Check JPEG_FOUND before finding the JPEG package

[SenorBlanco]

Check for JPEG_FOUND before calling find_package(JPEG). This allows a project which depends libjpeg-turbo already via add_subdirectory() to share that implementation with libultrahdr.

[ram-mohan]

If UHDR_BUILD_DEPS is set then the project clones and Build project dependencies and not use pre-installed packages. This is not the correct change.

[SenorBlanco]

Here's the problem: I already have libjpeg-turbo in my project (a particular version added via add_subdirectory()), and I don't want libultrahdr to download and build another copy, since the symbols will conflict. I also don't want libultrahdr to use FindPackage to find it (since it may not be available, e.g. on Windows) or may be the wrong version. I just want libultrahdr to use the version I'm already linking against. I can achieve this by setting JPEG_LIBRARIES, JPEG_INCLUDE_DIRS and by setting JPEG_FOUND.

If there's another alternative, I'm happy to try it.

[kmilos]

a particular version added via add_subdirectory()

I also don't want libultrahdr to use FindPackage

If there's another alternative, I'm happy to try it.

Try pointing the existing find_package() to your local, particular libjpg-turbo version by passing JPEG_ROOT (or JPEG_DIR), they should have priority over the default search paths? (Might need to force CONFIG mode though...)

Edit: Forget it, and sorry for any wild goose chase - libjpeg-turbo in config mode needs to be changed to find_package(libjpeg-turbo CONFIG) and defines a libjpeg-turbo::jpeg target, not a drop-in replacement for JPEG::JPEG...

However, pointing JPEG_INCLUDE_DIR (not JPEG_INCLUDE_DIRS) and JPEG_LIBRARY (not JPEG_LIBRARIES) might work for regular find_package(JPEG)...

[SenorBlanco]

Try pointing the existing find_package() to your local, particular libjpg-turbo version by passing JPEG_ROOT (or JPEG_DIR), they should have priority over the default search paths? (Might need to force CONFIG mode though...)

Edit: Forget it, and sorry for any wild goose chase - libjpeg-turbo in config mode needs to be changed to find_package(libjpeg-turbo CONFIG) and defines a libjpeg-turbo::jpeg target, not a drop-in replacement for JPEG::JPEG...

No worries! I appreciate the help.

However, pointing JPEG_INCLUDE_DIR (not JPEG_INCLUDE_DIRS) and JPEG_LIBRARY (not JPEG_LIBRARIES) might work for regular find_package(JPEG)...

Setting those is enough to satisfy find_package(), but unfortunately the compile fails with

FAILED: third_party/libultrahdr/CMakeFiles/core.dir/lib/src/editorhelper.cpp.obj
C:\PROGRA~1\MICROS~1\2022\COMMUN~1\VC\Tools\MSVC\1444~1.352\bin\Hostx64\x64\cl.exe  /nologo /TP -DSTACK_SIZE=4194304 -D_CRT_SECURE_NO_WARNINGS -IC:\Users\Stephen\src\toucan\third_party\libultrahdr\lib\include -I\third_party\libjpeg-turbo -IC:\Users\Stephen\src\toucan\third_party\libultrahdr\third_party\image_io\includes -IC:\Users\Stephen\src\toucan\third_party\libultrahdr /DWIN32 /D_WINDOWS /EHsc /O2 /Ob2 /DNDEBUG -std:c++17 -MD -DUHDR_ENABLE_INTRINSICS -DUHDR_WRITE_ISO /wd4244 /wd4267 /wd4305 /wd4838 /wd26812 /showIncludes /Fothird_party\libultrahdr\CMakeFiles\core.dir\lib\src\editorhelper.cpp.obj /Fdthird_party\libultrahdr\CMakeFiles\core.dir\core.pdb /FS -c C:\Users\Stephen\src\toucan\third_party\libultrahdr\lib\src\editorhelper.cpp
C:\Users\Stephen\src\toucan\third_party\libultrahdr\lib\include\ultrahdr/jpegdecoderhelper.h(27): fatal error C1083: Cannot open include file: 'jerror.h': No such file or directory

I suspect because JPEG clients need both jerror.h (from the source directory) and jconfig.h (from the binary directory). I think this is why libultrahdr's does this when building libjpegturbo with UHDR_BUILD_DEPS:

set(JPEG_INCLUDE_DIRS ${JPEGTURBO_SOURCE_DIR} ${JPEGTURBO_BINARY_DIR})

[kmilos]

I suspect because JPEG clients need both jerror.h (from the source directory) and jconfig.h (from the binary directory).

Sounds like your local libjpeg-turbo wasn't installed properly out of its source tree (extra step after just building it)? No problems w/ compiling w/ system libjpeg-turbo packages in Linux distros or e.g. MSYS2 for Windows. All the header files should get installed in the same location, see e.g. file listings in

https://packages.msys2.org/packages/mingw-w64-ucrt-x86_64-libjpeg-turbo
https://archlinux.org/packages/extra/x86_64/libjpeg-turbo/files/
https://packages.fedoraproject.org/pkgs/libjpeg-turbo/libjpeg-turbo-devel/fedora-44.html#files

etc.

I think this is why libultrahdr's does this when building libjpegturbo with UHDR_BUILD_DEPS

Bundling dependencies and building everything in-tree probably requires many custom workarounds...