title: TToolbar stops displaying button captions after a while
body: <p>Any idea why TToolbar with TToolButtons would stop displaying button captions after a while? This happens to all toolbars on auto-created forms across the whole application. Toolbars on dynamically created forms work fine even after this problem.</p>
  
  <p>I have only seen this happen on one Windows 7 notebook. No errors are raised when this happens and I can't reproduce the problem on command. The only solution is restarting the application.</p>
  
  <p>TToolbar.ShowCaptions is always True and never changed. This is also visible on the image below because icons are vertically aligned when ShowCaptions is False.</p>
  
  <p><a href="https://i.stack.imgur.com/fl9br.png" rel="noreferrer"><img src="https://i.stack.imgur.com/fl9br.png" alt="Toolbar with missing captions"></a></p>
  
  <p>A similar problem happened before on a Windows 8 PC. However this time captions were replaced with other text.</p>
  
  <p><a href="https://i.stack.imgur.com/1X8W4.png" rel="noreferrer"><img src="https://i.stack.imgur.com/1X8W4.png" alt="Toolbar with weird captions"></a></p>
  
  <p>EDIT: </p>
  
  <p>I was able to reproduce the problem by calling TImageList.Change between 5-10k times. I only have Delphi 2010, so I can't say if this is a Delphi or Windows issue.</p>
  
  <p>Unit:</p>
  
  <pre><code>unit Unit1;
  
  interface
  
  uses
    Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
    Dialogs, ImgList, ComCtrls, ToolWin, StdCtrls, Gauges;
  
  type
    TImageListHelper = class helper for TImageList
    public
      procedure DoChange;
    end;
  
    TForm1 = class(TForm)
      ToolBar1: TToolBar;
      ToolButton1: TToolButton;
      ToolButton2: TToolButton;
      ToolButton3: TToolButton;
      ToolButton4: TToolButton;
      ToolButton5: TToolButton;
      ToolButton6: TToolButton;
      ToolButton7: TToolButton;
      ToolButton8: TToolButton;
      ToolButton9: TToolButton;
      ToolButton10: TToolButton;
      ImageList1: TImageList;
      ProgressBar1: TProgressBar;
      procedure ToolButton1Click(Sender: TObject);
    private
    public
    end;
  
  var
    Form1: TForm1;
  
  implementation
  
  {$R *.dfm}
  
  procedure TForm1.ToolButton1Click(Sender: TObject);
  begin
    repeat
      ImageList1.DoChange;
      ProgressBar1.StepIt;
      Self.Update;
    until ProgressBar1.Position &gt;= ProgressBar1.Max;
  end;
  
  procedure TImageListHelper.DoChange;
  begin
    Self.Change;
  end;
  
  end.
  </code></pre>
  
  <p>Form:</p>
  
  <pre><code>object Form1: TForm1
    Left = 0
    Top = 0
    Caption = 'Form1'
    ClientHeight = 66
    ClientWidth = 711
    Color = clBtnFace
    Font.Charset = DEFAULT_CHARSET
    Font.Color = clWindowText
    Font.Height = -11
    Font.Name = 'Tahoma'
    Font.Style = []
    OldCreateOrder = False
    Position = poScreenCenter
    PixelsPerInch = 96
    TextHeight = 13
    object ToolBar1: TToolBar
      Left = 0
      Top = 0
      Width = 711
      Height = 41
      ButtonHeight = 36
      ButtonWidth = 71
      Caption = 'ToolBar1'
      Images = ImageList1
      ShowCaptions = True
      TabOrder = 0
      ExplicitWidth = 885
      object ToolButton1: TToolButton
        Left = 0
        Top = 0
        Caption = 'ToolButton1'
        ImageIndex = 0
        OnClick = ToolButton1Click
      end
      object ToolButton2: TToolButton
        Left = 71
        Top = 0
        Caption = 'ToolButton2'
        ImageIndex = 0
      end
      object ToolButton3: TToolButton
        Left = 142
        Top = 0
        Caption = 'ToolButton3'
        ImageIndex = 0
      end
      object ToolButton4: TToolButton
        Left = 213
        Top = 0
        Caption = 'ToolButton4'
        ImageIndex = 0
      end
      object ToolButton5: TToolButton
        Left = 284
        Top = 0
        Caption = 'ToolButton5'
        ImageIndex = 0
      end
      object ToolButton6: TToolButton
        Left = 355
        Top = 0
        Caption = 'ToolButton6'
        ImageIndex = 0
      end
      object ToolButton7: TToolButton
        Left = 426
        Top = 0
        Caption = 'ToolButton7'
        ImageIndex = 0
      end
      object ToolButton8: TToolButton
        Left = 497
        Top = 0
        Caption = 'ToolButton8'
        ImageIndex = 0
      end
      object ToolButton9: TToolButton
        Left = 568
        Top = 0
        Caption = 'ToolButton9'
        ImageIndex = 0
      end
      object ToolButton10: TToolButton
        Left = 639
        Top = 0
        Caption = 'ToolButton10'
        ImageIndex = 0
      end
    end
    object ProgressBar1: TProgressBar
      Left = 0
      Top = 49
      Width = 711
      Height = 17
      Align = alBottom
      Max = 10000
      Step = 1
      TabOrder = 1
      ExplicitTop = 48
    end
    object ImageList1: TImageList
      Left = 8
      Top = 16
      Bitmap = {
        494C010101000500040010001000FFFFFFFFFF10FFFFFFFFFFFFFFFF424D3600
        0000000000003600000028000000400000001000000001002000000000000010
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    end
  end
  </code></pre>