feat: About dialog with version, commit, build time and settings path

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

CMakeLists.txt

@@ -1,5 +1,5 @@
 cmake_minimum_required(VERSION 3.24)
-project(udpscope LANGUAGES C CXX)
+project(udpscope VERSION 0.1.0 LANGUAGES C CXX)
 
 set(CMAKE_CXX_STANDARD 20)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
@@ -51,9 +51,28 @@ add_custom_command(
   COMMENT "Compiling udpscope icon resources"
   VERBATIM)
 
+# --- build info: version, commit and timestamp compiled into the binary -------
+# Written at configure time so add_executable can name the file, and again on every
+# build so the commit and the timestamp belong to the binary that is running rather
+# than to whenever the tree was last configured.
+set(UDPSCOPE_BUILD_INFO ${CMAKE_CURRENT_BINARY_DIR}/build_info.cpp)
+set(UDPSCOPE_BUILD_INFO_ARGS
+    -DSRC=${CMAKE_CURRENT_SOURCE_DIR}
+    -DOUT=${UDPSCOPE_BUILD_INFO}
+    -DVERSION=${PROJECT_VERSION}
+    -P ${CMAKE_CURRENT_SOURCE_DIR}/cmake/write_build_info.cmake)
+execute_process(COMMAND ${CMAKE_COMMAND} ${UDPSCOPE_BUILD_INFO_ARGS})
+add_custom_target(udpscope_build_info
+  BYPRODUCTS ${UDPSCOPE_BUILD_INFO}
+  COMMAND ${CMAKE_COMMAND} ${UDPSCOPE_BUILD_INFO_ARGS}
+  COMMENT "Writing udpscope build info"
+  VERBATIM)
+set_source_files_properties(${UDPSCOPE_BUILD_INFO} PROPERTIES GENERATED TRUE)
+
 # --- the application ----------------------------------------------------------
 add_executable(udpscope
   ${CMAKE_CURRENT_BINARY_DIR}/udpscope_resources.c
+  ${UDPSCOPE_BUILD_INFO}
   src/main.cpp
   src/config.cpp
   src/channel.cpp
@@ -66,11 +85,13 @@ add_executable(udpscope
   src/source_dialog.cpp
   src/measure.cpp
   src/math_channel.cpp
+  src/help_window.cpp
   src/ui.cpp
 )
 
 target_include_directories(udpscope PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/src)
 target_link_libraries(udpscope PRIVATE plot::gtk4 udpsclient Threads::Threads)
+add_dependencies(udpscope udpscope_build_info)
 if(CMAKE_CXX_COMPILER_ID MATCHES "GNU|Clang")
   target_compile_options(udpscope PRIVATE -Wall -Wextra -Wpedantic)
 endif()