CMake: Make WrapVulkanHeaders target optional for QtGui consumers

If Vulkan headers are present on the system when qtbase is configured,
QtGui and QtOpenGL should be compiled with Vulkan support.

If a user project uses a Qt built with Vulkan support, but their system
is missing Vulkan headers, the project configuration needs to succeed.

The project will get compilation errors if it uses Vulkan headers, but
that's intended.

This use case was broken when fixing Vulkan to be found when building
Qt for Android.

Fix the regression with a combination of things
1) Mark the WrapVulkanHeaders package as optional (already the case)
2) Use the include directories directly when compiling Gui and OpenGL
3) Propagate WrapVulkanHeaders::WrapVulkanHeaders link requirement to
   consumers only if the target exists. It won't exist if Vulkan
   include dirs are not found

This also requires some changes in pri and prl file generation.

For prl file generation, we don't want to link to the
WrapVulkanHeaders target, so we filter out all dependencies that
use TARGET_NAME_IF_EXISTS for anything that calls
__qt_internal_walk_libs which includes qt_collect_libs.

For pri files, we make sure to generate a uses=vulkan/nolink clause
by inspecting a new _qt_is_nolink_target property on the target.

We also don't add include dirs to the pri file if the new
_qt_skip_include_dir_for_pri property is set.
This is intended for Vulkan, because there is separate qmake logic to
try and find the include dirs when configuring a user project.

As a drive-by, fix nolink handling for WrapOpenSSLHeaders.

Amends bb25536a3db657b41ae31e1690d230ef8722b57d
Amends 7b9904849fe1a43f0db8216076a9e974ebca5c78

Pick-to: 6.2
Fixes: QTBUG-95391
Change-Id: I21e2f4be5c386f9e40033e4691f4786a91ba0e2d
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Alexey Edelev <alexey.edelev@qt.io>
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>

7 files changed, 116 insertions, 4 deletions

diff --git a/cmake/FindWrapOpenSSLHeaders.cmake b/cmake/FindWrapOpenSSLHeaders.cmake
index ea422a68ba..afaf77ac48 100644
--- a/cmake/FindWrapOpenSSLHeaders.cmake
+++ b/cmake/FindWrapOpenSSLHeaders.cmake
@@ -28,6 +28,9 @@ if(OPENSSL_INCLUDE_DIR)
     add_library(WrapOpenSSLHeaders::WrapOpenSSLHeaders INTERFACE IMPORTED)
     target_include_directories(WrapOpenSSLHeaders::WrapOpenSSLHeaders INTERFACE
         ${OPENSSL_INCLUDE_DIR})
+
+    set_target_properties(WrapOpenSSLHeaders::WrapOpenSSLHeaders PROPERTIES
+        _qt_is_nolink_target TRUE)
 endif()
 
 include(FindPackageHandleStandardArgs)
diff --git a/cmake/FindWrapVulkanHeaders.cmake b/cmake/FindWrapVulkanHeaders.cmake
index 766f1e29eb..ccbcf7f708 100644
--- a/cmake/FindWrapVulkanHeaders.cmake
+++ b/cmake/FindWrapVulkanHeaders.cmake
@@ -18,6 +18,12 @@ if(Vulkan_INCLUDE_DIR)
     target_include_directories(WrapVulkanHeaders::WrapVulkanHeaders INTERFACE
         ${Vulkan_INCLUDE_DIR})
 
+    set_target_properties(WrapVulkanHeaders::WrapVulkanHeaders PROPERTIES
+        _qt_is_nolink_target TRUE)
+
+    set_target_properties(WrapVulkanHeaders::WrapVulkanHeaders PROPERTIES
+        _qt_skip_include_dir_for_pri TRUE)
+
     # Also propagate MoltenVK include directory on Apple platforms if found.
     # Assumes the folder structure of the LunarG Vulkan SDK.
     if(APPLE)
diff --git a/cmake/QtFindPackageHelpers.cmake b/cmake/QtFindPackageHelpers.cmake
index 9f8ae1a9a9..da0b19a8d5 100644
--- a/cmake/QtFindPackageHelpers.cmake
+++ b/cmake/QtFindPackageHelpers.cmake
@@ -269,6 +269,29 @@ function(qt_record_extra_qt_main_tools_package_dependency main_target_name
         "${main_target_name}" "${qtfied_package_name_versioned}" "${dep_package_version}")
 endfunction()
 
+# Record an extra 3rd party target as a dependency for ${main_target_name}.
+#
+# Adds a find_package(${dep_target_package_name}) in ${main_target_name}Dependencies.cmake.
+#
+# Needed to record a dependency on the package that provides WrapVulkanHeaders::WrapVulkanHeaders.
+# The package version, components, whether the package is optional, etc, are queried from the
+# ${dep_target} target properties.
+function(qt_record_extra_third_party_dependency main_target_name dep_target)
+    if(NOT TARGET "${main_target_name}")
+        qt_get_tool_target_name(main_target_name "${main_target_name}")
+    endif()
+    if(TARGET "${main_target_name}")
+        get_target_property(extra_deps "${main_target_name}" _qt_extra_third_party_dep_targets)
+        if(NOT extra_deps)
+            set(extra_deps "")
+        endif()
+
+        list(APPEND extra_deps "${dep_target}")
+        set_target_properties("${main_target_name}" PROPERTIES _qt_extra_third_party_dep_targets
+                                                               "${extra_deps}")
+    endif()
+endfunction()
+
 # This function stores the list of Qt targets a library depend on,
 # along with their version info, for usage in ${target}Depends.cmake file
 function(qt_register_target_dependencies target public_libs private_libs)
diff --git a/cmake/QtPostProcessHelpers.cmake b/cmake/QtPostProcessHelpers.cmake
index 5d3e949206..248989c81c 100644
--- a/cmake/QtPostProcessHelpers.cmake
+++ b/cmake/QtPostProcessHelpers.cmake
@@ -25,7 +25,7 @@ macro(qt_collect_third_party_deps target)
     endif()
     unset(_target_is_static)
 
-    foreach(dep ${${depends_var}} ${optional_public_depends})
+    foreach(dep ${${depends_var}} ${optional_public_depends} ${extra_third_party_deps})
         # Gather third party packages that should be found when using the Qt module.
         # Also handle nolink target dependencies.
         string(REGEX REPLACE "_nolink$" "" base_dep "${dep}")
@@ -138,6 +138,12 @@ function(qt_internal_create_module_depends_file target)
         list(APPEND target_deps "${extra_depends}")
     endif()
 
+    # Extra 3rd party targets who's packages should be considered dependencies.
+    get_target_property(extra_third_party_deps "${target}" _qt_extra_third_party_dep_targets)
+    if(NOT extra_third_party_deps)
+        set(extra_third_party_deps "")
+    endif()
+
     # Used for assembling the content of an include/Module/ModuleDepends.h header.
     set(qtdeps "")
 
diff --git a/cmake/QtPriHelpers.cmake b/cmake/QtPriHelpers.cmake
index 49d7310db4..fa31ea9a5c 100644
--- a/cmake/QtPriHelpers.cmake
+++ b/cmake/QtPriHelpers.cmake
@@ -36,7 +36,16 @@ function(qt_generate_qmake_libraries_pri_content module_name output_root_dir out
                     list(APPEND lib_libs "$<TARGET_LINKER_FILE:${lib_target}>")
                 endif()
                 list(APPEND lib_libdir  "$<TARGET_PROPERTY:${lib_target},INTERFACE_LINK_DIRECTORIES>")
-                list(APPEND lib_incdir  "$<TARGET_PROPERTY:${lib_target},INTERFACE_INCLUDE_DIRECTORIES>")
+
+                get_target_property(skip_include_dir "${lib_target}" _qt_skip_include_dir_for_pri)
+                if(skip_include_dir)
+                    set(target_include_dir "")
+                else()
+                    set(target_include_dir
+                        "$<TARGET_PROPERTY:${lib_target},INTERFACE_INCLUDE_DIRECTORIES>")
+                endif()
+
+                list(APPEND lib_incdir "${target_include_dir}")
                 list(APPEND lib_defines "$<TARGET_PROPERTY:${lib_target},INTERFACE_COMPILE_DEFINITIONS>")
             else()
                 if(lib_target MATCHES "/([^/]+).framework$")
@@ -120,14 +129,35 @@ function(qt_get_direct_module_dependencies target out_var)
 endfunction()
 
 # Return a list of qmake library names for a given list of targets.
-# For example, Vulkan::Vulkan_nolink is mapped to vulkan/nolink.
+# For example, Foo::Foo_nolink is mapped to foo/nolink.
+# Also targets with the _qt_is_nolink_target property are mapped to nolink as well.
 function(qt_internal_map_targets_to_qmake_libs out_var)
     set(result "")
     foreach(target ${ARGN})
+        # Unwrap optional targets. Needed for Vulkan.
+        if(target MATCHES "^\\$<TARGET_NAME_IF_EXISTS:(.*)>$")
+            set(target ${CMAKE_MATCH_1})
+        endif()
+
+        set(is_no_link_target FALSE)
+
+        # First case of detecting nolink targets (possibly not needed anymore)
         string(REGEX REPLACE "_nolink$" "" stripped_target "${target}")
+        if(NOT target STREQUAL stripped_target)
+            set(is_no_link_target TRUE)
+        endif()
+
+        # Second case of detecting nolink targets.
+        if(TARGET "${target}")
+            get_target_property(marked_as_no_link_target "${target}" _qt_is_nolink_target)
+            if(marked_as_no_link_target)
+                set(is_no_link_target TRUE)
+            endif()
+        endif()
+
         qt_internal_map_target_to_qmake_lib(${stripped_target} qmake_lib)
         if(NOT "${qmake_lib}" STREQUAL "")
-            if(NOT target STREQUAL stripped_target)
+            if(is_no_link_target)
                 string(APPEND qmake_lib "/nolink")
             endif()
             list(APPEND result "${qmake_lib}")
diff --git a/cmake/QtPublicWalkLibsHelpers.cmake b/cmake/QtPublicWalkLibsHelpers.cmake
index 19eef91356..7267bc9677 100644
--- a/cmake/QtPublicWalkLibsHelpers.cmake
+++ b/cmake/QtPublicWalkLibsHelpers.cmake
@@ -148,6 +148,13 @@ function(__qt_internal_walk_libs
                 continue()
             endif()
 
+            # Skip optional dependencies for now. They are likely to be handled manually for prl
+            # file purposes (like nolink handling). And for one of the other operations, we don't
+            # have a use case yet. This might be revisited.
+            if(lib MATCHES "^\\$<TARGET_NAME_IF_EXISTS:")
+                continue()
+            endif()
+
             # Strip any directory scope tokens.
             __qt_internal_strip_target_directory_scope_token("${lib}" lib)
 
diff --git a/cmake/QtTargetHelpers.cmake b/cmake/QtTargetHelpers.cmake
index 75642c70b0..96d6982319 100644
--- a/cmake/QtTargetHelpers.cmake
+++ b/cmake/QtTargetHelpers.cmake
@@ -772,3 +772,40 @@ function(qt_internal_link_internal_platform_for_object_library target)
     # Achieve this by compiling the cpp files with the PlatformModuleInternal compile flags.
     target_link_libraries("${target}" PRIVATE Qt::PlatformModuleInternal)
 endfunction()
+
+
+# Use ${dep_target}'s include dirs when building ${target} and optionally propagate the include
+# dirs to consumers of ${target}.
+
+# Assumes ${dep_target} is an INTERFACE_LIBRARY that only propagates include dirs and ${target}
+# is a Qt module / plugin.
+#
+# Building ${target} requires ${dep_target}'s include dirs.
+#
+# User projects that don't have ${dep_target}'s headers installed in their system should still
+# configure successfully.
+#
+# To achieve that, consumers of ${target} will only get the include directories of ${dep_target}
+# if the latter package and target exists.
+#
+# A find_package(dep_target) dependency is added to ${target}'s ModuleDependencies.cmake file.
+#
+# We use target_include_directories(PRIVATE) instead of target_link_libraries(PRIVATE) because the
+# latter would propagate a mandatory LINK_ONLY dependency on the ${dep_target} in a static Qt build.
+#
+# The main use case is for propagating WrapVulkanHeaders::WrapVulkanHeaders.
+function(qt_internal_add_target_include_dirs_and_optionally_propagate target dep_target)
+    if(NOT TARGET "${target}")
+        message(FATAL_ERROR "${target} is not a valid target.")
+    endif()
+    if(NOT TARGET "${dep_target}")
+        message(FATAL_ERROR "${dep_target} is not a valid target.")
+    endif()
+
+    target_include_directories("${target}" PRIVATE
+        "$<TARGET_PROPERTY:${dep_target},INTERFACE_INCLUDE_DIRECTORIES>")
+
+    target_link_libraries("${target}" INTERFACE "$<TARGET_NAME_IF_EXISTS:${dep_target}>")
+
+    qt_record_extra_third_party_dependency("${target}" "${dep_target}")
+endfunction()