Implemented qt port + e2e

Client/streamhub/PlotPanel.cpp

@@ -225,6 +225,20 @@ void RenderPlotPanel(App& app, int plotIdx, bool& paused) {
         if (!anyData) { useHistData = false; }
     }
 
+    /* Visible X window to read from the ring.  Reading only the visible slice
+     * (binary-searched) instead of the entire ring — which can hold a million
+     * points — is what keeps live rendering fluid; the full-ring readLast()
+     * copied tens of MB per signal per frame.  A 10% margin keeps a sample on
+     * each side so the later fine clip still has its boundary points. */
+    double visT0, visT1;
+    if (live) { visT1 = wallNow; visT0 = wallNow - app.windowSec(); }
+    else      { visT1 = app.plotXMax(plotIdx); visT0 = app.plotXMin(plotIdx); }
+    {
+        double margin = (visT1 - visT0) * 0.1;
+        if (!(margin > 0.0)) { margin = 1.0; }
+        visT0 -= margin; visT1 += margin;
+    }
+
     /* Fill tStore/vStore[si] from the frozen view (paused) or the live ring */
     auto readBase = [&](size_t si, const Signal& sig, const std::string& key) {
         if (paused && snap.valid) {
@@ -236,7 +250,7 @@ void RenderPlotPanel(App& app, int plotIdx, bool& paused) {
                 }
             }
         }
-        (void) sig.buf.readLast((size_t)app.maxPoints(), tStore[si], vStore[si]);
+        (void) sig.buf.readRange(visT0, visT1, tStore[si], vStore[si]);
     };
 
     for (size_t si = 0; si < slots.size(); si++) {