Implement smallFont in Kirigami plugin

Test Plan: {F8273961} {F8273893}

Reviewers: #kirigami, mart

Reviewed By: #kirigami, mart

Subscribers: filipf, ngraham, plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D29307

CMakeLists.txt

@@ -32,7 +32,7 @@ include(KDEInstallDirs)
 include(KDECMakeSettings)
 include(KDEFrameworkCompilerSettings NO_POLICY_SCOPE)
 
-find_package(Qt5 ${REQUIRED_QT_VERSION} REQUIRED NO_MODULE COMPONENTS Core Quick Gui Widgets QuickControls2)
+find_package(Qt5 ${REQUIRED_QT_VERSION} REQUIRED NO_MODULE COMPONENTS Core Quick Gui Widgets QuickControls2 DBus)
 
 find_package(KF5 ${KF5_DEP_VERSION} REQUIRED COMPONENTS Config Kirigami2)
 

kirigami-plasmadesktop-integration/CMakeLists.txt

@@ -13,6 +13,7 @@ target_link_libraries(org.kde.desktop
         Qt5::Core
         KF5::Kirigami2
     PRIVATE
+        Qt5::DBus
         Qt5::Qml
         Qt5::Quick
         KF5::ConfigWidgets

kirigami-plasmadesktop-integration/plasmadesktoptheme.cpp

@@ -14,6 +14,8 @@
 #include <KIconLoader>
 
 #include <KColorScheme>
+#include <KConfigGroup>
+#include <QDBusConnection>
 
 class IconLoaderSingleton
 {
@@ -156,8 +158,17 @@ PlasmaDesktopTheme::PlasmaDesktopTheme(QObject *parent)
                 });
     }
 
+    // Use DBus in order to listen for kdeglobals changes directly, as the
+    // QApplication doesn't expose the font variants we're looking for,
+    // namely smallFont.
+    QDBusConnection::sessionBus().connect( QString(),
+        QStringLiteral( "/KGlobalSettings" ),
+        QStringLiteral( "org.kde.KGlobalSettings" ),
+        QStringLiteral( "notifyChange" ), this, SLOT(configurationChanged()));
+
     //TODO: correct? depends from https://codereview.qt-project.org/206889
     connect(qGuiApp, &QGuiApplication::fontDatabaseChanged, this, [this]() {setDefaultFont(qApp->font());});
+    configurationChanged();
 
     connect(this, &PlasmaDesktopTheme::colorSetChanged,
             this, &PlasmaDesktopTheme::syncColors);
@@ -172,6 +183,21 @@ PlasmaDesktopTheme::PlasmaDesktopTheme(QObject *parent)
 
 PlasmaDesktopTheme::~PlasmaDesktopTheme() = default;
 
+void PlasmaDesktopTheme::configurationChanged()
+{
+    KSharedConfigPtr ptr = KSharedConfig::openConfig();
+    KConfigGroup general( ptr->group("general") );
+    setSmallFont(general.readEntry("smallestReadableFont", []() {
+        auto smallFont = qApp->font();
+        if (smallFont.pixelSize() != -1) {
+            smallFont.setPixelSize(smallFont.pixelSize()-2);
+        } else {
+            smallFont.setPointSize(smallFont.pointSize()-2);
+        }
+        return smallFont;
+    }()));
+}
+
 QIcon PlasmaDesktopTheme::iconFromTheme(const QString &name, const QColor &customColor)
 {
     QPalette pal = palette();

kirigami-plasmadesktop-integration/plasmadesktoptheme.h

@@ -53,6 +53,9 @@ public:
 Q_SIGNALS:
     void colorsChanged();
 
+protected Q_SLOTS:
+    void configurationChanged();
+
 private:
     QPointer<QQuickItem> m_parentItem;
     QPointer<QWindow> m_window;