Reduced memory allocations by wifiscanmenu by reusing removed menu entries from a pool

src/containermenudefinition.h

@@ -42,9 +42,12 @@ public:
     }
 
     template<typename T, typename... Args>
-    void constructItem(Args&&... args)
+    T &constructItem(Args&&... args)
     {
-        emplaceItem(std::make_unique<T>(std::forward<Args>(args)...));
+        auto ptr = std::make_unique<T>(std::forward<Args>(args)...);
+        T &ref = *ptr;
+        emplaceItem(std::move(ptr));
+        return ref;
     }
 
     void emplaceItem(std::unique_ptr<MenuItem> &&ptr)
@@ -57,6 +60,16 @@ public:
         m_items.clear();
     }
 
+    std::unique_ptr<MenuItem> takeLast()
+    {
+        if (m_items.empty())
+            throw "aua";
+
+        std::unique_ptr<MenuItem> ptr = std::move(m_items.back());
+        m_items.pop_back();
+        return ptr;
+    }
+
 private:
     std::vector<std::unique_ptr<MenuItem>> m_items;
 };

src/displays/menus/wifiscanmenu.h

@@ -1,14 +1,12 @@
 #pragma once
 
-// system includes
-#include <vector>
-
 // Arduino includes
 #include <Arduino.h>
 #include <WiFi.h>
 
 // local includes
 #include "menudisplay.h"
+#include "containermenudefinition.h"
 #include "utils.h"
 #include "actions/multiaction.h"
 #include "actions/switchscreenaction.h"
@@ -23,7 +21,7 @@ class WifiSettingsMenu;
 } // namespace
 
 namespace {
-class WifiScanMenu : public MenuDisplay, public BackActionInterface<SwitchScreenAction<WifiSettingsMenu>>
+class WifiScanMenu : public MenuDisplay, public BackActionInterface<SwitchScreenAction<WifiSettingsMenu>>, public ContainerMenuDefinition
 {
     using Base = MenuDisplay;
 
@@ -34,55 +32,15 @@ public:
     void update() override;
     void stop() override;
 
-    std::size_t size() const override { return 1 + vec.size(); }
-
-    MenuItem& getMenuItem(std::size_t index) override
-    {
-        if (index < vec.size())
-            return vec[index];
-
-        if (index == vec.size())
-            return m_backItem;
-
-        throw "aua";
-    }
-
-    const MenuItem& getMenuItem(std::size_t index) const override
-    {
-        if (index < vec.size())
-            return vec[index];
-
-        if (index == vec.size())
-            return m_backItem;
-
-        throw "aua";
-    }
-
-    void runForEveryMenuItem(std::function<void(MenuItem&)> &&callback) override
-    {
-        for (auto &item : vec)
-            callback(item);
-        callback(m_backItem);
-    }
-
-    void runForEveryMenuItem(std::function<void(const MenuItem&)> &&callback) const override
-    {
-        for (auto &item : vec)
-            callback(item);
-        callback(m_backItem);
-    }
-
 private:
-    makeComponent<MenuItem, StaticText<TEXT_BACK>, SwitchScreenAction<WifiSettingsMenu>, StaticMenuItemIcon<&icons::back>> m_backItem;
-
-    std::vector<makeComponent<MenuItem, ChangeableText, DummyAction>> vec;
-
     millis_t m_lastScanComplete;
+
+    std::vector<std::unique_ptr<makeComponent<MenuItem, ChangeableText, DummyAction>>> m_reusableItems;
 };
 
 String WifiScanMenu::text() const
 {
-    auto text = String{vec.size()} + " found";
+    auto text = String{size()-1} + " found";
     switch (WiFi.scanComplete())
     {
     case WIFI_SCAN_RUNNING: text += " (scanning)"; break;
@@ -93,6 +51,8 @@ String WifiScanMenu::text() const
 
 void WifiScanMenu::start()
 {
+    constructItem<makeComponent<MenuItem, StaticText<TEXT_BACK>, SwitchScreenAction<WifiSettingsMenu>, StaticMenuItemIcon<&icons::back>>>();
+
     Base::start();
 
     m_lastScanComplete = 0;
@@ -105,26 +65,40 @@ void WifiScanMenu::update()
     const auto n = WiFi.scanComplete();
     if (n >= 0)
     {
-        if (n != vec.size())
-        {
-            while (n > vec.size())
-            {
-                vec.emplace_back();
-                vec.back().start();
-            }
-
-            while (n < vec.size())
-            {
-                vec.back().stop();
-                vec.pop_back();
-            }
-        }
-
         const auto now = millis();
         if (!m_lastScanComplete)
         {
-            for (auto iter = std::begin(vec); iter != std::end(vec); iter++)
+            auto backButton = takeLast();
-                iter->setTitle(WiFi.SSID(std::distance(std::begin(vec), iter)));
+
+            for (std::size_t i = 0; i < n; i++)
+            {
+                const auto ssid = WiFi.SSID(i);
+                if (size() <= i)
+                {
+                    if (m_reusableItems.empty())
+                    {
+                        auto &item = constructItem<makeComponent<MenuItem, ChangeableText, DummyAction>>();
+                        item.setTitle(ssid);
+                    }
+                    else
+                    {
+                        std::unique_ptr<makeComponent<MenuItem, ChangeableText, DummyAction>> ptr = std::move(m_reusableItems.back());
+                        m_reusableItems.pop_back();
+                        ptr->setTitle(ssid);
+                        emplaceItem(std::move(ptr));
+                    }
+                }
+                else
+                {
+                    auto &item = *(makeComponent<MenuItem, ChangeableText, DummyAction>*)(&getMenuItem(i));
+                    item.setTitle(ssid);
+                }
+            }
+
+            while (size() > n)
+                m_reusableItems.emplace_back((makeComponent<MenuItem, ChangeableText, DummyAction>*)takeLast().release());
+
+            emplaceItem(std::move(backButton));
 
             m_lastScanComplete = now;
         }