Created attachment 254829 [details] [review]
Select proper message on delete for 3.8.5

When deleting multiple messages from the message list in threaded mode, the message selected after the deletion is incorrect. The user expects that the immediately following message will be selected (barring thread reflowing) but evolution will select the Nth message after that, with N being the number of messages deleted.

ie, with the following in the message tree, with threading turned on:

Msg 1
 + Msg 2
 + Msg 3
Msg 4
Msg 5
Msg 6

Selecting Msg 1 to Msg 3 (using CTRL, or SHIFT, doesn't matter) and then deleting will cause Msg 6 to selected after the operation, when Msg 4 should be.

This issue does not occur if the message tree is not threaded, or if deleted messages are displayed.

This worked properly in 3.4.4, was broken in 3.6.4 and 3.8.5, and I suspect it is still broken in master based on code inspection.

In mail/message-list.c:build_tree() gets the proper next message from find_next_selectable() -- Msg 6 -- but its call to e_tree_set_cursor() is overwritten before before returning to message_list_regen_done_cb(), so that function attempts to set the cursor to the last row viewed (message_list->cursor_uid is NULL).

The reason that e_tree_set_cursor() is ineffective is that the call to message_list_tree_model_freeze() saves the current tree cursor (NULL) via e-util/e-tree-selection-model.c:etsm_pre_change(), and restores it when we call message_list_tree_model_thaw() via etsm_node_changed() and restore_cursor().

I've attached patches for 3.8.5 and master that moves the e_tree_set_cursor() outside of the freeze/thaw pairing. While it seems to work for me, I'm not 100% sure it is the proper fix.