Created attachment 7413 Test script I found a small regression while investigating bug 13960, the icon view used to be wrap file/folder labels, although it was already a bit clumsy and sometimes wouldn't break words, now it doesn't wrap nor ellipsizes. The attached script should be useful for testing.
Created attachment 7414 thunar-gtk2 screenshot
Created attachment 7415 thunar-gtk3 screenshot
Same problem for me on Fedora 27 (recent upgrade) Kernel: 4.13.12-300.fc27.x86_64 xfce4-session-4.12.1-12.fc27.x86_64 Thunar-1.6.12-3.fc27.x86_64
For thunar 1.6.x, there is a patch available here: bug 12126. For thunar master/gtk3, things are different. While moving to gtk3 Jonas Kümmerlin removed the complete thunar-text-renderer in commit 81e645d8faaab8c91f6b6b907f1667052a760a76 and replaced it by GtkCellRendererText. ( Thats why the patch of bug 12126 does not work for master ) For GtkCellRendererText it seems not to be possible to pass "wrap-mode" and "ellipsize" together in a meaningful way. As soon as "ellipsize" is passed, the text is not wrapped any more, but directly ellipsized. According to https://wiki.gnome.org/HowDoI/Labels one needs to adjust gtk_label_set_lines as well to have both in parallel. Not sure where this can be done. Maybe somewhere in exo. Nemo has a nice implementation on that. Label is wrapped to 3 lines, ellipsized if longer. Hover on the item shows full label.
Nautilus as well uses GtkCellRendererText, and it seems to succeed in using PANGO_ELLIPSIZE_END together with some kind of line-wrap. As far as I can tell, a line of interest is this one: https://github.com/GNOME/nautilus/blob/ee55096a9e36e7246afe655134c2f1bfb135a5bb/src/nautilus-list-view.c#L2129 However with just using the same configuration for the thunar GtkCellRendererText ( thunar_icon_view_init ) , I cannot fix things. Seems like something else is missing regarding the line-wrap ... search ongoing.
Here a simple example for playing with GtkCellRendererText can be found: https://en.wikibooks.org/wiki/GTK%2B_By_Example/Tree_View/Columns_and_Renderers
Created attachment 7714 thunar-now Revisiting this bug, to my surprise I can't reproduce the previous behavior. It's not as nice as Nemo and Nautilus that limit filenames to 3 lines and expose them on selection, but it's not too bad either as before. Probably gtk or pango have changed since then. I can't say this is a regression anymore, although there's room for improvement.
Closing this bug. There's already bug 12126 requesting to truncate filename for Icon and Compact views