inputmethod: Allow forcing the display of the input method

Adds support to the new information offered by KWin. Now it can tell us
that the current client doesn't support Wayland input methods.

Therefore, it sets the plasmoid in a new "unsupported" state that will
offer to force an activation when triggered. KWin will then be able to
emulate a keyboard and it all should work to some extent.

Depends on https://invent.kde.org/plasma/kwin/-/merge_requests/2907

BUG: 439911

applets/manage-inputmethod/contents/ui/manage-inputmethod.qml

@@ -19,12 +19,16 @@ Item {
     id: root
     property var overlays: []
 
-    Plasmoid.onActivated: if (!Keyboards.KWinVirtualKeyboard.available) {
-        root.action_settings()
-    } else if (Keyboards.KWinVirtualKeyboard.visible) {
-        Keyboards.KWinVirtualKeyboard.active = false
-    } else {
-        Keyboards.KWinVirtualKeyboard.enabled = !Keyboards.KWinVirtualKeyboard.enabled
+    Plasmoid.onActivated: {
+        if (!Keyboards.KWinVirtualKeyboard.available) {
+            root.action_settings()
+        } else if (unsupportedState.when) {
+            Keyboards.KWinVirtualKeyboard.forceActivate()
+        } else if (Keyboards.KWinVirtualKeyboard.visible) {
+            Keyboards.KWinVirtualKeyboard.active = false
+        } else {
+            Keyboards.KWinVirtualKeyboard.enabled = !Keyboards.KWinVirtualKeyboard.enabled
+        }
     }
     Plasmoid.preferredRepresentation: Plasmoid.compactRepresentation
     Plasmoid.fullRepresentation: Plasmoid.compactRepresentation
@@ -67,7 +71,7 @@ Item {
 
     states: [
         State {
-            name: "available"
+            name: "unavailable"
             when: !Keyboards.KWinVirtualKeyboard.available
             PropertyChanges {
                 target: Plasmoid.self
@@ -88,6 +92,20 @@ Item {
             }
             PropertyChanges { target: root; overlays: [] }
         },
+        State {
+            id: unsupportedState
+            name: "unsupported"
+            when: Keyboards.KWinVirtualKeyboard.available && !Keyboards.KWinVirtualKeyboard.activeClientSupportsTextInput
+            // When the current client doesn't support input methods, we can force
+            // the display of the virtual keyboard so it emulates a hardware keyboard instead
+            PropertyChanges {
+                target: Plasmoid.self
+                icon: "arrow-up"
+                toolTipSubText: i18n("Show Virtual Keyboard")
+                status: Kirigami.Settings.tabletMode ? PlasmaCore.Types.ActiveStatus : PlasmaCore.Types.PassiveStatus
+            }
+            PropertyChanges { target: root; overlays: [] }
+        },
         State {
             name: "visible"
             when: Keyboards.KWinVirtualKeyboard.available && Keyboards.KWinVirtualKeyboard.visible

components/keyboardlayout/virtualkeyboard.h

@@ -15,6 +15,7 @@ class KwinVirtualKeyboardInterface : public OrgKdeKwinVirtualKeyboardInterface
     Q_PROPERTY(bool enabled READ enabled WRITE setEnabled NOTIFY enabledChanged)
     Q_PROPERTY(bool visible READ visible NOTIFY visibleChanged)
     Q_PROPERTY(bool available READ available NOTIFY availableChanged)
+    Q_PROPERTY(bool activeClientSupportsTextInput READ activeClientSupportsTextInput NOTIFY activeClientSupportsTextInputChanged)
 public:
     KwinVirtualKeyboardInterface();
 };