Apply Windows Theme to Office Com add-in

Question

For ages, Delphi has supported the Enable runtime themes switch on the Application Settings tab. However, this only works for executables. DLLs are assumed to take

Answer 1

I've done this for my COM add-in. I used activation contexts. It's pretty easy for a COM add-in because the surface area of the add-in interface is so small. I could post code but I won't be at a machine with it on until tomorrow. Hope this helps!

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UPDATE

As promised, here is the code that I use:

type
  (* TActivationContext is a loose wrapper around the Windows Activation Context API and can be used
     to ensure that comctl32 v6 and visual styles are available for UI elements created from a DLL .*)
  TActivationContext = class
  private
    FCookie: LongWord;
    FSucceeded: Boolean;
  public
    constructor Create;
    destructor Destroy; override;
  end;

var
  ActCtxHandle: THandle=INVALID_HANDLE_VALUE;
  CreateActCtx: function(var pActCtx: TActCtx): THandle; stdcall;
  ActivateActCtx: function(hActCtx: THandle; var lpCookie: LongWord): BOOL; stdcall;
  DeactivateActCtx: function(dwFlags: DWORD; ulCookie: LongWord): BOOL; stdcall;
  ReleaseActCtx: procedure(hActCtx: THandle); stdcall;

constructor TActivationContext.Create;
begin
  inherited;
  FSucceeded := (ActCtxHandle<>INVALID_HANDLE_VALUE) and ActivateActCtx(ActCtxHandle, FCookie);
end;

destructor TActivationContext.Destroy;
begin
  if FSucceeded then begin
    DeactivateActCtx(0, FCookie);
  end;
  inherited;
end;

procedure InitialiseActivationContext;
var
  ActCtx: TActCtx;
  hKernel32: HMODULE;
begin
  if IsLibrary then begin
    hKernel32 := GetModuleHandle(kernel32);
    CreateActCtx := GetProcAddress(hKernel32, 'CreateActCtxW');
    if Assigned(CreateActCtx) then begin
      ReleaseActCtx := GetProcAddress(hKernel32, 'ReleaseActCtx');
      ActivateActCtx := GetProcAddress(hKernel32, 'ActivateActCtx');
      DeactivateActCtx := GetProcAddress(hKernel32, 'DeactivateActCtx');
      ZeroMemory(@ActCtx, SizeOf(ActCtx));
      ActCtx.cbSize := SizeOf(ActCtx);
      ActCtx.dwFlags := ACTCTX_FLAG_RESOURCE_NAME_VALID or ACTCTX_FLAG_HMODULE_VALID;
      ActCtx.lpResourceName := MakeIntResource(2);//ID of manifest resource in isolation aware DLL
      ActCtx.hModule := HInstance;
      ActCtxHandle := CreateActCtx(ActCtx);
    end;
  end;
end;

procedure FinaliseActivationContext;
begin
  if ActCtxHandle<>INVALID_HANDLE_VALUE then begin
    ReleaseActCtx(ActCtxHandle);
  end;
end;

initialization
  InitialiseActivationContext;

finalization
  FinaliseActivationContext;

When you want to use this, you simply write code like so:

var
  ActivationContext: TActivationContext;
....
ActivationContext := TActivationContext.Create;
try
  //GUI code in here will support XP themes
finally
  ActivationContext.Free;
end;

You need each entry point that does GUI work to be wrapped in such code.

Note that in my COM add-in DLL I have taken special measures to avoid running code during DLLMain, and so my calls to InitialiseActivationContext and FinaliseActivationContext are not in unit initialization/finalization sections. However, I see no reason why this code would not be safe to place there.