Experimental: Remove TDBConnection.OnDBObjectsCleared, which was used to implicitly refresh db items and tree nodes after items were cleared somewhere. Callers already did a refresh in some cases, which lead to duplicated "SHOW xyz FROM db" blocks. This again caused the "Database" tab to forget its scroll position within refreshes. Should fix issue #3409.

source/dbconnection.pas

@@ -257,7 +257,6 @@ type
       FOnLog: TDBLogEvent;
       FOnConnected: TDBEvent;
       FOnDatabaseChanged: TDBEvent;
-      FOnDBObjectsCleared: TDBEvent;
       FRowsFound: Int64;
       FRowsAffected: Int64;
       FWarningCount: Cardinal;
@@ -389,7 +388,6 @@ type
       property OnLog: TDBLogEvent read FOnLog write FOnLog;
       property OnConnected: TDBEvent read FOnConnected write FOnConnected;
       property OnDatabaseChanged: TDBEvent read FOnDatabaseChanged write FOnDatabaseChanged;
-      property OnDBObjectsCleared: TDBEvent read FOnDBObjectsCleared write FOnDBObjectsCleared;
   end;
   TDBConnectionList = TObjectList<TDBConnection>;
 
@@ -959,7 +957,6 @@ end;
 destructor TDBConnection.Destroy;
 begin
   if Active then Active := False;
-  FOnDBObjectsCleared := nil;
   ClearCache(True);
   FKeepAliveTimer.Free;
   FFavorites.Free;
@@ -2840,15 +2837,11 @@ end;
 procedure TDBConnection.ClearDbObjects(db: String);
 var
   i: Integer;
-  TriggerClearEvent: Boolean;
 begin
   // Free cached database object list
   for i:=FDatabaseCache.Count-1 downto 0 do begin
     if FDatabaseCache[i].Database = db then begin
-      TriggerClearEvent := FDatabaseCache[i].OnlyNodeType=lntNone;
       FDatabaseCache.Delete(i);
-      if TriggerClearEvent and Assigned(FOnDBObjectsCleared) then
-        FOnDBObjectsCleared(Self, db);
     end;
   end;
 end;

source/main.pas

@@ -995,7 +995,6 @@ type
     function ConfirmTabClose(PageIndex: Integer): Boolean;
     procedure UpdateFilterPanel(Sender: TObject);
     procedure ConnectionReady(Connection: TDBConnection; Database: String);
-    procedure DBObjectsCleared(Connection: TDBConnection; Database: String);
     procedure DatabaseChanged(Connection: TDBConnection; Database: String);
     procedure UpdateLineCharPanel;
     procedure SetSnippetFilenames;
@@ -3013,6 +3012,7 @@ begin
         Conn.Query('SET FOREIGN_KEY_CHECKS=@OLD_FOREIGN_KEY_CHECKS');
       // Refresh ListTables + dbtree so the dropped tables are gone:
       Conn.ClearDbObjects(ActiveDatabase);
+      RefreshTree;
       SetActiveDatabase(Conn.Database, Conn);
     except
       on E:EDatabaseError do
@@ -3397,7 +3397,6 @@ begin
   Connection := Params.CreateConnection(Self);
   Connection.OnLog := LogSQL;
   Connection.OnConnected := ConnectionReady;
-  Connection.OnDBObjectsCleared := DBObjectsCleared;
   Connection.OnDatabaseChanged := DatabaseChanged;
   Connection.ObjectNamesInSelectedDB := SynSQLSyn1.TableNames;
   try
@@ -7738,36 +7737,6 @@ begin
 end;
 
 
-procedure TMainForm.DBObjectsCleared(Connection: TDBConnection; Database: String);
-var
-  Node: PVirtualNode;
-  WasExpanded: Boolean;
-begin
-  // Avoid AVs while processing FormDestroy
-  if csDestroying in ComponentState then
-    Exit;
-  // Reload objects in ListTables ...
-  InvalidateVT(ListTables, VTREE_NOTLOADED, False);
-  // ... and in database tree
-  Node := FindDBNode(DBTree, Connection, Database);
-  if Assigned(Node) then begin
-    WasExpanded := DBTree.Expanded[Node];
-    // Will trigger OnFocusChanged:
-    DBTree.ResetNode(Node);
-    DBtree.Expanded[Node] := WasExpanded;
-    {
-    // Earlier code, replaced by above ResetNode, not sure if that causes new errors.
-    // See issue #2645
-    Tree.ReinitNode(Node, False);
-    if Tree.Expanded[Node] then
-      Tree.ReinitChildren(Node, False)
-    else
-      Tree.ResetNode(Node);
-    }
-  end;
-end;
-
-
 procedure TMainForm.DatabaseChanged(Connection: TDBConnection; Database: String);
 begin
   // Immediately force db icons to repaint, so the user sees the active db state