I recently imported to Lightroom a few thousand photos that I had scanned. Then I tagged faces in them. Lightroom slowed down until it started disappearing and reappearing. I noticed that the task manager could no longer display graphs. These are symptoms of a handle leak, so I rebooted.
Having rebooted I restarted Lightroom and continued tagging faces. In Task Manager I kept an eye on the columns: Handles, Threads, User Objects, and GDI objects. This is how they looked at the beginning:
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And this is how they looked after a lot of tagging:
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All four counters have increased significantly. In particular "User Objects" has increased from 2,526 to 5,588 items. This indicates a Window leak.
So I brought up Spy++ and looked at all the windows on the system.
There were hundreds and hundreds of top-level listboxes!
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All these ListBoxes are owned by Lightroom, but it is not their parent. Their owner is "Lightroom Catalog-2-v10 - Adobe Photoshop Lightroom Classic - Library".
The ListBoxes are probably empty -- their size is "(0, 0)-(0, 4), 0x4".
In fact the Windows hierarchy is full of lots of little top-level windows owned by Lightroom, of very uncertain use.
These include Windows of type ComboLBox and tooltips_class32. Some of these have larger client areas.
I don't think I need to explain any more? Lightroom is leaking window handles. Eventually this corrupts the whole system.
Does Adobe actually test Lightroom on Windows? Checking for handle leaks is pretty easy -- I just showed you how.
Thanks