CMake: optionally disable QML

This makes it possible to remove QML from Calamares, possibly yielding
a smaller, lighter installer; it takes with it the nice slideshow,
modern configurable navigation and the QML UIs built for various modules.

By default, WITH_QML is on and the "normal" feature set is retained.

- look for Qml modules only when WITH_QML is on (the default)
- look for Network, since that's pulled in only implicitly
- disable the QML Calamares models (modules/*q) if no QML is
  enabled; longer-term plan is to merge the **pages** back to
  the "upstream" modules, and have things be run-time switchable,
  but that's not here yet. Also disable the notesqml module when
  QML is off.

CMakeLists.txt

@@ -56,7 +56,8 @@ option( WITH_KF5DBus "Use DBus service for unique-application." OFF )
 # When adding WITH_* that affects the ABI offered by libcalamares,
 # also update libcalamares/CalamaresConfig.h.in
 option( WITH_PYTHON "Enable Python modules API (requires Boost.Python)." ON )
-option( WITH_PYTHONQT "Enable next generation Python modules API (experimental, requires PythonQt)." OFF )
+option( WITH_PYTHONQT "Enable Python view modules API (deprecated, requires PythonQt)." OFF )
+option( WITH_QML "Enable QML UI options." ON )
 
 # Possible debugging flags are:
 #  - DEBUG_TIMEZONES draws latitude and longitude lines on the timezone
@@ -253,7 +254,10 @@ include( CMakeColors )
 
 ### DEPENDENCIES
 #
-find_package( Qt5 ${QT_VERSION} CONFIG REQUIRED Concurrent Core Gui Widgets LinguistTools Svg Quick QuickWidgets )
+find_package( Qt5 ${QT_VERSION} CONFIG REQUIRED Concurrent Core Gui LinguistTools Network Svg Widgets )
+if( WITH_QML )
+    find_package( Qt5 ${QT_VERSION} CONFIG REQUIRED Quick QuickWidgets )
+endif()
 if( Qt5_VERSION VERSION_GREATER 5.12.1 )
     # At least Qt 5.12.2 seems to support Esperanto in QLocale
     if( "eo" IN_LIST _tx_incomplete )

src/libcalamares/CalamaresConfig.h.in

@@ -11,5 +11,6 @@
 //cmakedefines for CMake variables (e.g. for optdepends) go here
 #cmakedefine WITH_PYTHON
 #cmakedefine WITH_PYTHONQT
+#cmakedefine WITH_QML
 
 #endif  // CALAMARESCONFIG_H

src/modules/keyboardq/CMakeLists.txt

@@ -1,3 +1,8 @@
+if( NOT WITH_QML )
+    calamares_skip_module( "keyboardq (QML is not supported in this build)" )
+    return()
+endif()
+
 set( _keyboard ${CMAKE_CURRENT_SOURCE_DIR}/../keyboard )
 
 include_directories( ${_keyboard} )

src/modules/localeq/CMakeLists.txt

@@ -1,3 +1,8 @@
+if( NOT WITH_QML )
+    calamares_skip_module( "localeq (QML is not supported in this build)" )
+    return()
+endif()
+
 # When debugging the timezone widget, add this debugging definition
 # to have a debugging-friendly timezone widget, debug logging,
 # and no intrusive timezone-setting while clicking around.

src/modules/notesqml/CMakeLists.txt

@@ -1,3 +1,8 @@
+if( NOT WITH_QML )
+    calamares_skip_module( "notesqml (QML is not supported in this build)" )
+    return()
+endif()
+
 calamares_add_plugin( notesqml
     TYPE viewmodule
     EXPORT_MACRO PLUGINDLLEXPORT_PRO

src/modules/welcomeq/CMakeLists.txt

@@ -1,6 +1,11 @@
 # This is a re-write of the welcome module using QML view steps
 # instead of widgets.
 
+if( NOT WITH_QML )
+    calamares_skip_module( "welcomeq (QML is not supported in this build)" )
+    return()
+endif()
+
 set( _welcome ${CMAKE_CURRENT_SOURCE_DIR}/../welcome )
 
 include_directories( ${PROJECT_BINARY_DIR}/src/libcalamaresui ${CMAKE_CURRENT_SOURCE_DIR}/../../libcalamares ${_welcome} )