Window: calculate m_rows

src/gui/Window.cc

@@ -256,6 +256,7 @@ void Window::resize()
     m_columns = m_width / m_font.get_advance();
     if (m_columns < 1)
         m_columns = 1;
+    m_rows = (m_height + m_font.get_line_height() - 1) / m_font.get_line_height();
 }
 
 void Window::redraw()

src/gui/Window.h

@@ -31,6 +31,7 @@ protected:
 
     Font m_font;
     int m_columns;
+    int m_rows;
 
     std::shared_ptr<Buffer> m_buffer;