Merge pull request #353 from webdevtodayjason/trim-keeps-clip-gain

Keep the clip gain line where a clip is trimmed or separated

contributors/people.toml

@@ -40,3 +40,6 @@ sync_github_name = true
 real_name = "Vikram Bhaskaran"
 display_name = "Vikram Bhaskaran"
 sync_github_name = false
+
+[people.webdevtodayjason]
+display_name = "Jason Brashear"

crates/model/src/clip.rs

@@ -215,7 +215,12 @@ impl Clip {
         self.length -= delta;
         self.start = new_start;
         self.clamp_fades();
-        self.gain_env = self.gain_env.iter().filter_map(|&(t, v)| (t - delta >= 0).then_some((t - delta, v))).collect();
+        // Keep the gain at the cut when earlier breakpoints are dropped.
+        if self.gain_env.iter().any(|&(t, _)| t < delta) && self.gain_env.iter().all(|&(t, _)| t != delta) {
+            self.gain_env.insert(0, (delta, env_value(&self.gain_env, delta)));
+        }
+        self.gain_env.retain(|&(t, _)| t >= delta);
+        self.gain_env.iter_mut().for_each(|(t, _)| *t = t.saturating_sub(delta));
     }
 
     /// Move the end edge to `new_end`.
@@ -282,6 +287,27 @@ mod tests {
         assert!((c.gain_at(500) - db_to_gain(-10.0)).abs() < 1e-4);
     }
 
+    #[test]
+    fn trim_start_keeps_gain_envelope_at_cut() {
+        for (env, cut, expected) in [
+            (vec![(0, 0.0), (1000, -20.0)], 500, vec![(0, -10.0), (500, -20.0)]),
+            (vec![(0, 0.0), (100, -20.0)], 500, vec![(0, -20.0)]),
+            (vec![(0, 0.0), (500, -10.0), (1000, -20.0)], 500, vec![(0, -10.0), (500, -20.0)]),
+            (vec![], 500, vec![]),
+            (vec![(100, -3.0)], 0, vec![(100, -3.0)]),
+            (vec![(100, -3.0)], -100, vec![(200, -3.0)]),
+        ] {
+            let mut clip = Clip::audio(ClipId(1), "a", SourceId(1), 100, 0, 1000);
+            clip.gain_env = env;
+            let gain_at_cut = clip.gain_at(cut);
+            clip.trim_start_to(cut);
+            assert_eq!(clip.gain_env, expected);
+            if cut > 0 {
+                assert!((clip.gain_at(0) - gain_at_cut).abs() < 1e-6);
+            }
+        }
+    }
+
     #[test]
     fn trims_keep_material_anchored() {
         let mut c = Clip::audio(ClipId(1), "a", SourceId(1), 1000, 100, 1000);