timeline: snap pointer and import operations to timebase

If frame rates are mixed, ensures that video doesn't end up falling or ending on half frames which potentially make the entire sequence awkward

app/widget/timelinewidget/tool/import.cpp

@@ -149,9 +149,10 @@ void ImportTool::DragMove(TimelineViewMouseEvent *event)
       }
 
       // Generate tooltip (showing earliest in point of imported clip)
-      int64_t earliest_timestamp = Timecode::time_to_timestamp(earliest_ghost, parent()->GetToolTipTimebase());
+      rational tooltip_timebase = parent()->GetTimebaseForTrackType(event->GetTrack().type());
+      int64_t earliest_timestamp = Timecode::time_to_timestamp(earliest_ghost, tooltip_timebase);
       QString tooltip_text = Timecode::timestamp_to_timecode(earliest_timestamp,
-                                                             parent()->GetToolTipTimebase(),
+                                                             tooltip_timebase,
                                                              Core::instance()->GetTimecodeDisplay());
 
       // Force tooltip to update (otherwise the tooltip won't move as written in the documentation, and could get in the way
@@ -271,6 +272,12 @@ void ImportTool::FootageToGhosts(rational ghost_start, const QList<DraggedFootag
       footage_duration = Config::Current()["DefaultStillLength"].value<rational>();
     }
 
+    // Snap footage duration to timebase
+    rational snap_mvmt = SnapMovementToTimebase(footage_duration, 0, dest_tb);
+    if (!snap_mvmt.isNull()) {
+      footage_duration += snap_mvmt;
+    }
+
     foreach (TimelineViewGhostItem* ghost, footage_ghosts) {
       ghost->SetIn(ghost_start);
       ghost->SetOut(ghost_start + footage_duration);