KDE keyboard layout config investigation for KDE Wayland keyboard layout stack

Patch tracked upstream

This diff is preserved for inspection, but the current handoff is the upstream review linked below. The original harvest blockers remain visible as historical context for the retained local artifact.

KDE Wayland keyboard layout stack likely remains stuck in a desktop input config mismatch loop. A diagnosis report and patch proposal were created locally.

kcms/keyboard: preserve last-used layout across spare-layout swaps

diff --git a/kcms/keyboard/keyboard_daemon.cpp b/kcms/keyboard/keyboard_daemon.cpp
index ebf2d4e..767b9dc 100644
--- a/kcms/keyboard/keyboard_daemon.cpp
+++ b/kcms/keyboard/keyboard_daemon.cpp
@@ -114,7 +114,7 @@ void KeyboardDaemon::registerShortcut()
 
         QAction *lastUsedLayoutAction = actionCollection->getLastUsedLayoutAction();
         connect(lastUsedLayoutAction, &QAction::triggered, this, [this]() {
-            auto layoutsList = X11Helper::getLayoutsList();
+            const auto layoutsList = logicalLayouts();
             if (!lastUsedLayout.has_value() || layoutsList.count() <= *lastUsedLayout) {
                 switchToPreviousLayout();
             } else {
@@ -222,46 +222,40 @@ bool KeyboardDaemon::setLayout(QAction *action)
 
 bool KeyboardDaemon::setLayout(uint index)
 {
-    if (keyboardSettings->layoutLoopCount() != KeyboardConfig::NO_LOOPING && index >= uint(keyboardSettings->layoutLoopCount())) {
-        QList<LayoutUnit> layouts = X11Helper::getLayoutsList();
-        const uint indexOfLastMainLayoutInConfig = keyboardConfig->layouts().lastIndexOf(layouts.takeLast());
-        const uint indexOfLastMainLayoutInXKB = layouts.size();
-
-        // Re-calculate indexes for layout switching Actions
-        const auto &actions = actionCollection->actions();
-        for (const auto &action : actions) {
-            // clang-format off
-            if (action->data().toUInt() == indexOfLastMainLayoutInXKB) {
-                action->setData(indexOfLastMainLayoutInConfig < index ?
-                                    indexOfLastMainLayoutInConfig + 1 :
-                                    indexOfLastMainLayoutInConfig);
-            } else if (action->data().toUInt() == index) {
-                action->setData(indexOfLastMainLayoutInXKB);
-            } else if (index < indexOfLastMainLayoutInConfig
-                       && index < action->data().toUInt() && action->data().toUInt() <= indexOfLastMainLayoutInConfig) {
-                action->setData(action->data().toUInt() - 1);
-            } else if (indexOfLastMainLayoutInConfig < index
-                       && indexOfLastMainLayoutInConfig < action->data().toUInt() && action->data().toUInt() < index) {
-                action->setData(action->data().toUInt() + 1);
-            }
-            // clang-format on
+    const auto configuredLayouts = keyboardConfig->layouts();
+    if (index >= uint(configuredLayouts.size())) {
+        return false;
+    }
+
+    const uint previousLayout = getLayout();
+
+    if (useLogicalLayoutOrder()) {
+        QList<LayoutUnit> runtimeLayouts = keyboardConfig->getDefaultLayouts();
+        if (runtimeLayouts.isEmpty()) {
+            return false;
         }
 
-        if (index <= indexOfLastMainLayoutInConfig) {
-            // got to a shifted diapason due to previously selected spare layout, so adjusting the index accordingly
-            --index;
+        if (index >= uint(runtimeLayouts.size())) {
+            runtimeLayouts.last() = configuredLayouts.at(index);
+            index = runtimeLayouts.size() - 1;
+        }
+
+        if (X11Helper::getLayoutsList() != runtimeLayouts) {
+            XkbHelper::initializeKeyboardLayouts(runtimeLayouts);
         }
-        // spare layout preempts last one in the loop
-        layouts.append(keyboardConfig->layouts().at(index));
-        XkbHelper::initializeKeyboardLayouts(layouts);
-        index = indexOfLastMainLayoutInXKB;
     }
-    setLastUsedLayoutValue(getLayout());
+    setLastUsedLayoutValue(previousLayout);
     return X11Helper::setGroup(index);
 }
 
 uint KeyboardDaemon::getLayout() const
 {
+    if (useLogicalLayoutOrder()) {
+        const int logicalIndex = keyboardConfig->layouts().indexOf(X11Helper::getCurrentLayout());
+        if (logicalIndex >= 0) {
+            return logicalIndex;
+        }
+    }
     return X11Helper::getGroup();
 }
 
@@ -269,15 +263,7 @@ QList<LayoutNames> KeyboardDaemon::getLayoutsList() const
 {
     QList<LayoutNames> ret;
 
-    auto layoutsList = X11Helper::getLayoutsList();
-    if (keyboardSettings->layoutLoopCount() != KeyboardConfig::NO_LOOPING) {
-        // extra layouts list overlaps with the main layouts loop initially by 1 position
-        auto extraLayouts = keyboardConfig->layouts().mid(keyboardSettings->layoutLoopCount() - 1);
-        // spare layout currently placed in the loop is removed from the extra layouts
-        // as it was already "moved" to the last loop position
-        extraLayouts.removeOne(layoutsList.last());
-        layoutsList.append(extraLayouts);
-    }
+    const auto layoutsList = logicalLayouts();
     for (auto &layoutUnit : std::as_const(layoutsList)) {
         QString displayName = layoutUnit.getDisplayName();
         const auto configDefaultLayouts = keyboardConfig->getDefaultLayouts();
@@ -298,12 +284,27 @@ QList<LayoutNames> KeyboardDaemon::getLayoutsList() const
 
 void KeyboardDaemon::setLastUsedLayoutValue(uint newValue)
 {
-    auto layoutsList = X11Helper::getLayoutsList();
+    const auto layoutsList = logicalLayouts();
     if (layoutsList.count() > 1) {
         lastUsedLayout = std::optional<uint>{newValue};
     }
 }
 
+bool KeyboardDaemon::useLogicalLayoutOrder() const
+{
+    const int loopCount = keyboardSettings->layoutLoopCount();
+    return loopCount != KeyboardConfig::NO_LOOPING && keyboardConfig->layouts().size() > loopCount;
+}
+
+QList<LayoutUnit> KeyboardDaemon::logicalLayouts() const
+{
+    if (useLogicalLayoutOrder()) {
+        return keyboardConfig->layouts();
+    }
+
+    return X11Helper::getLayoutsList();
+}
+
 #include "keyboard_daemon.moc"
 
 #include "moc_keyboard_daemon.cpp"
diff --git a/kcms/keyboard/keyboard_daemon.h b/kcms/keyboard/keyboard_daemon.h
index 519bc31..9800783 100644
--- a/kcms/keyboard/keyboard_daemon.h
+++ b/kcms/keyboard/keyboard_daemon.h
@@ -37,6 +37,8 @@ class Q_DECL_EXPORT KeyboardDaemon : public KDEDModule
     void unregisterListeners();
     void unregisterShortcut();
     void setLastUsedLayoutValue(uint newValue);
+    bool useLogicalLayoutOrder() const;
+    QList<LayoutUnit> logicalLayouts() const;
 
 private Q_SLOTS:
     void configureKeyboard();