CMake: Implement configure -list-features

Extend qt_configure_get_padded_string to make the feature list look like
qmake's.

Fixes: QTBUG-88144
Change-Id: I714f2b2f3537b506365a03b5b6bc3413e9cab167
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>

cmake/QtBuildInformation.cmake

@@ -140,13 +140,32 @@ macro(qt_configure_add_report_padded label message)
     set(__qt_configure_reports "${__qt_configure_reports}" PARENT_SCOPE)
 endmacro()
 
+# Pad 'label' and 'value' with dots like this:
+# "label ............... value"
+#
+# PADDING_LENGTH specifies the number of characters from the start to the last dot.
+#                Default is 30.
+# MIN_PADDING    specifies the minimum number of dots that are used for the padding.
+#                Default is 0.
 function(qt_configure_get_padded_string label value out_var)
-    set(pad_string ".........................................")
+    cmake_parse_arguments(arg "" "PADDING_LENGTH;MIN_PADDING" "" ${ARGN})
+    if("${arg_MIN_PADDING}" STREQUAL "")
+        set(arg_MIN_PADDING 0)
+    endif()
+    if(arg_PADDING_LENGTH)
+        set(pad_string "")
+        math(EXPR n "${arg_PADDING_LENGTH} - 1")
+        foreach(i RANGE ${n})
+            string(APPEND pad_string ".")
+        endforeach()
+    else()
+        set(pad_string ".........................................")
+    endif()
     string(LENGTH "${label}" label_len)
     string(LENGTH "${pad_string}" pad_len)
     math(EXPR pad_len "${pad_len}-${label_len}")
     if(pad_len LESS "0")
-        set(pad_len "0")
+        set(pad_len ${arg_MIN_PADDING})
     endif()
     string(SUBSTRING "${pad_string}" 0 "${pad_len}" pad_string)
     set(output "${label} ${pad_string} ${value}")

cmake/QtProcessConfigureArgs.cmake

@@ -9,6 +9,7 @@
 # TOP_LEVEL: TRUE, if this is a top-level build.
 
 include(${CMAKE_CURRENT_LIST_DIR}/QtFeatureCommon.cmake)
+include(${CMAKE_CURRENT_LIST_DIR}/QtBuildInformation.cmake)
 
 cmake_policy(SET CMP0007 NEW)
 cmake_policy(SET CMP0057 NEW)
@@ -60,6 +61,8 @@ while(configure_args)
         set(auto_detect_generator FALSE)
     elseif(arg STREQUAL "-no-guess-compiler")
         set(auto_detect_compiler FALSE)
+    elseif(arg STREQUAL "-list-features")
+        set(list_features TRUE)
     elseif(arg STREQUAL "-skip")
         list(POP_FRONT configure_args qtrepo)
         push("-DBUILD_${qtrepo}=OFF")
@@ -94,7 +97,10 @@ endwhile()
 set_property(GLOBAL PROPERTY COMMANDLINE_KNOWN_FEATURES "")
 
 function(qt_feature feature)
+    cmake_parse_arguments(arg "" "PURPOSE;SECTION;" "" ${ARGN})
     set_property(GLOBAL APPEND PROPERTY COMMANDLINE_KNOWN_FEATURES "${feature}")
+    set_property(GLOBAL PROPERTY COMMANDLINE_FEATURE_PURPOSE_${feature} "${arg_PURPOSE}")
+    set_property(GLOBAL PROPERTY COMMANDLINE_FEATURE_SECTION_${feature} "${arg_SECTION}")
 endfunction()
 
 macro(defstub name)
@@ -405,6 +411,26 @@ function(qt_call_function func)
     endif()
 endfunction()
 
+if(list_features)
+    unset(lines)
+    foreach(feature ${commandline_known_features})
+        get_property(section GLOBAL PROPERTY COMMANDLINE_FEATURE_SECTION_${feature})
+        get_property(purpose GLOBAL PROPERTY COMMANDLINE_FEATURE_PURPOSE_${feature})
+        if(purpose)
+            if(NOT "${section}" STREQUAL "")
+                string(APPEND section ": ")
+            endif()
+            qt_configure_get_padded_string("${feature}" "${section}${purpose}" line
+                PADDING_LENGTH 25 MIN_PADDING 1)
+            list(APPEND lines "${line}")
+        endif()
+    endforeach()
+    list(SORT lines)
+    list(JOIN lines "\n" lines)
+    message("${lines}")
+    return()
+endif()
+
 while(1)
     qtConfHasNextCommandlineArg(has_next)
     if(NOT has_next)

config_help.txt

@@ -48,6 +48,8 @@ Configure meta:
 
   -feature-<feature> ... Enable <feature>
   -no-feature-<feature>  Disable <feature> [none]
+  -list-features ....... List available features. Note that some features
+                         have dedicated command line options as well.
 
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