def alignment_display(self):
        """Fills screen with uppercase E's for screen focus and alignment."""
        self.dirty.update(range(self.lines))
        for y in range(self.lines):
            for x in range(self.columns):
                self.buffer[y][x] = self.buffer[y][x]._replace(data="E")
Fills screen with uppercase E's for screen focus and alignment.