reasampler/tests/test_deck_groups_measured.cpp

// Layout-BUDGET tests for reasampler::instrument::ui::deck_groups, split from
// test_deck_groups.cpp on the seam CMakeLists.txt already named: these fixtures need
// sample_bands (the window-floor constants, computeSampleBands) and master_meter
// (kMeterColumnW, MASTER's reserve), which test_deck_groups.cpp's WHICH-descriptors fixtures do
// not. Pins the editor floor's derivation from the deck's width budget, the row/gutter
// justification arithmetic at and above the floor, the pinned Gate group widths, and MASTER's
// interior to the pixel. test_deck_groups.cpp pins WHICH descriptors the deck carries; this
// file pins what the width budget MEASURES them at.

#include "../src/core/instrument/ui/deck_groups.h"
#include "../src/core/instrument/ui/master_meter.h"  // kMeterColumnW: MASTER's reserve IS this
#include "../src/core/instrument/ui/sample_bands.h"

#include <cstdio>
#include <vector>

using namespace reasampler;
using namespace reasampler::instrument::ui;

static int g_fail = 0;
#define CHECK(cond) do { if(!(cond)) { \
    std::printf("FAIL line %d: %s\n", __LINE__, #cond); ++g_fail; } } while(0)

// The editor's floor width, which is also its default (checkSizeConstraint clamps to it), less
// the band allocator's kPad inset on each side.
static constexpr int kAvailAtMinWidth = kEditorMinWidth - 2 * kPad;

static int indexOfGroup(const std::vector<DeckGroupDesc>& g, int id) {
    for (std::size_t i = 0; i < g.size(); ++i) {
        if (g[i].id == id) return static_cast<int>(i);
    }
    return -1;
}

static int cell(DeckParam p) { return static_cast<int>(p); }

// The guard the raised floor exists to provide: at the smallest window the host can produce,
// the deck band still lands inside the client area AND the waveform still gets its two-lane
// floor. Growing the deck past what the floor height can hold fails HERE instead of silently pushing
// FILTER ENV / AMP / VOICE / MASTER off-screen, where there is no scroll to reach them.
static void testDeckFitsInsideTheEnforcedMinimumWindow() {
    for (PlayMode mode : {PlayMode::Gate, PlayMode::Trigger}) {
        const std::vector<DeckGroupDesc> g = sampleDeckGroups(mode);
        const int h = deckHeight(g);
        const SampleBands b = computeSampleBands(kEditorMinWidth, kEditorMinHeight, h);
        CHECK(deckRowCount(g) == 2);  // either face
        CHECK(b.decks.height == h);
        // The reflow's 112 px land in the waveform: at two rows the deck band is 216 and the
        // waveform 358, against 328/246 before. Pinned now that both are reached by
        // construction rather than by a pack outcome.
        CHECK(b.decks.height == 2 * kDeckGroupH + kDeckRowGap);
        CHECK(b.waveform.height == 358);
        // Bottom-anchored INSIDE the pad is the whole assertion: the degrade path pushes the
        // deck down until the waveform hits its floor, so any deck too tall to fit stops
        // landing on this exact line. A `<= kEditorMinHeight` bound would not catch it — the
        // degrade can still leave the deck ending at the window edge.
        CHECK(b.decks.bottom() == kEditorMinHeight - kPad);
        CHECK(b.waveform.height >= kWaveformMinHeight);
    }
}

// The floor is a DERIVED number, and this is the one place the derivation is written down —
// sample_bands stays independent of knob_deck, so neither header can hold it. This fixture is
// the only one that includes both.
static void testTheEditorFloorIsDerivedFromTheDeckWidthBudget() {
    CHECK(kDeckRowBlockW + kDeckGroupGap + kDeckSpanningW + 2 * kPad == kEditorMinWidth);
    // The budget: what is left between the derived floor and the hard ceiling, and it is spent
    // once. A cell costs 60 of it.
    CHECK(kEditorCeilingWidth - kEditorMinWidth == 82);
    // 82 still buys one more deck cell (60), which is the only purchase the ledger promises —
    // the widen below spent 8 px of slack, not the layout's purchasing power.
    CHECK(kEditorCeilingWidth - kEditorMinWidth >= kDeckCellW);
    // The reflow's 112 px goes entirely to the waveform, so the height does not move.
    CHECK(kEditorMinHeight == 680);
    // 1190 + 8: the row block was widened 1020 -> 1028 to put the two rows' filter edges on
    // one pixel, which is the only reason the floor moved off its originally specified value.
    CHECK(kEditorMinWidth == 1198);
    CHECK(kEditorMinWidth <= kEditorCeilingWidth);
    CHECK(kEditorMinHeight <= 720);
    // And the row block really is what the two rows justify inside — derived from the floor
    // and the spanning reserve, not restated.
    CHECK(kEditorMinWidth - 2 * kPad - kDeckSpanningW - kDeckGroupGap == kDeckRowBlockW);
}

// Both rows fit their block, in BOTH play modes. The filter mod depth's move across the rows is
// what these two numbers now carry: SOUND loses one cell (980 -> 920) and CONTOUR gains one
// (876 -> 936). Row 2's 936 is mode-stable because FILTER ENV's and AMP's reserve slots hold
// them at 372/312 in Trigger too — asserted here rather than assumed.
static void testBothRowsAndTheSpanningDeckFitTheBudget() {
    for (PlayMode mode : {PlayMode::Gate, PlayMode::Trigger}) {
        const std::vector<DeckGroupDesc> g = sampleDeckGroups(mode);
        int width[3] = {0, 0, 0};
        int count[3] = {0, 0, 0};
        for (const DeckGroupDesc& d : g) {
            const int r = static_cast<int>(deckRowFor(static_cast<DeckGroupId>(d.id)));
            width[r] += deckGroupWidth(d);
            ++count[r];
        }
        const int sound = static_cast<int>(DeckRow::Sound);
        const int contour = static_cast<int>(DeckRow::Contour);
        const int spanning = static_cast<int>(DeckRow::Spanning);

        CHECK(count[sound] == 4);
        CHECK(width[sound] == 920);   // 192 + 372 + 192 + 164
        CHECK(count[contour] == 3);
        CHECK(width[contour] == 936);  // 252 + 372 + 312
        CHECK(count[spanning] == 1);
        CHECK(width[spanning] == kDeckSpanningW);  // 142 exactly — the reserve is now spent

        for (int r : {sound, contour}) {
            CHECK(width[r] <= kDeckRowBlockW);
            // Slack enough that no gutter in the row falls under the minimum.
            CHECK(kDeckRowBlockW - width[r] >= (count[r] - 1) * kDeckGroupGap);
        }
    }
}

// The gutters the justification law produces at the floor — and the alignment it no longer
// buys. THE FILTER TIE-LINE IS GONE, and it is recorded here as a LOSS rather than left to be
// rediscovered: moving the mod depth from FILTER to FILTER ENV made the two filter groups
// EQUAL in width (372 each), and under space-between two equal groups whose rows carry
// different preceding widths can only share a right edge at one block width — which the
// arithmetic below shows is far below the width either row needs. It is unreachable, not
// merely missed, so kDeckRowBlockW and the editor floor are deliberately NOT moved to chase it.
static void testGutterArithmeticAndTheLostFilterTieLineAtTheFloor() {
    const std::vector<DeckGroupDesc> g = sampleDeckGroups(PlayMode::Gate);
    const DeckLayout dl = layoutDeck(g, kPad, 0, kAvailAtMinWidth);

    const auto box = [&](int id) {
        return dl.groups[static_cast<std::size_t>(indexOfGroup(g, id))].box;
    };
    // Row 1: flush left, flush right on the block, and three EQUAL gutters — 108 divides by 3
    // with no residue, so no gutter carries a leftover pixel.
    CHECK(box(kGroupPitch).x == kPad);
    CHECK(box(kGroupFilter).x - box(kGroupPitch).right() == 36);
    CHECK(box(kGroupVelocity).x - box(kGroupFilter).right() == 36);
    CHECK(box(kGroupVoice).x - box(kGroupVelocity).right() == 36);
    CHECK(box(kGroupVoice).right() == kPad + kDeckRowBlockW);

    // Row 2: flush left, flush right, two gutters exactly equal — 92 over two.
    CHECK(box(kGroupPitchEnv).x == kPad);
    CHECK(box(kGroupFilterEnv).x - box(kGroupPitchEnv).right() == 46);
    CHECK(box(kGroupAmpEnv).x - box(kGroupFilterEnv).right() == 46);
    CHECK(box(kGroupAmpEnv).right() == kPad + kDeckRowBlockW);

    // The loss, block-relative and exact: row 1's filter edge lands 70 px LEFT of row 2's.
    CHECK(box(kGroupFilter).right() - kPad == 600);
    CHECK(box(kGroupFilterEnv).right() - kPad == 670);
    CHECK(box(kGroupFilter).right() != box(kGroupFilterEnv).right());

    // And it is unreachable at any block width, which is the part that makes it a loss rather
    // than a tuning problem. Solving 192 + (W-920)/3 == 252 + (W-936)/2 over the reals gives
    // W = 608 — narrower than either row's own content (920 and 936), so no block that can
    // hold the deck at all can also tie the two edges.
    const double tieAt = 608.0;
    for (int W : {920, 936, kDeckRowBlockW}) CHECK(static_cast<double>(W) > tieAt);
    CHECK(192.0 + (tieAt - 920.0) / 3.0 == 252.0 + (tieAt - 936.0) / 2.0);

    // MASTER is right-anchored outside the block, one kDeckGroupGap clear of it.
    CHECK(box(kGroupMaster).x - box(kGroupVoice).right() == kDeckGroupGap);
    CHECK(box(kGroupMaster).right() == kPad + kAvailAtMinWidth);
}

// No gutter is ever narrower than kDeckGroupGap at or above the floor, and both rows stay
// flush at every width — the property the exact-at-the-floor numbers above are one point of.
// The two filter edges SEPARATE monotonically with width, which is accepted and deliberate:
// row 1 divides its slack over three gutters and row 2 over two, so row 2's filter edge pulls
// right past row 1's and the gap only opens. Encoded as EXPECTED, not as a failure.
//
// Checked per ROW (tracking the last-seen box in each of the two categorical rows while
// walking dl.groups in deck order), not just deck-order neighbours: two same-row groups can
// sit apart in deck order with a different-row group between them, and a deck-order-only
// check would silently skip that gutter.
static void testGuttersHoldTheirMinimumAndTheTieLineDriftsAboveTheFloor() {
    for (PlayMode mode : {PlayMode::Gate, PlayMode::Trigger}) {
        const std::vector<DeckGroupDesc> g = sampleDeckGroups(mode);
        int lastDrift = 1 << 20;  // sentinel above any real drift
        for (int avail = kAvailAtMinWidth; avail <= kAvailAtMinWidth + 600; avail += 37) {
            const DeckLayout dl = layoutDeck(g, kPad, 0, avail);
            const DeckGroupLayout* prevInRow[2] = {nullptr, nullptr};
            for (const DeckGroupLayout& gl : dl.groups) {
                const DeckRow row = deckRowFor(static_cast<DeckGroupId>(gl.id));
                if (row == DeckRow::Spanning) continue;
                const int r = row == DeckRow::Contour ? 1 : 0;
                if (prevInRow[r]) {
                    CHECK(gl.box.x - prevInRow[r]->box.right() >= kDeckGroupGap);
                }
                prevInRow[r] = &gl;
            }
            const auto right = [&](int id) {
                return dl.groups[static_cast<std::size_t>(indexOfGroup(g, id))].box.right();
            };
            // Flush right on the block at every width, both rows.
            CHECK(right(kGroupVoice) == right(kGroupAmpEnv));
            // Monotone in width rather than oscillating: row 2's two gutters absorb slack
            // faster than row 1's three, so the gap only ever opens.
            const int drift = right(kGroupFilter) - right(kGroupFilterEnv);
            CHECK(drift <= lastDrift);
            lastDrift = drift;
        }
        // It really does open up, from the −70 the floor already carries.
        CHECK(lastDrift < -70);
    }
}

// MASTER's interior, exact to the pixel (§1.4). The two left slots sit on the two rows' own
// knob baselines — that is what "stitched to both rows" means — and the meter is ONE rect
// across both, never a readout per row.
static void testTheMasterDeckInteriorLandsOnBothRowBaselines() {
    const std::vector<DeckGroupDesc> g = sampleDeckGroups(PlayMode::Gate);
    const DeckLayout dl = layoutDeck(g, kPad, 0, kAvailAtMinWidth);
    const DeckGroupLayout& m =
        dl.groups[static_cast<std::size_t>(indexOfGroup(g, kGroupMaster))];

    CHECK(m.box.width == kDeckSpanningW);
    CHECK(m.box.height == 216);
    // 6 + 60 + 8 + 62 + 6 — the decomposition, not just the total, and the 62 is the meter
    // module's own kMeterColumnW rather than a copy of it. That link is the whole point: the
    // column is banked to GROW (§1.2), and a reserve that did not track it would leave the
    // interior underfilling or overrunning with every test still green.
    CHECK(kDeckGroupPadX + kDeckCellW + kDeckColumnGap + kMeterColumnW + kDeckGroupPadX ==
          kDeckSpanningW);
    CHECK(m.column.id == cell(DeckParam::kMasterMeter));
    CHECK(m.column.box.width == kMeterColumnW);

    // One cell drawn (gain) and one slot RESERVED below it: the reserve is height at a fixed
    // position and draws nothing.
    CHECK(m.cells.size() == 1);
    CHECK(m.cells[0].id == cell(DeckParam::kMasterGain));
    CHECK(m.cells[0].cell.y - m.box.y == 26);
    const int reserveTop = m.cells[0].cell.y + kDeckGroupH + kDeckRowGap;
    CHECK(reserveTop - m.box.y == 138);

    // The two baselines are row 1's and row 2's own.
    const DeckGroupLayout& filter =
        dl.groups[static_cast<std::size_t>(indexOfGroup(g, kGroupFilter))];
    const DeckGroupLayout& amp =
        dl.groups[static_cast<std::size_t>(indexOfGroup(g, kGroupAmpEnv))];
    CHECK(m.cells[0].cell.y == filter.cells[0].cell.y);
    CHECK(reserveTop == amp.cells[0].cell.y);

    // The meter: one rect spanning both baselines, 62 x 186.
    CHECK(m.column.id == cell(DeckParam::kMasterMeter));
    CHECK(m.column.box.width == kMeterColumnW);
    CHECK(m.column.box.height == 186);
    CHECK(m.column.box.y == m.cells[0].cell.y);
    CHECK(m.column.box.bottom() - m.box.y == 212);
}

// The regression guard for the rule most likely to be "generalised" wrongly: MASTER's left
// column is FIXED slots at the two baselines, NOT knob_deck's horizontal run-division law
// applied vertically — which would stretch the one gain knob over the whole 186 px.
static void testTheMasterColumnDoesNotDivideItsRunVertically() {
    const std::vector<DeckGroupDesc> g = sampleDeckGroups(PlayMode::Gate);
    const DeckLayout dl = layoutDeck(g, kPad, 0, kAvailAtMinWidth);
    const DeckGroupLayout& m =
        dl.groups[static_cast<std::size_t>(indexOfGroup(g, kGroupMaster))];
    CHECK(m.cells[0].cell.height == kDeckCellH);
    CHECK(m.cells[0].cell.width == kDeckCellW);
    // Under the run-division law the lone present cell would take the whole two-slot run;
    // here it takes exactly one slot and leaves the rest empty.
    CHECK(m.cells[0].cell.height < m.column.box.height);
    CHECK(m.cells[0].cell.bottom() < m.column.box.bottom());
    CHECK(m.cells[0].knob.width == kDeckKnobSize && m.cells[0].knob.height == kDeckKnobSize);
    // And dropping the reserve does not move the gain knob or the meter — the slot below it is
    // reserved height, so nothing above it depends on whether it is there.
    std::vector<DeckGroupDesc> noReserve = g;
    for (DeckGroupDesc& d : noReserve) {
        if (d.id == kGroupMaster) d.cellIds = {cell(DeckParam::kMasterGain)};
    }
    const DeckLayout dl2 = layoutDeck(noReserve, kPad, 0, kAvailAtMinWidth);
    const DeckGroupLayout& m2 =
        dl2.groups[static_cast<std::size_t>(indexOfGroup(noReserve, kGroupMaster))];
    CHECK(m2.cells[0].cell == m.cells[0].cell);
    CHECK(m2.column.box == m.column.box);
}

// MASTER is the group that BINDS the single-button enable width, and it has ZERO slack: its
// knob row measures kDeckSpanningW − 2·pad, so the caption row (46 + gap + button + gap + the
// GR lamp) may reach exactly that and no more. Past 64 the caption row takes over, the spanning
// deck grows, and the growth comes straight out of the 82 px between the editor's floor and its
// ceiling. Pinned at the boundary in both directions rather than as an inequality.
static void testTheLimiterButtonIsAtMostSixtyFourPxBeforeMasterGrows() {
    const std::vector<DeckGroupDesc> g = sampleDeckGroups(PlayMode::Gate);
    const DeckGroupDesc& m = g[static_cast<std::size_t>(indexOfGroup(g, kGroupMaster))];
    CHECK(m.captionToggle.id == cell(DeckParam::kLimiterEnable));
    CHECK(m.captionToggle.style == DeckToggleStyle::kEnable);
    CHECK(deckGroupWidth(m) == kDeckSpanningW);
    // The knob row IS the measurement, and it is exactly the group's inner width.
    CHECK(kDeckCellW + kDeckColumnGap + kMeterColumnW == kDeckSpanningW - 2 * kDeckGroupPadX);

    DeckGroupDesc probe = m;
    probe.captionToggle.width = 64;
    CHECK(deckGroupWidth(probe) == kDeckSpanningW);  // at the ceiling, still knob-row-driven
    probe.captionToggle.width = 65;
    CHECK(deckGroupWidth(probe) > kDeckSpanningW);   // one past it, the spanning deck grows
    // And the shipped width is inside the ceiling, so the budget below stays unspent.
    CHECK(m.captionToggle.width <= 64);
}

// hitTestKnobFace resolves against the drawn CIRCLES and runs no toggle-precedence pass, so it
// is only correct while no toggle rect reaches a dial. The single-button styles made every
// button on the deck wider, so the claim is re-checked here over the SHIPPED descriptors in
// both faces — test_knob_deck's peer proves the geometry over a synthetic group; this proves it
// for the buttons that actually ship. Rect disjointness rather than a pixel sweep: inKnobFace
// answers only inside the knob rect, so no overlapping pixel can exist without one.
static void testNoShippedToggleReachesADrawnKnobFace() {
    const auto disjoint = [](const Rect& a, const Rect& b) {
        return a.empty() || b.empty() || a.right() <= b.x || b.right() <= a.x ||
               a.bottom() <= b.y || b.bottom() <= a.y;
    };
    for (PlayMode mode : {PlayMode::Gate, PlayMode::Trigger}) {
        const std::vector<DeckGroupDesc> g = sampleDeckGroups(mode);
        const DeckLayout dl = layoutDeck(g, kPad, 0, kAvailAtMinWidth);
        int swept = 0;
        for (const DeckGroupLayout& lay : dl.groups) {
            for (const DeckToggleLayout* t : {&lay.captionToggle, &lay.captionToggle2,
                                              &lay.rowToggle}) {
                if (t->id < 0) continue;
                ++swept;
                for (const Rect& seg : {t->seg0, t->seg1}) {
                    // Against every group's cells, not just this one's: the row toggle anchors
                    // past its own run and a neighbour is what it would reach first.
                    for (const DeckGroupLayout& other : dl.groups) {
                        for (const DeckCellLayout& c : other.cells) CHECK(disjoint(seg, c.knob));
                    }
                }
            }
        }
        CHECK(swept == 11);  // every shipped toggle was actually reached by the sweep
    }
}

// The 82 px between the floor and the ceiling is untouched by this whole reflow — the mod
// depth's move is a swap between the two rows, not a purchase.
static void testTheEditorWidthBudgetIsStillUnspent() {
    CHECK(kEditorMinWidth == 1198);
    CHECK(kEditorCeilingWidth - kEditorMinWidth == 82);
    CHECK(kDeckRowBlockW == 1028);
    CHECK(kDeckSpanningW == 142);
}

// Widen the caption reserve alone (as a wider caption or a limiter-toggle change would) and the
// column must still land flush against the group's own right padding, derived from innerRight
// rather than measured past the cell slots — the bug a balanced caption row once hid.
static void testMasterColumnStaysRightAnchoredWhenCaptionRowOutgrowsTheKnobRow() {
    const std::vector<DeckGroupDesc> g = sampleDeckGroups(PlayMode::Gate);
    DeckGroupDesc probe = g[static_cast<std::size_t>(indexOfGroup(g, kGroupMaster))];
    probe.captionWidth += 40;  // unbalances it: the caption row now measures past the knob row
    const std::vector<DeckGroupDesc> one = {probe};
    const DeckLayout dl = layoutDeck(one, kPad, 0, kAvailAtMinWidth);
    const DeckGroupLayout& m = dl.groups[0];
    CHECK(m.box.width > kDeckSpanningW);  // the widen is real, not absorbed elsewhere
    CHECK(m.column.box.right() == m.box.right() - kDeckGroupPadX);
}

// The three mode toggles ride each env group's caption slack, on the CONTOUR row: raising
// their segment width past the caption headroom would widen that row and eat its gutters,
// not add a row — row count is a property of the group inventory, not of width.
static void testTheModeTogglesCostNoGroupWidth() {
    for (PlayMode mode : {PlayMode::Gate, PlayMode::Trigger}) {
        for (const DeckGroupDesc& g : sampleDeckGroups(mode)) {
            if (g.captionToggle2.id < 0) continue;
            DeckGroupDesc without = g;
            without.captionToggle2 = DeckToggleDesc{};
            CHECK(deckGroupWidth(g) == deckGroupWidth(without));
        }
    }
}

// PITCH/RATE carries three cells and measures exactly 192 — the KNOB row (3 x kDeckCellW plus
// padding) is what it measures from, and the caption row must stay under that. The ceiling is
// asserted by construction rather than as a comment: at a caption reserve of 80 the group is
// still 192, and at 81 it is not, which is the whole content of "hard ceiling 80". Widening the
// group is not the remedy if the caption text ever outgrows it — narrowing the mode toggle is.
static void testThePitchRateGroupIsKnobRowDrivenAtExactlyOneNinetyTwo() {
    const std::vector<DeckGroupDesc> g = sampleDeckGroups(PlayMode::Gate);
    const DeckGroupDesc* pitch = nullptr;
    for (const DeckGroupDesc& d : g) if (d.id == kGroupPitch) pitch = &d;
    CHECK(pitch != nullptr);
    if (!pitch) return;
    CHECK(pitch->cellIds.size() == 3);
    CHECK(pitch->cellIds[0] == static_cast<int>(DeckParam::kKeyTrack));
    CHECK(pitch->cellIds[1] == static_cast<int>(DeckParam::kRate));
    CHECK(pitch->cellIds[2] == static_cast<int>(DeckParam::kPitch));
    CHECK(deckGroupWidth(*pitch) == 192);
    CHECK(3 * kDeckCellW + 2 * kDeckGroupPadX == 192);  // the knob row IS the measurement

    DeckGroupDesc probe = *pitch;
    probe.captionWidth = 80;
    CHECK(deckGroupWidth(probe) == 192);  // at the ceiling the caption row still fits under it
    probe.captionWidth = 81;
    CHECK(deckGroupWidth(probe) > 192);   // one past it, the caption row takes over
}

// The kEnvModeW ceilings recorded in deck_groups.cpp's own comment (PITCH ENV binds at 122,
// AMP at 126) pinned against the descriptors they derive from, the same way the Pitch/Rate
// caption ceiling above is: a change to either group's caption width or its enable button
// would otherwise invalidate the recorded numbers with nothing failing.
static void testEnvModeCeilingsArePinnedForPitchEnvAndAmp() {
    const std::vector<DeckGroupDesc> g = sampleDeckGroups(PlayMode::Gate);
    const DeckGroupDesc& penv = g[static_cast<std::size_t>(indexOfGroup(g, kGroupPitchEnv))];
    const DeckGroupDesc& amp  = g[static_cast<std::size_t>(indexOfGroup(g, kGroupAmpEnv))];
    CHECK(deckGroupWidth(penv) == 252);
    CHECK(deckGroupWidth(amp) == 312);

    DeckGroupDesc penvProbe = penv;
    penvProbe.captionToggle2.width = 122;
    CHECK(deckGroupWidth(penvProbe) == 252);  // at the ceiling, still knob-row-driven
    penvProbe.captionToggle2.width = 123;
    CHECK(deckGroupWidth(penvProbe) > 252);   // one past it, the caption row takes over

    DeckGroupDesc ampProbe = amp;
    ampProbe.captionToggle2.width = 126;
    CHECK(deckGroupWidth(ampProbe) == 312);
    ampProbe.captionToggle2.width = 127;
    CHECK(deckGroupWidth(ampProbe) > 312);
    // The two ceilings above are what make PITCH ENV the binding group: 122 < 126, so the
    // shipped width has to clear PITCH ENV's, and it does.
    CHECK(penv.captionToggle2.width <= 122);
}

// Every group's width, in BOTH play modes, against the measured layout table
// (instrument-control-surface.md §1.2). Mode-independence is the second half of the claim: the
// reserve slots hold the two mode-dependent groups at 312 either way, which is what makes the
// contour row's 876 a constant rather than a Gate-only fact.
static void testEveryGroupWidthMatchesTheMeasuredLayout() {
    const struct { int id; int width; } want[] = {
        {kGroupPitch, 192}, {kGroupPitchEnv, 252}, {kGroupFilter, 372},
        {kGroupFilterEnv, 372}, {kGroupAmpEnv, 312}, {kGroupVelocity, 192},
        {kGroupVoice, 164}, {kGroupMaster, 142},
    };
    for (PlayMode mode : {PlayMode::Gate, PlayMode::Trigger}) {
        const std::vector<DeckGroupDesc> g = sampleDeckGroups(mode);
        CHECK(g.size() == sizeof(want) / sizeof(want[0]));
        const DeckLayout dl = layoutDeck(g, kPad, 0, kAvailAtMinWidth);
        for (const auto& w : want) {
            const int i = indexOfGroup(g, w.id);
            CHECK(i >= 0);
            if (i < 0) continue;
            CHECK(deckGroupWidth(g[static_cast<std::size_t>(i)]) == w.width);
            const DeckGroupLayout& lay =
                dl.groups[static_cast<std::size_t>(indexOfGroup(g, w.id))];
            CHECK(lay.box.width == w.width);
        }
        // EVERY cell is kDeckCellW in EITHER mode — the spacing law. Trigger's two reduced
        // faces keep the same reserved run and spend it on end margins, not on wider knobs.
        for (const DeckGroupLayout& lay : dl.groups) {
            for (const DeckCellLayout& c : lay.cells) CHECK(c.cell.width == kDeckCellW);
        }
    }
}

// THE Gate-face regression pin. Every group box and every cell rect at the editor's floor,
// block-relative, against the pre-reflow measurements. Three of the eight are the whole point:
//   FILTER    432 -> 372, one cell narrower — the mod depth left it.
//   FILTER ENV 312 -> 372, one cell wider — the mod depth arrived.
//   VELOCITY  its box translates 20 px LEFT. Nothing about the group changed; row 1's freed
//             60 px is divided over three gutters by the space-between law, and every group
//             between the narrowed one and the row's flush-right end shifts by the share it
//             did not absorb. That translation is the law working, not a second edit.
// Everything else — PITCH/RATE, PITCH ENV, AMP ENV, VOICE, MASTER — is pinned UNCHANGED to the
// pixel, boxes and cells alike, which is the criterion this reflow is measured against.
static void testTheGateFaceIsPixelIdenticalApartFromTheTwoFilterGroups() {
    const std::vector<DeckGroupDesc> g = sampleDeckGroups(PlayMode::Gate);
    const DeckLayout dl = layoutDeck(g, kPad, 0, kAvailAtMinWidth);
    const auto lay = [&](int id) -> const DeckGroupLayout& {
        return dl.groups[static_cast<std::size_t>(indexOfGroup(g, id))];
    };
    // {group, block-relative box x, width, cell count} — the pre-reflow numbers for the five
    // untouched groups, and the derived ones for the three the move implicates.
    const struct { int id; int x; int w; std::size_t cells; } want[] = {
        {kGroupPitch,     0, 192, 3},   // unchanged
        {kGroupFilter,  228, 372, 6},   // was x=208 w=432 with 7 cells
        {kGroupVelocity, 636, 192, 3},  // unchanged group, box translated from x=656
        {kGroupVoice,    864, 164, 1},  // unchanged
        {kGroupPitchEnv,   0, 252, 4},  // unchanged
        {kGroupFilterEnv, 298, 372, 6}, // was x=328 w=312 with 5 cells
        {kGroupAmpEnv,   716, 312, 5},  // unchanged
    };
    for (const auto& w : want) {
        const DeckGroupLayout& l = lay(w.id);
        CHECK(l.box.x - kPad == w.x);
        CHECK(l.box.width == w.w);
        CHECK(l.cells.size() == w.cells);
        // Cells: natural pitch, abutting, starting flush at the group's inner left (no Gate
        // group carries a reserve, so the centring offset is zero everywhere here).
        CHECK(l.cells.front().cell.x == l.box.x + kDeckGroupPadX);
        for (std::size_t k = 0; k < l.cells.size(); ++k) {
            CHECK(l.cells[k].cell.width == kDeckCellW);
            CHECK(l.cells[k].cell.x - l.box.x == kDeckGroupPadX +
                                                    static_cast<int>(k) * kDeckCellW);
        }
    }
    // The two filter groups moved by EXACTLY one cell, in opposite directions.
    CHECK(lay(kGroupFilter).box.width + kDeckCellW == 432);
    CHECK(lay(kGroupFilterEnv).box.width - kDeckCellW == 312);
}

int main() {
    testDeckFitsInsideTheEnforcedMinimumWindow();
    testTheGateFaceIsPixelIdenticalApartFromTheTwoFilterGroups();
    testTheEditorFloorIsDerivedFromTheDeckWidthBudget();
    testBothRowsAndTheSpanningDeckFitTheBudget();
    testGutterArithmeticAndTheLostFilterTieLineAtTheFloor();
    testGuttersHoldTheirMinimumAndTheTieLineDriftsAboveTheFloor();
    testTheMasterDeckInteriorLandsOnBothRowBaselines();
    testTheMasterColumnDoesNotDivideItsRunVertically();
    testTheLimiterButtonIsAtMostSixtyFourPxBeforeMasterGrows();
    testNoShippedToggleReachesADrawnKnobFace();
    testTheEditorWidthBudgetIsStillUnspent();
    testMasterColumnStaysRightAnchoredWhenCaptionRowOutgrowsTheKnobRow();
    testTheModeTogglesCostNoGroupWidth();
    testThePitchRateGroupIsKnobRowDrivenAtExactlyOneNinetyTwo();
    testEnvModeCeilingsArePinnedForPitchEnvAndAmp();
    testEveryGroupWidthMatchesTheMeasuredLayout();
    if (g_fail == 0) std::printf("deck_groups_measured: all tests passed\n");
    return g_fail == 0 ? 0 : 1;
}