vis: perform undo snapshotting more rarerly

Do not take snapshots after every operation in insert/replace mode.
As an example up until now we would take a snapshot after every
<Backspace>/<Delete> press, hence when undoing changes each character
would be restored individually. The same applies for <C-w> and related
actions.

From now on we only snaphost when:

 - transitioning from insert/replace mode to normal mode (but not when
   switching to operator pending mode)

 - an operation takes place from normal mode

 - an idle time expires in normal/replace mode

1 files changed, 3 insertions, 1 deletions

diff --git a/vis.c b/vis.c
index d48e857..7edc2cd 100644
--- a/vis.c
+++ b/vis.c
@@ -718,7 +718,9 @@ void vis_do(Vis *vis) {
 		} else if (vis->mode->visual) {
 			vis_mode_switch(vis, VIS_MODE_NORMAL);
 		}
-		text_snapshot(txt);
+
+		if (vis->mode == &vis_modes[VIS_MODE_NORMAL])
+			text_snapshot(txt);
 		vis_draw(vis);
 	}