How to fix a delayed declaration in UxTheme

Question

In Delphi XE UxTheme unit there is the following declaration

function DrawThemeTextEx(hTheme: HTHEME; hdc: HDC; iPartId: Integer;  iStateId: Integer;
  pszText: LPCWSTR; cchText: Integer; dwTextFlags: DWORD; pRect: PRect;
  var pOptions: TDTTOpts): HResult; stdcall; 
  external themelib name 'DrawThemeTextEx' delayed;

My Windows XP Professional with SP3 does not have such function in the uxtheme.dll (checked with dllexp.exe from http://www.nirsoft.net/utils/dll_export_viewer.html)

It seems like my application does delayed loading of the procedure and fails runtime with the following error:

Project mtgstudio.exe raised exception class EExternalException 
with message 'External exception C0FB007F'.

The issue was encountered in JVCL as well but resolved there as per http://andy.jgknet.de/blog/2009/09/once-upon-a-delayed-jvcl-time/

I need UxTheme fixed because they are used by the DevExpress components as well.

Is there a way to patch/fix the UxTheme.pas DrawThemeTextEx declaration to be non-delayed?

Also reported for JVCL at http://issuetracker.delphi-jedi.org/view.php?id=4934 — Gad D Lord, Aug 23 '11 at 11:52
Similar delayed issue also reported at http://embarcadero.newsgroups.archived.at/public.delphi.language.delphi.win32/200906/0906224130.html — Gad D Lord, Aug 23 '11 at 12:13
Andy's blog post seems to explain the problem (and how to fix it) very clearly. You can then fix the DevEx components (until they do) by changing their code to use the Jvcl version instead of the normal UxTheme. — Ken White, Aug 23 '11 at 12:33
@mj2008: I didn't think it provided enough detail to make it an answer. :) — Ken White, Aug 23 '11 at 12:50
@Gad: So you want the app to crasch on startup instead of later on? — Andreas Rejbrand, Aug 23 '11 at 13:58

score 6 · Accepted Answer · answered Aug 23 '11 at 13:26

The fundamental problem is that this API was introduced in Vista and is not available in XP.

The whole point of the delayed keyword is to allow functions like this to be made available easily to developers who want to take advantage of newer API functions. But to do so the developer typically must also provide fallback implementations for older OS versions, which DevExpress appear to have failed to do.

The bug is therefore not in UxTheme.pas, but in the DevExpress component that calls an API that is not implemented on the platform. The fix is to re-work the DevExpress code to avoid calling this API on XP.

I suggest you contact DevExpress who quite probably already have a fix in their latest versions.

How to fix a delayed declaration in UxTheme

1 Answers1