Retire the zone system: one capture = one parameter set, and re-seam the engine and Sample face into bands

src/core/instrument/ui/sample_bands.cpp

@@ -0,0 +1,54 @@
+// sample_bands.cpp — see sample_bands.h. Pure math; no host types.
+
+#include "core/instrument/ui/sample_bands.h"
+
+#include <algorithm>
+
+namespace reasampler::instrument::ui {
+
+SampleBands computeSampleBands(int w, int h, int deckHeight) {
+    const int cw = std::max(0, w);
+    const int ch = std::max(0, h);
+    const int deckH = std::max(0, deckHeight);
+
+    SampleBands b;
+    const int chromeH = std::min(kTitleHeight + kChromeRowHeight, ch);
+    b.chrome = Rect::ltrb(0, 0, cw, chromeH);
+
+    // Decks are bottom-anchored so the deck row sits on the window edge at any height; the
+    // waveform absorbs whatever is left. When that leaves less than the two-lane floor the
+    // FLOOR WINS and the deck band is pushed past the window bottom (clipped) rather than
+    // squeezing the waveform into an unreadable sliver.
+    int deckTop = ch - kPad - deckH;
+    int waveTop = chromeH + kBandGap;
+    int waveBottom = deckTop - kBandGap;
+    if (waveBottom - waveTop < kWaveformMinHeight) {
+        waveBottom = waveTop + kWaveformMinHeight;
+        deckTop = waveBottom + kBandGap;
+    }
+
+    b.waveform = Rect::ltrb(kPad, waveTop, std::max(kPad, cw - kPad), waveBottom);
+    b.decks = Rect::ltrb(kPad, deckTop, std::max(kPad, cw - kPad), deckTop + deckH);
+    return b;
+}
+
+WaveformLanes waveformLanes(const Rect& waveform, bool stereo) {
+    WaveformLanes lanes;
+    if (waveform.empty()) return lanes;
+    if (!stereo) {
+        lanes.upper = waveform;  // one lane; `lower` stays empty
+        return lanes;
+    }
+    // Split the usable height evenly, giving the seam to the gap. An odd remainder goes to
+    // the upper (left) lane so the two lanes never disagree about the seam row.
+    const int usable = std::max(0, waveform.height - kLaneGap);
+    const int lowerH = usable / 2;
+    const int upperH = usable - lowerH;
+    const int upperBottom = waveform.y + upperH;
+    lanes.upper = Rect::ltrb(waveform.x, waveform.y, waveform.right(), upperBottom);
+    lanes.lower = Rect::ltrb(waveform.x, upperBottom + kLaneGap, waveform.right(),
+                             waveform.bottom());
+    return lanes;
+}
+
+}  // namespace reasampler::instrument::ui