add Buffer::erase_code_point()

src/core/Buffer.cc

@@ -180,3 +180,21 @@ void Buffer::insert_code_point(uint32_t code_point)
         m_insert_position += bytes;
     }
 }
+
+void Buffer::erase_code_point(const Buffer::Iterator & position)
+{
+    if (position.valid())
+    {
+        uint8_t bytes = 0u;
+        uint32_t code_point = Encoding::decode(m_encoding, position.address(), &bytes);
+        m_gap_buffer->erase(position.offset(), bytes);
+        ssize_t lines = (code_point == '\n') ? -1 : 0;
+        for (auto iterator : m_iterators)
+        {
+            if (*iterator > position)
+            {
+                iterator->warp(-(ssize_t)bytes, lines);
+            }
+        }
+    }
+}

src/core/Buffer.h

@@ -106,6 +106,7 @@ public:
     void exit_insert_mode();
     bool insert_mode() const { return m_insert_mode; }
     void insert_code_point(uint32_t code_point);
+    void erase_code_point(const Buffer::Iterator & position);
 
 protected:
     bool m_eol_at_eof;