VCL Fix Pack 1.4

The VCL Fix Pack is a Delphi unit that fixes VCL and RTL bugs at runtime by patching the original functions. If you want all IDE Fix Pack fixes in your application this unit is what you are looking for. Adding the unit to your project (Delphi and C++Builder) automatically installs the patches that are available for your Delphi/C++Builder version.

Here is the list of runtime-patches that the VCLFixPack.pas unit applies depending on the Delphi version you use.

  • QC #74646: Buffer overflow in TCustomClientDataSet.DataConvert with ftWideString (2006-2009)
  • QC #7393: App with no main form showing a form with hints freezes (6-2009)
  • QC #68647: Infinite loop in Forms.GetNonToolWindowPopupParent (2006-2009 1.2)
  • QC #68740: Lost focus after TOpenDialog when MainFormOnTaskBar is set (2007-2009 1.2)
  • QC #59963: Closing non-modal forms after a task switch can deactivate the application (2005-2009)
  • QC #66892: Closing forms deactivates the application (missing “stdcall”) (2009 1.2)
  • Control resize bugfix for kernel stack overflow due to WH_CALLWNDPROC hook (6-2007)
  • QC #59654: TActionList access already released FActions field (6-2007)
  • QC #54286 : Parent-PopupMenu overrides standard context menu (edit, memo, combobox, …) (6-2007)
  • QC #50097: ObjAuto access violation on XEON (Data Execution Prevention bug) (2006-2007)
  • Classes.MakeObjectInstance memory leak fix (for usage in a DLL) (6-2009)
  • QC #58938: MainForm Minimize minimizes in the background (2007)
  • QC #64484: SysUtils.Abort can raise an AccessViolation (6-2009 1.2)
  • QC #58939: No taskbar button when starting from ShellLink with Show=Minimized (2007)
  • QC #35001: MDIChild’s active control focus is not set correctly (6-2009 .12)
  • QC #56252: TPageControl flickers a lot with active theming (7-2009)
  • QC #68730: TLabel is not painted on a themed, double-buffered TTabSheet in Vista (7-2009)
  • TLabels on TTabSheet are not painted (themes) if a TWinControl like TMemo is on the TTabSheet (TWinControl.PaintWindow bug) (7-2009)
  • Grid flickers with active theming (DBGrid, StringGrid and DrawGrid only, no derived classes) (7-2009)
  • QC #69112: TSpeedButton is painted as a black rectangle on a double buffered panel on a sheet of glass. (2009)
  • QC #69294: TProgressBar fails with PBS_MARQUEE and disabled Themes (Vista)
  • Workaround for Windows Vista CompareString bug (Workaround is disabled by default, define “VistaCompareStringFix” to activate it) (Vista)
  • QC #69294: TProgressBar fails with PBS_MARQUEE and disabled Themes (Vista)
  • QC #52439: DbNavigator paints incorrectly when flat=true in themed mode (2007-2009)
  • QC #70441: ToUpper and ToLower modify a Const argument (2009 1.2)
  • QC #69752: ToUpper and ToLower with NullString (2009 .12)
  • QC #67564, QC #69875: StringBuilder.Replace is incorrect (2009)


Add the VCLFixPack.pas unit to your Delphi or C++Project project. C++Builder will automatically call the Delphi compiler for the unit.


Mozilla Public License Version 1.1


Name IDE Version File Size Downloads Added
VCL Fix Pack 1.2 6-2009 19.89 KB 6015 times 2009-03-03
VCL Fix Pack 1.3 2009.3 21.11 KB 2689 times 2009-05-30
VCL Fix Pack 1.4 6-2009.3 21.7 KB 16315 times 2009-09-03
Fix for QC 90511 (Atom leak) 6-XE ControlsAtomFix1.7z 3.78 KB 3714 times 2014-04-18

Changelog from 1.3 to 1.4:

  • Added: QC #74646: Buffer overflow in TCustomClientDataSet.DataConvert with ftWideString
  • Fixed: TTabSheet looked strange if used with SilverThemes

Changelog from 1.2 to 1.3:

  • Changed: Disabled all patches that are fixed by Delphi 2009 Update 3
  • Added: QC #7393: App with no main form showing a form with hints freezes

Changelog from 1.1 to 1.2:

  • Fixed: Rewritten patch for QC #59963 (AppDeActivateZOrderFix) to fix the cause instead of the symptom
  • Added: QC #52439: DbNavigator paints incorrectly when flat=true in themed mode
  • Added: QC #70441: ToUpper and ToLower modify a Const argument
  • Added: QC #69752: ToUpper and ToLower with NullString
  • Added: QC #69875, #67564: StringBuilder.Replace is incorrect + a much faster implementation

Changelog from 1.0 to 1.1:

  • Fixed: DBGrid ScrollBar gab wasn’t painted correctly in BiDiMode <> bdLeftToRight
  • Fixed: TTabSheet could throw an access violation if no PageControl was assigned to it
  • Changed: Rewritten TaskModalDialog bugfix
  • Added: QC #69294: TProgressBar fails with PBS_MARQUEE and disabled Themes (Vista)


The VCL Fix Pack superseeds the following CodeCentral items

46 thoughts on “VCL Fix Pack 1.4

  1. Thomas Speck

    Hello Andreas,

    with VCLFixPack, is there any need for TaskModalBugFix and AppDeActivateZOrderFix ? For Delphi 2007, do we need any longer ContextMenuBugFix and ControlResizeBugFix and MkObjInstLeakFix and RTLVCLOptimize ? For Delphi 2009, do we need HideStackTrashingFix ?

    Were all of these Fixes included in VCLFixPack ?

  2. Edwin Yip

    Wow! Excellent! This is especially useful for users who are using the old versions of Delphi that will not be updated anymore.


  3. Laurent

    Hi Andreas,

    Thank you very much for this great work. I don’t understand why CodeGear/Embarcadero has not yet implemented these code fix… It will stay a mystery.

  4. Ralf

    Hi Andreas,
    I habe some additional fixes for your unit. The source can be found in QC!

    CodeRedirect(GetActualAddr(Getllmulo), @__llmulo);

    CodeRedirect(GetActualAddr(Getllushr), @__llushr);

    //CodeRedirect(GetActualAddr(Getllshr), @__llshr);

    CodeRedirect(GetActualAddr(Getllshl), @__llshl);

    CodeRedirect(GetActualAddr(Getllumod), @__llumod);

    CodeRedirect(GetActualAddr(Getlldiv), @__lldiv);

    CodeRedirect(GetActualAddr(Getllmul), @__llmul);

    //__llmodo replaced by __llmod
    CodeRedirect(GetActualAddr(Getllmodo), GetActualAddr(Getllmod));

    CodeRedirect(@StrUtils.StuffString, @StuffString);

    CodeRedirect(@StrUtils.DupeString, @DupeString);

    CodeRedirect(@SysUtils.DecodeDateFully, @DecodeDateFully);

    CodeRedirect(@SysUtils.IsLeapYear, @IsLeapYear);

    CodeRedirect(@Math.ArcCscH, @ArcCscH);

  5. Ralf

    What about a new name scheme?


    IDE Fix Pack
    VCL Fix Pack


    IDE Speed Pack (a.k.a. DelphiSpeedUp)
    VCL Speed Pack (a.k.a. RtlVclOptimize)

  6. Rich

    Amazing work Andreas!!!

    I wonder if this bug might be a good candidate for the next VCL Fix Pack:

    “LowerCase() and UpperCase() functions in AnsiStrings unit do not set proper codepage”

    I just got rid of a hard-to-find bug by not using UpperCase() in Delphi 2009 + BlackFish SQL–funny thing, I was using Unicode (the bug report is for AnsiString). Maybe the same problem exists for both AnsiString and Unicode.

  7. Seefall

    Hello Andreas,
    Thank you for your great work. But when I write programs with your VCL-Fix Pack, my programs became about 300k bigger than before. Why not providing the pas directly to fix it?

  8. Andreas Hausladen Post author

    I provide the *.pas file. Or do you mean that I should violate the license and publish the fixed RTL and VCL units? This would also cause problems with future Delphi/C++Builder updates where the update tool will revert the update or doesn’t allow to install the update because the installed files do not match the CRC of the installed files.

  9. Wessel

    Hello Andreas,

    Thank you very much for this great work, please get a job at CodeGear !.

  10. Wolf

    I had the same increase here.
    Disabled the following two defines what fixed this major increase in my case:

    {.$DEFINE GridFlickerFix}

    Works superb now!

  11. stanleyxu2005

    Hi Andreas again,

    Your patch unit looks great.
    I (maybe other guys) would be glad to contribute something to fix VCL issues as well.
    Could you please write some technical articles about Delphi Patching?

    Best regards and happy new year ^^)

  12. MarkF

    Hi Andreas,

    Thank you for making this available! This solved a problem in my code related to the control resizing bug that only seemed to happen in Vista 64. Great job!! Have a safe and happy New Year!


  13. Ronald

    The fix for “WH_CALLWNDPROC hook (6-2007)” have a problem with the DevExpress Bars Ribbons.
    When you minimize a maximized Application – with Ribbon on MDIForm and a maximized MDIChildrn – and restore it,
    the aligment doesn’t work correct. Without your patch, everything is Ok.

    Any ideas?

  14. Andreas Hausladen Post author

    I don’t have the DevExpress components so I can’t test this. But if a control is based on the assumption that an endless resizing recursion fixes the alignment, it will be broken because the new align control code aborts the (now) endless loop that isn’t catched by the kernel stack overflow.

    Delphi 2009 also uses the this code (even my comments are in the Controls.pas).

  15. MarkF

    Hi Andreas,

    I was wondering what the status of OPTIMIZED_RESIZE_REDRAW is. Has anyone run into any problems with it? I’ve enabled it in a few of my test programs and haven’t seen any problems yet. Is this the right place to ask? Thanks again for this! I recently noticed QC #59963 in one of my programs and the VCLFixPack solved my problem!


  16. Stefan

    Hi Andreas,

    Does the unit add around 400kB to the size of the compiled executable or am I doing something wrong?
    Thanks anyway for the fixes,

  17. Andreas Hausladen Post author

    The unit itself doesn’t add the 400 KB to your project but the units that it patches are now part of your project. For example if your project doesn’t use database units (DBGrids, DBCtrls) then it now uses it. But you can tell VclFixPack to not patch those units by removing the “{$DEFINE VCLFIXPACK_DB_SUPPORT}” condition in the VclFixPack.pas.

  18. Anthony Frazier

    Thanks very much for these fixes!

    I don’t know if you’re considering any requests, but if you could generate patches for the various problems with 2009’s TDictionary (e.g. QCs 67620, 67558, 68234)

  19. Andreas Hausladen Post author

    I can’t patch TDictionary. Everything that includes generics can’t be patched without altering the unit code itself what will cause interface changes and leads to the “unit xy was compiled with a different version of ab” compiler error.

  20. IL

    Andreas, strange thing happens while trying to open
    also for #59963 it is said “Sorry, you don’t have access to this submission.”
    My main reason was to read about bug #59963 more thoroughly, as I think I have the similar case of out-of-order modal windows not shown above all windows of my application.
    Could you give me advice how to apply more information about it. Thanks for attention.

  21. Mohamed Koker

    Hi Andreas,

    Do these fixes work for applications that use run-time packages?

    Also, do they include a fix for the ValidateTimeStamp function that causes the dreaded ‘0.0 is not a valid timestamp’ error when querying certain tables using the BDE?

  22. Andreas Hausladen Post author

    > Do these fixes work for applications that use run-time packages?


    > Also, do they include a fix for the ValidateTimeStamp function

    Not in the list, so it is not fixed.

  23. Salvor Hardin

    Hi Andy,

    Thanks for VCLFixPack! I use it in all my Delphi 2009 projects.

    I came across a post about a Delphi 2009 memory corruption bug in TDictionary.TPairEnumerator.MoveNext

    Just mentioning in case you were looking another challenge for the next VCLFixPack.

    The post and code snippet was found here (it turned out to have nothing to do with Eurekalog):

  24. Andreas Hausladen Post author

    Copy&Paste from a comment by me:

    I can’t patch TDictionary. Everything that includes generics can’t be patched without altering the unit code itself what will cause interface changes and leads to the “unit xy was compiled with a different version of ab” compiler error.

  25. Mike

    First, thanks for your excellent work.
    Second, are you aware about this patch, based on your VCLFixPack: D7DoubleBufferedThemeFix? The patch solves the double-buffering problems at least for Delphi 7 and XP themes. I’ve found it here:
    (you have to register in order to download the file).

    I’ve tried it and it worked after I applied the following procedure to the form:

    procedure SetDoubleBufferedDeep(WinControl: TWinControl);
    I: Integer;
    WinControl.DoubleBuffered := True;
    for I := 0 to WinControl.ControlCount – 1 do
    if WinControl.Controls[I] is TWinControl then

    Maybe you decide to include this fix to your VCLFixPack.

  26. MarkF

    Hi Andreas,

    I’m noticing that the new improved fix for the z-order issue seems to not work all the time for me. The situation is where my program puts up a modal form while the main form is behind another application. I click on the modal form, bringing it to the front, and close it. The main form is now (usually?) behind the other application instead of in front of it. I didn’t notice this issue with the 1.1 version. This is on my 32bit XP SP3 system by the way. I just thought I’d mention it and also how much I appreciate your fantastic work and the fact that you make this publicly available!


  27. Christian

    Hi there,

    when I use your FixPack with Advantage Local Server v9.1, it somehow blocks the password property I set to its TAdsConnection and the user must manually enter it.
    That problem only exists as long as the VCLFIXPACK_DB_SUPPORT define is set.

    I just thought I’d mention it.

  28. Andreas Hausladen Post author

    Are you sure that it is the VCLFIXPACK_DB_SUPPORT define? Because this only patches the TDBGrid.WMEraseBkGnd method (flicker reduction) and the TDBNavigator.SetFlat method (ControlStyle:=ControlStyle+/-[csOpace]). So only visual things.
    It also adds DBGrids and DBCtrls to the uses clause and that may change the order of unit initialization.

  29. Christian

    Yes, I just reconfirmed it.
    Compiled with the define active – app asked for the password.
    Compiled without the define – worked without any problems.

    As I don’t need those changes in the FixPack, I don’t really care about that behaviour. Just thought every “bug” (on whichever side it is) should be reported. 🙂

  30. Richard Dufour:

    Hi Andreas,

    First of all, thanks for releasing this.

    I noticed the following issue since we installed the VCLFixPack.

    I have a panel aligned alLeft, that is anchored [ akLeft, akTop, akBottom ]. It is beside a splitter and another panel.

    At run time, my panel (on the left) doesn’t respect the akBottom value.

    As soon as something gets resized (the splitter beside it or the form being resized) then my panel is repainted with the akBottom correctly .

    If I also include akRight at design time, the akBottom is respected but I do not want it anchored to the right. Somehow, the VCLFixPack gets rid of my akBottom value, when the program loads.

  31. Richard Dufour:

    Sorry, I should specify, the control I am having an issue here is not the panel but the TTreeView that’s on it.


  32. Richard Dufour:

    Oh and I’m using Delphi 2007.

    When the panel it sits on has akRight, the TreeView (which is alClient [ akLeft, akTop, akRight, akBottom ] stretches as it should. So it seems to be the parent panel that is affecting the child treeview.

  33. Richard Dufour:

    By adding the following code on the form show, I get around the issue.

    procedure TMyForm.FormShow(Sender: TObject);
    // We need the combination of the following 2 lines:
    MyTreeView.Align := alLeft; // Should really be alClient as in design time but doesn’t work
    //if set to alClient
    MyTreeView.Anchors := [ akLeft, akTop, akRight, akBottom ];


  34. sip

    I’ve fixed this one very annoying QC #67729: Converting Array of String to Variant fails

    *** C:\VCLFixPack.pas 2009-03-03 23:07:24.000000000 -0700
    — R:\VCLFixPack.pas 2009-05-26 19:32:02.000000000 -0700
    *** 132,144 ****
    — 132,148 —-
    QC #69752: ToUpper and ToLower with NullString

    – [2009]
    QC #69875: StringBuilder.Replace is incorrect
    QC #67564: Error in TStringBuilder.Replace

    + – [2009]
    + QC #67729: Converting Array of String to Variant fails
    + (

    Fixed: Rewritten patch for QC #59963 (AppDeActivateZOrderFix) to fix the cause instead of the symptom
    Added: QC #52439: DbNavigator paints incorrectly when flat=true in themed mode
    Added: QC #70441: ToUpper and ToLower modify a Const argument
    Added: QC #69752: ToUpper and ToLower with NullString
    *** 236,247 ****
    — 240,255 —-
    {$IF (CompilerVersion >= 18.5) and (CompilerVersion = 20.0}
    DBGrids, DBCtrls,
    + {$IFDEF DynArrayVarTypeFix}
    + Variants,
    + {$ENDIF DynArrayVarTypeFix}
    Graphics, Controls, Forms, Dialogs, StdCtrls, Grids, ComCtrls, Buttons,

    { —————————————————————————- }
    { Helper functions, shared }
    *** 2650,2661 ****
    — 2661,2748 —-
    VirtualFree(JumpTable, 0, MEM_RELEASE);
    JumpTable := nil;
    {$ENDIF VistaCompareStringFix}
    { —————————————————————————- }
    + { QC #67729: Converting Array of String to Variant fails }
    + {$IFDEF DynArrayVarTypeFix}
    + const
    + tkDynArray = 17;
    + var
    + DynArrayVarTypeHook: TXRedirCode;
    + function VariantsDynArrayVarType(typeInfo: PDynArrayTypeInfo): Integer;
    + begin
    + Result := varNull;
    + if (typeInfo nil) and (typeInfo.Kind = tkDynArray) then
    + begin
    + Inc(PAnsiChar(typeInfo), Length(;
    + Result := typeInfo.varType;
    + { NOTE: DECL.H and SYSTEM.PAS have different values for varString }
    + if Result = $48 then
    + Result := varString;
    + if Result = $4A then
    + Result := varUString;
    + end;
    + { Validate the Result }
    + if (Result varInt64) and not ((Result = varString) or (Result = varUString))) then
    + VarCastError;
    + end;
    + function GetDynArrayVarTypeAddr : pointer;
    + var
    + P: PAnsiChar;
    + Len: Integer;
    + begin
    + P := GetActualAddr(@Variants.DynArrayToVariant);
    + Dec(P);
    + Len := 0;
    + while Len <= 80 do begin
    + if (P[0] = #$53) and // push ebx
    + (P[1] = #$BB) and // mov ebx, $00000001
    + (P[2] = #$01) and
    + (P[3] = #$00) and
    + (P[4] = #$00) and
    + (P[5] = #$00) and
    + (P[6] = #$85) and // test eax, eax
    + (P[7] = #$C0)
    + then begin
    + Result:= P;
    + Exit;
    + end;
    + Dec(P);
    + Inc(Len);
    + end;
    + Result:= nil;
    + end;
    + var
    + DynArrayVarTypeAddr : pointer;
    + procedure InitDynArrayVarTypeFix;
    + begin
    + DebugLog(‘DynArrayVarTypeFix’);
    + DynArrayVarTypeAddr:= GetDynArrayVarTypeAddr;
    + if DynArrayVarTypeAddr nil then
    + HookProc(DynArrayVarTypeAddr, @VariantsDynArrayVarType, DynArrayVarTypeHook);
    + end;
    + procedure FiniDynArrayVarTypeFix;
    + begin
    + if DynArrayVarTypeAddr nil then
    + UnhookProc(DynArrayVarTypeAddr, DynArrayVarTypeHook);
    + end;
    + {$ENDIF SysUtilsAbortFix}
    + { —————————————————————————- }

    {$IFDEF GetNonToolWindowPopupParentFix}
    {$ENDIF GetNonToolWindowPopupParentFix}

    *** 2737,2750 ****
    — 2824,2845 —-
    {$ENDIF StringBuilderFix}

    {$IFDEF VistaCompareStringFix}
    {$ENDIF VistaCompareStringFix}

    + {$IFDEF DynArrayVarTypeFix}
    + InitDynArrayVarTypeFix;
    + {$ENDIF DynArrayVarTypeFix}
    // In revers order
    + {$IFDEF DynArrayVarTypeFix}
    + FiniDynArrayVarTypeFix;
    + {$ENDIF DynArrayVarTypeFix}

    {$IFDEF VistaCompareStringFix}
    {$ENDIF VistaCompareStringFix}

    {$IFDEF StringBuilderFix}

Comments are closed.