feat(cmake): disable PCPP by default (#8126)

docs/src/details/integration/building/cmake.rst

@@ -26,6 +26,7 @@ You need to install
 - CMake
 - Ninja (for Linux builds). Be sure to Add ninja to your PATH!
 - The prerequisites listed in ``scripts/install-prerequisites.sh/bat``
+- A python3 interpreter if you wish to use KConfig.
 
 
 How to build this project using cmake
@@ -87,7 +88,7 @@ Here is how to build using the presets:
 Build with IDE
 ~~~~~~~~~~~~~~
 
-The recommend way for consuming CMakePresets is a CMakePresets aware IDE such as
+The recommended way for consuming CMakePresets is a CMakePresets aware IDE such as
 
 - VS 2022
 - VS Code
@@ -183,4 +184,6 @@ These cmake options are available to configure LVGL:
 - ``LV_DEFCONFIG_PATH`` (STRING): Specify to use a defconfig file instead of the current .config in a Kconfig setup.
 - ``LV_CONF_BUILD_DISABLE_EXAMPLES`` (BOOLEAN): Disable building the examples if set.
 - ``LV_CONF_BUILD_DISABLE_DEMOS`` (BOOLEAN): Disable building the demos if set.
-- ``LV_CONF_BUILD_DISABLE_THORVG_INTERNAL``: Disable the internal compilation of ThorVG.
+- ``LV_CONF_BUILD_DISABLE_THORVG_INTERNAL``: Disable the internal compilation of ThorVG.
+- ``LV_CMAKE_CREATE_CONF_VARS`` (BOOLEAN) : Disable the creation of variables from ``lv_conf_internal.h`` this feature is disabled by default.
+  It is enabled automatically if ``LV_USE_KCONFIG`` is enabled. This feature requires a python3 interpreter with support for the *pip* and *venv* modules

env_support/cmake/custom.cmake

@@ -14,6 +14,7 @@ find_package(Python REQUIRED)
 
 option(LV_CONF_SKIP "Skip including lv_conf.h during configuration" OFF)
 option(LV_USE_KCONFIG "Use Kconfig to configure LVGL" OFF)
+option(LV_CMAKE_CREATE_CONF_VARS "Create variables from the options defined in lv_conf_internal.h - required for KConfig" OFF)
 
 # Option LV_CONF_PATH, which should be the path for lv_conf.h
 # If set parent path LV_CONF_DIR is added to includes
@@ -41,10 +42,15 @@ if ( LV_USE_KCONFIG )
   # and autoconf.h, which will be used by lv_conf_kconfig.h
   include(${CMAKE_CURRENT_LIST_DIR}/kconfig.cmake)
 
-  set(LV_KCONFIG_IGNORE OFF)
+  # If KConfig is used - creating CMAKE variables from lv_conf_internal.h is required,
+  # so PCPP is used to pre-process lv_conf_internal.h
+  set(LV_CMAKE_CREATE_CONF_VARS TRUE)
+
   # Set the flag to specify we are using kconfig, needed for the
   # generate_cmake_variables.py script
+  set(LV_KCONFIG_IGNORE OFF)
   set(KCONFIG_FLAG --kconfig)
+
   # If using Kconfig, we need to define additional definitions
   list(APPEND PCPP_DEFINITIONS_LIST "LV_CONF_SKIP" "LV_CONF_KCONFIG_EXTERNAL_INCLUDE=\"${LV_CONF_KCONFIG_EXTERNAL_INCLUDE}\"")
 else()
@@ -75,36 +81,39 @@ target_compile_definitions(
               $<$<BOOL:${LV_CONF_SKIP}>:LV_CONF_SKIP>
 )
 
-# Use the portable pcpp to preprocess lv_conf_internal.h
-execute_process(
-  COMMAND ${Python_EXECUTABLE} ${LVGL_ROOT_DIR}/scripts/preprocess_lv_conf_internal.py
-  --input ${LVGL_ROOT_DIR}/src/lv_conf_internal.h
-  --tmp_file ${CMAKE_CURRENT_BINARY_DIR}/tmp.h
-  --output ${CMAKE_CURRENT_BINARY_DIR}/lv_conf_expanded.h
-  --workfolder ${CMAKE_CURRENT_BINARY_DIR}
-  ${PCPP_ADDITIONAL_DEFS}
-  --include ${LVGL_ROOT_DIR} ${LVGL_ROOT_DIR}/.. ${LVGL_ROOT_DIR}/src ${LV_CONF_DIR}
-  RESULT_VARIABLE ret
-)
-if(NOT "${ret}" STREQUAL "0")
-  message(FATAL_ERROR "preprocess_lv_conf_internal.py failed with return code: ${ret}")
-endif()
+if ( LV_CMAKE_CREATE_CONF_VARS )
+    # Use the portable pcpp to preprocess lv_conf_internal.h
+    execute_process(
+      COMMAND ${Python_EXECUTABLE} ${LVGL_ROOT_DIR}/scripts/preprocess_lv_conf_internal.py
+      --input ${LVGL_ROOT_DIR}/src/lv_conf_internal.h
+      --tmp_file ${CMAKE_CURRENT_BINARY_DIR}/tmp.h
+      --output ${CMAKE_CURRENT_BINARY_DIR}/lv_conf_expanded.h
+      --workfolder ${CMAKE_CURRENT_BINARY_DIR}
+      ${PCPP_ADDITIONAL_DEFS}
+      --include ${LVGL_ROOT_DIR} ${LVGL_ROOT_DIR}/.. ${LVGL_ROOT_DIR}/src ${LV_CONF_DIR}
+      RESULT_VARIABLE ret
+    )
+    if(NOT "${ret}" STREQUAL "0")
+      message(FATAL_ERROR "preprocess_lv_conf_internal.py failed with return code: ${ret}")
+    endif()
 
-# Convert the expanded lv_conf_expanded.h to cmake variables
-execute_process(
-  COMMAND ${Python_EXECUTABLE}
-    ${LVGL_ROOT_DIR}/scripts/generate_cmake_variables.py
-    --input ${CMAKE_CURRENT_BINARY_DIR}/lv_conf_expanded.h
-    --output ${CMAKE_CURRENT_BINARY_DIR}/lv_conf.cmake
-    ${KCONFIG_FLAG}
-    RESULT_VARIABLE ret
-)
-if(NOT "${ret}" STREQUAL "0")
-  message(FATAL_ERROR "generate_cmake_variables.py command failed with return code: ${ret}")
-endif()
+    # Convert the expanded lv_conf_expanded.h to cmake variables
+    execute_process(
+      COMMAND ${Python_EXECUTABLE}
+        ${LVGL_ROOT_DIR}/scripts/generate_cmake_variables.py
+        --input ${CMAKE_CURRENT_BINARY_DIR}/lv_conf_expanded.h
+        --output ${CMAKE_CURRENT_BINARY_DIR}/lv_conf.cmake
+        --parentscope
+        ${KCONFIG_FLAG}
+        RESULT_VARIABLE ret
+    )
+    if(NOT "${ret}" STREQUAL "0")
+      message(FATAL_ERROR "generate_cmake_variables.py command failed with return code: ${ret}")
+    endif()
 
-# This will set all CONFIG_LV_USE_* variables in cmake
-include(${CMAKE_CURRENT_BINARY_DIR}/lv_conf.cmake)
+    # This will set all CONFIG_LV_USE_* variables in cmake
+    include(${CMAKE_CURRENT_BINARY_DIR}/lv_conf.cmake)
+endif()
 
 # Add definition of LV_CONF_PATH only if needed
 # Do not redefine it if already defined in tests/CMakeLists.txt

scripts/generate_cmake_variables.py

@@ -5,10 +5,12 @@
 # preprocessed lv_conf_internal.h
 #
 # Author: David TRUAN (david.truan@edgemtech.ch)
+# Author: Erik Tagirov (erik.tagirov@edgemtech.ch)
 #
 
 import os
 import argparse
+import re
 
 def fatal(msg):
     print()
@@ -29,6 +31,10 @@ def get_args():
 
     parser.add_argument("--kconfig", action="store_true", help="Enable kconfig flag")
 
+    parser.add_argument("--debug", action="store_true", required=False, help="Show unhandled expressions")
+
+    parser.add_argument("--parentscope", action="store_true", required=False, help="Additionaly set the variables in the parent scope")
+
     args = parser.parse_args()
 
     # The input must exist
@@ -37,7 +43,15 @@ def get_args():
 
     return args
 
-def generate_cmake_variables(path_input: str, path_output: str, kconfig: bool):
+def write_set_cmd(fout, expr, is_parent_scope):
+
+    fout.write(f'set({expr})\n')
+
+    # This makes the variable usable from the top level directory
+    if is_parent_scope == True:
+        fout.write(f'set({expr} PARENT_SCOPE)\n')
+
+def generate_cmake_variables(path_input: str, path_output: str, kconfig: bool, debug: bool, is_parent_scope: bool):
     fin = open(path_input)
     fout = open(path_output, "w", newline='')
 
@@ -70,7 +84,7 @@ def generate_cmake_variables(path_input: str, path_output: str, kconfig: bool):
 
             name = name.replace("STDLIB", type)
 
-            fout.write(f'set({CONFIG_PREFIX}{name} 1)\n')
+            write_set_cmd(fout, f'{CONFIG_PREFIX}{name} 1', is_parent_scope)
 
         # Treat the LV_USE_OS config in a special way, as we need
         # to convert the define to full config with 1 value when enabled
@@ -87,11 +101,12 @@ def generate_cmake_variables(path_input: str, path_output: str, kconfig: bool):
 
             name += type
 
-            fout.write(f'set({CONFIG_PREFIX}{name} 1)\n')
+            write_set_cmd(fout, f'{CONFIG_PREFIX}{name} 1', is_parent_scope)
 
-        # For the rest of config, simply add CONFIG_ and write
-        # all LV_USE_* configs, as these are the one needed in cmake
-        elif line.startswith(f'{CONFIG_PATTERN}'):
+        # For the rest of the configs, simply add CONFIG_ and write the name of the define
+        # all LV_USE_* configs where the value is 0 or 1, as these are the one needed in cmake
+        # To detect the configuration of LVGL to perform conditional compilation/linking
+        elif re.search(f'{CONFIG_PATTERN}.* +[01] *$', line):
 
             parts = line.split()
             if len(parts) < 3:
@@ -100,10 +115,16 @@ def generate_cmake_variables(path_input: str, path_output: str, kconfig: bool):
             name = parts[1]
             value = parts[2].strip()
 
-            fout.write(f'set({CONFIG_PREFIX}{name} {value})\n')
+            write_set_cmd(fout, f'{CONFIG_PREFIX}{name} {value}', is_parent_scope)
+
+        else:
+            # Useful for debugging expressions that are unhandled,
+            # if the script fails in 'unexpected ways'
+            if debug == True:
+                print(f"DBG: Skipping expression: '{line} - not handled'")
 
 
 if __name__ == '__main__':
     args = get_args()
 
-    generate_cmake_variables(args.input, args.output, args.kconfig)
+    generate_cmake_variables(args.input, args.output, args.kconfig, args.debug, args.parentscope)