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>

1 files changed, 33 insertions, 29 deletions

diff --git a/src/gui/kernel/qpalette.cpp b/src/gui/kernel/qpalette.cpp
index 627731ff20..d5b17fa665 100644
--- a/src/gui/kernel/qpalette.cpp
+++ b/src/gui/kernel/qpalette.cpp
@@ -41,6 +41,7 @@
 
 #include "qpalette.h"
 #include "qguiapplication.h"
+#include "qguiapplication_p.h"
 #include "qdatastream.h"
 #include "qvariant.h"
 #include "qdebug.h"
@@ -64,6 +65,29 @@ static QColor qt_mix_colors(QColor a, QColor b)
                   (a.blue() + b.blue()) / 2, (a.alpha() + b.alpha()) / 2);
 }
 
+static void qt_palette_from_color(QPalette &pal, const QColor &button)
+{
+    int h, s, v;
+    button.getHsv(&h, &s, &v);
+    // inactive and active are the same..
+    const QBrush baseBrush = QBrush(v > 128 ? Qt::white : Qt::black);
+    const QBrush foregroundBrush = QBrush(v > 128 ? Qt::black : Qt::white);
+    const QBrush buttonBrush = QBrush(button);
+    const QBrush buttonBrushDark = QBrush(button.darker());
+    const QBrush buttonBrushDark150 = QBrush(button.darker(150));
+    const QBrush buttonBrushLight150 = QBrush(button.lighter(150));
+    const QBrush whiteBrush = QBrush(Qt::white);
+    pal.setColorGroup(QPalette::Active, foregroundBrush, buttonBrush, buttonBrushLight150,
+                      buttonBrushDark, buttonBrushDark150, foregroundBrush, whiteBrush,
+                      baseBrush, buttonBrush);
+    pal.setColorGroup(QPalette::Inactive, foregroundBrush, buttonBrush, buttonBrushLight150,
+                      buttonBrushDark, buttonBrushDark150, foregroundBrush, whiteBrush,
+                      baseBrush, buttonBrush);
+    pal.setColorGroup(QPalette::Disabled, buttonBrushDark, buttonBrush, buttonBrushLight150,
+                      buttonBrushDark, buttonBrushDark150, buttonBrushDark,
+                      whiteBrush, buttonBrush, buttonBrush);
+}
+
 /*!
    \fn const QColor &QPalette::color(ColorRole role) const
 
@@ -488,40 +512,20 @@ static QColor qt_mix_colors(QColor a, QColor b)
     \sa QApplication::setPalette(), QApplication::palette()
 */
 QPalette::QPalette()
-    : d(QGuiApplication::palette().d),
-      current_group(Active),
-      resolve_mask(0)
-{
-    d->ref.ref();
-}
-
-static void qt_palette_from_color(QPalette &pal, const QColor & button)
+    : d(0), current_group(Active), resolve_mask(0)
 {
-    QColor bg = button,
-           btn = button,
-           fg, base;
-    int h, s, v;
-    bg.getHsv(&h, &s, &v);
-    if(v > 128) {
-        fg   = Qt::black;
-        base = Qt::white;
+    // Initialize to application palette if present, else default to black.
+    // This makes it possible to instantiate QPalette outside QGuiApplication,
+    // for example in the platform plugins.
+    if (QGuiApplicationPrivate::app_pal) {
+        d = QGuiApplicationPrivate::app_pal->d;
+        d->ref.ref();
     } else {
-        fg   = Qt::white;
-        base = Qt::black;
+        init();
+        qt_palette_from_color(*this, Qt::black);
     }
-    //inactive and active are the same..
-    pal.setColorGroup(QPalette::Active, QBrush(fg), QBrush(btn), QBrush(btn.lighter(150)),
-                      QBrush(btn.darker()), QBrush(btn.darker(150)), QBrush(fg), QBrush(Qt::white),
-                      QBrush(base), QBrush(bg));
-    pal.setColorGroup(QPalette::Inactive, QBrush(fg), QBrush(btn), QBrush(btn.lighter(150)),
-                      QBrush(btn.darker()), QBrush(btn.darker(150)), QBrush(fg), QBrush(Qt::white),
-                      QBrush(base), QBrush(bg));
-    pal.setColorGroup(QPalette::Disabled, QBrush(btn.darker()), QBrush(btn), QBrush(btn.lighter(150)),
-                      QBrush(btn.darker()), QBrush(btn.darker(150)), QBrush(btn.darker()),
-                      QBrush(Qt::white), QBrush(bg), QBrush(bg));
 }
 
-
 /*!
   Constructs a palette from the \a button color. The other colors are
   automatically calculated, based on this color. \c Window will be