remove feature for automatic jpeg/png/zlib library download and build

this is a post-stable feature and would require a general rewrite of offline processing

cmake/CMakeLists.txt

@@ -421,55 +421,9 @@ endif()
 # tweak jpeg library names to avoid linker errors with MinGW cross-compilation
 set(JPEG_NAMES libjpeg libjpeg-62)
 find_package(JPEG QUIET)
-find_package(PNG QUIET)
-find_package(ZLIB QUIET)
-
-check_for_internet_connection(HAVE_INTERNET)
-
-# if we have a working internet connection. download and build missing libs
-if(HAVE_INTERNET AND (CMAKE_VERSION VERSION_GREATER_EQUAL 3.16))
-  include(ExternalCMakeProject)
-  if(NOT JPEG_FOUND)
-    set(LIBJPEG_URL https://sourceforge.net/projects/libjpeg-turbo/files/2.1.3/libjpeg-turbo-2.1.3.tar.gz)
-    set(LIBJPEG_MD5 85244dedeaf06f636a9e7ddea6d236d8)
-    mark_as_advanced(LIBJPEG_URL)
-    mark_as_advanced(LIBJPEG_MD5)
-    ExternalCmakeProject(libjpeg ${LIBJPEG_URL} ${LIBJPEG_MD5} libjpeg-turbo . CMakeLists.jpeg)
-    add_library(JPEG::JPEG ALIAS jpeg-static)
-    target_include_directories(lammps PRIVATE "${CMAKE_BINARY_DIR}/_deps/libjpeg-src")
-    target_include_directories(lammps PRIVATE "${CMAKE_BINARY_DIR}/_deps/libjpeg-build")
-    set(JPEG_FOUND TRUE)
-  endif()
-  if(NOT ZLIB_FOUND)
-    set(LIBZ_URL http://prdownloads.sourceforge.net/libpng/zlib-1.2.11.tar.gz)
-    set(LIBZ_MD5 1c9f62f0778697a09d36121ead88e08e)
-    mark_as_advanced(LIBZ_URL)
-    mark_as_advanced(LIBZ_MD5)
-    ExternalCmakeProject(libz ${LIBZ_URL} ${LIBZ_MD5} zlib . CMakeLists.zlib)
-    add_library(ZLIB::ZLIB ALIAS zlibstatic)
-    target_include_directories(lammps PRIVATE "${CMAKE_BINARY_DIR}/_deps/libz-src")
-    target_include_directories(lammps PRIVATE "${CMAKE_BINARY_DIR}/_deps/libz-build")
-    set(ZLIB_FOUND TRUE)
-    set(ZLIB_INCLUDE_DIR "${CMAKE_BINARY_DIR}/_deps/libz-src;${CMAKE_BINARY_DIR}/_deps/libz-build")
-  endif()
-  if(NOT PNG_FOUND)
-    set(LIBPNG_URL http://prdownloads.sourceforge.net/libpng/libpng-1.6.37.tar.gz)
-    set(LIBPNG_MD5 6c7519f6c75939efa0ed3053197abd54)
-    mark_as_advanced(LIBPNG_URL)
-    mark_as_advanced(LIBPNG_MD5)
-    ExternalCmakeProject(libpng ${LIBPNG_URL} ${LIBPNG_MD5} libpng . CMakeLists.png)
-    add_library(PNG::PNG ALIAS png_static)
-    target_include_directories(lammps PRIVATE "${CMAKE_BINARY_DIR}/_deps/libpng-src")
-    target_include_directories(lammps PRIVATE "${CMAKE_BINARY_DIR}/_deps/libpng-build")
-    set(PNG_FOUND TRUE)
-  endif()
-endif()
-
 option(WITH_JPEG "Enable JPEG support" ${JPEG_FOUND})
 if(WITH_JPEG)
-  if(NOT JPEG_FOUND)
-    find_package(JPEG REQUIRED)
-  endif() 
+  find_package(JPEG REQUIRED)
   target_compile_definitions(lammps PRIVATE -DLAMMPS_JPEG)
   if(CMAKE_VERSION VERSION_LESS 3.12)
     target_include_directories(lammps PRIVATE ${JPEG_INCLUDE_DIRS})
@@ -479,18 +433,16 @@ if(WITH_JPEG)
   endif()
 endif()
 
+find_package(PNG QUIET)
+find_package(ZLIB QUIET)
 if(PNG_FOUND AND ZLIB_FOUND)
   option(WITH_PNG "Enable PNG support" ON)
 else()
   option(WITH_PNG "Enable PNG support" OFF)
 endif()
 if(WITH_PNG)
-  if(NOT PNG_FOUND)
-    find_package(PNG REQUIRED)
-  endif()
-  if(NOT ZLIB_FOUND)
-    find_package(ZLIB REQUIRED)
-  endif()
+  find_package(PNG REQUIRED)
+  find_package(ZLIB REQUIRED)
   target_link_libraries(lammps PRIVATE PNG::PNG ZLIB::ZLIB)
   target_compile_definitions(lammps PRIVATE -DLAMMPS_PNG)
 endif()

cmake/Modules/LAMMPSUtils.cmake

@@ -105,23 +105,6 @@ function(FetchPotentials pkgfolder potfolder)
   endif()
 endfunction(FetchPotentials)
 
-# Check and record if we have a working internet connection
-function(check_for_internet_connection variable)
-  message("Checking internet connection... ")
-  if((CMAKE_SYSTEM_NAME STREQUAL "Windows") AND (NOT CMAKE_CROSSCOMPILING))
-    execute_process(COMMAND ping www.google.com -n 2
-      OUTPUT_QUIET ERROR_QUIET RESULT_VARIABLE PING_STATUS)
-  else()
-    execute_process(COMMAND ping www.google.com -c 2
-      OUTPUT_QUIET ERROR_QUIET RESULT_VARIABLE PING_STATUS)
-  endif()
-  if(PING_STATUS EQUAL 0)
-    set(${variable} TRUE PARENT_SCOPE)
-  else()
-    set(${variable} FALSE PARENT_SCOPE)
-  endif()
-endfunction(check_for_internet_connection)
-
 # set CMAKE_LINUX_DISTRO and CMAKE_DISTRO_VERSION on Linux
 if((CMAKE_SYSTEM_NAME STREQUAL "Linux") AND (EXISTS /etc/os-release))
   file(STRINGS /etc/os-release distro REGEX "^NAME=")

cmake/Modules/Packages/COMPRESS.cmake

@@ -1,10 +1,4 @@
-if(NOT ZLIB_FOUND)
-  find_package(ZLIB)
-  if(NOT ZLIB_FOUND)
-    message(WARNING "zlib library not found skipping COMPRESS package")
-    return()
-  endif()
-endif()
+find_package(ZLIB REQUIRED)
 target_link_libraries(lammps PRIVATE ZLIB::ZLIB)
 
 find_package(PkgConfig QUIET)

cmake/presets/windows.cmake

@@ -9,7 +9,6 @@ set(WIN_PACKAGES
   CLASS2
   COLLOID
   COLVARS
-  COMPRESS
   CORESHELL
   DIELECTRIC
   DIFFRACTION

doc/src/Build_settings.rst

@@ -297,15 +297,15 @@ requires the following settings:
       .. code-block:: bash
 
          -D WITH_JPEG=value      # yes or no
-                                 # default = yes
+                                 # default = yes if CMake finds JPEG files, else no
          -D WITH_PNG=value       # yes or no
-                                 # default = yes
+                                 # default = yes if CMake finds PNG and ZLIB files, else no
          -D WITH_FFMPEG=value    # yes or no
                                  # default = yes if CMake can find ffmpeg, else no
 
-      Usually these settings are all that is needed.  If those libraries
-      or executables are installed but CMake cannot find the graphics header,
-      library, or executable files, you can set these variables accordingly:
+      Usually these settings are all that is needed.  If CMake cannot
+      find the graphics header, library, executable files, you can set
+      these variables:
 
       .. code-block:: bash
 
@@ -317,9 +317,6 @@ requires the following settings:
          -D ZLIB_LIBRARY=path        # path to libz.a (.so) file
          -D FFMPEG_EXECUTABLE=path   # path to ffmpeg executable
 
-      Otherwise, CMake will attempt to download, build, and link with
-      jpeg, png, and zlib libraries statically from source code.
-
    .. tab:: Traditional make
 
       .. code-block:: make