Folder icons in directory mode cause significant performance drop

[mantacid]

When the yellow folder icon is displayed in directory mode, I get roughly 2 frames per second.

Steps to reproduce:

1. Open Lem's directory mode and sort by name.
2. scroll down.

Expected result:

Scrolling is unaffected by the presence of folder icons.

Observed Results:

Scrolling when folder icons are visible tanks the performance.

[mantacid]

Would it maybe be possible to use a character icon for folders, similar to the ones used for the file MIMEtypes? It would look more visually consistent, allow for the folder color to be changed, and probably be better performance-wise.