only set the clear color once

src/gui/Window.cc

@@ -150,6 +150,8 @@ bool Window::create(std::shared_ptr<Buffer> buffer)
     m_scroll_offset = 5;
     m_target_column = m_cursor->column;
 
+    glClearColor (0.0, 0.0, 0.0, 0.0);
+
     resize();
 
     return true;
@@ -454,7 +456,6 @@ void Window::resize()
 
 void Window::redraw()
 {
-    glClearColor (0.0, 0.0, 0.0, 0.0);
     glClear(GL_COLOR_BUFFER_BIT);
 
     draw_text();