BufferView updates cursor screen row to follow moved cursor

src/core/BufferView.cc

@@ -34,12 +34,14 @@ BufferView::Iterator BufferView::vert_iter()
     return Iterator(*this);
 }
 
-/**************************************************************************
- * Internal functions
- *************************************************************************/
-
 void BufferView::update()
 {
+    /* Update the cursor screen row in case the cursor position changed. */
+    m_cursor_screen_row = determine_new_cursor_screen_row();
+
+    /* Limit the cursor screen row taking into account view dimensions,
+     * available buffer contents above and below the current line, and scroll
+     * offset. */
     std::list<std::pair<int, std::shared_ptr<Buffer::Iterator>>> backward_lines;
     auto start_of_line = std::make_shared<Buffer::Iterator>(*m_iterator);
     start_of_line->go_start_of_line();
@@ -93,6 +95,34 @@ void BufferView::update()
     }
 }
 
+/**************************************************************************
+ * Internal functions
+ *************************************************************************/
+
+int BufferView::determine_new_cursor_screen_row()
+{
+    if (m_lines.size() > 0)
+    {
+        if (m_iterator->line() < m_lines.begin()->line->line())
+        {
+            return 0;
+        }
+        if (m_iterator->line() > m_lines.rbegin()->line->line())
+        {
+            return m_height;
+        }
+        for (const LineDescriptor & screen_line : m_lines)
+        {
+            if (screen_line.line->line() == m_iterator->line())
+            {
+                calculate_rows_in_cursor_line(screen_line.line);
+                return screen_line.row_offset + m_cursor_row_offset;
+            }
+        }
+    }
+    return 0;
+}
+
 int BufferView::calculate_rows_in_line(std::shared_ptr<Buffer::Iterator> start_of_line)
 {
     int saved_row_offset = 0;

src/core/BufferView.h

@@ -89,6 +89,7 @@ protected:
     {
         return std::min(m_scroll_offset, (m_height - 1) / 2);
     }
+    int determine_new_cursor_screen_row();
     int calculate_rows_in_line(std::shared_ptr<Buffer::Iterator> start_of_line);
     int calculate_rows_in_cursor_line(std::shared_ptr<Buffer::Iterator> start_of_line);
     int screen_rows_below_line(std::shared_ptr<Buffer::Iterator> line);