Thundebird drag-and-drop does not work.....

[donald]

Selecting a message and starting to move it (e.g. to drop it into a folder) has a strange looking (whole text line is moved). It is nearly impossible to drop at the right place, because it is not clear, where the "hot spot" on the line is.

Possible reason (from strace) : cursors/dnd-move cursor not found, which would change the cursor to a document icon. Such a files exists in /usr/share/icons/Adwaita/cursors/dnd-move but is not looked up there:

openat(AT_FDCWD, "/home/buczek/.icons/cursors/dnd-move", O_RDONLY) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/usr/share/icons/cursors/dnd-move", O_RDONLY) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/usr/share/pixmaps/cursors/dnd-move", O_RDONLY) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/home/buczek/.icons/default/cursors/dnd-move", O_RDONLY) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/usr/share/icons/default/cursors/dnd-move", O_RDONLY) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/usr/share/pixmaps/default/cursors/dnd-move", O_RDONLY) = -1 ENOENT (No such file or directory)

[donald]

Aside from the non existent cursors there may be transparency issue: On Windows the whole line is selecte4d (made blue) but also made about 50% opaque which enables the user to look though the text to identify the drop target. At the same time the cursor changes depending on whether it si over a valid drop location or not (supposedly dnd-none and dnd-move). This looks so familiar, I guess its the old Mariux behavior as well.

[donald]

Went back to bee packages as of 8f80e37 (July), old kernel, reboot.... No change....

[thomas]

It looks like a change in the defaults.

If I set nglayout.enable_drag_images to false, I can happily push the mails around as before.

[donald]

Good finding.
Its not just a changed default.
They didn't change the defaults

https://hg.mozilla.org/mozilla-central/annotate/409f3966645a651c8cb8d6d1e2f3fa995b69c739/modules/libpref/init/all.js#l1103 was "true" from the time the added the preference 2007. Maybe it tried to do "drag images", but used to fail for whatever problem, and now it works, its just that the result is worse.

Do we want to change the default to "False" as a work around? If people do it manually, the "False" would get frozen into individual user settings and we can't change it back, even if the underlying problem is fixed some day.