reasampler/src/core/instrument/ui/envelope_overlay.cpp

// envelope_overlay.cpp — see envelope_overlay.h. Pure geometry; no host types.

#include "core/instrument/ui/envelope_overlay.h"

#include "core/util/clamp01.h"

#include <algorithm>

namespace reasampler::instrument::ui {

using util::clamp01;  // the ONE unit-interval clamp (Q-W1, T4-24)

int timeToX(const Rect& area, double totalSeconds, double t) {
    const int w = std::max(0, area.width);
    if (w <= 0 || totalSeconds <= 0.0) return area.x;
    if (t < 0.0) t = 0.0;
    // Linear map, clamped on BOTH sides (FA2 bounds invariant): t past totalSeconds pins to the
    // last in-bounds column area.right()-1. Clamp in DOUBLE space BEFORE the integer cast — a huge
    // t would overflow a 32-bit long (Windows) and wrap to the WRONG edge — then round.
    double px = (t / totalSeconds) * static_cast<double>(w);
    if (px > static_cast<double>(w - 1)) px = static_cast<double>(w - 1);
    return area.x + static_cast<int>(px + 0.5);
}

int gateTimedWidth(const Rect& area) {
    const int w = std::max(0, area.width);
    if (w <= 0) return 0;
    const int sustainPx =
        static_cast<int>(kGateSustainDisplayFraction * static_cast<double>(w) + 0.5);
    return std::max(1, w - sustainPx);
}

double gatePxPerSecond(const Rect& area) {
    const int timedW = gateTimedWidth(area);
    if (timedW <= 0) return 0.0;
    // Usable width = timed region minus the four per-segment separation bases and the last
    // in-bounds column, floored at 1 px so the scale never degenerates; the domain is the four
    // stages end-to-end at their schematic maxima (param-domain scale — sample-length-free).
    const double usable =
        std::max(1.0, static_cast<double>(timedW - 1 - 4 * kGateNodeSepPx));
    return usable / (4.0 * kGateStageMaxSeconds);
}

int levelToY(const Rect& area, double level) {
    const int h = std::max(0, area.height);
    if (h <= 0) return area.y;
    if (level < 0.0) level = 0.0;
    if (level > 1.0) level = 1.0;
    // Level 1 -> top row, level 0 -> bottom row (bottom-1 under the half-open convention). The
    // range spans (h-1) pixels so both endpoints land ON a drawable row.
    const int span = h - 1;
    const long dy = static_cast<long>((1.0 - level) * static_cast<double>(span) + 0.5);
    return area.y + static_cast<int>(dy);
}

namespace {

EnvVertex vtx(EnvNode node, const Rect& area, double totalSeconds, double t, double level) {
    EnvVertex v;
    v.node = node;
    v.x = timeToX(area, totalSeconds, t);
    v.y = levelToY(area, level);
    v.level = level;
    return v;
}

// One Gate vertex from a pixel offset inside the area (the Gate schematic works in px space —
// timed px + the fixed sustain-plateau reserve — not through the plain timeToX map). Clamps x in
// DOUBLE space to the last in-bounds column BEFORE the integer cast (FA2 bounds invariant; a
// huge px would overflow a 32-bit long on Windows and wrap to the WRONG edge).
EnvVertex gateVtx(EnvNode node, const Rect& area, double px, double level) {
    const int w = std::max(1, area.width);
    if (px < 0.0) px = 0.0;
    if (px > static_cast<double>(w - 1)) px = static_cast<double>(w - 1);
    EnvVertex v;
    v.node = node;
    v.x = area.x + static_cast<int>(px + 0.5);
    v.y = levelToY(area, level);
    v.level = level;
    return v;
}

std::vector<EnvVertex> gatePolyline(const AmpEnvelope& env, const Rect& area) {
    // Non-negative segment durations (a stored negative would be an upstream bug; clamp defensively).
    const double a = std::max(0.0, env.attackSeconds);
    const double h = std::max(0.0, env.holdSeconds);
    const double d = std::max(0.0, env.decaySeconds);
    const double r = std::max(0.0, env.releaseSeconds);
    const double sus = clamp01(env.sustainLevel);

    // BOUNDED SCHEMATIC (FA2): A/H/D and R map onto the TIMED region (canvas minus the reserved
    // sustain-plateau width) at the PARAM-DOMAIN scale — sample-length-free — and every segment
    // gets a kGateNodeSepPx base so consecutive nodes never coincide (every node individually
    // grabbable at any params, incl. the tier-0 zero-hold/zero-decay defaults). The sustain
    // plateau is the fixed reserve between DecayEnd and ReleaseStart.
    const int W = std::max(1, area.width);
    const double sustainPx = static_cast<double>(W - gateTimedWidth(area));
    const double sep = static_cast<double>(kGateNodeSepPx);
    const double pps = gatePxPerSecond(area);

    double xAttack  = sep + a * pps;              // AttackEnd
    double xHold    = xAttack + sep + h * pps;    // HoldEnd
    double xDecay   = xHold + sep + d * pps;      // DecayEnd (sustain node)
    double xPlateau = xDecay + sustainPx;         // ReleaseStart (schematic note-off)
    double xRelease = xPlateau + sep + r * pps;   // ReleaseEnd

    // Right-edge overrun (a stored stage beyond the schematic domain): compress from the RIGHT
    // preserving the minimum gaps, so trailing nodes stay individually separated instead of
    // piling on the last column. The re-floor pass only bites when the canvas is too narrow to
    // hold the minimum gaps at all — then gateVtx's [0, W-1] clamp wins (in-bounds > separation).
    const double xMax = static_cast<double>(W - 1);
    if (xRelease > xMax) {
        xRelease = xMax;
        xPlateau = std::min(xPlateau, xRelease - sep);
        xDecay   = std::min(xDecay, xPlateau - sustainPx);
        xHold    = std::min(xHold, xDecay - sep);
        xAttack  = std::min(xAttack, xHold - sep);
        xAttack  = std::max(xAttack, sep);
        xHold    = std::max(xHold, xAttack + sep);
        xDecay   = std::max(xDecay, xHold + sep);
        xPlateau = std::max(xPlateau, xDecay + sustainPx);
        xRelease = std::max(xRelease, xPlateau + sep);
    }

    std::vector<EnvVertex> pts;
    pts.reserve(6);
    pts.push_back(gateVtx(EnvNode::Origin,       area, 0.0,      0.0));
    pts.push_back(gateVtx(EnvNode::AttackEnd,    area, xAttack,  1.0));
    pts.push_back(gateVtx(EnvNode::HoldEnd,      area, xHold,    1.0));
    pts.push_back(gateVtx(EnvNode::DecayEnd,     area, xDecay,   sus));  // sustain node
    pts.push_back(gateVtx(EnvNode::ReleaseStart, area, xPlateau, sus));  // plateau end
    pts.push_back(gateVtx(EnvNode::ReleaseEnd,   area, xRelease, 0.0));
    return pts;
}

std::vector<EnvVertex> triggerPolyline(const AmpEnvelope& env, const Rect& area,
                                       double totalSeconds) {
    // The played span is lengthFraction of the whole sample; fades are fractions OF that span.
    const double len   = clamp01(env.lengthFraction);
    double fadeIn      = clamp01(env.fadeInFraction);
    double fadeOut     = clamp01(env.fadeOutFraction);
    // Fades cannot overlap: clamp so fadeIn + fadeOut <= 1 (of the played span), mirroring the
    // engine's TriggerParams clamp. Trim the LATER fade (fade-out) first, matching the engine.
    if (fadeIn + fadeOut > 1.0) fadeOut = std::max(0.0, 1.0 - fadeIn);

    const double playSeconds  = len * totalSeconds;
    const double tFadeInEnd   = fadeIn * playSeconds;
    const double tFadeOutStart = playSeconds - fadeOut * playSeconds;  // where fade-out begins

    std::vector<EnvVertex> pts;
    pts.reserve(4);
    pts.push_back(vtx(EnvNode::Origin,       area, totalSeconds, 0.0,           0.0));
    pts.push_back(vtx(EnvNode::FadeInEnd,    area, totalSeconds, tFadeInEnd,    1.0));
    pts.push_back(vtx(EnvNode::FadeOutStart, area, totalSeconds, tFadeOutStart, 1.0));  // unity end
    pts.push_back(vtx(EnvNode::LengthEnd,    area, totalSeconds, playSeconds,   0.0));  // playEnd
    return pts;
}

}  // namespace

std::vector<EnvVertex> buildEnvelopePolyline(const AmpEnvelope& env, const Rect& area,
                                             double totalSeconds) {
    if (area.width <= 0 || area.height <= 0 || totalSeconds <= 0.0) {
        // Degenerate surface: a two-point flat baseline at level 0 so the shell always has a line.
        return {vtx(EnvNode::Origin, area, 1.0, 0.0, 0.0),
                vtx(EnvNode::ReleaseEnd, area, 1.0, 1.0, 0.0)};
    }
    // Gate is a param-domain schematic — totalSeconds only gates the degenerate branch above
    // (no loaded duration -> baseline); Trigger is PCM-aligned and consumes it.
    return env.mode == EnvMode::Gate ? gatePolyline(env, area)
                                     : triggerPolyline(env, area, totalSeconds);
}

}  // namespace reasampler::instrument::ui