Wt

Without JavaScript enabled, WTree neither raises signals nor allows collapsing/expanding.
In Wt 3.3.10 that works.

Reproduce:

Start with the official Wt 3.3.10 and Wt 4.0.3 Tarballs, and a tool like stow to allow their coexistence.
Untar and compile both, including the examples (for this to work in v3.3.10, I had to delete a few examples, namely onethread, feature/broadcast and feature/serverpush and/or remove them from their CMakeLists.txt, otherwise there were "undefined reference" errors).

Then try out the widget-gallery example (or treelist, which suffers the same problem, though not using a WTree).

For ex., I did:

tar xzf wt-4.0.3.tar.gz
cd wt-4.0.3
mkdir build
cd build
cmake -DWT_WRASTERIMAGE_IMPLEMENTATION=GraphicsMagick -DCMAKE_INSTALL_PREFIX:PATH=/usr/local/stow/wt-4.0.3 ..
make
sudo make install

1. unstow previous Wt build, if any
   (cd /usr/local/stow; sudo stow wt-4.0.3;) # stow new build
   make -C examples
2. try out Trees & Tables > Trees in widget-gallery example

1. all the above for wt-3.3.10 (delete problematic examples, if any, see above note)