Implement portamentoup/portamentodown effects

src/reskit/soundtrack/engines/echo.rs

@@ -306,6 +306,44 @@ fn apply_effects_to_channel( channel: &mut Channel, effects: &LinkedHashSet<Effe
                     channel.active_effects.insert_if_absent( Effect::DacEnable { enabled: true } );
                 }
             },
+            Effect::PortamentoUp { speed } => {
+                let speed = *speed;
+
+                // Remove all prior portamentos (you cannot portamento up and down at the same time)
+                channel.active_effects = channel.active_effects
+                                                .clone()
+                                                .into_iter()
+                                                .filter( | effect |
+                                                    !(
+                                                        matches!( effect, Effect::PortamentoDown { speed: _ } ) ||
+                                                        matches!( effect, Effect::PortamentoUp { speed: _ } )
+                                                    )
+                                                )
+                                                .collect();
+
+                if speed > 0 {
+                    channel.active_effects.insert( Effect::PortamentoUp { speed } );
+                }
+            },
+            Effect::PortamentoDown { speed } => {
+                let speed = *speed;
+
+                // Remove all prior portamentos (you cannot portamento up and down at the same time)
+                channel.active_effects = channel.active_effects
+                                                .clone()
+                                                .into_iter()
+                                                .filter( | effect |
+                                                    !(
+                                                        matches!( effect, Effect::PortamentoDown { speed: _ } ) ||
+                                                        matches!( effect, Effect::PortamentoUp { speed: _ } )
+                                                    )
+                                                )
+                                                .collect();
+
+                if speed > 0 {
+                    channel.active_effects.insert( Effect::PortamentoDown { speed } );
+                }
+            },
             Effect::SetPanning { left, right } => {
                 let left = *left;
                 let right = *right;
@@ -357,6 +395,8 @@ fn compact_delays( events: Vec<EchoEvent> ) -> Result<Vec<EchoEvent>, Box<dyn Er
                 // Continue to push delay events into current_sequence
                 current_sequence.push( event );
             } else {
+                // Encountered a non-delay event - we will always push something here,
+                // but let's check first if we need to push a current_sequence of waits.
                 // Coalesce all current delays in current_sequence and push them
                 // onto the new event stream.
                 let mut cumulative_delay: u16 = 0;