Ω-W1-T3: run the master meter on its own 60 FPS timer, and make a meter frame cost one rect

src/shell/instrument/reasampler_editor.h

@@ -7,6 +7,7 @@
 
 #pragma once
 
+#include <chrono>
 #include <optional>
 #include <string>
 #include <unordered_map>
@@ -118,7 +119,13 @@ private:
     FaceLayout faceLayout(int w, int h) const;
 
 #ifdef _WIN32
-    void paint(HDC hdc);
+    // `dirty` is the host's WM_PAINT update rect: a region inside the meter's bar field redraws
+    // that field alone, anything else re-composes the face, and either way only the dirty region
+    // is blitted out of the retained back buffer (a per-paint client-area LICE_SysBitmap is what
+    // the meter's rate would otherwise cost).
+    void paint(HDC hdc, const RECT& dirty);
+    LICE_IBitmap* ensureBackBuffer(int w, int h);
+    void releaseBackBuffer();
     void paintSample(LICE_IBitmap* bmp, int w, int h);        // home face (band composition)
     void paintBrowse(LICE_IBitmap* bmp, int w, int h);        // modal picker overlay
     void paintEmptyState(LICE_IBitmap* bmp, const Rect& area);
@@ -137,6 +144,7 @@ private:
     // Decks: the group fence + caption + compact caption toggles + radial knobs with
     // label<->value swap on hover/drag.
     void paintDeck(LICE_IBitmap* bmp, const FaceLayout& fl);
+    void paintMeterField(LICE_IBitmap* bmp);  // the bar field alone, off meterRects_
 
     // A deck cell's mini curve thumbnail (the VELOCITY group) and the modal editor it summons.
     void paintCurveButton(LICE_IBitmap* bmp, const Rect& r, CurveTarget target, bool disabled,
@@ -231,10 +239,16 @@ private:
     // never yanks the edit surface.
     void onSyncTimer();
 
+    // The meter tick (its own WM_TIMER id, UI thread only): drains the bus, advances the
+    // ballistics, repaints the bar field. Its own clock — see editor_platform.cpp's timer ids.
+    void onMeterTimer();
+
     static LRESULT CALLBACK wndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam);
     void invalidate();
+    void invalidateMeter();  // the bar field only; falls back to invalidate() before first paint
 
     HWND childHwnd_ = nullptr;
+    LICE_IBitmap* backBuffer_ = nullptr;  // owned; see ensureBackBuffer
 #endif
 
     // Re-read the bank (samples + banks) from the live bridge and snapshot the instrument's
@@ -280,10 +294,16 @@ private:
     // thread only (file I/O); cleared with the thumbnail cache on refresh.
     const std::vector<AudioSample>& monoPcmFor(const std::string& sampleId);
 
+    // The hero waveform's binned envelope: the band's most expensive draw, and a function of the
+    // capture and the bin count alone. UI thread only (may decode).
+    const Envelope& heroEnvelope(std::size_t bins, int laneCount);
+
     // The interleaved source PCM behind the stereo waveform lanes.
     struct ChannelPcm {
         std::vector<AudioSample> interleaved;  // frame-interleaved source frames
         int channelCount = 0;                  // 0 = nothing decoded
+        Envelope heroEnv;         // binned from `interleaved`, so every path that drops the
+        std::size_t heroBins = 0; // decode drops it too. 0 = not computed
         std::int64_t frameCount() const {
             return channelCount > 0
                        ? static_cast<std::int64_t>(interleaved.size()) / channelCount
@@ -471,11 +491,14 @@ private:
     std::string searchQuery_;             // type-to-filter narrow; "" = no search
     bool searchFocused_ = false;          // whether the search box has keyboard focus
 
-    // The MASTER deck's meter, advanced from the published block magnitudes on the sync tick
-    // (see onSyncTimer for why it runs mid-drag too, and why the first read is discarded).
-    // meterTickMs_ 0 = never ticked.
+    // The MASTER deck's meter, advanced from the published block magnitudes on its own timer
+    // (see onMeterTimer for why it runs mid-drag too, and why the first read is discarded).
+    // A default-constructed meterTick_ means never ticked. meterRects_ is the column interior
+    // resolved at the last FULL paint; an empty field means "not on screen" (no layout yet, the
+    // empty state, a modal sheet over it) and sends the tick down the whole-client path.
     instrument::ui::MasterMeterUi masterMeter_;
-    unsigned long long meterTickMs_ = 0;
+    std::chrono::steady_clock::time_point meterTick_{};
+    instrument::ui::MeterRects meterRects_;
 
     // Hover state (transient, never persisted).
     HoverTarget hover_;                   // the interactive element under the pointer