QMake moc files confused by namespaces

Question

I have a file that looks like:

#ifndef ENGINE_PLATFORM_AREAEDITOR_H
#define ENGINE_PLATFORM_AREAEDITOR_H

#include <QWidget>
#include "../Widgets/QtSfmlWidget.h"

namespace Engine { namespace World { class Area; } }

//This tell's Qt's qmake to ignore the code between MOC_SKIP_BEGIN and MOC_SKIP_END
// MOC_SKIP_BEGIN
#include "Engine/World/Area.h"
// MOC_SKIP_END

namespace Ui {
class AreaEditor;
}

class AreaEditor : public QWidget
{
    Q_OBJECT

public:
    Engine::World::Area area;

public:
    explicit AreaEditor(QWidget *parent = 0);
    ~AreaEditor();

    //...stuff....

private slots:
    void on_markerTextEdit_textChanged();

    void onDrawAreaScreen(sf::RenderTarget &renderTarget);
    void onDrawAreaResized(const WindowSize &windowSize);

private:
    Ui::AreaEditor *ui;

    //...stuff....
};

#endif //ENGINE_PLATFORM_AREAEDITOR_H

However, when Qt is generating the _moc file, it incorrectly thinks 'AreaEditor' is in the namespace 'Engine', which then causes the compile to fail.

Here's an example snippet of the moc file that QMake is generating:

      ______/---------<-< Wrong       
     V      V
void Engine::AreaEditor::qt_static_metacall(QObject *_o, QMetaObject::Call _c, int _id, void **_a)
{
    if (_c == QMetaObject::InvokeMetaMethod) {
        AreaEditor *_t = static_cast<AreaEditor *>(_o);
        switch (_id) {
        case 0: _t->on_markerTextEdit_textChanged(); break;
        case 1: _t->onDrawAreaScreen((*reinterpret_cast< sf::RenderTarget(*)>(_a[1]))); break;
        case 2: _t->onDrawAreaResized((*reinterpret_cast< const WindowSize(*)>(_a[1]))); break;
        default: ;
        }
    }
}

Here's what it should be:

void AreaEditor::qt_static_metacall(QObject *_o, QMetaObject::Call _c, int _id, void **_a)

The header file "Engine/World/Area.h" has a class called 'Area' that is in a namespace 'Engine' (actually, it's in 'Engine::World::", two nested namespaces). It seems like this is confusing QMake in some way!

If I remove the #include, commenting it out, everything compiles fine (except I have to pre-declare 'Area', and then can only use it as a pointer or a reference in the class).

So I tried wrapping the #include in a "MOC_SKIP_BEGIN", which I can find seemingly archaic references to online, hoping QMake will skip that header. Nope, still fails to compile.

Is there a way I can get this to compile while still being able to include the header I want to include?

Answer 1

From the documentation:

http://qt-project.org/doc/qt-5.0/qtdoc/moc.html#command-line-options

You can explicitly tell the moc not to parse parts of a header file. moc defines the preprocessor symbol Q_MOC_RUN. Any code surrounded by

#ifndef Q_MOC_RUN
...
#endif

is skipped by the moc.