Fix build without Qt4 headers.

src/core/mainwindow.cpp

@@ -28,6 +28,7 @@
 #include <memory>
 #include <cmath>
 
+#include <QMainWindow>
 #include <QCloseEvent>
 #include <QDir>
 #include <QFileDialog>
@@ -38,11 +39,15 @@
 #include <QSettings>
 #include <QShortcut>
 #include <QSignalMapper>
-#include <QSortFilterProxyModel>
 #include <QStatusBar>
 #include <QtDebug>
 #include <QTimer>
 #include <QUndoStack>
+#include <QSystemTrayIcon>
+#include <QAction>
+#include <QList>
+#include <QModelIndex>
+#include <QSortFilterProxyModel>
 
 #ifdef Q_OS_WIN32
   #include <qtsparkle/Updater>

src/core/mainwindow.h

@@ -28,6 +28,12 @@
 #include <QMainWindow>
 #include <QSettings>
 #include <QSystemTrayIcon>
+#include <QAction>
+#include <QTimer>
+#include <QMenu>
+#include <QList>
+#include <QModelIndex>
+#include <QSortFilterProxyModel>
 
 #include "core/lazy.h"
 #include "core/mac_startup.h"

src/widgets/stylehelper.cpp

@@ -29,14 +29,14 @@
 
 #include "stylehelper.h"
 
-#include <QtGui/QPixmapCache>
-#include <QtGui/QWidget>
-#include <QtCore/QRect>
-#include <QtGui/QPainter>
-#include <QtGui/QApplication>
-#include <QtGui/QPalette>
-#include <QtGui/QStyleOption>
-#include <QtCore/QObject>
+#include <QObject>
+#include <QWidget>
+#include <QApplication>
+#include <QPainter>
+#include <QPalette>
+#include <QRect>
+#include <QPixmapCache>
+#include <QStyleOption>
 
 // Clamps float color values within (0, 255)
 static int clamp(float x)

src/widgets/stylehelper.h

@@ -30,8 +30,8 @@
 #ifndef STYLEHELPER_H
 #define STYLEHELPER_H
 
-#include <QtGui/QColor>
-#include <QtGui/QStyle>
+#include <QColor>
+#include <QStyle>
 
 #include "core/qt_blurimage.h"