fb: Added support for typing backspaces.

libk/src/drivers/io/ascii/mod.rs

@@ -64,13 +64,19 @@ impl Writer {
         self.font = font;
     }
 
+    /// This is sent when the user types a backspace.
+    const BACKSPACE: u16 = 8;
+
     pub fn write_glyph(&mut self, c: u16) {
-        if c as u8 == b'\n' {
+        if c == b'\n' as u16 {
             self.newline();
             return;
+        } else if c == Self::BACKSPACE {
+            self.backspace();
+            return;
         }
 
-        // get the character data from the font array. -- each byte is a row of pixels
+        // Get the character data from the font array. -- each byte is a row of pixels
         let data: &[u8] = &self.font.0[c as usize];
 
         if let Some(writer) = FRAMEBUFFER_WRITER.lock().as_mut() {
@@ -80,17 +86,17 @@ impl Writer {
                     let pixel_y: u32 = self.text_line * FONT_HEIGHT + row as u32;
 
                     if line & (0x80 >> col) != 0 {
-                        // write the foreground color
+                        // Write the foreground color
                         writer.write_pixel(pixel_x as usize, pixel_y as usize, self.fg_color);
                     } else {
-                        // write the background color
+                        // Write the background color
                         writer.write_pixel(pixel_x as usize, pixel_y as usize, self.bg_color);
                     }
                 }
             }
         }
 
-        // go to next position
+        // Go to next position
         if self.text_col + 1 >= self.screen_width {
             self.newline();
         } else {
@@ -121,6 +127,17 @@ impl Writer {
         }
     }
 
+    /// Handles the backspace character. TODO: Implement VT-100 style terminal control
+    /// codes alongside a shell. Not simple.
+    pub fn backspace(&mut self) {
+        if self.text_col > 0 {
+            self.text_col -= 1;
+            // Blank out the previous char.
+            self.write_glyph(' ' as u16);
+            self.text_col -= 1;
+        }
+    }
+
     pub fn write_string(&mut self, s: &str) {
         for c in s.chars() {
             self.write_glyph(c as u16);