From 49f05b043e382761dbf913677af5072f95d2df19 Mon Sep 17 00:00:00 2001
From: Oliver Eftevaag <oliver.eftevaag@qt.io>
Date: Fri, 28 Mar 2025 09:56:27 +0100
Subject: [PATCH] GnomeTheme: read the initial color-scheme value from dbus

The initial color-scheme value was never initialized, and would thus,
always be 'Unknown', until the user changes the color scheme in the
system settings.

The xdg settings portal method ReadAll is currently omitting the
contrast setting from the reply. Because of this, two separate dbus
calls are necessary to get both the initial color-scheme and contrast
setting.

Change-Id: Ie32371efd830e19727922efd2c9c32595395d11a
Reviewed-by: Axel Spoerl <axel.spoerl@qt.io>
---
 src/gui/platform/unix/qgnometheme.cpp | 57 ++++++++++++++++++---------
 1 file changed, 39 insertions(+), 18 deletions(-)

diff --git a/src/gui/platform/unix/qgnometheme.cpp b/src/gui/platform/unix/qgnometheme.cpp
index bce0eca0629..1095a665324 100644
--- a/src/gui/platform/unix/qgnometheme.cpp
+++ b/src/gui/platform/unix/qgnometheme.cpp
@@ -31,30 +31,51 @@ const char *QGnomeTheme::name = "gnome";
 QGnomeThemePrivate::QGnomeThemePrivate()
 {
 #ifndef QT_NO_DBUS
-    QDBusMessage message = QDBusMessage::createMethodCall(QLatin1String("org.freedesktop.portal.Desktop"),
-                                             QLatin1String("/org/freedesktop/portal/desktop"),
-                                             QLatin1String("org.freedesktop.portal.Settings"),
-                                             QLatin1String("ReadOne"));
     static constexpr QLatin1String appearanceNamespace("org.freedesktop.appearance");
+    static constexpr QLatin1String colorSchemeKey("color-scheme");
     static constexpr QLatin1String contrastKey("contrast");
 
-    message << appearanceNamespace << contrastKey;
-
     QDBusConnection dbus = QDBusConnection::sessionBus();
-    if (!dbus.isConnected())
-        qCWarning(lcQpaThemeGnome) << "dbus connection failed. Last error: " << dbus.lastError();
+    if (dbus.isConnected()) {
+        // ReadAll appears to omit the contrast setting on Ubuntu.
+        QDBusMessage message = QDBusMessage::createMethodCall(QLatin1String("org.freedesktop.portal.Desktop"),
+                                                              QLatin1String("/org/freedesktop/portal/desktop"),
+                                                              QLatin1String("org.freedesktop.portal.Settings"),
+                                                              QLatin1String("ReadOne"));
 
-    QDBusPendingCall pendingCall = dbus.asyncCall(message);
-    QDBusPendingCallWatcher *watcher = new QDBusPendingCallWatcher(pendingCall);
-    QObject::connect(watcher, &QDBusPendingCallWatcher::finished, watcher, [this](QDBusPendingCallWatcher *watcher) {
-        if (!watcher->isError()) {
-            QDBusPendingReply<QVariant> reply = *watcher;
-            if (Q_LIKELY(reply.isValid()))
-                m_contrast = static_cast<Qt::ContrastPreference>(reply.value().toUInt());
+        message << appearanceNamespace << colorSchemeKey;
+        QDBusReply<QVariant> reply = dbus.call(message);
+        if (Q_LIKELY(reply.isValid())) {
+            uint xdgColorSchemeValue = reply.value().toUInt();
+            switch (xdgColorSchemeValue) {
+            case 1:
+                m_colorScheme = Qt::ColorScheme::Dark;
+                QWindowSystemInterface::handleThemeChange();
+                break;
+            case 2:
+                m_colorScheme = Qt::ColorScheme::Light;
+                QWindowSystemInterface::handleThemeChange();
+                break;
+            default:
+                break;
+            }
         }
-        watcher->deleteLater();
-        initDbus();
-    });
+
+        message.setArguments({});
+        message << appearanceNamespace << contrastKey;
+        QDBusPendingCallWatcher *watcher = new QDBusPendingCallWatcher(dbus.asyncCall(message));
+        QObject::connect(watcher, &QDBusPendingCallWatcher::finished, watcher, [this](QDBusPendingCallWatcher *watcher) {
+            if (!watcher->isError()) {
+                QDBusPendingReply<QVariant> reply = *watcher;
+                if (Q_LIKELY(reply.isValid()))
+                    updateHighContrast(static_cast<Qt::ContrastPreference>(reply.value().toUInt()));
+            }
+            initDbus();
+            watcher->deleteLater();
+        });
+    } else {
+        qCWarning(lcQpaThemeGnome) << "dbus connection failed. Last error: " << dbus.lastError();
+    }
 #endif // QT_NO_DBUS
 }
 QGnomeThemePrivate::~QGnomeThemePrivate()