Refactor theme plugin loading.

In the old implementation, the QPlatformIntegration was asked
for the theme first, so there was no way of overriding that
by a custom plugin. Also, there was a memory leak in case
the platform theme was actually created by a plugin.

QGuiApplication now asks the QPlatformIntegration for a list
of potential theme names first, tries to load them using
the plugin loader and finally invokes a factory method of
QPlatformIntegration in case that fails. The theme is now
owned by QGuiApplication.

In the XCB plugin, the environment variable DESKTOP_SESSION
is queried and appended to the list of themes, making it possible
to load plugins for other session types.

Change-Id: I1a4b4e061815bca16c65b23e591bb7563a3e44e2
Reviewed-by: Samuel Rødal <samuel.rodal@nokia.com>

11 files changed, 49 insertions, 21 deletions

diff --git a/src/plugins/platforms/cocoa/qcocoaintegration.h b/src/plugins/platforms/cocoa/qcocoaintegration.h
index 2389fc2a55..9248df0d37 100644
--- a/src/plugins/platforms/cocoa/qcocoaintegration.h
+++ b/src/plugins/platforms/cocoa/qcocoaintegration.h
@@ -93,7 +93,9 @@ public:
     QPlatformAccessibility *accessibility() const;
     QPlatformDrag *drag() const;
 
-    QPlatformTheme *platformTheme() const;
+    QStringList themeNames() const;
+    QPlatformTheme *createPlatformTheme(const QString &name) const;
+
 private:
 
     QScopedPointer<QPlatformFontDatabase> mFontDb;
diff --git a/src/plugins/platforms/cocoa/qcocoaintegration.mm b/src/plugins/platforms/cocoa/qcocoaintegration.mm
index d490495be4..96027e0925 100644
--- a/src/plugins/platforms/cocoa/qcocoaintegration.mm
+++ b/src/plugins/platforms/cocoa/qcocoaintegration.mm
@@ -93,7 +93,6 @@ QCocoaIntegration::QCocoaIntegration()
     , mEventDispatcher(new QCocoaEventDispatcher())
     , mInputContext(new QCocoaInputContext)
     , mAccessibility(new QPlatformAccessibility)
-    , mPlatformTheme(new QCocoaTheme)
     , mCocoaDrag(new QCocoaDrag)
 {
     QCocoaAutoReleasePool pool;
@@ -212,9 +211,16 @@ QPlatformDrag *QCocoaIntegration::drag() const
     return mCocoaDrag.data();
 }
 
-QPlatformTheme *QCocoaIntegration::platformTheme() const
+QStringList QCocoaIntegration::themeNames() const
 {
-    return mPlatformTheme.data();
+    return QStringList(QLatin1String(QCocoaTheme::name));
+}
+
+QPlatformTheme *QCocoaIntegration::createPlatformTheme(const QString &name) const
+{
+    if (name == QLatin1String(QCocoaTheme::name))
+        return new QCocoaTheme;
+    return QPlatformIntegration::createPlatformTheme(name);
 }
 
 QT_END_NAMESPACE
diff --git a/src/plugins/platforms/cocoa/qcocoatheme.h b/src/plugins/platforms/cocoa/qcocoatheme.h
index 030db1822c..5cb6f7437d 100644
--- a/src/plugins/platforms/cocoa/qcocoatheme.h
+++ b/src/plugins/platforms/cocoa/qcocoatheme.h
@@ -64,6 +64,9 @@ public:
     const QFont *font(Font type = SystemFont) const;
 
     QVariant themeHint(ThemeHint hint) const;
+
+    static const char *name;
+
 private:
     mutable QPalette *m_systemPalette;
     mutable QHash<QPlatformTheme::Palette, QPalette*> m_palettes;
diff --git a/src/plugins/platforms/cocoa/qcocoatheme.mm b/src/plugins/platforms/cocoa/qcocoatheme.mm
index 8ec6e3801e..d17ee30096 100644
--- a/src/plugins/platforms/cocoa/qcocoatheme.mm
+++ b/src/plugins/platforms/cocoa/qcocoatheme.mm
@@ -49,6 +49,8 @@
 
 QT_BEGIN_NAMESPACE
 
+const char *QCocoaTheme::name = "cocoa";
+
 QCocoaTheme::QCocoaTheme()
     :m_systemPalette(0)
 {
diff --git a/src/plugins/platforms/windows/qwindowscontext.cpp b/src/plugins/platforms/windows/qwindowscontext.cpp
index e8050d5027..f61e40ef77 100644
--- a/src/plugins/platforms/windows/qwindowscontext.cpp
+++ b/src/plugins/platforms/windows/qwindowscontext.cpp
@@ -788,7 +788,8 @@ bool QWindowsContext::windowsProc(HWND hwnd, UINT message,
         QWindowSystemInterface::handleCloseEvent(platformWindow->window());
         return true;
     case QtWindows::ThemeChanged: // ### fixme: Compress these events?
-        QWindowsTheme::instance()->windowsThemeChanged(platformWindow->window());
+        if (QWindowsTheme *theme = QWindowsTheme::instance())
+            theme->windowsThemeChanged(platformWindow->window());
         return true;
     default:
         break;
diff --git a/src/plugins/platforms/windows/qwindowsintegration.cpp b/src/plugins/platforms/windows/qwindowsintegration.cpp
index 7510cded50..ee58a19ca9 100644
--- a/src/plugins/platforms/windows/qwindowsintegration.cpp
+++ b/src/plugins/platforms/windows/qwindowsintegration.cpp
@@ -183,7 +183,6 @@ struct QWindowsIntegrationPrivate
     QOpenGLStaticContextPtr m_staticOpenGLContext;
     QWindowsInputContext m_inputContext;
     QWindowsAccessibility m_accessibility;
-    QWindowsTheme m_theme;
     QWindowsServices m_services;
 };
 
@@ -362,9 +361,16 @@ QAbstractEventDispatcher * QWindowsIntegration::guiThreadEventDispatcher() const
     return d->m_eventDispatcher;
 }
 
-QPlatformTheme *QWindowsIntegration::platformTheme() const
+QStringList QWindowsIntegration::themeNames() const
 {
-    return &d->m_theme;
+    return QStringList(QLatin1String(QWindowsTheme::name));
+}
+
+QPlatformTheme *QWindowsIntegration::createPlatformTheme(const QString &name) const
+{
+    if (name == QLatin1String(QWindowsTheme::name))
+        return new QWindowsTheme;
+    return QPlatformIntegration::createPlatformTheme(name);
 }
 
 QPlatformServices *QWindowsIntegration::services() const
diff --git a/src/plugins/platforms/windows/qwindowsintegration.h b/src/plugins/platforms/windows/qwindowsintegration.h
index 6dd65a02e4..20fd790bfe 100644
--- a/src/plugins/platforms/windows/qwindowsintegration.h
+++ b/src/plugins/platforms/windows/qwindowsintegration.h
@@ -69,7 +69,8 @@ public:
     virtual QPlatformAccessibility *accessibility() const;
     virtual QPlatformNativeInterface *nativeInterface() const;
     virtual QPlatformFontDatabase *fontDatabase() const;
-    virtual QPlatformTheme *platformTheme() const;
+    virtual QStringList themeNames() const;
+    virtual QPlatformTheme *createPlatformTheme(const QString &name) const;
     QPlatformServices *services() const;
     virtual QVariant styleHint(StyleHint hint) const;
 
diff --git a/src/plugins/platforms/windows/qwindowstheme.cpp b/src/plugins/platforms/windows/qwindowstheme.cpp
index f10595fa79..f3a9d91d00 100644
--- a/src/plugins/platforms/windows/qwindowstheme.cpp
+++ b/src/plugins/platforms/windows/qwindowstheme.cpp
@@ -229,8 +229,12 @@ static inline QPalette *menuBarPalette(const QPalette &menuPalette)
     return result;
 }
 
+const char *QWindowsTheme::name = "windows";
+QWindowsTheme *QWindowsTheme::m_instance = 0;
+
 QWindowsTheme::QWindowsTheme()
 {
+    m_instance = this;
     qFill(m_fonts, m_fonts + NFonts, static_cast<QFont *>(0));
     qFill(m_palettes, m_palettes + NPalettes, static_cast<QPalette *>(0));
     refresh();
@@ -240,11 +244,7 @@ QWindowsTheme::~QWindowsTheme()
 {
     clearPalettes();
     clearFonts();
-}
-
-QWindowsTheme *QWindowsTheme::instance()
-{
-    return static_cast<QWindowsTheme *>(QWindowsIntegration::instance()->platformTheme());
+    m_instance = 0;
 }
 
 static inline QStringList iconThemeSearchPaths()
diff --git a/src/plugins/platforms/windows/qwindowstheme.h b/src/plugins/platforms/windows/qwindowstheme.h
index 37346eed3a..7515a13a72 100644
--- a/src/plugins/platforms/windows/qwindowstheme.h
+++ b/src/plugins/platforms/windows/qwindowstheme.h
@@ -57,7 +57,7 @@ public:
     QWindowsTheme();
     ~QWindowsTheme();
 
-    static QWindowsTheme *instance();
+    static QWindowsTheme *instance() { return m_instance; }
 
     virtual bool usePlatformNativeDialog(DialogType type) const;
     virtual QPlatformDialogHelper *createPlatformDialogHelper(DialogType type) const;
@@ -69,6 +69,8 @@ public:
 
     void windowsThemeChanged(QWindow *window);
 
+    static const char *name;
+
 private:
     void refresh() { refreshPalettes(); refreshFonts(); }
     void clearPalettes();
@@ -76,6 +78,7 @@ private:
     void clearFonts();
     void refreshFonts();
 
+    static QWindowsTheme *m_instance;
     QPalette *m_palettes[NPalettes];
     QFont *m_fonts[NFonts];
 };
diff --git a/src/plugins/platforms/xcb/qxcbintegration.cpp b/src/plugins/platforms/xcb/qxcbintegration.cpp
index fe33bd7153..0db9ef9e64 100644
--- a/src/plugins/platforms/xcb/qxcbintegration.cpp
+++ b/src/plugins/platforms/xcb/qxcbintegration.cpp
@@ -88,8 +88,7 @@ QT_BEGIN_NAMESPACE
 
 QXcbIntegration::QXcbIntegration(const QStringList &parameters)
     : m_eventDispatcher(createUnixEventDispatcher()),
-      m_services(new QGenericUnixServices),
-      m_theme(QGenericUnixTheme::createUnixTheme())
+      m_services(new QGenericUnixServices)
 {
     QGuiApplicationPrivate::instance()->setEventDispatcher(m_eventDispatcher);
 
@@ -277,9 +276,14 @@ QPlatformServices *QXcbIntegration::services() const
     return m_services.data();
 }
 
-QPlatformTheme *QXcbIntegration::platformTheme() const
+QStringList QXcbIntegration::themeNames() const
 {
-    return m_theme.data();
+    return QGenericUnixTheme::themeNames();
+}
+
+QPlatformTheme *QXcbIntegration::createPlatformTheme(const QString &name) const
+{
+    return QGenericUnixTheme::createUnixTheme(name);
 }
 
 QT_END_NAMESPACE
diff --git a/src/plugins/platforms/xcb/qxcbintegration.h b/src/plugins/platforms/xcb/qxcbintegration.h
index 457f90d6e0..4c335f2f06 100644
--- a/src/plugins/platforms/xcb/qxcbintegration.h
+++ b/src/plugins/platforms/xcb/qxcbintegration.h
@@ -85,7 +85,8 @@ public:
 
     QPlatformServices *services() const;
 
-    QPlatformTheme *platformTheme() const;
+    QStringList themeNames() const;
+    QPlatformTheme *createPlatformTheme(const QString &name) const;
 
 private:
     QList<QXcbConnection *> m_connections;
@@ -103,7 +104,6 @@ private:
 #endif
 
     QScopedPointer<QPlatformServices> m_services;
-    QScopedPointer<QPlatformTheme> m_theme;
 };
 
 QT_END_NAMESPACE