files hangs on hover over huge thumbnails

This is presumably related to the Overlay bar? In which case it should not happen in List view, where the Overlay is not displayed.

The crash still occurs in list view.

My guess is that the code that brightens an icon on hover is working with the full file data instead of the 48x48 icon, loading the entire .JP2 file's pixel data into the RAM.

OK, thanks. I'll need to create some large JP2 files and try to reproduce this bug. I assume it does not happen with ordinary jpg or other image files? Looking at the code, it appear the OverLay bar still updates in list view - it just isnt shown. So it could still be the OverLay as this attempts to determine image properties like resolution for image files.

I can confirm that Files UI blocks when hovering over 18.8 MB .JP2 file (in Icon View) for several seconds and the cpu usage climbs to 100% for one core. The memory usage temporarily increases by about 400 MB during this time but drops back to about 40 MB more each time.

As far as I have been able to ascertain, this being caused by the Gdk.PixbufLoader that is used to determine the image dimensions. It requires the whole of the JP2 file being loaded in before it can determine the dimensions (which is slow and also blocks the UI) and then leaks memory when closed.

Until a better solution is found I will add JP2 files to the list of image types that are skipped by the OverlayBar as far as determining the resolution is concerned.

PropertiesWindow also blocks for several seconds when used on large JP2 files although it uses a different method to determine the image dimensions, but at least it does not leak memory.