Ah. Thanks for that. I had it in one place, removing that cleared up my code.

But…

Now these lines would never work in /vstgui/vstgui.h : 68

#if !defined (VSTGUI_DISABLE_GLOBAL_NAMESPACE_POLLUTION) || VSTGUI_DISABLE_GLOBAL_NAMESPACE_POLLUTION == 0
using namespace VSTGUI;
#endif

So that macro needs to be defined always?

When I define it in my project it seems we need a couple of fixes in aeffguieditor.h/cpp

aeffguieditor.h : 21
class AEffGUIEditor : public AEffEditor, public **VSTGUI::**VSTGUIEditorInterface

aeffguieditor.h : 59
virtual bool beforeSizeChange (const **VSTGUI::**CRect& newSize, const **VSTGUI::**CRect& oldSize);

and the same in aeffguieditor.cpp : 113
int32_t AEffGUIEditor::knobMode = **VSTGUI::**kCircularMode;

and aeffguieditor.cpp : 204
bool AEffGUIEditor::beforeSizeChange (const **VSTGUI::**CRect& newSize, const **VSTGUI::**CRect& oldSize)

Am I missing something else?

=====
EDIT next day:

I managed to compile without the VSTGUI_DISABLE_GLOBAL_NAMESPACE_POLLUTION macro,
while also getting away from the IDropTarget redefinition errors.

This is done by moving
#include <windows.h>

so that it precedes any vstgui header inclusion.
At least in aeffguieditor.cpp as well as any of your own files (your AudioEffectX implementation file for instance)

And you need to
#undef max
#undef min

EDIT next day
(and define UNICODE in preprocessor flags, else aeffguieditor.cpp fails. I probably lost that while fiddling the other flags)
Was in this edit, but it’s irrelevant to thread topic, so removed now.

Thanks,
/rasmus