Add display clear

src/main.rs

@@ -56,6 +56,7 @@ fn kmain() -> ! {
     }
 
     if let Some(mut display) = VC::init_fb(Size2d { x: 800, y: 600 } /*, &mut uart*/) {
+        display.clear(Color::black());
         display.rect(10, 10, 250, 250, Color::rgb(32, 96, 64));
         display.draw_text(50, 50, "Hello there!", Color::rgb(128, 192, 255));
 

src/platform/display.rs

@@ -14,6 +14,10 @@ impl Color {
         Color(u32::from(b) << 16 | u32::from(g) << 8 | u32::from(r))
     }
 
+    pub fn black() -> Color {
+        Color::rgb(0, 0, 0)
+    }
+
     pub fn white() -> Color {
         Color::rgb(255, 255, 255)
     }
@@ -150,6 +154,10 @@ impl Display {
         }
     }
 
+    pub fn clear(&mut self, color: Color) {
+        self.rect(0, 0, self.width, self.height, color)
+    }
+
     pub fn draw_text(&mut self, x: u32, y: u32, text: &str, color: Color) {
         for i in 0..8 {
             // Take an 8 bit slice from each array value.