CMake: Fix painting examples to build as standalone projects

The examples use an intermediate object library to avoid duplicate
file compilation. The examples worked when built as part of Qt
because the shared directory was always added, and Qt::OpenGL is
available implicitly.

Change each project to add_subdirectory(../shared) if the object
library is not available, thus making the examples build as standalone
projects.

Call find_package inside the shared project, to ensure the Qt packages
are found.

Create an alias called 'painting_shared::painting_shared' and link
against that to ensure that any failure is caught at configure time
rather than build time.

Adapt the pathstroke example to use the object library.

Comment out the code for the OpenGL scopes, because it's handled
by the object library.

Make sure the OpenGL dependency is public.
Make sure to run moc and compile the OpenGL specific files as well.

Task-number: QTBUG-87444
Change-Id: Ib0ecb68948581c5267ca04f19d8043fa44ff3d54
Reviewed-by: Joerg Bornemann <joerg.bornemann@qt.io>

1 files changed, 18 insertions, 9 deletions

diff --git a/examples/widgets/painting/deform/CMakeLists.txt b/examples/widgets/painting/deform/CMakeLists.txt
index 61b28f1b3a..c2517ac66f 100644
--- a/examples/widgets/painting/deform/CMakeLists.txt
+++ b/examples/widgets/painting/deform/CMakeLists.txt
@@ -37,11 +37,17 @@ target_include_directories(deform PUBLIC
     ../shared
 )
 
+# special case begin
+if(NOT TARGET painting_shared::painting_shared)
+  add_subdirectory(../shared painting_shared)
+endif()
+# special case end
+
 target_link_libraries(deform PUBLIC
     Qt::Core
     Qt::Gui
     Qt::Widgets
-    painting_shared # special case
+    painting_shared::painting_shared # special case
 )
 
 
@@ -209,15 +215,18 @@ qt6_add_resources(deform "deform"
         ${deform_resource_files}
 )
 
-if(QT_FEATURE_opengl)
-    target_sources(deform PUBLIC
-        ../shared/fbopaintdevice.cpp ../shared/fbopaintdevice.h
-    )
+# special case begin
+# remove files from ../shared
+#if(QT_FEATURE_opengl)
+    #target_sources(affine PUBLIC
+        #../shared/fbopaintdevice.cpp ../shared/fbopaintdevice.h
+    #)
 
-    target_link_libraries(deform PUBLIC
-        Qt::OpenGL
-    )
-endif()
+    #target_link_libraries(affine PUBLIC
+        #Qt::OpenGL
+    #)
+#endif()
+# special case end
 
 install(TARGETS deform
     RUNTIME DESTINATION "${INSTALL_EXAMPLEDIR}"