First chnage for #832: Turn TVirtualNode.Parent into a readonly property.

Author: joachimmarder

Source/VirtualTrees.BaseTree.pas

@@ -4328,7 +4328,7 @@ procedure TBaseVirtualTree.InitRootNode(OldSize: Cardinal = 0);
     // Indication that this node is the root node.
     PrevSibling := FRoot;
     NextSibling := FRoot;
-    Parent := Pointer(Self);
+    SetParent(Pointer(Self));
     States := [vsInitialized, vsExpanded, vsHasChildren, vsVisible];
     TotalHeight := FDefaultNodeHeight;
     TotalCount := 1;
@@ -5049,7 +5049,7 @@ procedure TBaseVirtualTree.SetChildCount(Node: PVirtualNode; NewChildCount: Card
             Child.PrevSibling := Node.LastChild;
             if Assigned(Node.LastChild) then
               Node.LastChild.NextSibling := Child;
-            Child.Parent := Node;
+            Child.SetParent(Node);
             Node.LastChild := Child;
             if Node.FirstChild = nil then
               Node.FirstChild := Child;
@@ -13775,7 +13775,7 @@ procedure TBaseVirtualTree.InternalConnectNode(Node, Destination: PVirtualNode;
           Node.PrevSibling := Destination.PrevSibling;
           Destination.PrevSibling := Node;
           Node.NextSibling := Destination;
-          Node.Parent := Destination.Parent;
+          Node.SetParent(Destination.Parent);
           Node.Index := Destination.Index;
           if Node.PrevSibling = nil then
             Node.Parent.FirstChild := Node
@@ -13795,7 +13795,7 @@ procedure TBaseVirtualTree.InternalConnectNode(Node, Destination: PVirtualNode;
           Node.NextSibling := Destination.NextSibling;
           Destination.NextSibling := Node;
           Node.PrevSibling := Destination;
-          Node.Parent := Destination.Parent;
+          Node.SetParent(Destination.Parent);
           if Node.NextSibling = nil then
             Node.Parent.LastChild := Node
           else
@@ -13827,7 +13827,7 @@ procedure TBaseVirtualTree.InternalConnectNode(Node, Destination: PVirtualNode;
             Node.NextSibling := nil;
           end;
           Node.PrevSibling := nil;
-          Node.Parent := Destination;
+          Node.SetParent(Destination);
           Node.Index := 0;
           // reindex all following nodes
           Run := Node.NextSibling;
@@ -13854,7 +13854,7 @@ procedure TBaseVirtualTree.InternalConnectNode(Node, Destination: PVirtualNode;
             Node.PrevSibling := nil;
           end;
           Node.NextSibling := nil;
-          Node.Parent := Destination;
+          Node.SetParent(Destination);
           if Assigned(Node.PrevSibling) then
             Node.Index := Node.PrevSibling.Index + 1
           else
@@ -15137,7 +15137,7 @@ function TBaseVirtualTree.ReadChunk(Stream: TStream; Version: Integer; Node: PVi
             else
               Node.FirstChild := Run;
             Node.LastChild := Run;
-            Run.Parent := Node;
+            Run.SetParent(Node);
 
             ReadNode(Stream, Version, Run);
             System.Dec(ChunkBody.ChildCount);

Source/VirtualTrees.Types.pas

@@ -893,11 +893,15 @@   TScrollBarOptions = class(TPersistent)
     // Note: Some copy routines require that all pointers (as well as the data area) in a node are
     //       located at the end of the node! Hence if you want to add new member fields (except pointers to internal
     //       data) then put them before field Parent.
-    Parent,                  // reference to the node's parent (for the root this contains the treeview)
+  private
+    fParent:  PVirtualNode; // link to the node's last child...
+  public                  // reference to the node's parent (for the root this contains the treeview)
     PrevSibling,             // link to the node's previous sibling or nil if it is the first node
     NextSibling,             // link to the node's next sibling or nil if it is the last node
     FirstChild,              // link to the node's first child...
     LastChild: PVirtualNode; // link to the node's last child...
+    procedure SetParent(const pParent: PVirtualNode); inline; //internal method, do not call directly but use Parent[Node] := x on tree control.
+    property Parent: PVirtualNode read fParent;
   private
     Data: record end;        // this is a placeholder, each node gets extra data determined by NodeDataSize
   public
@@ -1165,6 +1169,11 @@ procedure TVirtualNode.SetData<T>(pUserData: T);
   Include(Self.States, vsOnFreeNodeCallRequired);
 end;
 
+procedure TVirtualNode.SetParent(const pParent: PVirtualNode);
+begin
+  fParent := pParent;
+end;
+
 //----------------------------------------------------------------------------------------------------------------------