Remove unused tesseract engines after some time

src/ocr/recognizerworker.cpp

@@ -33,6 +33,9 @@ void RecognizeWorker::handle(const TaskPtr &task)
   if (result->recognized.isEmpty())
     result->error = engine->error();
 
+  lastGenerations_[task->sourceLanguage] = task->generation;
+  removeUnused(task->generation);
+
   emit finished(result);
 }
 
@@ -44,3 +47,17 @@ void RecognizeWorker::reset(const QString &tessdataPath)
   tessdataPath_ = tessdataPath;
   engines_.clear();
 }
+
+void RecognizeWorker::removeUnused(Generation current)
+{
+  const auto keepGenerations = 10;
+  for (auto it = lastGenerations_.begin(), end = lastGenerations_.end();
+       it != end;) {
+    if (current - it->second < keepGenerations) {
+      ++it;
+      continue;
+    }
+    engines_.erase(it->first);
+    it = lastGenerations_.erase(it);
+  }
+}

src/ocr/recognizerworker.h

@@ -19,6 +19,9 @@ signals:
   void finished(const TaskPtr &task);
 
 private:
+  void removeUnused(Generation current);
+
   std::map<QString, std::unique_ptr<Tesseract>> engines_;
+  std::map<QString, Generation> lastGenerations_;
   QString tessdataPath_;
 };