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>

src/gui/kernel/qguiapplication.cpp

@@ -538,13 +538,22 @@ static void init_platform(const QString &pluginArgument, const QString &platform
     }
 
     // Create the platform theme:
-    // 1) Ask the platform integration to create a platform theme
-    QGuiApplicationPrivate::platform_theme = QGuiApplicationPrivate::platform_integration->platformTheme();
+    // 1) Ask the platform integration for a list of names.
+    const QStringList themeNames = QGuiApplicationPrivate::platform_integration->themeNames();
+    foreach (const QString &themeName, themeNames) {
+        QGuiApplicationPrivate::platform_theme = QPlatformThemeFactory::create(themeName, platformPluginPath);
+        if (QGuiApplicationPrivate::platform_theme)
+            break;
+    }
 
     // 2) If none found, look for a theme plugin. Theme plugins are located in the
     // same directory as platform plugins.
     if (!QGuiApplicationPrivate::platform_theme) {
-        QGuiApplicationPrivate::platform_theme = QPlatformThemeFactory::create(name, platformPluginPath);
+        foreach (const QString &themeName, themeNames) {
+            QGuiApplicationPrivate::platform_theme = QGuiApplicationPrivate::platform_integration->createPlatformTheme(themeName);
+            if (QGuiApplicationPrivate::platform_theme)
+                break;
+        }
         // No error message; not having a theme plugin is allowed.
     }
 
@@ -748,6 +757,7 @@ QGuiApplicationPrivate::~QGuiApplicationPrivate()
 
     qt_cleanupFontDatabase();
 
+    delete  platform_theme;
     delete platform_integration;
     platform_integration = 0;
 }

src/gui/kernel/qplatformintegration_qpa.cpp

@@ -44,6 +44,7 @@
 #include <QtGui/QPlatformFontDatabase>
 #include <QtGui/QPlatformClipboard>
 #include <QtGui/QPlatformAccessibility>
+#include <QtGui/QPlatformTheme>
 #include <QtGui/private/qguiapplication_p.h>
 #include <QtGui/private/qpixmap_raster_p.h>
 #include <QtGui/private/qplatformscreen_qpa_p.h>
@@ -315,9 +316,15 @@ void QPlatformIntegration::screenAdded(QPlatformScreen *ps)
     emit qGuiApp->screenAdded(screen);
 }
 
-class QPlatformTheme *QPlatformIntegration::platformTheme() const
+QStringList QPlatformIntegration::themeNames() const
 {
-    return 0;
+    return QStringList();
+}
+
+class QPlatformTheme *QPlatformIntegration::createPlatformTheme(const QString &name) const
+{
+    Q_UNUSED(name)
+    return new QPlatformTheme;
 }
 
 QT_END_NAMESPACE

src/gui/kernel/qplatformintegration_qpa.h

@@ -126,7 +126,8 @@ public:
 
     virtual Qt::KeyboardModifiers queryKeyboardModifiers() const;
 
-    virtual QPlatformTheme *platformTheme() const;
+    virtual QStringList themeNames() const;
+    virtual QPlatformTheme *createPlatformTheme(const QString &name) const;
 
 protected:
     void screenAdded(QPlatformScreen *screen);

src/platformsupport/themes/genericunix/qgenericunixthemes.cpp

@@ -77,6 +77,8 @@ void ResourceHelper::clear()
     \ingroup qpa
 */
 
+const char *QGenericUnixTheme::name = "generic";
+
 // Helper to return the icon theme paths from XDG.
 QStringList QGenericUnixTheme::xdgIconThemePaths()
 {
@@ -159,6 +161,8 @@ static inline bool readKdeSystemPalette(const QSettings &kdeSettings, QPalette *
     \ingroup qpa
 */
 
+const char *QKdeTheme::name = "kde";
+
 QKdeTheme::QKdeTheme(const QString &kdeHome, int kdeVersion) :
     m_kdeHome(kdeHome), m_kdeVersion(kdeVersion),
     m_toolButtonStyle(Qt::ToolButtonTextBesideIcon), m_toolBarIconSize(0)
@@ -329,6 +333,8 @@ QPlatformTheme *QKdeTheme::createKdeTheme()
     \ingroup qpa
 */
 
+const char *QGnomeTheme::name = "gnome";
+
 QVariant QGnomeTheme::themeHint(QPlatformTheme::ThemeHint hint) const
 {
     switch (hint) {
@@ -358,23 +364,38 @@ QVariant QGnomeTheme::themeHint(QPlatformTheme::ThemeHint hint) const
     \brief Creates a UNIX theme according to the detected desktop environment.
 */
 
-QPlatformTheme *QGenericUnixTheme::createUnixTheme()
+QPlatformTheme *QGenericUnixTheme::createUnixTheme(const QString &name)
 {
-    QPlatformTheme *result = 0;
+    if (name == QLatin1String(QGenericUnixTheme::name))
+        return new QGenericUnixTheme;
+    if (name == QLatin1String(QKdeTheme::name))
+        if (QPlatformTheme *kdeTheme = QKdeTheme::createKdeTheme())
+            return kdeTheme;
+    if (name == QLatin1String(QGnomeTheme::name))
+        return new QGnomeTheme;
+    return new QGenericUnixTheme;
+}
+
+QStringList QGenericUnixTheme::themeNames()
+{
+    QStringList result;
     if (QGuiApplication::desktopSettingsAware()) {
         switch (QGenericUnixServices::desktopEnvironment()) {
-        case QGenericUnixServices::DE_UNKNOWN:
-            break;
         case QGenericUnixServices::DE_KDE:
-            result = QKdeTheme::createKdeTheme();
+            result.push_back(QLatin1String(QKdeTheme::name));
             break;
         case QGenericUnixServices::DE_GNOME:
-            result = new QGnomeTheme;
+            result.push_back(QLatin1String(QGnomeTheme::name));
+            break;
+        case QGenericUnixServices::DE_UNKNOWN:
             break;
         }
-    }
-    if (!result)
-        result = new QGenericUnixTheme;
+        const QByteArray session = qgetenv("DESKTOP_SESSION");
+        if (!session.isEmpty() && session != "default")
+            result.push_back(QString::fromLocal8Bit(session));
+    } // desktopSettingsAware
+    if (result.isEmpty())
+        result.push_back(QLatin1String(QGenericUnixTheme::name));
     return result;
 }
 

src/platformsupport/themes/genericunix/qgenericunixthemes_p.h

@@ -67,11 +67,14 @@ class QGenericUnixTheme : public QPlatformTheme
 public:
     QGenericUnixTheme() {}
 
-    static QPlatformTheme *createUnixTheme();
+    static QPlatformTheme *createUnixTheme(const QString &name);
+    static QStringList themeNames();
 
     virtual QVariant themeHint(ThemeHint hint) const;
 
     static QStringList xdgIconThemePaths();
+
+    static const char *name;
 };
 
 class QKdeTheme : public QPlatformTheme
@@ -88,6 +91,8 @@ public:
     virtual const QFont *font(Font type) const
         { return m_resources.fonts[type]; }
 
+    static const char *name;
+
 private:
     QString globalSettingsFile() const;
     void refresh();
@@ -109,6 +114,8 @@ public:
     QGnomeTheme() {}
     virtual QVariant themeHint(ThemeHint hint) const;
 
+    static const char *name;
+
 private:
 };
 

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;

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

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;

src/plugins/platforms/cocoa/qcocoatheme.mm

@@ -49,6 +49,8 @@
 
 QT_BEGIN_NAMESPACE
 
+const char *QCocoaTheme::name = "cocoa";
+
 QCocoaTheme::QCocoaTheme()
     :m_systemPalette(0)
 {

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;

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

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;
 

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()

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];
 };

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

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