Make validation interface capable of signalling header presync

This makes a number of changes:
- Get rid of the verification_progress argument in the node interface
  NotifyHeaderTip (it was always 0.0).
- Instead of passing a CBlockIndex* in the UI interface's NotifyHeaderTip,
  send separate height, timestamp fields. This is becuase in headers presync,
  no actual CBlockIndex object is available.
- Add a bool presync argument to both of the above, to identify signals
  pertaining to the first headers sync phase.

src/interfaces/node.h

@@ -260,7 +260,7 @@ public:
 
     //! Register handler for header tip messages.
     using NotifyHeaderTipFn =
-        std::function<void(SynchronizationState, interfaces::BlockTip tip, double verification_progress)>;
+        std::function<void(SynchronizationState, interfaces::BlockTip tip, bool presync)>;
     virtual std::unique_ptr<Handler> handleNotifyHeaderTip(NotifyHeaderTipFn fn) = 0;
 
     //! Get and set internal node context. Useful for testing, but not

src/node/interface_ui.cpp

@@ -53,7 +53,7 @@ void CClientUIInterface::NotifyNetworkActiveChanged(bool networkActive) { return
 void CClientUIInterface::NotifyAlertChanged() { return g_ui_signals.NotifyAlertChanged(); }
 void CClientUIInterface::ShowProgress(const std::string& title, int nProgress, bool resume_possible) { return g_ui_signals.ShowProgress(title, nProgress, resume_possible); }
 void CClientUIInterface::NotifyBlockTip(SynchronizationState s, const CBlockIndex* i) { return g_ui_signals.NotifyBlockTip(s, i); }
-void CClientUIInterface::NotifyHeaderTip(SynchronizationState s, const CBlockIndex* i) { return g_ui_signals.NotifyHeaderTip(s, i); }
+void CClientUIInterface::NotifyHeaderTip(SynchronizationState s, int64_t height, int64_t timestamp, bool presync) { return g_ui_signals.NotifyHeaderTip(s, height, timestamp, presync); }
 void CClientUIInterface::BannedListChanged() { return g_ui_signals.BannedListChanged(); }
 
 bool InitError(const bilingual_str& str)

src/node/interface_ui.h

@@ -105,7 +105,7 @@ public:
     ADD_SIGNALS_DECL_WRAPPER(NotifyBlockTip, void, SynchronizationState, const CBlockIndex*);
 
     /** Best header has changed */
-    ADD_SIGNALS_DECL_WRAPPER(NotifyHeaderTip, void, SynchronizationState, const CBlockIndex*);
+    ADD_SIGNALS_DECL_WRAPPER(NotifyHeaderTip, void, SynchronizationState, int64_t height, int64_t timestamp, bool presync);
 
     /** Banlist did change. */
     ADD_SIGNALS_DECL_WRAPPER(BannedListChanged, void, void);

src/node/interfaces.cpp

@@ -377,9 +377,8 @@ public:
     std::unique_ptr<Handler> handleNotifyHeaderTip(NotifyHeaderTipFn fn) override
     {
         return MakeHandler(
-            ::uiInterface.NotifyHeaderTip_connect([fn](SynchronizationState sync_state, const CBlockIndex* block) {
-                fn(sync_state, BlockTip{block->nHeight, block->GetBlockTime(), block->GetBlockHash()},
-                    /* verification progress is unused when a header was received */ 0);
+            ::uiInterface.NotifyHeaderTip_connect([fn](SynchronizationState sync_state, int64_t height, int64_t timestamp, bool presync) {
+                fn(sync_state, BlockTip{(int)height, timestamp, uint256{}}, presync);
             }));
     }
     NodeContext* context() override { return m_context; }

src/qt/clientmodel.cpp

@@ -267,8 +267,8 @@ void ClientModel::subscribeToCoreSignals()
             TipChanged(sync_state, tip, verification_progress, /*header=*/false);
         });
     m_handler_notify_header_tip = m_node.handleNotifyHeaderTip(
-        [this](SynchronizationState sync_state, interfaces::BlockTip tip, double verification_progress) {
-            TipChanged(sync_state, tip, verification_progress, /*header=*/true);
+        [this](SynchronizationState sync_state, interfaces::BlockTip tip, bool presync) {
+            if (!presync) TipChanged(sync_state, tip, /*verification_progress=*/0.0, /*header=*/true);
         });
 }
 

src/validation.cpp

@@ -2944,7 +2944,7 @@ static bool NotifyHeaderTip(CChainState& chainstate) LOCKS_EXCLUDED(cs_main) {
     }
     // Send block tip changed notifications without cs_main
     if (fNotify) {
-        uiInterface.NotifyHeaderTip(GetSynchronizationState(fInitialBlockDownload), pindexHeader);
+        uiInterface.NotifyHeaderTip(GetSynchronizationState(fInitialBlockDownload), pindexHeader->nHeight, pindexHeader->nTime, false);
     }
     return fNotify;
 }