Add missing functions to the gradient object. (#5528)

Co-authored-by: PgBiel <9021226+PgBiel@users.noreply.github.com>
Co-authored-by: Laurenz <laurmaedje@gmail.com>

crates/typst-library/src/visualize/gradient.rs

@@ -697,6 +697,8 @@ impl Gradient {
     }
 
     /// Returns the angle of this gradient.
+    ///
+    /// Returns `{none}` if the gradient is neither linear nor conic.
     #[func]
     pub fn angle(&self) -> Option<Angle> {
         match self {
@@ -706,6 +708,54 @@ impl Gradient {
         }
     }
 
+    /// Returns the center of this gradient.
+    ///
+    /// Returns `{none}` if the gradient is neither radial nor conic.
+    #[func]
+    pub fn center(&self) -> Option<Axes<Ratio>> {
+        match self {
+            Self::Linear(_) => None,
+            Self::Radial(radial) => Some(radial.center),
+            Self::Conic(conic) => Some(conic.center),
+        }
+    }
+
+    /// Returns the radius of this gradient.
+    ///
+    /// Returns `{none}` if the gradient is not radial.
+    #[func]
+    pub fn radius(&self) -> Option<Ratio> {
+        match self {
+            Self::Linear(_) => None,
+            Self::Radial(radial) => Some(radial.radius),
+            Self::Conic(_) => None,
+        }
+    }
+
+    /// Returns the focal-center of this gradient.
+    ///
+    /// Returns `{none}` if the gradient is not radial.
+    #[func]
+    pub fn focal_center(&self) -> Option<Axes<Ratio>> {
+        match self {
+            Self::Linear(_) => None,
+            Self::Radial(radial) => Some(radial.focal_center),
+            Self::Conic(_) => None,
+        }
+    }
+
+    /// Returns the focal-radius of this gradient.
+    ///
+    /// Returns `{none}` if the gradient is not radial.
+    #[func]
+    pub fn focal_radius(&self) -> Option<Ratio> {
+        match self {
+            Self::Linear(_) => None,
+            Self::Radial(radial) => Some(radial.focal_radius),
+            Self::Conic(_) => None,
+        }
+    }
+
     /// Sample the gradient at a given position.
     ///
     /// The position is either a position along the gradient (a [ratio] between