cmake: added feature for using external vcpkg installation

CMakeLists.txt

@@ -16,11 +16,9 @@ if(${CMAKE_VERSION} VERSION_LESS "3.0.2")
 	endmacro()
 endif()
 
-if(VCPKG_TARGET_ANDROID)
-	include(VcpkgAndroid)
-endif()
-
 include(VcpkgIntegration)
+include(VcpkgAndroid)
+
 option(BUILD_CLIENT "Build client library" ON)
 option(BUILD_SERVER "Build server library" ON)
 option(BUILD_UTILS "Build developer utilities (map/models compilers, etc.)" ON)

cmake/VcpkgAndroid.cmake

@@ -81,7 +81,11 @@ if (VCPKG_TARGET_ANDROID)
     # However, vcpkg provides a way to preload and additional toolchain, 
     # with the VCPKG_CHAINLOAD_TOOLCHAIN_FILE option.
     set(VCPKG_CHAINLOAD_TOOLCHAIN_FILE $ENV{ANDROID_NDK_HOME}/build/cmake/android.toolchain.cmake)
-    set(CMAKE_TOOLCHAIN_FILE ${CMAKE_SOURCE_DIR}/external/vcpkg/scripts/buildsystems/vcpkg.cmake)
+
+    set(VCPKG_INSTANCE_PATH "")
+	get_vcpkg_instance_path(VCPKG_INSTANCE_PATH)
+    set(CMAKE_TOOLCHAIN_FILE ${VCPKG_INSTANCE_PATH})
+
     message("VcpkgAndroid.cmake: CMAKE_TOOLCHAIN_FILE was set to ${CMAKE_TOOLCHAIN_FILE}")
     message("VcpkgAndroid.cmake: VCPKG_CHAINLOAD_TOOLCHAIN_FILE was set to ${VCPKG_CHAINLOAD_TOOLCHAIN_FILE}")
 

cmake/VcpkgIntegration.cmake

@@ -1,13 +1,27 @@
+
+function(get_vcpkg_instance_path RESULT_VAR)
+	if(DEFINED ENV{VCPKG_ROOT})
+		set(${RESULT_VAR} "$ENV{VCPKG_ROOT}/scripts/buildsystems/vcpkg.cmake" PARENT_SCOPE)
+		message(STATUS "External vcpkg installation found at path: $ENV{VCPKG_ROOT}")
+	else()
+		set(${RESULT_VAR} "${CMAKE_SOURCE_DIR}/external/vcpkg/scripts/buildsystems/vcpkg.cmake" PARENT_SCOPE)
+		message(STATUS "External vcpkg installation not found, submodule will be used")
+	endif()
+endfunction()
+
 # allows to transparently pass in custom toolchain file along with vcpkg toolchain
 # include this module in main CMakeLists.txt script BEFORE project() directive
 if(NOT VCPKG_TARGET_ANDROID)
+	set(VCPKG_INSTANCE_PATH "")
+	get_vcpkg_instance_path(VCPKG_INSTANCE_PATH)
+
 	if(CMAKE_TOOLCHAIN_FILE) 
 		if (NOT CMAKE_TOOLCHAIN_FILE MATCHES "vcpkg.cmake$")
 			set(VCPKG_CHAINLOAD_TOOLCHAIN_FILE "${CMAKE_TOOLCHAIN_FILE}")
-			set(CMAKE_TOOLCHAIN_FILE "${CMAKE_SOURCE_DIR}/external/vcpkg/scripts/buildsystems/vcpkg.cmake")
+			set(CMAKE_TOOLCHAIN_FILE "${VCPKG_INSTANCE_PATH}")
 		endif()
 	else()
-		set(CMAKE_TOOLCHAIN_FILE "${CMAKE_SOURCE_DIR}/external/vcpkg/scripts/buildsystems/vcpkg.cmake")
+		set(CMAKE_TOOLCHAIN_FILE "${VCPKG_INSTANCE_PATH}")
 	endif()
 endif()