Add palette() and further hints to QtGui/QPlatformTheme.

- Move palette() from deprecated QtWidgets/QGuiPlatformPlugin
  to  QtGui/QPlatformTheme, Make it return a const * since
  QPalette does not have isNull().
- Initialize QGuiApplication::palette() and
  QApplication::systemPalette() from it.
- Do not initialize QPalette from QGuiApplication::palette()
  unless app_pal is non-null (default to Qt::black if it is 0).
  This avoids initialization order crashes/recursions in the
  QPA plugin. Streamline initialization function.
- Remove styleName(), systemIconThemeName() and iconSearchPaths()
  from QGuiPlatformPlugin and re-add them as
  QPlatformTheme::themeHint().
- Remove styleHint() from QGuiPlatformPlugin, add it to
  QPlatformTheme::themeHint().
- Add UNIX themes with factory function (Generic,
  KDE, Gnome), taking it from Qt 4.8 code (stripping the
  KDE 3 code).
- Implement Windows palettes.

Task-number: QTBUG-24204

Change-Id: Ie27ec035df4f84c42deaffc4816b2e53ce705462
Reviewed-by: Morten Johan Sørvig <morten.sorvig@nokia.com>

2 files changed, 11 insertions, 1 deletions

diff --git a/src/plugins/platforms/xcb/qxcbintegration.cpp b/src/plugins/platforms/xcb/qxcbintegration.cpp
index c976e75dbf..e7cdef4da9 100644
--- a/src/plugins/platforms/xcb/qxcbintegration.cpp
+++ b/src/plugins/platforms/xcb/qxcbintegration.cpp
@@ -70,6 +70,7 @@
 #endif
 
 #include <private/qplatforminputcontextfactory_qpa_p.h>
+#include <private/qgenericunixthemes_p.h>
 #include <qplatforminputcontext_qpa.h>
 
 #if defined(XCB_USE_GLX)
@@ -87,7 +88,8 @@ QT_BEGIN_NAMESPACE
 
 QXcbIntegration::QXcbIntegration(const QStringList &parameters)
     : m_eventDispatcher(createUnixEventDispatcher()),
-      m_services(new QGenericUnixServices)
+      m_services(new QGenericUnixServices),
+      m_theme(QGenericUnixTheme::createUnixTheme())
 {
     QGuiApplicationPrivate::instance()->setEventDispatcher(m_eventDispatcher);
 
@@ -278,4 +280,9 @@ QPlatformServices *QXcbIntegration::services() const
     return m_services.data();
 }
 
+QPlatformTheme *QXcbIntegration::platformTheme() const
+{
+    return m_theme.data();
+}
+
 QT_END_NAMESPACE
diff --git a/src/plugins/platforms/xcb/qxcbintegration.h b/src/plugins/platforms/xcb/qxcbintegration.h
index 0f20658c70..457f90d6e0 100644
--- a/src/plugins/platforms/xcb/qxcbintegration.h
+++ b/src/plugins/platforms/xcb/qxcbintegration.h
@@ -85,6 +85,8 @@ public:
 
     QPlatformServices *services() const;
 
+    QPlatformTheme *platformTheme() const;
+
 private:
     QList<QXcbConnection *> m_connections;
 
@@ -101,6 +103,7 @@ private:
 #endif
 
     QScopedPointer<QPlatformServices> m_services;
+    QScopedPointer<QPlatformTheme> m_theme;
 };
 
 QT_END_NAMESPACE