Add imgui build to cmake

CMakeLists.txt

@@ -128,6 +128,7 @@ if (NOT WITHOUT_CSCORE)
 endif()
 
 if (WITH_SIMULATION_MODULES AND NOT USE_EXTERNAL_HAL)
+    add_subdirectory(imgui)
     add_subdirectory(simulation)
 endif()
 

imgui/CMakeLists.txt

@@ -0,0 +1,35 @@
+# Download and unpack imgui at configure time
+configure_file(CMakeLists.txt.in imgui-download/CMakeLists.txt)
+
+execute_process(COMMAND ${CMAKE_COMMAND} -G "${CMAKE_GENERATOR}" .
+  RESULT_VARIABLE result
+  WORKING_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/imgui-download )
+if(result)
+  message(FATAL_ERROR "CMake step for imgui failed: ${result}")
+endif()
+execute_process(COMMAND ${CMAKE_COMMAND} --build .
+  RESULT_VARIABLE result
+  WORKING_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/imgui-download )
+if(result)
+  message(FATAL_ERROR "Build step for imgui failed: ${result}")
+endif()
+
+# Add imgui directly to our build.
+set(SAVE_BUILD_SHARED_LIBS ${BUILD_SHARED_LIBS})
+set(BUILD_SHARED_LIBS OFF)
+add_subdirectory(${CMAKE_CURRENT_BINARY_DIR}/glfw-src
+                 ${CMAKE_CURRENT_BINARY_DIR}/glfw-build
+                 EXCLUDE_FROM_ALL)
+set_property(TARGET glfw PROPERTY POSITION_INDEPENDENT_CODE ON)
+set(BUILD_SHARED_LIBS ${SAVE_BUILD_SHARED_LIBS})
+add_subdirectory(${CMAKE_CURRENT_BINARY_DIR}/gl3w-src
+                 ${CMAKE_CURRENT_BINARY_DIR}/gl3w-build
+                 EXCLUDE_FROM_ALL)
+
+set(imgui_srcdir ${CMAKE_CURRENT_BINARY_DIR}/imgui-src)
+file(GLOB imgui_sources ${imgui_srcdir}/*.cpp)
+add_library(imgui STATIC ${imgui_sources} ${imgui_srcdir}/examples/imgui_impl_glfw.cpp ${imgui_srcdir}/examples/imgui_impl_opengl3.cpp)
+target_link_libraries(imgui PUBLIC gl3w glfw)
+target_include_directories(imgui PUBLIC "$<BUILD_INTERFACE:${imgui_srcdir}>" "$<BUILD_INTERFACE:${imgui_srcdir}/examples>")
+
+set_property(TARGET imgui PROPERTY POSITION_INDEPENDENT_CODE ON)

imgui/CMakeLists.txt.in

@@ -0,0 +1,33 @@
+cmake_minimum_required(VERSION 2.8.2)
+
+project(imgui-download NONE)
+
+include(ExternalProject)
+ExternalProject_Add(glfw3
+  GIT_REPOSITORY    https://github.com/glfw/glfw.git
+  GIT_TAG           7105ff2dfd004a46bd732c1d0c9f461bae6d51b3
+  SOURCE_DIR        "${CMAKE_CURRENT_BINARY_DIR}/glfw-src"
+  BINARY_DIR        "${CMAKE_CURRENT_BINARY_DIR}/glfw-build"
+  CONFIGURE_COMMAND ""
+  BUILD_COMMAND     ""
+  INSTALL_COMMAND   ""
+  TEST_COMMAND      ""
+)
+ExternalProject_Add(gl3w
+  GIT_REPOSITORY    https://github.com/skaslev/gl3w
+  GIT_TAG           7729692af8a2322cddb636b90393a42c130b1c85
+  SOURCE_DIR        "${CMAKE_CURRENT_BINARY_DIR}/gl3w-src"
+  BINARY_DIR        "${CMAKE_CURRENT_BINARY_DIR}/gl3w-build"
+  INSTALL_COMMAND   ""
+  TEST_COMMAND      ""
+)
+ExternalProject_Add(imgui
+  GIT_REPOSITORY    https://github.com/ocornut/imgui.git
+  GIT_TAG           v1.72b
+  SOURCE_DIR        "${CMAKE_CURRENT_BINARY_DIR}/imgui-src"
+  BINARY_DIR        "${CMAKE_CURRENT_BINARY_DIR}/imgui-build"
+  CONFIGURE_COMMAND ""
+  BUILD_COMMAND     ""
+  INSTALL_COMMAND   ""
+  TEST_COMMAND      ""
+)