Attempt at fixing issue #725: TBaseVirtualTree.GetLastVisibleNoInit

The code causes exponential slowdowns when traversing very large trees. I copied the code of GetLastNoInit and replaced the GetLastChildNoInit calls with GetLastVisibleChildNoInit calls.

For better performance the 2nd GetLastVisibleChildNoInit call has been replaced with code extracted from GetLastVisibleChildNoInit. This prevents unnecessary calls to FullyVisible while recursing the tree.

Author: ElminsterAU

Source/VirtualTrees.pas

@@ -27832,19 +27832,24 @@ function TBaseVirtualTree.GetLastVisibleNoInit(Node: PVirtualNode = nil;
 
 // Returns the very last visible node in the tree while optionally considering toChildrenAbove.
 // No initialization is performed.
+var
+  Next: PVirtualNode;
 
 begin
-  Result := GetLastNoInit(Node, ConsiderChildrenAbove);
-  while Assigned(Result) and (Result <> Node) do
-  begin
-    if FullyVisible[Result] and
-       (IncludeFiltered or not IsEffectivelyFiltered[Result]) then
-      Break;
-    Result := GetPreviousNoInit(Result, ConsiderChildrenAbove);
-  end;
-
-  if (Result = Node) then // i.e. there is no visible node
-    Result := nil;
+  Result := GetLastVisibleChildNoInit(Node, IncludeFiltered);
+  if not ConsiderChildrenAbove or not (toChildrenAbove in FOptions.FPaintOptions) then
+    while Assigned(Result) and (vsExpanded in Result.States) do
+    begin
+      // Test if there is a next last child. If not keep the node from the last run.
+      // Otherwise use the next last child.
+      Next := GetLastChildNoInit(Result);
+      if Assigned(Next) and (not (vsVisible in Next.States) or
+         (not IncludeFiltered and IsEffectivelyFiltered[Next])) then
+        Next := GetPreviousVisibleSiblingNoInit(Next, IncludeFiltered);
+      if Next = nil then
+        Break;
+      Result := Next;
+    end;
 end;
 
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