Release v0.6.8: add background image OCR and optional Tesseract

src/app.h

@@ -61,6 +61,7 @@ class App
     void recognizeEntry(std::wstring);
     void captureHistory();
     void enqueue(std::function<void()>);
+    void enqueueHistorySearch(std::function<void()>);
     void report(const std::wstring &);
     void trayMenu();
     void addTray();
@@ -83,6 +84,14 @@ class App
     std::condition_variable jobsReady;
     std::deque<std::function<void()>> jobs;
     std::thread worker;
+    std::thread historySearchWorker;
+    std::condition_variable historySearchReady;
+    std::function<void()> pendingHistorySearch;
+    std::thread historyOcrWorker;
+    std::condition_variable historyOcrReady;
+    bool historyOcrRequested{};
+    Settings historyOcrSettings;
+    void scheduleHistoryOcr(const Settings &);
     std::thread updateWorker;
     bool updateRunning{}, installingUpdate{};
     std::wstring availableUpdate, notifiedUpdate;