Report unavailable protocols and services; send combos as real keys

Diagnostics collects what this session doesn't allow, logs it, and lists
it in the settings panel (with a dot on the gear): KWin not launching
sloposk as its keyboard (detected by WAYLAND_SOCKET, since KWin offers the
input-method global to every client), fake input missing or too old,
org.kde.keyboard unreachable, and the D-Bus control name taken.

Modifier combos go through fake input even in text fields: KWin drops
the input method's modifier mask for most clients, so Ctrl+A typed "a".

The desktop file is generated with an absolute Exec, which KWin needs to
match it: one for the installed binary, one for the build's.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/app/Checks.cpp

@@ -0,0 +1,62 @@
+#include "Checks.h"
+
+#include "SystemLayouts.h"
+#include "backend/KWinInputMethod.h"
+#include "diagnostics/Diagnostics.h"
+
+#include <QCoreApplication>
+
+namespace {
+
+QString tr(const char *text)
+{
+    return QCoreApplication::translate("Checks", text);
+}
+
+QString fakeInputProblem(const KWinFakeInput &fakeInput)
+{
+    const QString lost = tr("Hold Keys, shortcuts like Ctrl+A and typing outside text fields don't work.");
+    if (!fakeInput.isActive())
+        return tr("KWin doesn't let sloposk send key events (it allows the virtual keyboard it launched). ") + lost;
+    return tr("KWin's fake input is too old (version %1, needs %2). ")
+               .arg(fakeInput.boundVersion())
+               .arg(KWinFakeInput::RequiredVersion)
+        + lost;
+}
+
+} // namespace
+
+void watchInputMethod(Diagnostics &diagnostics, const KWinInputMethod &backend, bool launchedByKWin)
+{
+    // Qt binds globals KWin already announced on construction, so the first
+    // check is final unless KWin restarts.
+    const auto checkInputMethod = [&] {
+        diagnostics.check(QStringLiteral("input-method"), launchedByKWin && backend.isAvailable(),
+                          tr("Not running as KWin's virtual keyboard, so it can't type into text fields: "
+                             "choose sloposk in System Settings → Keyboard → Virtual Keyboard."));
+    };
+    const KWinFakeInput &fakeInput = backend.fakeInput();
+    const auto checkFakeInput = [&] {
+        diagnostics.check(QStringLiteral("fake-input"), fakeInput.canSendKeysyms(), fakeInputProblem(fakeInput));
+    };
+    QObject::connect(&backend, &KWinInputMethod::availableChanged, &diagnostics, checkInputMethod);
+    QObject::connect(&fakeInput, &QWaylandClientExtension::activeChanged, &diagnostics, checkFakeInput);
+    checkInputMethod();
+    checkFakeInput();
+}
+
+void watchSystemLayouts(Diagnostics &diagnostics, const SystemLayouts &layouts)
+{
+    QObject::connect(&layouts, &SystemLayouts::serviceChecked, &diagnostics, [&](bool available) {
+        diagnostics.check(QStringLiteral("system-layouts"), available,
+                          tr("KWin's keyboard layout service (org.kde.keyboard) isn't reachable: "
+                             "the globe key switches only the on-screen layout."));
+    });
+}
+
+void reportDBusControl(Diagnostics &diagnostics, bool registered)
+{
+    diagnostics.check(QStringLiteral("dbus-control"), registered,
+                      tr("Couldn't claim org.sloposk.Keyboard on D-Bus (is another sloposk running?): "
+                         "show/hide commands won't reach this one."));
+}

src/app/Checks.h

@@ -0,0 +1,14 @@
+#pragma once
+
+class Diagnostics;
+class KWinInputMethod;
+class SystemLayouts;
+
+// Reports to `diagnostics` what this session doesn't allow, and keeps the
+// reports current as protocols and services come and go.
+// KWin offers the input-method global to every client but only activates
+// the process it launched, which it hands a connection: `launchedByKWin` is
+// whether WAYLAND_SOCKET was set at startup.
+void watchInputMethod(Diagnostics &diagnostics, const KWinInputMethod &backend, bool launchedByKWin);
+void watchSystemLayouts(Diagnostics &diagnostics, const SystemLayouts &layouts);
+void reportDBusControl(Diagnostics &diagnostics, bool registered);

src/app/SystemLayouts.cpp

@@ -27,7 +27,7 @@ SystemLayouts::SystemLayouts(QObject *parent)
     bus.connect(Service, Path, Interface, QStringLiteral("layoutChanged"), this, SLOT(setCurrent(uint)));
     auto *watcher = new QDBusServiceWatcher(Service, bus, QDBusServiceWatcher::WatchForOwnerChange, this);
     connect(watcher, &QDBusServiceWatcher::serviceRegistered, this, &SystemLayouts::fetchCurrent);
-    connect(watcher, &QDBusServiceWatcher::serviceUnregistered, this, [this] { m_system = false; });
+    connect(watcher, &QDBusServiceWatcher::serviceUnregistered, this, [this] { setSystem(false); });
     fetchCurrent();
 }
 
@@ -38,10 +38,9 @@ void SystemLayouts::fetchCurrent()
     connect(watcher, &QDBusPendingCallWatcher::finished, this, [this](QDBusPendingCallWatcher *watcher) {
         watcher->deleteLater();
         const QDBusPendingReply<uint> reply = *watcher;
-        if (reply.isError())
-            return;
-        m_system = true;
-        setCurrent(reply.value());
+        setSystem(!reply.isError());
+        if (m_system)
+            setCurrent(reply.value());
     });
 }
 
@@ -56,6 +55,12 @@ void SystemLayouts::next(quint32 count)
         setCurrent(index);
 }
 
+void SystemLayouts::setSystem(bool system)
+{
+    m_system = system;
+    Q_EMIT serviceChecked(system);
+}
+
 void SystemLayouts::setCurrent(uint index)
 {
     if (index == m_current)

src/app/SystemLayouts.h

@@ -19,12 +19,15 @@ public:
 
 Q_SIGNALS:
     void currentChanged();
+    // After each attempt to reach the service, and when it goes away.
+    void serviceChecked(bool available);
 
 private Q_SLOTS:
     void setCurrent(uint index);
 
 private:
     void fetchCurrent();
+    void setSystem(bool system);
 
     bool m_system = false;
     quint32 m_current = 0;