wip: running interface in separate or combined mode

also disassociating render functions from state structs

src/mixer/_tui.rs

@@ -0,0 +1,39 @@
+use super::Mixer;
+
+impl<W: Write> Input<TUI<W>, bool> for Mixer {
+    fn handle (&mut self, engine: &mut TUI<W>) -> Result<Option<bool>> {
+        Ok(None)
+    }
+}
+
+impl<W: Write> Output<TUI<W>, [u16;2]> for Mixer {
+    fn render (&self, envine: &mut TUI<W>) -> Result<Option<[u16;2]>> {
+
+        let tracks_table = Columns::new()
+            .add(titles)
+            .add(input_meters)
+            .add(gains)
+            .add(gain_meters)
+            .add(pres)
+            .add(pre_meters)
+            .add(levels)
+            .add(pans)
+            .add(pan_meters)
+            .add(posts)
+            .add(routes)
+
+        Rows::new()
+            .add(Columns::new()
+                .add(Rows::new()
+                    .add("[Arrows]".bold())
+                    .add("Navigate"))
+                .add(Rows::new()
+                    .add("[+/-]".bold())
+                    .add("Adjust"))
+                .add(Rows::new()
+                    .add("[Ins/Del]".bold())
+                    .add("Add/remove track")))
+            .add(tracks_table)
+            .render(engine)
+    }
+}