Implemented history writer

Client/streamhub/App.h

@@ -232,6 +232,18 @@ public:
     /** @brief Full key "src:sig" for an assignment (empty if invalid). */
     std::string slotKey(const PlotAssignment& a) const;
 
+    /* ---- History ------------------------------------------------------------ */
+
+    /** @brief History info received from the hub. */
+    const HistoryInfoMsg& historyInfo() const { return historyInfo_; }
+
+    /** @brief Send a historyZoom request. */
+    void requestHistoryZoom(int plotIdx, double t0, double t1,
+                            const std::string& signalsCsv);
+
+    /** @brief Hi-res history zoom cache (per plot, parallel to zoomCache_). */
+    PlotZoomCache& histZoomCache(int i) { return histZoomCache_[i]; }
+
     /** @brief True if the stats panel is open. */
     bool& showStats()    { return showStats_; }
     bool& showAddSrc()   { return showAddSrc_; }
@@ -253,6 +265,8 @@ private:
     void onStats(const std::string& json);
     void onTriggerState(const std::string& json);
     void onZoom(const std::string& json);
+    void onHistoryZoom(const std::string& json);
+    void onHistoryInfo(const std::string& json);
     void onMaxPointsUpdated(const std::string& json);
 
     /* ---- Rendering ------------------------------------------------------ */
@@ -296,8 +310,12 @@ private:
     /* Zoom history + hi-res zoom cache */
     std::vector<std::pair<double,double>> zoomHist_[kMaxPlotSlots];
     PlotZoomCache zoomCache_[kMaxPlotSlots];
+    PlotZoomCache histZoomCache_[kMaxPlotSlots];
     uint32_t      nextZoomReqId_ = 1;
 
+    /* History info from the hub */
+    HistoryInfoMsg historyInfo_;
+
     /* UI state */
     bool showStats_   = false;
     bool showAddSrc_  = false;