Install QtOpcUa to local prefix instead of system Qt directory

Add QTOPCUA_INSTALL_DIR and CMAKE_INSTALL_PREFIX so QtOpcUa installs
to build/deps/qtopcua-install/ rather than polluting ~/Qt/6.10.2/.
Use QT_ADDITIONAL_PACKAGES_PREFIX_PATH so Qt's find_package resolves
OpcUa from the local install.

3 files changed, 17 insertions, 14 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 2607734..6a9265f 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -8,9 +8,9 @@ set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
 # Build external dependencies (open62541, qtopcua) if not already built
 include(cmake/BuildDeps.cmake)
 
-# Local QtOpcUa must come before system Qt so find_package picks up our build
-# instead of any system-installed QtOpcUa.
-list(PREPEND CMAKE_PREFIX_PATH "${QTOPCUA_BUILD_DIR}")
+# Tell Qt's find_package to also look in our local QtOpcUa install for
+# components (Qt6Config.cmake only searches its own install dir by default).
+list(PREPEND QT_ADDITIONAL_PACKAGES_PREFIX_PATH "${QTOPCUA_INSTALL_DIR}")
 list(PREPEND CMAKE_PREFIX_PATH "${OPEN62541_INSTALL_DIR}")
 
 find_package(Qt6 6.10.2 REQUIRED COMPONENTS Core Qml Quick OpcUa)
@@ -27,7 +27,8 @@ set(QML_IMPORT_PATH
 
 # Ensure the local QtOpcUa and open62541 libs are findable at runtime (needed
 # because the Qt plugin loader dlopen's the open62541 backend).
-set(CMAKE_BUILD_RPATH "${QTOPCUA_BUILD_DIR}/lib" "${OPEN62541_INSTALL_DIR}/lib")
+set(CMAKE_BUILD_RPATH "${QTOPCUA_INSTALL_DIR}/lib"
+                      "${OPEN62541_INSTALL_DIR}/lib")
 
 add_subdirectory(src)
 add_subdirectory(demo)
diff --git a/cmake/BuildDeps.cmake b/cmake/BuildDeps.cmake
index d105419..1b8eae3 100644
--- a/cmake/BuildDeps.cmake
+++ b/cmake/BuildDeps.cmake
@@ -1,11 +1,11 @@
 # ======================================
-#  BuildDeps.cmake
+# BuildDeps.cmake
 #
-#  Configure, build, and install open62541 and QtOpcUa from
-#  git submodules under deps/.
+# Configure, build, and install open62541 and QtOpcUa from git submodules under
+# deps/.
 #
-#  Skip detection: if the built .so already exists, the
-#  corresponding dep is skipped. Delete the file to rebuild.
+# Skip detection: if the built .so already exists, the corresponding dep is
+# skipped. Delete the file to rebuild.
 # ======================================
 
 set(OPEN62541_SOURCE_DIR "${CMAKE_SOURCE_DIR}/deps/open62541")
@@ -13,6 +13,7 @@ set(OPEN62541_BUILD_DIR "${CMAKE_BINARY_DIR}/deps/open62541-build")
 set(OPEN62541_INSTALL_DIR "${CMAKE_BINARY_DIR}/deps/open62541-install")
 set(QTOPCUA_SOURCE_DIR "${CMAKE_SOURCE_DIR}/deps/qtopcua")
 set(QTOPCUA_BUILD_DIR "${CMAKE_BINARY_DIR}/deps/qtopcua-build")
+set(QTOPCUA_INSTALL_DIR "${CMAKE_BINARY_DIR}/deps/qtopcua-install")
 
 # Verify submodules are initialized
 if(NOT EXISTS "${OPEN62541_SOURCE_DIR}/CMakeLists.txt")
@@ -29,7 +30,7 @@ if(NOT EXISTS "${QTOPCUA_SOURCE_DIR}/CMakeLists.txt")
 endif()
 
 # ======================================
-#  open62541
+# open62541
 # ======================================
 if(NOT EXISTS "${OPEN62541_INSTALL_DIR}/lib/libopen62541.so")
 
@@ -73,12 +74,12 @@ else()
 endif()
 
 # ======================================
-#  QtOpcUa
+# QtOpcUa
 # ======================================
 
 find_program(QT_CMAKE_COMMAND bin/qt-cmake REQUIRED)
 
-if(NOT EXISTS "${QTOPCUA_BUILD_DIR}/lib/libQt6OpcUa.so")
+if(NOT EXISTS "${QTOPCUA_INSTALL_DIR}/lib/libQt6OpcUa.so")
 
   message(STATUS "Configuring qtopcua in ${QTOPCUA_BUILD_DIR}...")
   set(_cmd
@@ -89,6 +90,7 @@ if(NOT EXISTS "${QTOPCUA_BUILD_DIR}/lib/libQt6OpcUa.so")
       "${QTOPCUA_BUILD_DIR}"
       -G
       Ninja
+      -DCMAKE_INSTALL_PREFIX=${QTOPCUA_INSTALL_DIR}
       # Use our locally-built open62541, not the bundled copy
       -DINPUT_open62541=system
       -DCMAKE_PREFIX_PATH=${OPEN62541_INSTALL_DIR})
@@ -106,7 +108,7 @@ if(NOT EXISTS "${QTOPCUA_BUILD_DIR}/lib/libQt6OpcUa.so")
     message(FATAL_ERROR "${_cmd_str} failed: ${_result}")
   endif()
 
-  message(STATUS "Installing qtopcua to ${QTOPCUA_BUILD_DIR}...")
+  message(STATUS "Installing qtopcua to ${QTOPCUA_INSTALL_DIR}...")
   set(_cmd ${CMAKE_COMMAND} --install "${QTOPCUA_BUILD_DIR}")
   execute_process(COMMAND ${_cmd} RESULT_VARIABLE _result)
   if(_result)
diff --git a/demo/CMakeLists.txt b/demo/CMakeLists.txt
index efdfc72..03c19d3 100644
--- a/demo/CMakeLists.txt
+++ b/demo/CMakeLists.txt
@@ -18,4 +18,4 @@ target_link_libraries(BobinkDemo PRIVATE Qt6::Quick BobinkQtOpcUaplugin)
 
 # Tell the demo where to find the locally-built OpcUa plugin at runtime
 target_compile_definitions(
-  BobinkDemo PRIVATE QTOPCUA_PLUGIN_PATH="${QTOPCUA_BUILD_DIR}/plugins")
+  BobinkDemo PRIVATE QTOPCUA_PLUGIN_PATH="${QTOPCUA_INSTALL_DIR}/plugins")