added a static Writer to reuse in the program

Cargo.toml

@@ -17,3 +17,8 @@ panic = "abort" # disable stack unwinding on panic
 [dependencies]
 bootloader = "0.9"
 volatile = "0.2.6"
+spin = "0.5.2"
+
+[dependencies.lazy_static]
+version = "1.0"
+features = ["spin_no_std"]

src/main.rs

@@ -11,8 +11,10 @@ static HELLO: &[u8] = b"Hello toto :3";
 // looks for a function named `_start` by default
 #[unsafe(no_mangle)]
 pub extern "C" fn _start() -> ! {
-    vga_buffer::print_something();
+    use core::fmt::Write;
-    
+    vga_buffer::WRITER.lock().write_str("TOTOTO !!!! :3").unwrap();
+    write!(vga_buffer::WRITER.lock(), ", smoking cigarette in the shower when they get wet i just light another :{}", 3).unwrap();
+
     loop {}
 }
 

src/vga_buffer.rs

@@ -1,5 +1,15 @@
 use core::fmt;
 use volatile::Volatile;
+use lazy_static::lazy_static;
+use spin::Mutex;
+
+lazy_static! {
+    pub static ref WRITER: Mutex<Writer> = Mutex::new(Writer {
+        column_position: 0,
+        color_code: ColorCode::new(Color::Pink, Color::Black),
+        buffer: unsafe { &mut *(0xB8000 as *mut Buffer) },
+    });
+}
 
 #[allow(dead_code)]
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
@@ -103,20 +113,26 @@ impl Writer {
     }
 
     fn new_line(&mut self) {
-        todo!()
+        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;
+    }
+
+    // this method clears a row by overwriting all of its
+    // characters with a space character.
+    fn clear_row(&mut self, row: usize) {
+        let blank = ScreenChar {
+            ascii_carachter: b' ',
+            color_code: self.color_code,
+        };
+
+        for col in 0..BUFFER_WIDTH {
+            self.buffer.chars[row][col].write(blank);
+        }
     }
 }
-
-// function to test things: to be removed
-pub fn print_something() {
-    use core::fmt::Write;
-    let mut writer = Writer {
-        column_position: 0,
-        color_code: ColorCode::new(Color::Pink, Color::Black),
-        buffer: unsafe { &mut *(0xB8000 as *mut Buffer) },
-    };
-
-    writer.write_byte(b'H');
-    writer.write_string("ello ");
-    write!(writer, "The numbers are {} and {}", 42, 1.0/3.0).unwrap();
-}