animation: write a const Animation::new()

src/animation.rs

@@ -53,7 +53,14 @@ impl<S: Surface> AnimationActor for AnimatedSurface<S> {
 }
 
 impl Animation {
-    pub fn from(self, from: u8) -> Self {
+    pub const fn new() -> Self {
+        Self {
+            from: None,
+            to: None,
+            duration: Duration::from_ticks(0)
+        }
+    }
+    pub const fn from(self, from: u8) -> Self {
         Self {
             from: Some(from),
             to: self.to,
@@ -61,7 +68,7 @@ impl Animation {
         }
     }
 
-    pub fn to(self, to: u8) -> Self {
+    pub const fn to(self, to: u8) -> Self {
         Self {
             from: self.from,
             to: Some(to),
@@ -69,7 +76,7 @@ impl Animation {
         }
     }
 
-    pub fn duration(self, duration: Duration) -> Self {
+    pub const fn duration(self, duration: Duration) -> Self {
         Self {
             from: self.from,
             to: self.to,