Hi devs

I've recently been playing with piwigo with a view to using it to manage all my photographs. An important function for me is hierarchical keywords, because I use them to manage my RAW files in darktable and I want to have the same keyword hierarchy available for the exported JPEGs.

I've been playing with the piwigo code to the point where I have hacked together something that provides what I need, making use of the existing functionality, and without affecting how it works with flat tags. I would ideally like to package this as a plugin so that a) I do not have to maintain my own versions of piwigo core files and b) others can use and/or improve it if they want.

However, tags seem to be quite tightly integrated into piwigo (eg they are part of search, tag cloud, etc), so in addition to creating a tree-viewer, I have tweaked a few core files to provide the best user experience (eg making search work as expected). That's the background, no for my questions:

1) Is there any way for a plugin to override other functionality eg by changing the definition of global variables and/or functions that other components call?

2) My implementation relies on adding triggers to the existing "tag" and "image_tag" tables that call stored procedures to update my own tables when tags change. Is this kind of behaviour by plugins acceptable?