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, 14 insertions, 0 deletions

diff --git a/src/plugins/platforms/cocoa/qcocoatheme.h b/src/plugins/platforms/cocoa/qcocoatheme.h
index 08f813b906..a7dc973937 100644
--- a/src/plugins/platforms/cocoa/qcocoatheme.h
+++ b/src/plugins/platforms/cocoa/qcocoatheme.h
@@ -59,6 +59,8 @@ public:
 
     bool usePlatformNativeDialog(DialogType dialogType) const;
     QPlatformDialogHelper *createPlatformDialogHelper(DialogType dialogType) const;
+
+    QVariant themeHint(ThemeHint hint) const;
 };
 
 QT_END_NAMESPACE
diff --git a/src/plugins/platforms/cocoa/qcocoatheme.mm b/src/plugins/platforms/cocoa/qcocoatheme.mm
index a23faf438d..ad20c2fb27 100644
--- a/src/plugins/platforms/cocoa/qcocoatheme.mm
+++ b/src/plugins/platforms/cocoa/qcocoatheme.mm
@@ -102,4 +102,16 @@ QPlatformDialogHelper * QCocoaTheme::createPlatformDialogHelper(DialogType dialo
     }
 }
 
+QVariant QCocoaTheme::themeHint(ThemeHint hint) const
+{
+    switch (hint) {
+        case QPlatformTheme::StyleNames:
+            return QStringList() << QLatin1Literal("macintosh");
+        break;
+        default:
+            return QPlatformTheme::themeHint(hint);
+        break;
+    }
+}
+
 QT_END_NAMESPACE