fix: a lost packet reserves the samples it owed instead of vanishing from the timeline

src/model.cpp

@@ -654,7 +654,25 @@ void ScopeModel::set_display_epoch(f64 e) noexcept {
 }
 
 void ScopeModel::acquire_all() {
-  if (store_) store_->acquire_all();
+  if (store_) {
+    store_->acquire_all();
+    // Drop holes whose slots the time ring has already overwritten: their slot addresses
+    // would alias live slots once the ring wraps past them, and they can no longer be
+    // backfilled or drawn. `base()` is the absolute index of the oldest slot the ring
+    // still retains -- anything earlier has already been discarded.
+    forget_holes_before(store_->time().base());
+  }
+}
+
+void ScopeModel::note_hole(const Hole& h) {
+  if (holes_.size() >= kMaxHoles) holes_.erase(holes_.begin());
+  holes_.push_back(h);
+}
+
+void ScopeModel::forget_holes_before(u64 slot) {
+  // A hole whose last slot the ring has dropped can no longer be backfilled or drawn, and
+  // its address would alias a live slot once the ring wraps past it.
+  std::erase_if(holes_, [slot](const Hole& h) { return h.slot_begin + h.slot_count <= slot; });
 }
 
 void ScopeModel::set_trigger_enabled(bool on) {