QColorDialog: don't create widgets if the platform dialog will be used

It will save memory and also prevent bugs where it's assumed that if
the widgets exist, they should be painted, maintained and/or used as a
current value store.

Task-number: QTBUG-31998
Change-Id: I04e3b016018221a405dd7da1fd455e0ede2233fd
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Reviewed-by: J-P Nurmi <jpnurmi@digia.com>

src/widgets/dialogs/qcolordialog.cpp

@@ -1267,7 +1267,7 @@ inline bool QColorDialogPrivate::isAlphaVisible() const { return cs->isAlphaVisi
 
 QColor QColorDialogPrivate::currentQColor() const
 {
-    if (!options->testOption(QColorDialogOptions::DontUseNativeDialog) && nativeDialogInUse)
+    if (nativeDialogInUse)
         return platformColorDialogHelper()->currentColor();
     return cs->currentQColor();
 }
@@ -1410,16 +1410,20 @@ void QColorShower::updateQColor()
 //sets all widgets to display h,s,v
 void QColorDialogPrivate::_q_newHsv(int h, int s, int v)
 {
-    cs->setHsv(h, s, v);
-    cp->setCol(h, s);
-    lp->setCol(h, s, v);
+    if (!nativeDialogInUse) {
+        cs->setHsv(h, s, v);
+        cp->setCol(h, s);
+        lp->setCol(h, s, v);
+    }
 }
 
 //sets all widgets to display rgb
 void QColorDialogPrivate::setCurrentColor(QRgb rgb)
 {
-    cs->setRgb(rgb);
-    _q_newColorTypedIn(rgb);
+    if (!nativeDialogInUse) {
+        cs->setRgb(rgb);
+        _q_newColorTypedIn(rgb);
+    }
 }
 
 // hack; doesn't keep curCol in sync, so use with care
@@ -1481,10 +1485,12 @@ QColor QColorDialogPrivate::grabScreenColor(const QPoint &p)
 //sets all widgets except cs to display rgb
 void QColorDialogPrivate::_q_newColorTypedIn(QRgb rgb)
 {
-    int h, s, v;
-    rgb2hsv(rgb, h, s, v);
-    cp->setCol(h, s);
-    lp->setCol(h, s, v);
+    if (!nativeDialogInUse) {
+        int h, s, v;
+        rgb2hsv(rgb, h, s, v);
+        cp->setCol(h, s);
+        lp->setCol(h, s, v);
+    }
 }
 
 void QColorDialogPrivate::_q_newCustom(int r, int c)
@@ -1552,9 +1558,24 @@ void QColorDialogPrivate::init(const QColor &initial)
     q->setSizeGripEnabled(false);
     q->setWindowTitle(QColorDialog::tr("Select Color"));
 
+    // default: use the native dialog if possible.  Can be overridden in setOptions()
     nativeDialogInUse = (platformColorDialogHelper() != 0);
     screenColorPicking = false;
     nextCust = 0;
+
+    if (!nativeDialogInUse)
+        initWidgets();
+
+#ifdef Q_WS_MAC
+    delegate = 0;
+#endif
+
+    q->setCurrentColor(initial);
+}
+
+void QColorDialogPrivate::initWidgets()
+{
+    Q_Q(QColorDialog);
     QVBoxLayout *mainLay = new QVBoxLayout(q);
     // there's nothing in this dialog that benefits from sizing up
     mainLay->setSizeConstraint(QLayout::SetFixedSize);
@@ -1700,12 +1721,6 @@ void QColorDialogPrivate::init(const QColor &initial)
     QObject::connect(cancel, SIGNAL(clicked()), q, SLOT(reject()));
 
     retranslateStrings();
-
-#ifdef Q_WS_MAC
-    delegate = 0;
-#endif
-
-    q->setCurrentColor(initial);
 }
 
 void QColorDialogPrivate::initHelper(QPlatformDialogHelper *h)
@@ -1816,12 +1831,13 @@ QColorDialog::QColorDialog(const QColor &initial, QWidget *parent)
 void QColorDialog::setCurrentColor(const QColor &color)
 {
     Q_D(QColorDialog);
-    d->setCurrentColor(color.rgb());
-    d->selectColor(color);
-    d->setCurrentAlpha(color.alpha());
-
-    if (!testOption(QColorDialog::DontUseNativeDialog) && d->nativeDialogInUse)
+    if (d->nativeDialogInUse)
         d->platformColorDialogHelper()->setCurrentColor(color);
+    else {
+        d->setCurrentColor(color.rgb());
+        d->selectColor(color);
+        d->setCurrentAlpha(color.alpha());
+    }
 }
 
 QColor QColorDialog::currentColor() const
@@ -1891,10 +1907,14 @@ void QColorDialog::setOptions(ColorDialogOptions options)
         return;
 
     d->options->setOptions(QColorDialogOptions::ColorDialogOptions(int(options)));
-    d->buttons->setVisible(!(options & NoButtons));
-    d->showAlpha(options & ShowAlphaChannel);
-    if (options & DontUseNativeDialog)
+    if ((options & DontUseNativeDialog) && d->nativeDialogInUse) {
         d->nativeDialogInUse = false;
+        d->initWidgets();
+    }
+    if (!d->nativeDialogInUse) {
+        d->buttons->setVisible(!(options & NoButtons));
+        d->showAlpha(options & ShowAlphaChannel);
+    }
 }
 
 QColorDialog::ColorDialogOptions QColorDialog::options() const
@@ -1976,7 +1996,7 @@ void QColorDialog::setVisible(bool visible)
     }
 #else
 
-    if (!(options() & DontUseNativeDialog) && d->nativeDialogInUse) {
+    if (d->nativeDialogInUse) {
         d->setNativeDialogVisible(visible);
         // Set WA_DontShowOnScreen so that QDialog::setVisible(visible) below
         // updates the state correctly, but skips showing the non-native version:

src/widgets/dialogs/qcolordialog_p.h

@@ -82,6 +82,7 @@ public:
         { return static_cast<QPlatformColorDialogHelper *>(platformHelper()); }
 
     void init(const QColor &initial);
+    void initWidgets();
     QRgb currentColor() const;
     QColor currentQColor() const;
     void setCurrentColor(QRgb rgb);

src/widgets/dialogs/qdialog_p.h

@@ -111,7 +111,7 @@ public:
 
     QPointer<QEventLoop> eventLoop;
 
-    bool nativeDialogInUse; // Assigned in setVisible_sys() in derived classes.
+    bool nativeDialogInUse;
     QPlatformDialogHelper *platformHelper() const;
 
 private: