fix(ui): latch the DSP percentage readout at ~2 Hz

crates/halo/src/app.rs

@@ -517,6 +517,9 @@ pub struct HaloApp {
     kb_prev: [[bool; 8]; 2],
     /// Process CPU sampling: (last wall instant, last cpu seconds, percent).
     cpu_sample: (std::time::Instant, f64, f32),
+    /// DSP percentage latched for the toolbar readout: (last update, value).
+    /// The number would be unreadable at frame rate; the bar stays live.
+    dsp_display: (std::time::Instant, f32),
     status: String,
     /// Absolute x of the mixer column's center, captured while rendering the
     /// central panel and read a frame later by the toolbar to center the
@@ -670,6 +673,7 @@ impl HaloApp {
             available_devices: Vec::new(),
             kb_prev: [[false; 8]; 2],
             cpu_sample: (std::time::Instant::now(), process_cpu_secs(), 0.0),
+            dsp_display: (std::time::Instant::now(), 0.0),
             status,
             mixer_center_x: 0.0,
         };
@@ -1657,7 +1661,8 @@ impl HaloApp {
         }
     }
 
-    /// Sample process-wide CPU roughly once a second.
+    /// Sample process-wide CPU roughly once a second, and latch the DSP
+    /// readout a couple of times a second.
     fn update_cpu(&mut self) {
         let (last_at, last_cpu, _) = self.cpu_sample;
         let elapsed = last_at.elapsed().as_secs_f64();
@@ -1666,6 +1671,9 @@ impl HaloApp {
             let pct = ((cpu_now - last_cpu) / elapsed * 100.0) as f32;
             self.cpu_sample = (std::time::Instant::now(), cpu_now, pct.max(0.0));
         }
+        if self.dsp_display.0.elapsed().as_secs_f32() >= 0.5 {
+            self.dsp_display = (std::time::Instant::now(), self.mixer.cpu_load.load());
+        }
     }
 
     fn settings_window(&mut self, ctx: &egui::Context) {
@@ -2637,7 +2645,12 @@ impl eframe::App for HaloApp {
                             }
                         }
                         ui.separator();
-                        cpu_meter(ui, self.mixer.cpu_load.load(), self.cpu_sample.2);
+                        cpu_meter(
+                            ui,
+                            self.mixer.cpu_load.load(),
+                            self.dsp_display.1,
+                            self.cpu_sample.2,
+                        );
                         ui.separator();
                         // Right-to-left layout: the output bar lands between
                         // the DSP cluster and the master knob, i.e. just to
@@ -4305,9 +4318,10 @@ fn master_level_meter(ui: &mut egui::Ui, level: f32) {
 
 /// Toolbar meter: DSP = audio-callback load (render time ÷ buffer time,
 /// the number that matters for dropouts) with a bar; CPU = whole-process
-/// usage.
-fn cpu_meter(ui: &mut egui::Ui, dsp_load: f32, process_pct: f32) {
-    let dsp_pct = (dsp_load * 100.0).clamp(0.0, 999.0);
+/// usage. The bar fill tracks `dsp_load` live; the percentage text and
+/// color use `dsp_latched` (updated ~2×/s) so the readout is legible.
+fn cpu_meter(ui: &mut egui::Ui, dsp_load: f32, dsp_latched: f32, process_pct: f32) {
+    let dsp_pct = (dsp_latched * 100.0).clamp(0.0, 999.0);
     let color = if dsp_pct < 50.0 {
         egui::Color32::from_rgb(110, 200, 110)
     } else if dsp_pct < 80.0 {