qt packages that are built again just for opentoonz due to the modified libtiff:

qtbase           59.8 MiB
qtdeclarative    20.6 MiB
qtmultimedia      3.6 MiB
qtquickcontrols   4.9 MiB
qtscript          3.9 MiB
qtsvg             0.5 MiB
qttools          16.2 MiB
qtwayland         5.3 MiB

I verified that:

• nixpkgs-review pr 88591 works
• [nix-shell:~/.cache/nixpkgs-review/pr-88591]$ results/opentoonz/bin/opentoonz -help works
• application itself works

Bumping this MR, because it seems like checks are hanging.

from what I can see in the doc, qt doesn't need to be recompiled with the new libtiff. This would save a lot of compile time.

can this be done without the libtiff override?

This could be done without the qtbase libtiff override if qtbase's libdiff dependency is removed.

qtbase's libdiff dependency appears unnecessary. I chased that dependency back through the commit history a ways. It was added a long time ago & copy/pasted across many qt version bumps. Today, qtimageformats ought to have the libtiff dependency instead of qtbase.

Concretely, attempting to build libtoonz against the normal qtbase that brings in the normal libtiff results in both the normal libtiff and opentoonz's custom libtiff appearing in CMAKE_INCLUDE_PATH. The normal libtiff appears first, so opentoonz's #include finds the normal (wrong) libtiff headers and fails to build. Mechanically hacking around this narrow issue by just removing the other libtiff from the include path or something is begging for ODR troubles which are notoriously difficult to diagnose from the effects they cause.

Fixing qtbase's libdiff dependency is significant scope creep for adding this package. qtbase's libdiff dependency is in its propagatedBuildInputs, so removing it from qtbase will break any package that depends upon both qtbase and libtiff but failed to declare its dependency on libtiff. nixpkgs-review wants to download 16G and store 60G to rebuild the 1406 packages that depend upon qtbase to check them all. That's going to take a very long time on my hardware. I started on this, but didn't get very far because qt is currently broken at head (#96159).

I created PR #96210 to get the ball rolling on fixing qtbase's libdiff dependency.

oh thanks for the thorough explanation. So we can simplify things when libtiff and qtbase are seperated? sounds good, lets hope it will be done someday.