Re implement display

main/common/semaphore_guard.h

@@ -1,14 +1,18 @@
 #pragma once
 #include "freertos/semphr.h"
 #include "freertos/portmacro.h"
+#include "esp_log.h"
 
 struct SemaphoreGuard {
 public:
-  const SemaphoreHandle_t semaphore;
 
   SemaphoreGuard(SemaphoreHandle_t semaphore) : semaphore(semaphore) { }
 
   portBASE_TYPE take(TickType_t ticks_to_wait = portMAX_DELAY) {
+    if (this->semaphore == nullptr) {
+      ESP_LOGE("SemaphoreGuard", "Attempted to take a null semaphore");
+      return pdFALSE;
+    }
     portBASE_TYPE result = xSemaphoreTake(this->semaphore, ticks_to_wait);
     taken = (result == pdTRUE);
     return result;
@@ -20,9 +24,26 @@ public:
     }
   }
 
+  // allow move semantics
+  SemaphoreGuard(SemaphoreGuard&& other) noexcept
+    : semaphore(other.semaphore), taken(other.taken) {
+    other.taken = false;
+  }
+  SemaphoreGuard& operator=(SemaphoreGuard&& other) noexcept {
+    if (this != &other) {
+      // move from other
+      taken = other.taken;
+      other.taken = false;
+      semaphore = other.semaphore;
+      other.semaphore = nullptr;
+    }
+    return *this;
+  }
+
 private:
   // prevent copying
   SemaphoreGuard(const SemaphoreGuard&) = delete;
   SemaphoreGuard& operator=(const SemaphoreGuard&) = delete;
+  SemaphoreHandle_t semaphore = nullptr;
   bool taken = false;
 };