Steps to reproduce:
Use flat view -> no folders in a structure with many small .zip files. Select all zip files and do extract to->destination to some empty folder. Choose recreate folders.
While the unzip operation is running, try to use the vertical scroll bar to scroll down on the source file list (or any file list). While scrolling, the mouse button hold is interrupted all the time, as if the user lets go off the button randomly, even though it is constantly held down. It is as if the extract operation steals the mouse focus from the lister during the extract operation.
I am not sure if it matters, but I minimized the copy dialog to the small progress inside the lister window when I tested this.
I think that can happen if the folder you're looking at is constantly having new files/sub-folders added.
We could make it so displaying the new files is postponed until you let go of the scrollbar (in fact, I thought we already did this, but I may be thinking of something similar but not quite the same). I'm not sure how much better that would be though, since the content of the folder won't be in a stable position to work with until the extractions complete and the large number of changes stop happening.
You are right. If I stop displaying the destination folder, which constantly changes contents, then the problem disappears. I was surprised that the whole dual pane lister window is affected, not just say the right pane. The right pane shows a folder that constantly changes, so I wouldn't be surprised if scrolling the right pane shows interruptions. But the scrolling operation of the left pane, which shows a folder with constant contents, is also interrupted.
Something else: Is there some threshold that determines whether this type of massive unzip operation causes multiple small copy progress windows to appear, one at a type, closing and reopening themselves, or one single big copy window showing file progress without closing and reopening itself? I definitely prefer the one big window. Is it related to the duration of each unzip?