_impl(defaults, submenu);
+        }
+    }
+}
+
 #[doc(hidden)]
 pub struct PwtNavigationDrawer {
     node_ref: NodeRef,
     active: Option<Key>,
     selection: Selection,
-    menu_states: HashMap<Key, bool>, // true = open
+    default_collapsed: HashMap<Key, bool>,
+    state: NavigationDrawerState,
     _nav_ctx_handle: Option<ContextHandle<NavigationContext>>,
 }
 
@@ -269,16 +294,8 @@ impl PwtNavigationDrawer {
     ) {
         match item {
             MenuEntry::Item(child) => {
-                // An absent state means the user has not toggled this submenu yet, so fall back
-                // to its default: open, unless the item opted into starting collapsed. A submenu
-                // on the path to the active item is force-opened by open_ancestors, so a
-                // deep-linked target stays visible even under default_collapsed.
                 let open = match &child.key {
-                    Some(key) => self
-                        .menu_states
-                        .get(key)
-                        .copied()
-                        .unwrap_or(!child.default_collapsed),
+                    Some(key) => self.is_expanded(key),
                     None => false,
                 };
 
@@ -373,7 +390,8 @@ impl PwtNavigationDrawer {
                     if item.selectable {
                         Some(entry)
                     } else {
-                        self.menu_states.insert(desired.clone(), true);
+                        // the selection moves on to a child, so make sure the submenu is visible
+                        self.set_expanded(desired, true);
                         find_first_key_recursive(&submenu.children)
                     }
                 }
@@ -407,7 +425,7 @@ impl PwtNavigationDrawer {
         let mut path = Vec::new();
         if collect(&props.menu.children, key, &mut path) {
             for key in path {
-                self.menu_states.insert(key, true);
+                self.set_expanded(&key, true);
             }
         }
     }
@@ -439,6 +457,29 @@ impl PwtNavigationDrawer {
             }
         }
     }
+
+    fn toggle_expanded(&mut self, key: &Key) {
+        self.set_expanded(key, !self.is_expanded(key));
+    }
+
+    fn is_expanded(&self, key: &Key) -> bool {
+        let key_string = key.to_string();
+        let changed = self.state.changed_expanded.contains(&key_string);
+        let default_collapsed = *self.default_collapsed.get(key).unwrap_or(&false);
+        // open means either collapsed by default and toggled, or open by default and untouched
+        changed == default_collapsed
+    }
+
+    fn set_expanded(&mut self, key: &Key, expanded: bool) {
+        let key_string = key.to_string();
+        let default_open = !self.default_collapsed.get(key).unwrap_or(&false);
+        // only record the keys that deviate from their default, so the set stays minimal
+        if expanded == default_open {
+            self.state.changed_expanded.remove(&key_string);
+        } else {
+            self.state.changed_expanded.insert(key_string);
+        }
+    }
 }
 
 fn get_active_or_default(props: &NavigationDrawer, active: &Option<Key>) -> Option<Key> {
@@ -490,7 +531,8 @@ impl Component for PwtNavigationDrawer {
             node_ref: NodeRef::default(),
             active: active.clone(),
             selection,
-            menu_states: HashMap::new(),
+            default_collapsed: collect_default_collapse_states(&props.menu),
+            state: NavigationDrawerState::default(),
             _nav_ctx_handle,
         };
 
@@ -562,9 +604,7 @@ impl Component for PwtNavigationDrawer {
                             self.emit_item_activate(&key, ctx);
                         }
                         if toggle {
-                            let entry =
-                                *self.menu_states.entry(key.clone()).or_insert_with(|| true);
-                            self.menu_states.insert(key, !entry);
+                            self.toggle_expanded(&key);
                         }
                     }
                     return true;
@@ -592,16 +632,15 @@ impl Component for PwtNavigationDrawer {
                 true
             }
             Msg::MenuToggle(key) => {
-                let entry = *self.menu_states.entry(key.clone()).or_insert_with(|| true);
-                self.menu_states.insert(key, !entry);
+                self.toggle_expanded(&key);
                 true
             }
             Msg::MenuClose(key) => {
-                self.menu_states.insert(key, false);
+                self.set_expanded(&key, false);
                 true
             }
             Msg::MenuOpen(key) => {
-                self.menu_states.insert(key, true);
+                self.set_expanded(&key, true);
                 true
             }
         }
@@ -612,6 +651,22 @@ impl Component for PwtNavigationDrawer {
         if props.selection != old_props.selection {
             self.selection = Self::init_selection(ctx, props.selection.clone(), &self.active);
         }
+        if props.menu != old_props.menu {
+            let new_default_collapsed = collect_default_collapse_states(&props.menu);
+            // for all old keys where the default changed and still exist, toggle them
+            let mut keys = Vec::new();
+            for (key, old_default) in self.default_collapsed.iter() {
+                if let Some(new_default) = new_default_collapsed.get(key)
+                    && *new_default != *old_default
+                {
+                    keys.push(key.clone());
+                }
+            }
+            for key in keys {
+                self.toggle_expanded(&key);
+            }
+            self.default_collapsed = new_default_collapsed;
+        }
         true
     }
 
-- 
2.47.3