Remember and use last known mac address for immediate display

src/JsonSettingsIO.cpp

@@ -248,6 +248,7 @@ bool JsonSettingsIO::loadKOReader(KOReaderCredentialStore& store, const char* js
 bool JsonSettingsIO::saveWifi(const WifiCredentialStore& store, const char* path) {
   JsonDocument doc;
   doc["lastConnectedSsid"] = store.getLastConnectedSsid();
+  doc["lastKnownMacAddress"] = store.getLastKnownMacAddress();
 
   JsonArray arr = doc["credentials"].to<JsonArray>();
   for (const auto& cred : store.getCredentials()) {
@@ -271,6 +272,7 @@ bool JsonSettingsIO::loadWifi(WifiCredentialStore& store, const char* json, bool
   }
 
   store.lastConnectedSsid = doc["lastConnectedSsid"] | std::string("");
+  store.lastKnownMacAddress = doc["lastKnownMacAddress"] | std::string("");
 
   store.credentials.clear();
   JsonArray arr = doc["credentials"].as<JsonArray>();

src/WifiCredentialStore.cpp

@@ -168,9 +168,19 @@ void WifiCredentialStore::clearLastConnectedSsid() {
   }
 }
 
+void WifiCredentialStore::setLastKnownMacAddress(const std::string& mac) {
+  if (lastKnownMacAddress != mac) {
+    lastKnownMacAddress = mac;
+    saveToFile();
+  }
+}
+
+const std::string& WifiCredentialStore::getLastKnownMacAddress() const { return lastKnownMacAddress; }
+
 void WifiCredentialStore::clearAll() {
   credentials.clear();
   lastConnectedSsid.clear();
+  lastKnownMacAddress.clear();
   saveToFile();
   LOG_DBG("WCS", "Cleared all WiFi credentials");
 }

src/WifiCredentialStore.h

@@ -24,6 +24,7 @@ class WifiCredentialStore {
   static WifiCredentialStore instance;
   std::vector<WifiCredential> credentials;
   std::string lastConnectedSsid;
+  std::string lastKnownMacAddress;
 
   static constexpr size_t MAX_NETWORKS = 8;
 
@@ -63,6 +64,10 @@ class WifiCredentialStore {
   const std::string& getLastConnectedSsid() const;
   void clearLastConnectedSsid();
 
+  // Last known device MAC (formatted as AA-BB-CC-DD-EE-FF for instant UI display)
+  void setLastKnownMacAddress(const std::string& mac);
+  const std::string& getLastKnownMacAddress() const;
+
   // Clear all credentials
   void clearAll();
 };

src/activities/network/WifiSelectionActivity.cpp

@@ -13,6 +13,27 @@
 #include "components/UITheme.h"
 #include "fontIds.h"
 
+namespace {
+
+bool isLikelyValidMac(const uint8_t mac[6]) {
+  bool allZero = true;
+  bool allFF = true;
+  for (int i = 0; i < 6; i++) {
+    allZero = allZero && (mac[i] == 0x00);
+    allFF = allFF && (mac[i] == 0xFF);
+  }
+  return !allZero && !allFF;
+}
+
+std::string formatMacLabel(const uint8_t mac[6]) {
+  char macStr[64];
+  snprintf(macStr, sizeof(macStr), "%s %02x-%02x-%02x-%02x-%02x-%02x", tr(STR_MAC_ADDRESS), mac[0], mac[1], mac[2],
+           mac[3], mac[4], mac[5]);
+  return std::string(macStr);
+}
+
+}  // namespace
+
 void WifiSelectionActivity::onEnter() {
   Activity::onEnter();
 
@@ -23,6 +44,13 @@ void WifiSelectionActivity::onEnter() {
     WIFI_STORE.loadFromFile();
   }
 
+  // Show persisted MAC immediately so UI doesn't briefly display a bogus value.
+  if (!WIFI_STORE.getLastKnownMacAddress().empty()) {
+    cachedMacAddress = std::string(tr(STR_MAC_ADDRESS)) + " " + WIFI_STORE.getLastKnownMacAddress();
+  } else {
+    cachedMacAddress = std::string(tr(STR_MAC_ADDRESS)) + " --";
+  }
+
   // Reset state
   selectedNetworkIndex = 0;
   networks.clear();
@@ -36,13 +64,19 @@ void WifiSelectionActivity::onEnter() {
   forgetPromptSelection = 0;
   autoConnecting = false;
 
-  // Cache MAC address for display
+  // Refresh displayed MAC from live hardware value when valid.
   uint8_t mac[6];
   WiFi.macAddress(mac);
-  char macStr[64];
-  snprintf(macStr, sizeof(macStr), "%s %02x-%02x-%02x-%02x-%02x-%02x", tr(STR_MAC_ADDRESS), mac[0], mac[1], mac[2],
-           mac[3], mac[4], mac[5]);
-  cachedMacAddress = std::string(macStr);
+  if (isLikelyValidMac(mac)) {
+    cachedMacAddress = formatMacLabel(mac);
+    char persistedMac[18];
+    snprintf(persistedMac, sizeof(persistedMac), "%02x-%02x-%02x-%02x-%02x-%02x", mac[0], mac[1], mac[2], mac[3],
+             mac[4], mac[5]);
+    if (WIFI_STORE.getLastKnownMacAddress() != persistedMac) {
+      RenderLock lock(*this);
+      WIFI_STORE.setLastKnownMacAddress(persistedMac);
+    }
+  }
 
   // Trigger first update to show scanning message
   requestUpdate();