Once you have the TWinControl descendant with the class name longer than 64 characters you cannot construct it:

Related SO question: https://stackoverflow.com/questions/14446979/why-do-i-get-access-violations-when-a-controls-class-name-is-very-very-long

Related QC entry: http://qc.embarcadero.com/wc/qcmain.aspx?d=112101

The suggested solution does the local override of the CreateParams method. But you can do this permanently for whole VCL application if you wish so by adding the following unit to your project (it requires the beautiful Detours library):

unit uWinControlClassNameFix; interface implementation uses DDetours, Vcl.Controls, System.SysUtils, System.Hash; type TWinControlEx = class(TWinControl); TCreateParamsMethod = procedure (var AParams: TCreateParams) of object; TCreateParamsEx = record SourceParams: TCreateParams; Overflow: array [0..4096] of Char; end; var FOldCreateParams: Pointer; procedure CreateParamsFix(Sender: TObject; var AParams: TCreateParams); const HASH_LEN = 8; var LParams: TCreateParamsEx; LHash: String; LInherited: TCreateParamsMethod; begin TMethod(LInherited).Code := FOldCreateParams; TMethod(LInherited).Data := Sender; if Length(Sender.ClassName) < Length(AParams.WinClassName) then begin LInherited(AParams); Exit; end; LParams := Default(TCreateParamsEx); LParams.SourceParams := AParams; LInherited(LParams.SourceParams); LHash := IntToHex(THashBobJenkins.GetHashValue(LParams.SourceParams.WinClassName), HASH_LEN); Move(LHash[1], LParams.SourceParams.WinClassName[High(LParams.SourceParams.WinClassName) - HASH_LEN], HASH_LEN * SizeOf(Char)); LParams.SourceParams.WinClassName[High(LParams.SourceParams.WinClassName)] := #0; AParams := LParams.SourceParams; end; begin InterceptCreate(@TWinControlEx.CreateParams, @CreateParamsFix, FOldCreateParams); end.

P.S. I have used the code of Cosmin Prund for making this possible with some adjustments I believed are more compact and readable. The code is tested on Delphi Berlin 10.1.2. Feel free to use/modify and whatever you want with this 😉

But make sure you handle the use of FindWindow or similar API where you use the class name – because it will be different from actual ClassName!