Extract merge_overlapping as a free function template

src/normal.cc

@@ -1155,7 +1155,7 @@ void spaces_to_tabs(Context& context, int ts)
     }
 }
 
-static boost::optional<SelectionList> compute_modified_ranges(Buffer& buffer, size_t timestamp)
+static std::vector<Selection> compute_modified_ranges(Buffer& buffer, size_t timestamp)
 {
     std::vector<Selection> ranges;
     for (auto& change : buffer.changes_since(timestamp))
@@ -1183,29 +1183,25 @@ static boost::optional<SelectionList> compute_modified_ranges(Buffer& buffer, si
             ranges.insert(it, Selection{pos, pos});
         }
     }
-    if (ranges.empty())
-        return {};
-
     for (auto& sel : ranges)
     {
         sel.anchor() = buffer.clamp(sel.anchor());
         sel.cursor() = buffer.clamp(sel.cursor());
     }
 
-    SelectionList result{buffer, std::move(ranges)};
-
     auto touches = [&](const Selection& lhs, const Selection& rhs) {
         return lhs.min() <= rhs.min() ? buffer.char_next(lhs.max()) >= rhs.min()
                                       : lhs.min() <= buffer.char_next(rhs.max());
     };
-    result.merge_overlapping(touches);
+    size_t main = 0;
+    merge_overlapping(ranges.begin(), ranges.end(), main, touches);
 
-    for (auto& sel : result)
+    for (auto& sel : ranges)
     {
         if (sel.anchor() != sel.cursor())
             sel.cursor() = buffer.char_prev(sel.cursor());
     }
-    return result;
+    return ranges;
 }
 
 void undo(Context& context, int)
@@ -1216,8 +1212,8 @@ void undo(Context& context, int)
     if (res)
     {
         auto ranges = compute_modified_ranges(buffer, timestamp);
-        if (ranges)
+        if (not ranges.empty())
-            context.selections() = std::move(*ranges);
+            context.selections() = std::move(ranges);
     }
     else if (not res)
         context.print_status({ "nothing left to undo", get_color("Information") });
@@ -1232,8 +1228,8 @@ void redo(Context& context, int)
     if (res)
     {
         auto ranges = compute_modified_ranges(buffer, timestamp);
-        if (ranges)
+        if (not ranges.empty())
-            context.selections() = std::move(*ranges);
+            context.selections() = std::move(ranges);
     }
 
     else if (not res)

src/selection.cc

@@ -166,7 +166,7 @@ void SelectionList::update()
         sel.anchor() = m_buffer->clamp(sel.anchor());
         sel.cursor() = m_buffer->clamp(sel.cursor());
     }
-    merge_overlapping(overlaps);
+    m_selections.erase(merge_overlapping(begin(), end(), m_main, overlaps), end());
     check_invariant();
 
     m_timestamp = m_buffer->timestamp();
@@ -208,7 +208,7 @@ void SelectionList::sort_and_merge_overlapping()
                                    return begin < main_begin;
                            });
     std::stable_sort(begin(), end(), compare_selections);
-    merge_overlapping(overlaps);
+    m_selections.erase(merge_overlapping(begin(), end(), m_main, overlaps), end());
 }
 namespace
 {

src/selection.hh

@@ -71,6 +71,30 @@ enum class InsertMode : unsigned
     OpenLineAbove
 };
 
+template<typename Iterator, typename OverlapsFunc>
+Iterator merge_overlapping(Iterator begin, Iterator end, size_t& main, OverlapsFunc overlaps)
+{
+    kak_assert(std::is_sorted(begin, end, compare_selections));
+    size_t size = end - begin;
+    size_t i = 0;
+    for (size_t j = 1; j < size; ++j)
+    {
+        if (overlaps(begin[i], begin[j]))
+        {
+            begin[i].merge_with(begin[j]);
+            if (i < main)
+                --main;
+        }
+        else
+        {
+            ++i;
+            if (i != j)
+                begin[i] = std::move(begin[j]);
+        }
+    }
+    return begin + i + 1;
+}
+
 struct SelectionList
 {
     SelectionList(Buffer& buffer, Selection s);
@@ -122,30 +146,6 @@ struct SelectionList
     bool operator==(const SelectionList& other) const { return m_buffer == other.m_buffer and m_selections == other.m_selections; }
     bool operator!=(const SelectionList& other) const { return !((*this) == other); }
 
-    template<typename OverlapsFunc>
-    void merge_overlapping(OverlapsFunc overlaps)
-    {
-        kak_assert(std::is_sorted(begin(), end(), compare_selections));
-        size_t i = 0;
-        for (size_t j = 1; j < size(); ++j)
-        {
-            if (overlaps((*this)[i], (*this)[j]))
-            {
-                (*this)[i].merge_with((*this)[j]);
-                if (i < m_main)
-                    --m_main;
-            }
-            else
-            {
-                ++i;
-                if (i != j)
-                    (*this)[i] = std::move((*this)[j]);
-            }
-        }
-        m_selections.erase(begin() + i + 1, end());
-        kak_assert(std::is_sorted(begin(), end(), compare_selections));
-    }
-
     void sort_and_merge_overlapping();
 
     Buffer& buffer() const { return *m_buffer; }