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I ended up combining the code of @chkaufmann and @Lars Fosdal plus added the always-disabled property. The end result fully supports VCL styles and looks awesome! The full code became: Unit uHeaderMenuItem; Interface Uses Vcl.Menus, Vcl.Graphics, WinApi.Windows, System.Classes; Type THeaderMenuItem = Class(TMenuItem) strict private Procedure SetEnabled(Const inEnabled: Boolean); Function GetEnabled: Boolean; protected Procedure AdvancedDrawItem(ACanvas: TCanvas; ARect: TRect; State: TOwnerDrawState; TopLevel: Boolean); Override; Procedure DoAdvancedDrawItem(Sender: TObject; ACanvas: TCanvas; ARect: TRect; State: TOwnerDrawState); Procedure Loaded; Override; Public Constructor Create(AOwner: TComponent); Override; published Property Enabled: Boolean Read GetEnabled Write SetEnabled; End; Implementation Uses Vcl.Themes, System.SysUtils; Procedure THeaderMenuItem.AdvancedDrawItem(ACanvas: TCanvas; ARect: TRect; State: TOwnerDrawState; TopLevel: Boolean); Begin Self.DoAdvancedDrawItem(Self, ACanvas, ARect, State); End; Constructor THeaderMenuItem.Create(AOwner: TComponent); Begin inherited; Self.Enabled := False; OnAdvancedDrawItem := DoAdvancedDrawItem; End; Procedure THeaderMenuItem.DoAdvancedDrawItem(Sender: TObject; ACanvas: TCanvas; ARect: TRect; State: TOwnerDrawState); Begin ACanvas.Brush.Color := TStyleManager.ActiveStyle.GetStyleColor(scPanelDisabled); ACanvas.FillRect(ARect); ACanvas.Font.Color := TStyleManager.ActiveStyle.GetStyleFontColor(sfWindowTextNormal); ACanvas.Font.Style := [fsBold]; ACanvas.TextRect(ARect, ARect.Left + 3, ARect.Top + 3, StripHotkey(Caption)); End; Function THeaderMenuItem.GetEnabled: Boolean; Begin Result := inherited Enabled; End; Procedure THeaderMenuItem.Loaded; Begin inherited; Self.Enabled := False; End; Procedure THeaderMenuItem.SetEnabled(Const inEnabled: Boolean); Begin inherited Enabled := False; End; End.

Looks like a compiler defect - when changing this declaration: TOnMyIntfItemSelected<T: IMyIntfItem> = procedure(AItem: IMyIntfItem) of object; the code for TMyIntfItemA<T>.Select looks like this: List.Intf.pas.82: begin 007083E4 53 push ebx List.Intf.pas.83: if Assigned(FOnItemSelected) then 007083E5 6683781200 cmp word ptr [eax+$12],$00 007083EA 7411 jz $007083fd List.Intf.pas.84: FOnItemSelected(Self); 007083EC 8BD0 mov edx,eax 007083EE 85D2 test edx,edx 007083F0 7403 jz $007083f5 007083F2 83EAE8 sub edx,-$18 // this is where it turns Self into an IMyIntfItem, $18 is the offset where the interface method table pointer sits inside the object 007083F5 8BD8 mov ebx,eax 007083F7 8B4314 mov eax,[ebx+$14] 007083FA FF5310 call dword ptr [ebx+$10] List.Intf.pas.85: end; 007083FD 5B pop ebx 007083FE C3 ret but when it has the generic T parameter it looks like this: List.Intf.pas.82: begin 007083E4 53 push ebx List.Intf.pas.83: if Assigned(FOnItemSelected) then 007083E5 6683781200 cmp word ptr [eax+$12],$00 007083EA 740A jz $007083f6 List.Intf.pas.84: FOnItemSelected(Self); 007083EC 8BD8 mov ebx,eax 007083EE 8BD0 mov edx,eax // here it simply passes Self 007083F0 8B4314 mov eax,[ebx+$14] 007083F3 FF5310 call dword ptr [ebx+$10] List.Intf.pas.85: end; 007083F6 5B pop ebx 007083F7 C3 ret To explain this a bit more: when putting an interface type as generic type constraint this means for the compiler that the type you put for the generic type argument not only has to be that interface type but also that it can be a class that implements this interface. TMyIntfItemA<T> does this and thus satisfies the compiler when passing it to the argument of that event handler. However, inside the event handler, it is being treated as an interface and due to the lacking const parameter the compiler inserted an IntfAddRef call which blows up as the parameter that was passed was not really an interface reference but an object reference. Putting the const parameter makes it blow up a bit later though, namely when accessing Caption.

What it's like to be a Delphi Developer https://blogs.embarcadero.com/what-is-it-like-to-be-a-developer-joe-c-hecht/

I "played" with it briefly but had to move on to other things. Never got it to work. Maybe I'll try again and spend more time on it when I eventually upgrade to Rad Studio 11... or by some "magic" maybe they will fix C++ Code Insight in 11 and I won't have to waste time on it..

If you don't want instances, then don't make it a class - this ain't Java.

Suggestion: Throw the ENoConstructException from System.SysUtils, not a regular Exception 😉

There is another way to prevent instance creation - or at least misuse - having public constructor that raises exception. TSingleton = class private class var FInstance: TSingleton; constructor CreateSingleton; class destructor ClassDestroy; public constructor Create; class function Instance: TSingleton; static; end; class destructor TSingleton.ClassDestroy; begin FInstance.Free; end; constructor TSingleton.Create; begin raise Exception.Create('Singleton instance cannot be directly constructed'); end; constructor TSingleton.CreateSingleton; begin // actual constructor end; class function TSingleton.Instance: TSingleton; begin if not Assigned(FInstance) then FInstance := TSingleton.CreateSingleton; Result := FInstance; end;

Marco showed a preview of some of what's new in Delphi 11 yesterday - you can read his blog with screenshots, or watch the video replay, here. I'm also giving a talk today on Usability and Design, in general but also referring to the IDE and some decisions we made there. If you've ever wanted to see an internal mockup of things we did not do, this is the one to watch -- but also, I hope the talk in general will be helpful for anyone who wants to have good design in their app. Join this or the other (really good!) talks today and tomorrow here!

In some aspects VS is terrible. It is just a different terrible than the terrible RAD Studio.

That's a strange way to spell C# and Typescript