Make widget style configurable with Fusion as default

Up to now the UI appearance on all platforms was aligned as much as
possible with stylesheets. Since the base widget styles still were
platform dependent defaults, there were many small differences in
details and controls. Some of them were even broken. Instead of
trying to tweak all platform specific styles, default to one on all
platforms. This guarantees that the UI is truly cross platform and
all styles and fixes cover all platforms at the same time.
For users who want to change the default style, they have now a gui
setting. But it is strongly recommended to stick with the default.

refs #683

src/blackcore/application.h

@@ -457,7 +457,7 @@ namespace BlackCore
         #ifdef BLACK_USE_CRASHPAD
         std::unique_ptr<crashpad::CrashpadClient> m_crashpadClient;
         std::unique_ptr<crashpad::CrashReportDatabase> m_crashReportDatabase;
-        BlackMisc::CSetting<BlackCore::Application::TCrashDumpUploadEnabled> m_crashDumpUploadEnabled { this, &CApplication::crashDumpUploadEnabledChanged };
+        BlackMisc::CSettingReadOnly<BlackCore::Application::TCrashDumpUploadEnabled> m_crashDumpUploadEnabled { this, &CApplication::crashDumpUploadEnabledChanged };
         #endif
     };
 } // namespace

src/blackgui/components/settingscomponent.cpp

@@ -21,6 +21,7 @@
 #include <QLineEdit>
 #include <QSlider>
 #include <QString>
+#include <QStyleFactory>
 #include <QTabBar>
 #include <QToolButton>
 #include <QtGlobal>
@@ -43,6 +44,9 @@ namespace BlackGui
             ui(new Ui::CSettingsComponent)
         {
             ui->setupUi(this);
+            ui->cb_SettingsGuiWidgetStyle->clear();
+            ui->cb_SettingsGuiWidgetStyle->insertItems(0, QStyleFactory::keys());
+
             this->tabBar()->setExpanding(false);
             this->tabBar()->setUsesScrollButtons(true);
 
@@ -66,7 +70,11 @@ namespace BlackGui
             connected = this->connect(this->ui->cb_SettingsGuiFontStyle, SIGNAL(currentIndexChanged(QString)), this, SLOT(ps_fontChanged()));
             Q_ASSERT(connected);
             this->connect(this->ui->tb_SettingsGuiFontColor, &QToolButton::clicked, this, &CSettingsComponent::ps_fontColorDialog);
+            this->connect(this->ui->cb_SettingsGuiWidgetStyle, static_cast<void(QComboBox::*)(const QString &)>(&QComboBox::currentIndexChanged),
+                          this, &CSettingsComponent::widgetStyleChanged);
             Q_UNUSED(connected);
+
+            reloadWidgetStyleFromSettings();
         }
 
         CSettingsComponent::~CSettingsComponent()
@@ -132,5 +140,21 @@ namespace BlackGui
             this->ui->le_SettingsGuiFontColor->setText(this->m_fontColor.name());
             this->ps_fontChanged();
         }
+
+        void CSettingsComponent::reloadWidgetStyleFromSettings()
+        {
+            int index = ui->cb_SettingsGuiWidgetStyle->findText(m_settingsWidgetStyle.get());
+            ui->cb_SettingsGuiWidgetStyle->setCurrentIndex(index);
+        }
+
+        void CSettingsComponent::widgetStyleChanged(const QString &widgetStyle)
+        {
+            if (widgetStyle == m_settingsWidgetStyle.get()) { return; }
+            auto availableStyles = QStyleFactory::keys();
+            if (availableStyles.contains(widgetStyle))
+            {
+                m_settingsWidgetStyle.set(widgetStyle);
+            }
+        }
     }
 } // namespace

src/blackgui/components/settingscomponent.h

@@ -13,6 +13,7 @@
 #define BLACKGUI_COMPONENTS_SETTINGSCOMPONENT_H
 
 #include "blackgui/blackguiexport.h"
+#include "blackgui/settings/guisettings.h"
 
 #include <QColor>
 #include <QObject>
@@ -92,8 +93,12 @@ namespace BlackGui
             void ps_fontColorDialog();
 
         private:
+            void reloadWidgetStyleFromSettings();
+            void widgetStyleChanged(const QString &widgetStyle);
+
             QScopedPointer<Ui::CSettingsComponent> ui;
             QColor m_fontColor;
+            BlackMisc::CSetting<BlackGui::Settings::TWidgetStyle> m_settingsWidgetStyle { this, &CSettingsComponent::reloadWidgetStyleFromSettings };
         };
     }
 } // namespace

src/blackgui/components/settingscomponent.ui

@@ -290,14 +290,14 @@
          <string>General</string>
         </property>
         <layout class="QFormLayout" name="fl_GuiGeneral">
-         <item row="0" column="0">
+         <item row="1" column="0">
           <widget class="QLabel" name="lbl_SettingsGuiOpacity">
            <property name="text">
             <string>Opacity (0-100%)</string>
            </property>
           </widget>
          </item>
-         <item row="0" column="1">
+         <item row="1" column="1">
           <widget class="QSlider" name="hs_SettingsGuiOpacity">
            <property name="sizePolicy">
             <sizepolicy hsizetype="Preferred" vsizetype="Fixed">
@@ -319,6 +319,16 @@
            </property>
           </widget>
          </item>
+         <item row="2" column="1">
+          <widget class="QComboBox" name="cb_SettingsGuiWidgetStyle"/>
+         </item>
+         <item row="2" column="0">
+          <widget class="QLabel" name="lbl_SettingsGuiWidgetStyle">
+           <property name="text">
+            <string>Widget Style</string>
+           </property>
+          </widget>
+         </item>
         </layout>
        </widget>
       </item>

src/blackgui/guiapplication.cpp

@@ -27,7 +27,7 @@
 #include <QCloseEvent>
 #include <QApplication>
 #include <QCommandLineParser>
-#include <QCoreApplication>
+#include <QApplication>
 #include <QDesktopServices>
 #include <QDir>
 #include <QEventLoop>
@@ -38,6 +38,7 @@
 #include <QMessageBox>
 #include <QRegExp>
 #include <QSplashScreen>
+#include <QStyleFactory>
 #include <QStringList>
 #include <QStyle>
 #include <QUrl>
@@ -76,6 +77,7 @@ namespace BlackGui
             this->setWindowIcon(icon);
             sGui = this;
             connect(&this->m_styleSheetUtility, &CStyleSheetUtility::styleSheetsChanged, this, &CGuiApplication::styleSheetsChanged);
+            reloadWidgetStyleFromSettings();
         }
     }
 
@@ -542,4 +544,14 @@ namespace BlackGui
     {
         return true;
     }
+
+    void CGuiApplication::reloadWidgetStyleFromSettings()
+    {
+        auto widgetStyle = m_settingsWidgetStyle.get();
+        auto availableStyles = QStyleFactory::keys();
+        if (availableStyles.contains(widgetStyle))
+        {
+            QApplication::setStyle(QStyleFactory::create(widgetStyle));
+        }
+    }
 } // ns

src/blackgui/guiapplication.h

@@ -16,6 +16,7 @@
 #include "blackgui/blackguiexport.h"
 #include "blackgui/enableforframelesswindow.h"
 #include "blackgui/mainwindowaccess.h"
+#include "blackgui/settings/guisettings.h"
 #include "blackgui/stylesheetutility.h"
 #include "blackmisc/icons.h"
 #include "blackmisc/statusmessage.h"
@@ -193,8 +194,13 @@ namespace BlackGui
         QScopedPointer<QSplashScreen> m_splashScreen;             //!< splash screen
         BlackGui::Components::CApplicationCloseDialog *m_closeDialog = nullptr; //!< close dialog (no QScopedPointer because I need to set parent)
 
+        BlackMisc::CSettingReadOnly<BlackGui::Settings::TWidgetStyle> m_settingsWidgetStyle{ this, &CGuiApplication::reloadWidgetStyleFromSettings };
+
         //! Qt help message to formatted HTML
         static QString beautifyHelpMessage(const QString &helpText);
+
+        //! Reload widget style from settings
+        void reloadWidgetStyleFromSettings();
     };
 } // ns
 

src/blackgui/settings/guisettings.h

@@ -16,6 +16,8 @@
 #include "blackmisc/settingscache.h"
 #include "blackmisc/simulation/aircraftmodel.h"
 
+#include <QString>
+
 namespace BlackGui
 {
     namespace Settings
@@ -26,6 +28,17 @@ namespace BlackGui
             //! Key in data cache
             static const char *key() { return "guinownaircraftmodel"; }
         };
+
+        //! Widget Style
+        struct TWidgetStyle : public BlackMisc::TSettingTrait<QString>
+        {
+            //! \copydoc BlackCore::TSettingTrait::key
+            static const char *key() { return "application/widgetstyle"; }
+
+            //! \copydoc BlackCore::TSettingTrait::defaultValue
+            static QString defaultValue() { return QStringLiteral("Fusion"); }
+        };
+
     } // ns
 } // ns