Fix pasting after when selections are overlapping

With overlapping selections, pasting after breaks assumption of
SelectionList::for_each as our changes are no longer happening in
increasing locations.

We hence cannot rely on the ForwardChangeTracker in that case and
have to rely on the more general (and more costly) ranges update logic.

This interacts poorly with paste linewise pastes and we try to preserve
the current behaviour by tracking the last paste position.

Overall, this change really begs for overlapping selections to be
removed, but we will fix them like that for now.

Fixes #4779

1 files changed, 33 insertions, 10 deletions

diff --git a/src/selection.cc b/src/selection.cc
index cbf9bef2..f0f0270c 100644
--- a/src/selection.cc
+++ b/src/selection.cc
@@ -362,22 +362,45 @@ static void fix_overflowing_selections(Vector<Selection>& selections,
     }
 }
 
-void SelectionList::for_each(ApplyFunc func)
+bool any_overlaps(ConstArrayView<Selection> sels)
+{
+    for (int i = 0; i + 1 < sels.size(); ++i)
+    {
+        if (overlaps(sels[i], sels[i+1]))
+            return true;
+    }
+    return false;
+}
+
+void SelectionList::for_each(ApplyFunc func, bool may_append)
 {
     update();
 
-    ForwardChangesTracker changes_tracker;
-    for (size_t index = 0; index < m_selections.size(); ++index)
+    if (may_append and any_overlaps(m_selections))
+    {
+        size_t timestamp = m_buffer->timestamp();
+        for (size_t index = 0; index < m_selections.size(); ++index)
+        {
+            auto& sel = m_selections[index];
+            update_ranges(*m_buffer, timestamp, ArrayView<Selection>(sel));
+            func(index, sel);
+        }
+    }
+    else
     {
-        auto& sel = m_selections[index];
+        ForwardChangesTracker changes_tracker;
+        for (size_t index = 0; index < m_selections.size(); ++index)
+        {
+            auto& sel = m_selections[index];
 
-        sel.anchor() = changes_tracker.get_new_coord_tolerant(sel.anchor());
-        sel.cursor() = changes_tracker.get_new_coord_tolerant(sel.cursor());
-        kak_assert(m_buffer->is_valid(sel.anchor()) and m_buffer->is_valid(sel.cursor()));
+            sel.anchor() = changes_tracker.get_new_coord_tolerant(sel.anchor());
+            sel.cursor() = changes_tracker.get_new_coord_tolerant(sel.cursor());
+            kak_assert(m_buffer->is_valid(sel.anchor()) and m_buffer->is_valid(sel.cursor()));
 
-        func(index, sel);
+            func(index, sel);
 
-        changes_tracker.update(*m_buffer, m_timestamp);
+            changes_tracker.update(*m_buffer, m_timestamp);
+        }
     }
 
     // We might just have been deleting text if strings were empty,
@@ -414,7 +437,7 @@ void SelectionList::replace(ConstArrayView<String> strings)
 
     for_each([&](size_t index, Selection& sel) {
         Kakoune::replace(*m_buffer, sel, strings[std::min(strings.size()-1, index)]);
-    });
+    }, false);
 }
 
 void SelectionList::erase()