Build examples in isolated sub-builds using ExternalProject

Examples are intended to show how to build against an installed Qt.
Building them as part of the main build means the way the Qt targets
are defined and created are not representative of an end user's build.
By building them as separate projects using ExternalProject, we can
more closely replicate the intended audience's environment. This
should allow us to catch more problems earlier.

Having examples built as part of the main build also creates problems
with some static builds where a tool built by the main build is needed
during configure time. This happens with other repos like qtdeclarative
but not (currently) with qtbase. Converting the examples in qtbase to
be built using ExternalProject is intended as a demonstrator for how
other repos can do similar. Until other repos are converted, they will
continue to work as they did before, with examples as part of the main
build for non-static builds only.

The new build-externally behavior is only supported for non-prefix
builds with this change. Prefix builds will continue to use the old
non-external method. Support for building examples externally in
prefix builds will be a separate change.

Task-number: QTBUG-90820
Fixes: QTBUG-91068
Change-Id: I2304329940568dbdb7da18d54d5595ea7d8668bc
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>

11 files changed, 50 insertions, 51 deletions

diff --git a/examples/widgets/tutorials/CMakeLists.txt b/examples/widgets/tutorials/CMakeLists.txt
index c2fa4a81d7..733eb42151 100644
--- a/examples/widgets/tutorials/CMakeLists.txt
+++ b/examples/widgets/tutorials/CMakeLists.txt
@@ -4,4 +4,4 @@ add_subdirectory(addressbook)
 add_subdirectory(widgets)
 add_subdirectory(modelview)
 add_subdirectory(gettingStarted)
-add_subdirectory(notepad)
+qt_internal_add_example(notepad)
diff --git a/examples/widgets/tutorials/addressbook/CMakeLists.txt b/examples/widgets/tutorials/addressbook/CMakeLists.txt
index a8823d059a..cb00cbc084 100644
--- a/examples/widgets/tutorials/addressbook/CMakeLists.txt
+++ b/examples/widgets/tutorials/addressbook/CMakeLists.txt
@@ -1,9 +1,9 @@
 # Generated from addressbook.pro.
 
-add_subdirectory(part1)
-add_subdirectory(part2)
-add_subdirectory(part3)
-add_subdirectory(part4)
-add_subdirectory(part5)
-add_subdirectory(part6)
-add_subdirectory(part7)
+qt_internal_add_example(part1)
+qt_internal_add_example(part2)
+qt_internal_add_example(part3)
+qt_internal_add_example(part4)
+qt_internal_add_example(part5)
+qt_internal_add_example(part6)
+qt_internal_add_example(part7)
diff --git a/examples/widgets/tutorials/gettingStarted/CMakeLists.txt b/examples/widgets/tutorials/gettingStarted/CMakeLists.txt
index 2aa8163029..42cac47b96 100644
--- a/examples/widgets/tutorials/gettingStarted/CMakeLists.txt
+++ b/examples/widgets/tutorials/gettingStarted/CMakeLists.txt
@@ -1,2 +1 @@
-# Generated from gettingStarted.pro.
-
+add_subdirectory(gsQt)
diff --git a/examples/widgets/tutorials/gettingStarted/gsQt/CMakeLists.txt b/examples/widgets/tutorials/gettingStarted/gsQt/CMakeLists.txt
index 7a9ade8511..8302fd7598 100644
--- a/examples/widgets/tutorials/gettingStarted/gsQt/CMakeLists.txt
+++ b/examples/widgets/tutorials/gettingStarted/gsQt/CMakeLists.txt
@@ -1,7 +1,7 @@
 # Generated from gsqt.pro.
 
-add_subdirectory(part1)
-add_subdirectory(part2)
-add_subdirectory(part3)
-add_subdirectory(part4)
-add_subdirectory(part5)
+qt_internal_add_example(part1)
+qt_internal_add_example(part2)
+qt_internal_add_example(part3)
+qt_internal_add_example(part4)
+qt_internal_add_example(part5)
diff --git a/examples/widgets/tutorials/gettingStarted/gsQt/part1/CMakeLists.txt b/examples/widgets/tutorials/gettingStarted/gsQt/part1/CMakeLists.txt
index e2877a26ba..13ed19067b 100644
--- a/examples/widgets/tutorials/gettingStarted/gsQt/part1/CMakeLists.txt
+++ b/examples/widgets/tutorials/gettingStarted/gsQt/part1/CMakeLists.txt
@@ -1,7 +1,7 @@
 # Generated from part1.pro.
 
 cmake_minimum_required(VERSION 3.14)
-project(part1 LANGUAGES CXX)
+project(getting_started_part1 LANGUAGES CXX)
 
 set(CMAKE_INCLUDE_CURRENT_DIR ON)
 
@@ -19,20 +19,20 @@ find_package(Qt6 COMPONENTS Core)
 find_package(Qt6 COMPONENTS Gui)
 find_package(Qt6 COMPONENTS Widgets)
 
-qt_add_executable(part1
+qt_add_executable(getting_started_part1
     main.cpp
 )
-set_target_properties(part1 PROPERTIES
+set_target_properties(getting_started_part1 PROPERTIES
     WIN32_EXECUTABLE TRUE
     MACOSX_BUNDLE TRUE
 )
-target_link_libraries(part1 PUBLIC
+target_link_libraries(getting_started_part1 PUBLIC
     Qt::Core
     Qt::Gui
     Qt::Widgets
 )
 
-install(TARGETS part1
+install(TARGETS getting_started_part1
     RUNTIME DESTINATION "${INSTALL_EXAMPLEDIR}"
     BUNDLE DESTINATION "${INSTALL_EXAMPLEDIR}"
     LIBRARY DESTINATION "${INSTALL_EXAMPLEDIR}"
diff --git a/examples/widgets/tutorials/gettingStarted/gsQt/part2/CMakeLists.txt b/examples/widgets/tutorials/gettingStarted/gsQt/part2/CMakeLists.txt
index 65a3ff3539..4f72a9ede8 100644
--- a/examples/widgets/tutorials/gettingStarted/gsQt/part2/CMakeLists.txt
+++ b/examples/widgets/tutorials/gettingStarted/gsQt/part2/CMakeLists.txt
@@ -1,7 +1,7 @@
 # Generated from part2.pro.
 
 cmake_minimum_required(VERSION 3.14)
-project(part2 LANGUAGES CXX)
+project(getting_started_part2 LANGUAGES CXX)
 
 set(CMAKE_INCLUDE_CURRENT_DIR ON)
 
@@ -19,20 +19,20 @@ find_package(Qt6 COMPONENTS Core)
 find_package(Qt6 COMPONENTS Gui)
 find_package(Qt6 COMPONENTS Widgets)
 
-qt_add_executable(part2
+qt_add_executable(getting_started_part2
     main.cpp
 )
-set_target_properties(part2 PROPERTIES
+set_target_properties(getting_started_part2 PROPERTIES
     WIN32_EXECUTABLE TRUE
     MACOSX_BUNDLE TRUE
 )
-target_link_libraries(part2 PUBLIC
+target_link_libraries(getting_started_part2 PUBLIC
     Qt::Core
     Qt::Gui
     Qt::Widgets
 )
 
-install(TARGETS part2
+install(TARGETS getting_started_part2
     RUNTIME DESTINATION "${INSTALL_EXAMPLEDIR}"
     BUNDLE DESTINATION "${INSTALL_EXAMPLEDIR}"
     LIBRARY DESTINATION "${INSTALL_EXAMPLEDIR}"
diff --git a/examples/widgets/tutorials/gettingStarted/gsQt/part3/CMakeLists.txt b/examples/widgets/tutorials/gettingStarted/gsQt/part3/CMakeLists.txt
index 4a9b79b00b..d8a72abd59 100644
--- a/examples/widgets/tutorials/gettingStarted/gsQt/part3/CMakeLists.txt
+++ b/examples/widgets/tutorials/gettingStarted/gsQt/part3/CMakeLists.txt
@@ -1,7 +1,7 @@
 # Generated from part3.pro.
 
 cmake_minimum_required(VERSION 3.14)
-project(part3 LANGUAGES CXX)
+project(getting_started_part3 LANGUAGES CXX)
 
 set(CMAKE_INCLUDE_CURRENT_DIR ON)
 
@@ -19,20 +19,20 @@ find_package(Qt6 COMPONENTS Core)
 find_package(Qt6 COMPONENTS Gui)
 find_package(Qt6 COMPONENTS Widgets)
 
-qt_add_executable(part3
+qt_add_executable(getting_started_part3
     main.cpp
 )
-set_target_properties(part3 PROPERTIES
+set_target_properties(getting_started_part3 PROPERTIES
     WIN32_EXECUTABLE TRUE
     MACOSX_BUNDLE TRUE
 )
-target_link_libraries(part3 PUBLIC
+target_link_libraries(getting_started_part3 PUBLIC
     Qt::Core
     Qt::Gui
     Qt::Widgets
 )
 
-install(TARGETS part3
+install(TARGETS getting_started_part3
     RUNTIME DESTINATION "${INSTALL_EXAMPLEDIR}"
     BUNDLE DESTINATION "${INSTALL_EXAMPLEDIR}"
     LIBRARY DESTINATION "${INSTALL_EXAMPLEDIR}"
diff --git a/examples/widgets/tutorials/gettingStarted/gsQt/part4/CMakeLists.txt b/examples/widgets/tutorials/gettingStarted/gsQt/part4/CMakeLists.txt
index b1b224c70d..3e42635ae4 100644
--- a/examples/widgets/tutorials/gettingStarted/gsQt/part4/CMakeLists.txt
+++ b/examples/widgets/tutorials/gettingStarted/gsQt/part4/CMakeLists.txt
@@ -1,7 +1,7 @@
 # Generated from part4.pro.
 
 cmake_minimum_required(VERSION 3.14)
-project(part4 LANGUAGES CXX)
+project(getting_started_part4 LANGUAGES CXX)
 
 set(CMAKE_INCLUDE_CURRENT_DIR ON)
 
@@ -19,20 +19,20 @@ find_package(Qt6 COMPONENTS Core)
 find_package(Qt6 COMPONENTS Gui)
 find_package(Qt6 COMPONENTS Widgets)
 
-qt_add_executable(part4
+qt_add_executable(getting_started_part4
     main.cpp
 )
-set_target_properties(part4 PROPERTIES
+set_target_properties(getting_started_part4 PROPERTIES
     WIN32_EXECUTABLE TRUE
     MACOSX_BUNDLE TRUE
 )
-target_link_libraries(part4 PUBLIC
+target_link_libraries(getting_started_part4 PUBLIC
     Qt::Core
     Qt::Gui
     Qt::Widgets
 )
 
-install(TARGETS part4
+install(TARGETS getting_started_part4
     RUNTIME DESTINATION "${INSTALL_EXAMPLEDIR}"
     BUNDLE DESTINATION "${INSTALL_EXAMPLEDIR}"
     LIBRARY DESTINATION "${INSTALL_EXAMPLEDIR}"
diff --git a/examples/widgets/tutorials/gettingStarted/gsQt/part5/CMakeLists.txt b/examples/widgets/tutorials/gettingStarted/gsQt/part5/CMakeLists.txt
index 182c2e9a48..c92f60d535 100644
--- a/examples/widgets/tutorials/gettingStarted/gsQt/part5/CMakeLists.txt
+++ b/examples/widgets/tutorials/gettingStarted/gsQt/part5/CMakeLists.txt
@@ -1,7 +1,7 @@
 # Generated from part5.pro.
 
 cmake_minimum_required(VERSION 3.14)
-project(part5 LANGUAGES CXX)
+project(getting_started_part5 LANGUAGES CXX)
 
 set(CMAKE_INCLUDE_CURRENT_DIR ON)
 
@@ -19,20 +19,20 @@ find_package(Qt6 COMPONENTS Core)
 find_package(Qt6 COMPONENTS Gui)
 find_package(Qt6 COMPONENTS Widgets)
 
-qt_add_executable(part5
+qt_add_executable(getting_started_part5
     main.cpp
 )
-set_target_properties(part5 PROPERTIES
+set_target_properties(getting_started_part5 PROPERTIES
     WIN32_EXECUTABLE TRUE
     MACOSX_BUNDLE TRUE
 )
-target_link_libraries(part5 PUBLIC
+target_link_libraries(getting_started_part5 PUBLIC
     Qt::Core
     Qt::Gui
     Qt::Widgets
 )
 
-install(TARGETS part5
+install(TARGETS getting_started_part5
     RUNTIME DESTINATION "${INSTALL_EXAMPLEDIR}"
     BUNDLE DESTINATION "${INSTALL_EXAMPLEDIR}"
     LIBRARY DESTINATION "${INSTALL_EXAMPLEDIR}"
diff --git a/examples/widgets/tutorials/modelview/CMakeLists.txt b/examples/widgets/tutorials/modelview/CMakeLists.txt
index 10f2cf6ecf..49ca672e48 100644
--- a/examples/widgets/tutorials/modelview/CMakeLists.txt
+++ b/examples/widgets/tutorials/modelview/CMakeLists.txt
@@ -1,9 +1,9 @@
 # Generated from modelview.pro.
 
-add_subdirectory(1_readonly)
-add_subdirectory(2_formatting)
-add_subdirectory(3_changingmodel)
-add_subdirectory(4_headers)
-add_subdirectory(5_edit)
-add_subdirectory(6_treeview)
-add_subdirectory(7_selections)
+qt_internal_add_example(1_readonly)
+qt_internal_add_example(2_formatting)
+qt_internal_add_example(3_changingmodel)
+qt_internal_add_example(4_headers)
+qt_internal_add_example(5_edit)
+qt_internal_add_example(6_treeview)
+qt_internal_add_example(7_selections)
diff --git a/examples/widgets/tutorials/widgets/CMakeLists.txt b/examples/widgets/tutorials/widgets/CMakeLists.txt
index 1f4afee780..fcf0ed9ddd 100644
--- a/examples/widgets/tutorials/widgets/CMakeLists.txt
+++ b/examples/widgets/tutorials/widgets/CMakeLists.txt
@@ -1,6 +1,6 @@
 # Generated from widgets.pro.
 
-add_subdirectory(toplevel)
-add_subdirectory(childwidget)
-add_subdirectory(windowlayout)
-add_subdirectory(nestedlayouts)
+qt_internal_add_example(toplevel)
+qt_internal_add_example(childwidget)
+qt_internal_add_example(windowlayout)
+qt_internal_add_example(nestedlayouts)