Add support for write macros and newlines

src/vga_buffer.rs

@@ -1,4 +1,5 @@
 use volatile::Volatile;
+use core::fmt;
 
 #[allow(dead_code)]
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
@@ -86,18 +87,47 @@ impl Writer {
         }
     }
     
-    fn new_line(&mut self) {}
+    fn new_line(&mut self) {
+        for row in 1..BUFFER_HEIGHT {
+            for col in 0..BUFFER_WIDTH {
+                let character = self.buffer.chars[row][col].read();
+                self.buffer.chars[row - 1][col].write(character);
+            }
+        }
+
+        self.clear_row(BUFFER_HEIGHT - 1);
+        self.column_position = 0;
+    }
+
+    fn clear_row(&mut self, row: usize) {
+        let blank = ScreenChar {
+            ascii_character: b' ',
+            color_code: self.color_code,
+        };
+
+        for col in 0..BUFFER_WIDTH {
+            self.buffer.chars[row][col].write(blank);
+        }
+    }
+}
+
+impl fmt::Write for Writer {
+    fn write_str(&mut self, s: &str) -> fmt::Result {
+        self.write_string(s);
+        Ok(())
+    }
 }
 
 pub fn print_something() {
+    use core::fmt::Write;
     let mut writer = Writer {
         column_position: 0,
         color_code: ColorCode::new(Color::White, Color::Black),
         buffer: unsafe { &mut *(0xb8000 as *mut Buffer) }
     };
 
-    writer.write_byte(b'H');
-    writer.write_string("ello ");
-    writer.write_string("World!!!!!");
+    writeln!(writer, "Hello world!").unwrap();
+    writeln!(writer, "Hello again!").unwrap();
+
 }