unit VA2006Utils;

interface

uses
  Windows, Messages, SysUtils, Classes, Controls, ComCtrls, CommCtrl;

// Fixes bug in Delphi 2006, where clicking on a header control section after
// any other section have been added or deleted could cause access violations
procedure FixHeaderControlDelphi2006Bug(HeaderControl: THeaderControl);

implementation

uses
  VAUtils;

type
  THeaderControl2006BugFixer = class(TComponent)
  private
    FHeaderControl: THeaderControl;
    procedure HeaderControlMessageHandler(var Msg: TMessage; var Handled: Boolean);
  protected
    procedure Notification(AComponent: TComponent; Operation: TOperation); override;
  public
    constructor CreateWrapper(HeaderControl: THeaderControl);
  end;

procedure THeaderControl2006BugFixer.HeaderControlMessageHandler
                      (var Msg: TMessage; var Handled: Boolean);
var
  OnSectionClick: TSectionNotifyEvent;
begin
  if (Msg.Msg = CN_NOTIFY) and (PHDNotify(Msg.LParam)^.Hdr.code = HDN_ITEMCLICK) then
  begin
    Handled := TRUE;
    Msg.Result := 0;
    OnSectionClick := FHeaderControl.OnSectionClick;
    if assigned(OnSectionClick) then
      OnSectionClick(FHeaderControl, FHeaderControl.Sections[PHDNotify(Msg.lParam)^.Item]);
  end;
end;

procedure THeaderControl2006BugFixer.Notification(AComponent: TComponent;
  Operation: TOperation);
begin
  inherited;
  if (Operation = opRemove) and (AComponent = FHeaderControl) then
  begin
    RemoveMessageHandler(FHeaderControl, HeaderControlMessageHandler);
    Self.Free;
  end;
end;

constructor THeaderControl2006BugFixer.CreateWrapper(HeaderControl: THeaderControl);
begin
  inherited Create(nil);
  FHeaderControl := HeaderControl;
  FHeaderControl.FreeNotification(HeaderControl);
  AddMessageHandler(HeaderControl, HeaderControlMessageHandler);
end;

procedure FixHeaderControlDelphi2006Bug(HeaderControl: THeaderControl);
begin
  THeaderControl2006BugFixer.CreateWrapper(HeaderControl);
end;

end.