ignition-msgs5: Add support for crosscompilation

Similar to the protobuf case, when cross-compiling it is required
that the port is already installed in the host machine triplet,
for now just x86-windows as for protobuf.

ports/ignition-msgs5/02-support-crosscompilation.patch

@@ -0,0 +1,70 @@
+From 8d3735616c34fdc266b45c614c6d179d72732066 Mon Sep 17 00:00:00 2001
+From: Silvio Traversaro <silvio.traversaro@iit.it>
+Date: Sat, 23 May 2020 12:09:15 +0200
+Subject: [PATCH] Add CMake options to support cross-compilation
+
+This commit adds two CMake options:
+* INSTALL_IGN_MSGS_GEN_EXECUTABLE if this option is enabled, the
+  ign_msgs_gen protobuf executable plugin is also installed, so
+  that this option can be enabled in host builds to permit
+  cross-compilation builds to use it to generate the messages.
+  As this executable is not side by side installable with other
+  ignition-msgs installations with different major versions and is an
+  advanced option meant just for packaging, by default it is set to OFF.
+* IGN_MSGS_GEN_EXECUTABLE: this string variable can be set to
+  have ign-msgs use a ign_msgs_gen executable plugin that was not
+  build by the project, to enable cross-compilation scenarios.
+
+Signed-off-by: Silvio Traversaro <silvio.traversaro@iit.it>
+---
+ CMakeLists.txt     | 13 ++++++++++++-
+ src/CMakeLists.txt |  6 +++++-
+ 2 files changed, 17 insertions(+), 2 deletions(-)
+
+diff --git a/CMakeLists.txt b/CMakeLists.txt
+index 62b56b1..1641489 100644
+--- a/CMakeLists.txt
++++ b/CMakeLists.txt
+@@ -20,7 +20,18 @@ ign_configure_project()
+ # Set project-specific options
+ #============================================================================
+
+-# ignition-msgs currently has no options that are unique to it
++option(
++  INSTALL_IGN_MSGS_GEN_EXECUTABLE
++  "Install the ign_msgs_gen executable."
++  OFF)
++mark_as_advanced(INSTALL_IGN_MSGS_GEN_EXECUTABLE)
++
++set(
++  IGN_MSGS_GEN_EXECUTABLE
++  "$<TARGET_FILE:ign_msgs_gen>"
++  CACHE STRING
++  "ign_msgs_gen executable used in the ign_msgs_protoc CMake function.")
++mark_as_advanced(IGN_MSGS_GEN_EXECUTABLE)
+
+ #============================================================================
+ # Search for project-specific dependencies
+diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
+index f68bf3d..1eb5e36 100644
+--- a/src/CMakeLists.txt
++++ b/src/CMakeLists.txt
+@@ -11,6 +11,9 @@ if (UNIX)
+   target_link_libraries(ign_msgs_gen pthread)
+ endif()
+
++if(INSTALL_IGN_MSGS_GEN_EXECUTABLE)
++  install(TARGETS ign_msgs_gen DESTINATION ${IGN_BIN_INSTALL_DIR})
++endif()
+
+ ##################################################
+ # A function that calls protoc on a protobuf file
+@@ -57,7 +61,7 @@ function(ign_msgs_protoc)
+     list(APPEND ${ign_msgs_protoc_OUTPUT_CPP_CC_VAR} ${output_source})
+     list(APPEND output_files ${output_header})
+     list(APPEND output_files ${output_source})
+-    list(APPEND protoc_args "--plugin=protoc-gen-ignmsgs=$<TARGET_FILE:ign_msgs_gen>")
++    list(APPEND protoc_args "--plugin=protoc-gen-ignmsgs=${IGN_MSGS_GEN_EXECUTABLE}")
+     list(APPEND protoc_args "--cpp_out=dllexport_decl=IGNITION_MSGS_VISIBLE:${ign_msgs_protoc_OUTPUT_CPP_DIR}")
+     list(APPEND protoc_args "--ignmsgs_out" "${ign_msgs_protoc_OUTPUT_CPP_DIR}")
+     set(${ign_msgs_protoc_OUTPUT_CPP_HH_VAR} ${${ign_msgs_protoc_OUTPUT_CPP_HH_VAR}} PARENT_SCOPE)

ports/ignition-msgs5/CONTROL

@@ -3,4 +3,4 @@ Version: 5.1.0
 Port-Version: 1
 Build-Depends: ignition-modularscripts, ignition-cmake2, ignition-math6, protobuf, tinyxml2
 Description: Middleware protobuf messages for robotics
-Supports: !(arm|linux|uwp)
+Supports: !(linux)

ports/ignition-msgs5/portfile.cmake

@@ -1,20 +1,46 @@
-# Explicitly disable cross-compilation until the upstream discussion
-# https://github.com/ignitionrobotics/ign-msgs/issues/34 is solved
-vcpkg_fail_port_install(ON_ARCH "arm" ON_TARGET "linux" "uwp") 
+vcpkg_fail_port_install(ON_TARGET "linux")
 
 include(${CURRENT_INSTALLED_DIR}/share/ignitionmodularscripts/ignition_modular_library.cmake)
 
+if(CMAKE_HOST_WIN32 AND NOT VCPKG_TARGET_ARCHITECTURE MATCHES "x64" AND NOT VCPKG_TARGET_ARCHITECTURE MATCHES "x86")
+  set(ignition_msgs_CROSSCOMPILING ON)
+else()
+  set(ignition_msgs_CROSSCOMPILING OFF)
+endif()
+
+if(CMAKE_HOST_WIN32)
+    set(HOST_EXECUTABLE_SUFFIX ".exe")
+else()
+    set(HOST_EXECUTABLE_SUFFIX "")
+endif()
+
 # This port needs  to generate protobuf messages with a custom plugin generator,
 # so it needs to have in Windows the relative protobuf dll available in the PATH
-set(path_backup $ENV{PATH})
-vcpkg_add_to_path(${CURRENT_INSTALLED_DIR}/bin)
-vcpkg_add_to_path(${CURRENT_INSTALLED_DIR}/debug/bin)
+if(NOT ignition_msgs_CROSSCOMPILING)
+  set(path_backup $ENV{PATH})
+  vcpkg_add_to_path(${CURRENT_INSTALLED_DIR}/bin)
+  vcpkg_add_to_path(${CURRENT_INSTALLED_DIR}/debug/bin)
+  set(CMAKE_OPTIONS "-DINSTALL_IGN_MSGS_GEN_EXECUTABLE:BOOL=ON")
+  set(TOOL_NAMES_OPTION TOOL_NAMES ign_msgs_gen)
+else()
+  if(NOT EXISTS ${CURRENT_INSTALLED_DIR}/../x86-windows/tools/${PORT})
+    message(FATAL_ERROR "Cross-targetting ${PORT} requires the x86-windows ${PORT} to be available. Please install ${PORT}:x86-windows first.")
+  endif()
+  set(CMAKE_OPTIONS "-DIGN_MSGS_GEN_EXECUTABLE=${CURRENT_INSTALLED_DIR}/../x86-windows/tools/${PORT}/ign_msgs_gen${HOST_EXECUTABLE_SUFFIX}")
+  set(TOOL_NAMES_OPTION "")
+endif()
 
 ignition_modular_library(NAME msgs
                          VERSION "5.1.0"
                          SHA512 db485f737c465b310602342a1a751c561473e330eb18d1b322b32d13de246536fe6a7efdf245faaaa9be1c9bfce662b2d39d1bb7cffc37e52690893cb47cc2ee
                          PATCHES
-                           "01-protobuf.patch")
+                           "01-protobuf.patch"
+                           # Backport https://github.com/ignitionrobotics/ign-msgs/pull/60
+                           "02-support-crosscompilation.patch"
+                         CMAKE_OPTIONS "${CMAKE_OPTIONS}"
+                         ${TOOL_NAMES_OPTION})
 
 # Restore old path
-set(ENV{PATH} "${path_backup}")
+if(NOT ignition_msgs_CROSSCOMPILING)
+  set(ENV{PATH} "${path_backup}")
+endif()