gstreamer: formatted values: Implement ClockTime::absdiff() and on related types

Fixes https://gitlab.freedesktop.org/gstreamer/gstreamer-rs/-/issues/494

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer-rs/-/merge_requests/1364>

gstreamer/src/format/clock_time.rs

@@ -1801,4 +1801,15 @@ mod tests {
         let neg = Signed::<ClockTime>::from_seconds_f64(-5.0);
         assert!(neg.is_negative());
     }
+
+    #[test]
+    fn absdiff() {
+        let t1 = ClockTime::from_seconds(10);
+        let t2 = ClockTime::from_seconds(4);
+
+        let d = ClockTime::from_seconds(6);
+
+        assert_eq!(t1.absdiff(t2), d);
+        assert_eq!(t2.absdiff(t1), d);
+    }
 }

gstreamer/src/format/macros.rs

@@ -93,6 +93,17 @@ macro_rules! impl_non_trait_op_same(
             pub const fn wrapping_sub(self, rhs: Self) -> Self {
                 self.overflowing_sub(rhs).0
             }
+
+            #[must_use = "this returns the result of the operation, without modifying the original"]
+            #[inline]
+            pub fn absdiff(self, rhs: Self) -> Self {
+                if self > rhs {
+                    self - rhs
+                } else {
+                    rhs - self
+                }
+            }
+
         }
     };
 );