progress bar should follow data amount rather than number of files

[Veenified]

It appears that the progress bar follows the number of files completed rather than the amount of data completed. A better representation of progress would be to have it follow how much data has been extracted and copied instead of the number of files.

[Pavel Strakhov (strahovp)]

For example, Ubuntu LiveCD contains filesystem.squashfs file with 656 Mb size. In this case number of files is useless at all, we need progress bar for file size.

[Arpad Kovacs (minhmeoke)]

Yes, the current behavior is suboptimal, but we cannot fix it yet because it is an upstream issue. Right now we are delegating the decompression to 7-zip, which only notifies us of file-based, rather than filesize-based progress. Other projects (eg file-roller) are also affected by this bug:
https://bugs.launchpad.net/ubuntu/+source/file-roller/+bug/18250
https://bugzilla.gnome.org/show_bug.cgi?id=153281#c17

[Dan Dascalescu (ddascalescu+launchpad)]

One simple workaround would be estimating the write speed based on the files successfully written so far (sum of sizes, divided by time elapse), and extrapolating the progress for the current file based on the time elapsed since that file started being written to disk.

When the file was completely written to disk, the progress could be adjusted if necessary, but probably the difference would be too small for the user to notice.