Merge branch 'feature/158-replace-hibernation-bug-hacks' into develop

Issue 158 / PR 160

Fixes #158
Closes #160

Author: delphidabbler

Src/FmMain.pas

@@ -526,12 +526,6 @@   TMainForm = class(THelpAwareForm)
       ///  <summary>Object that manages favourites.</summary>
       fFavouritesMgr: TFavouritesManager;
 
-    ///  <summary>Handles the <c>WM_POWERBROADCAST</c> messages to detect and
-    ///  respond to hibernation messages.</summary>
-    ///  <remarks>!! HACK necessary as part of the fix for an obscure bug. See
-    ///  https://github.com/delphidabbler/codesnip/issues/70</remarks>
-    procedure WMPowerBroadcast(var Msg: TMessage); message WM_POWERBROADCAST;
-
     ///  <summary>Displays view item given by TViewItemAction instance
     ///  referenced by Sender and adds to history list.</summary>
     procedure ActViewItemExecute(Sender: TObject);
@@ -1601,19 +1595,5 @@ procedure TMainForm.splitVertCanResize(Sender: TObject;
     Accept := False;
 end;
 
-procedure TMainForm.WMPowerBroadcast(var Msg: TMessage);
-begin
-  // !! HACK
-  // Sometimes when the computer is resumed from hibernation the tree view in
-  // the overview frame is destroyed and recreated by Windows. Unfortunately the
-  // IView instances associated with the recreated tree nodes are lost.
-  // Attempting to read those (now nil) IView instances was resulting in an
-  // access violation.
-  case Msg.WParam of
-    PBT_APMSUSPEND:
-      fMainDisplayMgr._HACK_PrepareForHibernate;
-  end;
-end;
-
 end.
 

Src/FrOverview.pas

@@ -18,6 +18,7 @@ interface
 
 uses
   // Delphi
+  Generics.Collections,
   ComCtrls, Controls, Classes, Windows, ExtCtrls, StdCtrls, ToolWin, Menus,
   // Project
   DB.USnippet, FrTitled, IntfFrameMgrs, IntfNotifier, UCommandBars,
@@ -26,29 +27,6 @@ interface
 
 type
 
-  // !! HACK
-  // Horrible hack to expose CreateWnd for overiding TTreeView.CreateWnd for the
-  // existing TTreeView component of TOverviewFrame. The hack avoids having to
-  // remove the component and replacing it with a descendant class that is
-  // manually constructed at run time.
-  // This is here to enable the tree view to be recreated with correctly
-  // instantiated TViewItemTreeNode nodes after Windows recreates the tree
-  // behind the scenes after resuming from hibernation.
-  // I am deeply ashamed of this hack.
-  TTreeView = class(ComCtrls.TTreeView)
-  strict private
-    var
-      _HACK_fOnAfterCreateNilViews: TNotifyEvent;
-  protected
-    procedure CreateWnd; override;
-  public
-    ///  <summary>!! HACK. Event triggered after the inherited CreateWnd is
-    ///  called. Only called if the tree view has nil references to IView
-    ///  objects.</summary>
-    property _HACK_OnAfterCreateNilViews: TNotifyEvent
-      read _HACK_fOnAfterCreateNilViews write _HACK_fOnAfterCreateNilViews;
-  end;
-
   {
   TOverviewFrame:
     Titled frame that displays lists of snippets grouped in various ways and
@@ -111,6 +89,8 @@       TTVDraw = class(TSnippetsTVDraw)
       end;
 
     var
+      fViewStore : TList<IView>;    // Stores references to IView instances that
+                                    // have weak references in tree nodes
       fTVDraw: TTVDraw;             // Object that renders tree view nodes
       fNotifier: INotifier;         // Notifies app of user initiated events
       fCanChange: Boolean;          // Whether selected node allowed to change
@@ -237,10 +217,6 @@       TTVDraw = class(TSnippetsTVDraw)
     procedure RestoreTreeState;
       {Restores last saved treeview expansion state from memory.
       }
-    ///  <summary>!! HACK: Sets an event handler on the tree view to work
-    ///  around a bug that can occur after resuming from hibernation.</summary>
-    ///  <remarks>Method of IOverviewDisplayMgr.</remarks>
-    procedure _HACK_SetHibernateHandler(const AHandler: TNotifyEvent);
     { IPaneInfo }
     function IsInteractive: Boolean;
       {Checks if the pane is currently interactive with user.
@@ -311,6 +287,7 @@ constructor TOverviewFrame.Create(AOwner: TComponent);
   TabIdx: Integer;  // loops through tabs
 begin
   inherited;
+  fViewStore := TList<IView>.Create;
   // Create delegated (contained) command bar manager for toolbar and popup menu
   fCommandBars := TCommandBarMgr.Create(Self);
   fCommandBars.AddCommandBar(
@@ -346,6 +323,7 @@ destructor TOverviewFrame.Destroy;
   fSelectedItem := nil;
   fSnippetList.Free;  // does not free referenced snippets
   fCommandBars.Free;
+  fViewStore.Free;
   inherited;
 end;
 
@@ -547,7 +525,7 @@ procedure TOverviewFrame.Redisplay;
       Exit;
     // Build new treeview using grouping determined by selected tab
     Builder := BuilderClasses[tcDisplayStyle.TabIndex].Create(
-      tvSnippets, fSnippetList
+      tvSnippets, fSnippetList, fViewStore
     );
     Builder.Build;
     // Restore state of treeview based on last time it was displayed
@@ -982,12 +960,6 @@ procedure TOverviewFrame.UpdateTreeState(const State: TTreeNodeAction);
   end;
 end;
 
-procedure TOverviewFrame._HACK_SetHibernateHandler(
-  const AHandler: TNotifyEvent);
-begin
-  tvSnippets._HACK_OnAfterCreateNilViews := AHandler;
-end;
-
 { TOverviewFrame.TTVDraw }
 
 function TOverviewFrame.TTVDraw.IsSectionHeadNode(
@@ -1026,24 +998,5 @@ function TOverviewFrame.TTVDraw.IsUserDefinedNode(
     Result := False;
 end;
 
-{ TTreeView }
-
-procedure TTreeView.CreateWnd;
-var
-  HasNilViews: Boolean;
-  Node: TTreeNode;
-begin
-  inherited;
-  HasNilViews := False;
-  for Node in Items do
-  begin
-    HasNilViews := not Assigned((Node as TViewItemTreeNode).ViewItem);
-    if HasNilViews then
-      Break;
-  end;
-  if HasNilViews and Assigned(_HACK_fOnAfterCreateNilViews) then
-    _HACK_fOnAfterCreateNilViews(Self);
-end;
-
 end.
 

Src/IntfFrameMgrs.pas

@@ -19,7 +19,6 @@ interface
 uses
   // Delphi
   SHDocVw, ActiveX,
-  Classes, // !! For HACK
   // Project
   Browser.IntfDocHostUI, DB.USnippet, Compilers.UGlobals, UCommandBars, UView;
 
@@ -146,9 +145,6 @@ interface
     ///  <summary>Restore expand / collapse state of treeview to last save
     ///  state.</summary>
     procedure RestoreTreeState;
-    ///  <summary>!! HACK: Sets an event handler on the tree view to work
-    ///  around a bug that can occur after resuming from hibernation.</summary>
-    procedure _HACK_SetHibernateHandler(const AHandler: TNotifyEvent);
   end;
 
 type

Src/UMainDisplayMgr.pas

@@ -165,11 +165,6 @@   TMainDisplayMgr = class(TObject)
     procedure DisplayViewItem(ViewItem: IView; Mode: TDetailPageDisplayMode);
       overload;
 
-    ///  <summary>!! HACK event handle to redisplay the overview pane treeview.
-    ///  Called only if Windows has mysteriously recreated the treeview and lost
-    ///  necessary object references.</summary>
-    procedure _HACK_HibernateHandler(Sender: TObject);
-
   public
     ///  <summary>Object contructor. Sets up object to work with given frame
     ///  manager objects.</summary>
@@ -297,13 +292,6 @@   TMainDisplayMgr = class(TObject)
     /// <summary>Prepares display ready for database to be reloaded.</summary>
     procedure PrepareForDBReload;
 
-    ///  <summary>!!HACK: gets the overview frame prepared for program
-    ///  hibernation.</summary>
-    ///  <remarks>Saves the overview tree view state ready for restoring after
-    ///  hibernation if Windows has recreated the overview pane's treeview,
-    ///  losing necessary IView object references..</remarks>
-    procedure _HACK_PrepareForHibernate;
-
   end;
 
 
@@ -704,21 +692,5 @@ procedure TMainDisplayMgr.UpdateOverviewTreeState(const State: TTreeNodeAction);
   (fOverviewMgr as IOverviewDisplayMgr).UpdateTreeState(State);
 end;
 
-procedure TMainDisplayMgr._HACK_HibernateHandler(Sender: TObject);
-begin
-  (fOverviewMgr as IOverviewDisplayMgr).Display(Query.Selection, True);
-  (fOverviewMgr as IOverviewDisplayMgr).RestoreTreeState;
-  // disable this handler until next resume from hibernation
-  (fOverviewMgr as IOverviewDisplayMgr)._HACK_SetHibernateHandler(nil);
-end;
-
-procedure TMainDisplayMgr._HACK_PrepareForHibernate;
-begin
-  (fOverviewMgr as IOverviewDisplayMgr).SaveTreeState;
-  (fOverviewMgr as IOverviewDisplayMgr)._HACK_SetHibernateHandler(
-    _HACK_HibernateHandler
-  );
-end;
-
 end.
 

Src/UOverviewTreeBuilder.pas

@@ -18,6 +18,7 @@ interface
 
 uses
   // Delphu
+  Generics.Collections,
   ComCtrls,
   // Project
   DB.USnippet, UGroups, UView, UViewItemTreeNode;
@@ -32,13 +33,23 @@ interface
   TOverviewTreeBuilder = class abstract(TObject)
   strict private
     var
-      fTreeView: TTreeView;       // Value of TreeView property
-      fSnippetList: TSnippetList; // Value of SnippetList property
+      // Property values
+      fTreeView: TTreeView;
+      fSnippetList: TSnippetList;
+      fViewStore: TList<IView>;
   strict protected
     property TreeView: TTreeView read fTreeView;
       {Reference to treeview populated by class}
     property SnippetList: TSnippetList read fSnippetList;
       {List of snippets to be displayed in treeview}
+    ///  <summary>List of <c>IView</c> instances referenced by treeview nodes.
+    ///  </summary>
+    ///  <remarks>This list is required to maintain reference counting of
+    ///  <c>IView</c>s because the tree nodes only store weak references.
+    ///  </remarks>
+    property ViewStore : TList<IView> read fViewStore;
+      {List of IView instances referenced (weakly) by treeview nodes. This list
+      maintains maintains reference counting}
     function AddViewItemNode(const ParentNode: TViewItemTreeNode;
       ViewItem: IView): TViewItemTreeNode;
       {Adds a new node to the tree view that represents a view item.
@@ -57,12 +68,16 @@   TOverviewTreeBuilder = class abstract(TObject)
         @return Required view item object.
       }
   public
-    constructor Create(const TV: TTreeView; const SnippetList: TSnippetList);
-      {Class constructor. Sets up object to populate a treeview with a list of
-      snippets.
-        @param TV [in] Treeview control to be populated.
-        @param SnippetList [in] List of snippets to be added to TV.
-      }
+    ///  <summary>Constructs an object to populate a tree view with a list of
+    ///  snippets.</summary>
+    ///  <param name="TV"><c>TTreeView</c> [in] Treeview control to be
+    ///  populated.</param>
+    ///  <param name="SnippetList"><c>TSnippetList</c> [in] List of snippets to
+    ///  be added to the treeview.</param>
+    ///  <param name="ViewStore"><c>TList&lt;IView&gt;</c> [in] Receives a list
+    ///  of view items, one per tree node.</param>
+    constructor Create(const TV: TTreeView; const SnippetList: TSnippetList;
+      const ViewStore: TList<IView>);
     procedure Build;
       {Populates the treeview.
       }
@@ -177,7 +192,9 @@ procedure TOverviewTreeBuilder.Build;
   ParentNode: TViewItemTreeNode;  // each section node in tree
   Grouping: TGrouping;            // groups snippets
   Group: TGroupItem;              // each group of snippets
+  View: IView;
 begin
+  ViewStore.Clear;
   // Create required grouping of snippets
   Grouping := CreateGrouping;
   try
@@ -186,11 +203,17 @@ procedure TOverviewTreeBuilder.Build;
     begin
       if not Group.IsEmpty or Preferences.ShowEmptySections then
       begin
-        ParentNode := AddViewItemNode(nil, CreateViewItemForGroup(Group));
+        View := CreateViewItemForGroup(Group);
+        ParentNode := AddViewItemNode(nil, View);
+        ViewStore.Add(View);
         for Snippet in Group.SnippetList do
+        begin
+          View := TViewFactory.CreateSnippetView(Snippet);
           AddViewItemNode(
-            ParentNode, TViewFactory.CreateSnippetView(Snippet)
+            ParentNode, View
           );
+          ViewStore.Add(View);
+        end;
       end;
     end;
   finally
@@ -199,16 +222,12 @@ procedure TOverviewTreeBuilder.Build;
 end;
 
 constructor TOverviewTreeBuilder.Create(const TV: TTreeView;
-  const SnippetList: TSnippetList);
-  {Class constructor. Sets up object to populate a treeview with a list of
-  snippets.
-    @param TV [in] Treeview control to be populated.
-    @param SnippetList [in] List of snippets to be added to TV.
-  }
+  const SnippetList: TSnippetList; const ViewStore: TList<IView>);
 begin
   inherited Create;
   fTreeView := TV;
   fSnippetList := SnippetList;
+  fViewStore := ViewStore;
 end;
 
 { TOverviewCategorisedTreeBuilder }

Src/UViewItemTreeNode.pas

@@ -24,21 +24,33 @@ interface
 
 
 type
-  {
-  TViewItemTreeNode:
-    Custom tree node class that adds ability to store reference to a view item
-    in a tree node.
-  }
+  ///  <summary>Custom tree node class that adds a property to store a weak
+  ///  reference to an <c>IView</c> instance in a tree node.</summary>
   TViewItemTreeNode = class(TTreeNode)
   strict private
-    var fViewItem: IView; // Value of ViewItem property
+    function GetViewItem: IView;
+    procedure SetViewItem(const Value: IView);
   public
-    property ViewItem: IView read fViewItem write fViewItem;
-      {View item associated with tree node}
+    ///  <summary>View item associated with tree node.</summary>
+    ///  <remarks>NOTE: This view item is stored as a weak reference via a
+    ///  pointer so the reference count is not updated.</remarks>
+    property ViewItem: IView read GetViewItem write SetViewItem;
   end;
 
 
 implementation
 
+{ TViewItemTreeNode }
+
+function TViewItemTreeNode.GetViewItem: IView;
+begin
+  Result := IView(Data);
+end;
+
+procedure TViewItemTreeNode.SetViewItem(const Value: IView);
+begin
+  Data := Pointer(Value);
+end;
+
 end.