[build] Clean up CMake files

CMakeLists.txt

@@ -12,6 +12,7 @@ endif()
 if("${CMAKE_HOST_SYSTEM_NAME}" STREQUAL "Windows")
     set(CMAKE_SYSTEM_VERSION 10.0.18362.0 CACHE STRING INTERNAL FORCE)
     set(CMAKE_VS_WINDOWS_TARGET_PLATFORM_VERSION 10.0.18362.0 CACHE STRING INTERNAL FORCE)
+    message(STATUS "Platform version: ${CMAKE_VS_WINDOWS_TARGET_PLATFORM_VERSION}")
 endif()
 
 cmake_minimum_required(VERSION 3.11)
@@ -23,19 +24,17 @@ if(POLICY CMP0135)
     cmake_policy(SET CMP0135 NEW)
 endif()
 
-message(STATUS "Platform version: ${CMAKE_VS_WINDOWS_TARGET_PLATFORM_VERSION}")
-
 set(WPILIB_BINARY_DIR ${CMAKE_CURRENT_BINARY_DIR})
 
 include(CPack)
+include(OptionValidation)
 
 set(CMAKE_WINDOWS_EXPORT_ALL_SYMBOLS TRUE)
 set_property(GLOBAL PROPERTY USE_FOLDERS ON)
 
 set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY ${WPILIB_BINARY_DIR}/lib)
 set(CMAKE_LIBRARY_OUTPUT_DIRECTORY ${WPILIB_BINARY_DIR}/lib)
 set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${WPILIB_BINARY_DIR}/bin)
-set(CMAKE_JAVA_TARGET_OUTPUT_DIR ${WPILIB_BINARY_DIR}/jar)
 
 # use, i.e. don't skip the full RPATH for the build tree
 set(CMAKE_SKIP_BUILD_RPATH FALSE)
@@ -87,28 +86,6 @@ if(NOT CMAKE_BUILD_TYPE)
     set(CMAKE_BUILD_TYPE "RelWithDebInfo" CACHE STRING "" FORCE)
 endif()
 
-if(WITH_JAVA AND NOT BUILD_SHARED_LIBS)
-    message(
-        FATAL_ERROR
-        "
-FATAL: Cannot build static libs with Java enabled.
-       Static libs requires both BUILD_SHARED_LIBS=OFF and
-       WITH_JAVA=OFF
-"
-    )
-endif()
-
-if(WITH_SIMULATION_MODULES AND NOT BUILD_SHARED_LIBS)
-    message(
-        FATAL_ERROR
-        "
-FATAL: Cannot build static libs with simulation modules enabled.
-       Static libs requires both BUILD_SHARED_LIBS=OFF and
-       WITH_SIMULATION_MODULES=OFF
-"
-    )
-endif()
-
 if(NOT WITH_JAVA OR NOT WITH_CSCORE)
     if(NOT "${OPENCV_JAVA_INSTALL_DIR}" STREQUAL "")
         message(
@@ -121,81 +98,24 @@ It will be ignored.
     endif()
 endif()
 
-if(NOT WITH_WPILIB AND WITH_SIMULATION_MODULES)
-    message(
-        FATAL_ERROR
-        "
-FATAL: Cannot build simulation modules with wpilib disabled.
-       Enable wpilib by setting WITH_WPILIB=ON
-"
-    )
-endif()
-
-if(NOT WITH_NTCORE AND WITH_CSCORE)
-    message(
-        FATAL_ERROR
-        "
-FATAL: Cannot build cameraserver without ntcore.
-       Enable ntcore by setting WITH_NTCORE=ON
-"
-    )
-endif()
+wpilib_config(OPTIONS WITH_JAVA REQUIRES BUILD_SHARED_LIBS)
 
-if(NOT WITH_NTCORE AND WITH_GUI)
-    message(
-        FATAL_ERROR
-        "
-FATAL: Cannot build GUI modules without ntcore.
-       Enable ntcore by setting WITH_NTCORE=ON
-"
-    )
-endif()
+wpilib_config(OPTIONS WITH_SIMULATION_MODULES REQUIRES BUILD_SHARED_LIBS WITH_WPILIB WITH_NTCORE)
 
-if(NOT WITH_NTCORE AND WITH_SIMULATION_MODULES)
-    message(
-        FATAL_ERROR
-        "
-FATAL: Cannot build simulation modules without ntcore.
-       Enable ntcore by setting WITH_NTCORE=ON
-"
-    )
-endif()
+wpilib_config(OPTIONS WITH_CSCORE REQUIRES WITH_NTCORE)
 
-if(NOT WITH_NTCORE AND WITH_WPILIB)
-    message(
-        FATAL_ERROR
-        "
-FATAL: Cannot build wpilib without ntcore.
-       Enable ntcore by setting WITH_NTCORE=ON
-"
-    )
-endif()
+wpilib_config(OPTIONS WITH_GUI REQUIRES WITH_NTCORE WITH_WPIMATH)
 
-if(NOT WITH_WPIMATH AND WITH_WPILIB)
-    message(
-        FATAL_ERROR
-        "
-FATAL: Cannot build wpilib without wpimath.
-       Enable wpimath by setting WITH_WPIMATH=ON
-"
-    )
-endif()
+wpilib_config(OPTIONS WITH_WPILIB REQUIRES WITH_NTCORE WITH_WPIMATH)
 
-if(NOT WITH_WPIUNITS AND WITH_WPIMATH AND WITH_JAVA)
-    message(
-        FATAL_ERROR
-        "
-FATAL: Cannot build Java wpimath without wpiunits.
-       Enable wpiunits by setting WITH_WPIUNITS=ON or disable the Java build by setting WITH_JAVA=OFF
-"
-    )
-endif()
+wpilib_config(OPTIONS WITH_WPIMATH WITH_JAVA REQUIRES WITH_WPIUNITS)
 
 set(include_dest include)
 set(java_lib_dest java)
-set(jni_lib_dest jni)
-if(WITH_JAVA)
+if(WITH_JAVA OR WITH_JAVA_SOURCE)
     set(CMAKE_JAVA_COMPILE_FLAGS "-encoding" "UTF8" "-Xlint:unchecked")
+    find_package(Java REQUIRED COMPONENTS Development)
+    find_package(JNI REQUIRED COMPONENTS JVM)
 endif()
 
 find_package(LIBSSH 0.7.1)
@@ -382,6 +302,7 @@ endif()
 if(WITH_CSCORE)
     set(CAMERASERVER_DEP_REPLACE "find_dependency(cameraserver)")
     set(CSCORE_DEP_REPLACE "find_dependency(cscore)")
+    find_package(OpenCV REQUIRED)
     add_subdirectory(cscore)
     add_subdirectory(cameraserver)
 endif()

README-CMAKE.md

@@ -108,6 +108,12 @@ After build, the easiest way to use the libraries is to install them. Run the fo
 sudo cmake --build . --target install
 ```
 
+## Preparing to use the installed libraries
+
+On Windows, make sure the directories for the libraries you built are on PATH. For wpilib, the default install location is `C:\Program Files (x86)\allwpilib`. If you built other libraries like OpenCV and protobuf from source, install them, and add the install directories to PATH. This ensures CMake can locate the libraries.
+
+You will also want to add the directories where the DLLs are located (usually the `bin` subdirectory of the install directory) to PATH so they can be loaded by your program. If you are using OpenCV and Java, the `opencv_java` DLL is located in either the `lib` subdirectory if you built but didn't install OpenCV, or the `java` subdirectory if you did install OpenCV.
+
 ## Using the installed libraries for C++.
 
 Using the libraries from C++ is the easiest way to use the built libraries.
@@ -134,12 +140,11 @@ cmake /path/to/folder/containing/CMakeLists
 
 After that, run `cmake --build .`. That will create your executable. Then you should be able to run `./my_vision_app` to run your application.
 
-
 ## Using the installed libraries for Java
 
-Using the built JARs is move involved than using the C++ libraries, but mostly consists of adding the correct directories to PATH.
+Using the built JARs is more involved than using the C++ libraries, but the additional work involves providing the paths to various libraries and JARs when needed.
 
-Add the directory where the JARs are located (e.g, `/usr/local/java`) to PATH. If you are on Windows, you also need to add the `lib`, `bin`, and `share` directories to PATH. Then, create a new folder to contain your project. Add the following code below to a `CMakeLists.txt` file in that directory.
+Create a new folder to contain your project. Add the following code below to a `CMakeLists.txt` file in that directory.
 
 ```cmake
 cmake_minimum_required(VERSION 3.11)

apriltag/CMakeLists.txt

@@ -27,8 +27,6 @@ set(APRILTAGLIB_SRCS
 file(GLOB apriltag_jni_src src/main/native/cpp/jni/AprilTagJNI.cpp)
 
 if(WITH_JAVA)
-    find_package(Java REQUIRED)
-    find_package(JNI REQUIRED)
     include(UseJava)
 
     set(CMAKE_JNI_TARGET true)
@@ -47,8 +45,6 @@ if(WITH_JAVA)
         NO_DEFAULT_PATH
     )
 
-    set(CMAKE_JAVA_INCLUDE_PATH apriltag.jar ${EJML_JARS} ${JACKSON_JARS})
-
     file(GLOB_RECURSE JAVA_SOURCES src/main/java/*.java)
     file(
         GLOB_RECURSE JAVA_RESOURCES
@@ -60,8 +56,15 @@ if(WITH_JAVA)
         SOURCES ${JAVA_SOURCES}
         RESOURCES
         NAMESPACE "edu/wpi/first/apriltag" ${JAVA_RESOURCES}
-        INCLUDE_JARS wpimath_jar wpiunits_jar ${EJML_JARS} wpiutil_jar ${OPENCV_JAR_FILE}
+        INCLUDE_JARS
+            wpimath_jar
+            wpiunits_jar
+            wpiutil_jar
+            ${EJML_JARS}
+            ${OPENCV_JAR_FILE}
+            ${JACKSON_JARS}
         OUTPUT_NAME apriltag
+        OUTPUT_DIR ${WPILIB_BINARY_DIR}/${java_lib_dest}
         GENERATE_NATIVE_HEADERS apriltag_jni_headers
     )
     set_property(TARGET apriltag_jar PROPERTY FOLDER "java")
@@ -83,7 +86,6 @@ if(WITH_JAVA)
 endif()
 
 if(WITH_JAVA_SOURCE)
-    find_package(Java REQUIRED)
     include(UseJava)
     file(GLOB APRILTAG_SOURCES src/main/java/edu/wpi/first/apriltag/*.java)
     add_jar(
@@ -94,6 +96,7 @@ if(WITH_JAVA_SOURCE)
             "edu/wpi/first/apriltag/jni"
             src/main/java/edu/wpi/first/apriltag/jni/AprilTagJNI.java
         OUTPUT_NAME apriltag-sources
+        OUTPUT_DIR ${WPILIB_BINARY_DIR}/${java_lib_dest}
     )
 
     get_property(APRILTAG_SRC_JAR_FILE TARGET apriltag_src_jar PROPERTY JAR_FILE)

cameraserver/CMakeLists.txt

@@ -3,15 +3,11 @@ project(cameraserver)
 include(CompileWarnings)
 include(AddTest)
 
-find_package(OpenCV REQUIRED)
-
 # Java bindings
 if(WITH_JAVA)
-    find_package(Java REQUIRED)
     include(UseJava)
 
-    #find java files, copy them locally
-
+    #find JAR file, copy it locally
     set(OPENCV_JAVA_INSTALL_DIR ${OpenCV_INSTALL_PATH}/share/java/opencv4)
 
     find_file(
@@ -32,6 +28,7 @@ if(WITH_JAVA)
         ${JAVA_SOURCES}
         INCLUDE_JARS wpiutil_jar cscore_jar ntcore_jar ${OPENCV_JAR_FILE}
         OUTPUT_NAME cameraserver
+        OUTPUT_DIR ${WPILIB_BINARY_DIR}/${java_lib_dest}
     )
     set_property(TARGET cameraserver_jar PROPERTY FOLDER "java")
 
@@ -44,7 +41,6 @@ if(WITH_JAVA)
 endif()
 
 if(WITH_JAVA_SOURCE)
-    find_package(Java REQUIRED)
     include(UseJava)
     file(GLOB CAMERASERVER_SOURCES src/main/java/edu/wpi/first/cameraserver/*.java)
     file(GLOB VISION_SOURCES src/main/java/edu/wpi/first/vision/*.java)
@@ -54,6 +50,7 @@ if(WITH_JAVA_SOURCE)
         NAMESPACE "edu/wpi/first/cameraserver" ${CAMERASERVER_SOURCES}
         NAMESPACE "edu/wpi/first/vision" ${VISION_SOURCES}
         OUTPUT_NAME cameraserver-sources
+        OUTPUT_DIR ${WPILIB_BINARY_DIR}/${java_lib_dest}
     )
 
     get_property(CAMERASERVER_SRC_JAR_FILE TARGET cameraserver_src_jar PROPERTY JAR_FILE)

cmake/modules/OptionValidation.cmake

@@ -0,0 +1,29 @@
+function(wpilib_config)
+    cmake_parse_arguments(config "" "" "OPTIONS;REQUIRES" ${ARGN})
+    foreach(opt ${config_OPTIONS})
+        if(NOT ${opt})
+            return()
+        endif()
+    endforeach()
+    foreach(required_opt ${config_REQUIRES})
+        if(NOT ${required_opt})
+            list(JOIN config_OPTIONS " and " options_list)
+            list(LENGTH config_OPTIONS option_len)
+            if(option_len GREATER 1)
+                set(requires require)
+                set(option_msg "one of the listed options")
+            else()
+                set(requires requires)
+                set(option_msg ${options_list})
+            endif()
+
+            message(
+                FATAL_ERROR
+                "
+FATAL: ${options_list} ${requires} ${required_opt}.
+       Either enable ${required_opt} or disable ${option_msg}.
+"
+            )
+        endif()
+    endforeach()
+endfunction()