Add opt-in per-channel/stereo-pair volume and meter display (multichannel-pairing)

src/config/char_set.rs

@@ -33,6 +33,16 @@ pub struct CharSetOverlay {
     meter_center_left_active: Option<String>,
     meter_center_right_inactive: Option<String>,
     meter_center_right_active: Option<String>,
+    meter_split_left_inactive: Option<String>,
+    meter_split_left_active: Option<String>,
+    meter_split_left_overload: Option<String>,
+    meter_split_right_inactive: Option<String>,
+    meter_split_right_active: Option<String>,
+    meter_split_right_overload: Option<String>,
+    meter_split_center_left_inactive: Option<String>,
+    meter_split_center_left_active: Option<String>,
+    meter_split_center_right_inactive: Option<String>,
+    meter_split_center_right_active: Option<String>,
     dropdown_icon: Option<String>,
     dropdown_selector: Option<String>,
     dropdown_more: Option<String>,
@@ -95,6 +105,26 @@ impl TryFrom<CharSetOverlay> for CharSet {
             };
         }
 
+        // Same as `validate_and_set!`, but for the optional
+        // `meter_split_*` fields, whose unset state (`None`) is itself
+        // meaningful (falls back to the corresponding stock
+        // `meter_left`/`meter_right`/`meter_center_*` field at render
+        // time) rather than just "use the built-in default character".
+        macro_rules! validate_and_set_optional {
+            ($field:ident, $length:expr) => {
+                if let Some(value) = overlay.$field {
+                    if $length > 0 && Span::raw(&value).width() != $length {
+                        anyhow::bail!(
+                            "{} must be {} characters wide",
+                            stringify!($field),
+                            $length
+                        );
+                    }
+                    char_set.$field = Some(value);
+                }
+            };
+        }
+
         validate_and_set!(default_device, 1);
         validate_and_set!(default_stream, 1);
         validate_and_set!(selector_top, 1);
@@ -115,6 +145,16 @@ impl TryFrom<CharSetOverlay> for CharSet {
         validate_and_set!(meter_center_left_active, 1);
         validate_and_set!(meter_center_right_inactive, 1);
         validate_and_set!(meter_center_right_active, 1);
+        validate_and_set_optional!(meter_split_left_inactive, 1);
+        validate_and_set_optional!(meter_split_left_active, 1);
+        validate_and_set_optional!(meter_split_left_overload, 1);
+        validate_and_set_optional!(meter_split_right_inactive, 1);
+        validate_and_set_optional!(meter_split_right_active, 1);
+        validate_and_set_optional!(meter_split_right_overload, 1);
+        validate_and_set_optional!(meter_split_center_left_inactive, 1);
+        validate_and_set_optional!(meter_split_center_left_active, 1);
+        validate_and_set_optional!(meter_split_center_right_inactive, 1);
+        validate_and_set_optional!(meter_split_center_right_active, 1);
         validate_and_set!(dropdown_icon, 1);
         validate_and_set!(dropdown_selector, 1);
         validate_and_set!(dropdown_more, 0);
@@ -155,6 +195,24 @@ impl Default for CharSet {
             meter_center_left_active: String::from("▮"),
             meter_center_right_inactive: String::from("▮"),
             meter_center_right_active: String::from("▮"),
+            // Unset here - this char_set's Unified-view meter is already
+            // a row of individually-inset filled rectangles ("▮"), so
+            // there's no seamless/disjoint distinction left to draw:
+            // Linked/Channels-view meters use exactly the same glyph,
+            // and the volume-bar split plus per-channel label remain the
+            // only visual cue a view has changed. Still overridable
+            // per-user. See CharSet::compat()'s own meter_split_*
+            // comment for the char_set where this distinction matters.
+            meter_split_left_inactive: None,
+            meter_split_left_active: None,
+            meter_split_left_overload: None,
+            meter_split_right_inactive: None,
+            meter_split_right_active: None,
+            meter_split_right_overload: None,
+            meter_split_center_left_inactive: None,
+            meter_split_center_left_active: None,
+            meter_split_center_right_inactive: None,
+            meter_split_center_right_active: None,
             dropdown_icon: String::from("▼"),
             dropdown_selector: String::from(">"),
             dropdown_more: String::from("•••"),
@@ -196,6 +254,24 @@ impl CharSet {
             meter_center_left_active: String::from("█"),
             meter_center_right_inactive: String::from("█"),
             meter_center_right_active: String::from("█"),
+            // Unlike CharSet::default()'s filled-block glyphs, this
+            // char_set's Unified-view meter is a *solid, seamlessly
+            // connected* line (box-drawing "┃"/"█" render with no gap
+            // between repeated cells). Linked/Channels views use a
+            // lighter-weight glyph pair in the same thin-bar/block family
+            // that renders with a natural vertical gap between repeated
+            // cells ("❘"/"▇"), so a split view is still visually distinct
+            // from Unified without introducing an unrelated shape.
+            meter_split_left_inactive: Some(String::from("❘")),
+            meter_split_left_active: Some(String::from("❘")),
+            meter_split_left_overload: Some(String::from("❘")),
+            meter_split_right_inactive: Some(String::from("❘")),
+            meter_split_right_active: Some(String::from("❘")),
+            meter_split_right_overload: Some(String::from("❘")),
+            meter_split_center_left_inactive: Some(String::from("▇")),
+            meter_split_center_left_active: Some(String::from("▇")),
+            meter_split_center_right_inactive: Some(String::from("▇")),
+            meter_split_center_right_active: Some(String::from("▇")),
             dropdown_icon: String::from("▼"),
             dropdown_selector: String::from(">"),
             dropdown_more: String::from("•••"),
@@ -227,6 +303,16 @@ impl CharSet {
             meter_center_left_active: String::from("["),
             meter_center_right_inactive: String::from("]"),
             meter_center_right_active: String::from("]"),
+            meter_split_left_inactive: None,
+            meter_split_left_active: None,
+            meter_split_left_overload: None,
+            meter_split_right_inactive: None,
+            meter_split_right_active: None,
+            meter_split_right_overload: None,
+            meter_split_center_left_inactive: None,
+            meter_split_center_left_active: None,
+            meter_split_center_right_inactive: None,
+            meter_split_center_right_active: None,
             dropdown_icon: String::from("\\"),
             dropdown_selector: String::from(">"),
             dropdown_more: String::from("~~~"),

src/config/keybinding.rs

@@ -48,6 +48,7 @@ impl Keybinding {
             (event(KeyCode::Char('9')), Action::SetAbsoluteVolume(0.90)),
             (event(KeyCode::Char('0')), Action::SetAbsoluteVolume(1.00)),
             (event(KeyCode::Char('?')), Action::Help),
+            (event(KeyCode::Char(' ')), Action::CycleView),
         ])
     }
 

src/config/theme.rs

@@ -27,6 +27,11 @@ pub struct ThemeOverlay {
     meter_overload: Option<StyleDef>,
     meter_center_inactive: Option<StyleDef>,
     meter_center_active: Option<StyleDef>,
+    meter_split_inactive: Option<StyleDef>,
+    meter_split_active: Option<StyleDef>,
+    meter_split_overload: Option<StyleDef>,
+    meter_split_center_inactive: Option<StyleDef>,
+    meter_split_center_active: Option<StyleDef>,
     config_device: Option<StyleDef>,
     config_profile: Option<StyleDef>,
     dropdown_icon: Option<StyleDef>,
@@ -89,6 +94,18 @@ impl TryFrom<ThemeOverlay> for Theme {
             };
         }
 
+        // Same as `set!`, but for the optional `meter_split_*` fields,
+        // whose unset state (`None`) is itself meaningful (falls back to
+        // the corresponding stock `meter_*` field at render time) rather
+        // than just "use the built-in default".
+        macro_rules! set_optional {
+            ($field:ident) => {
+                if let Some($field) = overlay.$field {
+                    theme.$field = Some($field.into());
+                }
+            };
+        }
+
         set!(default_device);
         set!(default_stream);
         set!(selector);
@@ -106,6 +123,11 @@ impl TryFrom<ThemeOverlay> for Theme {
         set!(meter_overload);
         set!(meter_center_inactive);
         set!(meter_center_active);
+        set_optional!(meter_split_inactive);
+        set_optional!(meter_split_active);
+        set_optional!(meter_split_overload);
+        set_optional!(meter_split_center_inactive);
+        set_optional!(meter_split_center_active);
         set!(config_device);
         set!(config_profile);
         set!(dropdown_icon);
@@ -141,6 +163,11 @@ impl Default for Theme {
             meter_overload: Style::default().fg(Color::Red),
             meter_center_inactive: Style::default().fg(Color::DarkGray),
             meter_center_active: Style::default().fg(Color::LightGreen),
+            meter_split_inactive: None,
+            meter_split_active: None,
+            meter_split_overload: None,
+            meter_split_center_inactive: None,
+            meter_split_center_active: None,
             config_device: Style::default(),
             config_profile: Style::default(),
             dropdown_icon: Style::default(),
@@ -185,6 +212,11 @@ impl Theme {
             meter_overload: Style::default().add_modifier(Modifier::BOLD),
             meter_center_inactive: Style::default().add_modifier(Modifier::DIM),
             meter_center_active: Style::default().add_modifier(Modifier::BOLD),
+            meter_split_inactive: None,
+            meter_split_active: None,
+            meter_split_overload: None,
+            meter_split_center_inactive: None,
+            meter_split_center_active: None,
             config_device: Style::default(),
             config_profile: Style::default(),
             dropdown_icon: Style::default(),
@@ -218,6 +250,11 @@ impl Theme {
             meter_overload: Style::default(),
             meter_center_inactive: Style::default(),
             meter_center_active: Style::default(),
+            meter_split_inactive: None,
+            meter_split_active: None,
+            meter_split_overload: None,
+            meter_split_center_inactive: None,
+            meter_split_center_active: None,
             config_device: Style::default(),
             config_profile: Style::default(),
             dropdown_icon: Style::default(),
@@ -309,4 +346,28 @@ mod tests {
             assert_eq!(theme.selector, builtin.selector);
         }
     }
+
+    #[test]
+    fn meter_split_colors_are_unset_by_default_and_configurable() {
+        for builtin in Theme::defaults().values() {
+            assert_eq!(builtin.meter_split_inactive, None);
+            assert_eq!(builtin.meter_split_active, None);
+            assert_eq!(builtin.meter_split_overload, None);
+            assert_eq!(builtin.meter_split_center_inactive, None);
+            assert_eq!(builtin.meter_split_center_active, None);
+        }
+
+        let config = r#"
+        meter_split_inactive = { fg = "Black" }
+        "#;
+        let overlay = toml::from_str::<ThemeOverlay>(config).unwrap();
+        let theme = Theme::try_from(overlay).unwrap();
+        assert_eq!(
+            theme.meter_split_inactive,
+            Some(Style::default().fg(Color::Black))
+        );
+        // Only the configured field changes - everything else, including
+        // the other meter_split_* fields, stays unset.
+        assert_eq!(theme.meter_split_active, None);
+    }
 }

src/lib.rs

@@ -1,5 +1,6 @@
 pub mod app;
 pub mod atomic_f32;
+pub mod channel_pairing;
 pub mod config;
 pub mod device_kind;
 pub mod device_widget;
@@ -24,10 +25,15 @@ mod mock {
     use std::collections::VecDeque;
     use std::sync::{atomic::AtomicBool, Arc};
 
+    // Variants intentionally share the `Node` prefix, mirroring
+    // CommandSender's own node_capture_start/node_capture_stop/
+    // node_volumes method names.
+    #[allow(clippy::enum_variant_names)]
     #[derive(Debug, PartialEq)]
     pub enum MockCommand {
         NodeCaptureStart(ObjectId),
         NodeCaptureStop(ObjectId),
+        NodeVolumes(ObjectId, Vec<f32>),
     }
 
     #[derive(Default)]
@@ -68,7 +74,13 @@ mod mock {
             }
         }
         fn node_mute(&self, _object_id: ObjectId, _mute: bool) {}
-        fn node_volumes(&self, _object_id: ObjectId, _volumes: Vec<f32>) {}
+        fn node_volumes(&self, object_id: ObjectId, volumes: Vec<f32>) {
+            if let Some(commands) = self.commands {
+                commands
+                    .borrow_mut()
+                    .push_back(MockCommand::NodeVolumes(object_id, volumes));
+            }
+        }
         fn device_mute(
             &self,
             _object_id: ObjectId,