Spike: KWin input-method backend with floating layer-shell window

Registers as KWin's virtual keyboard (input-method-unstable-v1), shows a
non-focusable layer-shell overlay, and commits Unicode text. Verified in a
nested headless KWin with the textprobe tool.

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

src/CMakeLists.txt

@@ -0,0 +1,42 @@
+qt_add_executable(sloposk
+    main.cpp
+    backend/TextBackend.h
+    backend/InputMethodProtocol.h
+    backend/KWinInputMethod.h backend/KWinInputMethod.cpp
+    backend/KWinInputContext.h backend/KWinInputContext.cpp
+    window/FloatingWindow.h window/FloatingWindow.cpp
+)
+
+qt6_generate_wayland_protocol_client_sources(sloposk PRIVATE_CODE FILES
+    ${WAYLAND_PROTOCOLS_DIR}/unstable/input-method/input-method-unstable-v1.xml
+)
+# Generated code lacks the core-protocol include (see backend/InputMethodProtocol.h).
+set_source_files_properties(${CMAKE_CURRENT_BINARY_DIR}/qwayland-input-method-unstable-v1.cpp
+    PROPERTIES COMPILE_OPTIONS "-include;wayland-client-protocol.h")
+
+# QML lives in the top-level qml/ dir; alias each file so the module sees it at its root.
+set(SLOPOSK_QML_FILES
+    Main.qml
+)
+list(TRANSFORM SLOPOSK_QML_FILES PREPEND ${PROJECT_SOURCE_DIR}/qml/ OUTPUT_VARIABLE sloposk_qml_paths)
+foreach(file IN LISTS SLOPOSK_QML_FILES)
+    set_source_files_properties(${PROJECT_SOURCE_DIR}/qml/${file} PROPERTIES QT_RESOURCE_ALIAS ${file})
+endforeach()
+
+qt_add_qml_module(sloposk
+    URI Sloposk
+    QML_FILES ${sloposk_qml_paths}
+)
+
+target_include_directories(sloposk PRIVATE ${CMAKE_CURRENT_SOURCE_DIR})
+
+target_link_libraries(sloposk PRIVATE
+    Qt6::Gui
+    Qt6::Quick
+    Qt6::WaylandClient
+    LayerShellQt::Interface
+    PkgConfig::XKB
+    PkgConfig::WAYLAND
+)
+
+install(TARGETS sloposk)