reasampler/src/shell/view/view.cpp

// See view.h. Compiled into the reaper_reasampler module; includes
// reaper_plugin_functions.h without REAPERAPI_IMPLEMENT (main.cpp owns that).
// Tree arithmetic lives in view_tree (pure) and one track's park/restore in
// view_fx_park; this file owns the plan iteration, lanes, parents and the one
// undo block they all ride.

#include "shell/view/view.h"

#include <cstdio>
#include <map>
#include <optional>
#include <set>
#include <string>
#include <unordered_map>
#include <utility>
#include <vector>

#include "shell/capture/item_read.h"
#include "core/view/fx_offline.h"
#include "core/view/lane_keys.h"
#include "core/view/solo_cache.h"
#include "shell/capture/track_guid.h"
#include "shell/view/view_fx_park.h"
#include "shell/view/view_solo.h"
#include "core/view/view_tree.h"

#define REAPERAPI_MINIMAL
#define REAPERAPI_WANT_CountTracks
#define REAPERAPI_WANT_EnumProjects
#define REAPERAPI_WANT_GetPlayStateEx
#define REAPERAPI_WANT_GetTrack
#define REAPERAPI_WANT_GetMediaTrackInfo_Value
#define REAPERAPI_WANT_SetMediaTrackInfo_Value
#define REAPERAPI_WANT_GetSetMediaTrackInfo_String
#define REAPERAPI_WANT_PreventUIRefresh
#define REAPERAPI_WANT_Undo_BeginBlock2
#define REAPERAPI_WANT_Undo_EndBlock2
#define REAPERAPI_WANT_TrackList_AdjustWindows
#define REAPERAPI_WANT_UpdateArrange
#define REAPERAPI_WANT_UpdateTimeline
#define REAPERAPI_WANT_ValidatePtr2
// Lane minting: item-side lane reads/writes assigning each item to its mode's lane.
#define REAPERAPI_WANT_CountTrackMediaItems
#define REAPERAPI_WANT_GetTrackMediaItem
#define REAPERAPI_WANT_GetMediaItemInfo_Value
#define REAPERAPI_WANT_SetMediaItemInfo_Value
#include "reaper_plugin_functions.h"

namespace reasampler {

using view::buildFolderTree;
using view::isOnManualLane;
using view::managedLaneKey;
using view::modeIdFromLaneName;
using view::TrackFolderEntry;

namespace {

// I_FREEMODE value for fixed lanes. SDK: 0=normal, 1=free item positioning, 2=fixed lanes.
constexpr int kFreeModeFixedLanes = 2;

// GetPlayStateEx bitmask. SDK: &1 playing, &2 paused, &4 recording — paused is
// deliberately excluded, nothing is moving there.
constexpr int kTransportMoving = 1 | 4;

// The domains one apply actually writes: track config/routing (visibility,
// B_MAINSEND, I_SOLO), item lane assignment, and the ext-state block
// (UNDO_STATE_MISCCFG covers extension state). NOT UNDO_STATE_ALL, which
// includes UNDO_STATE_FX and so makes every undo record carry every track's FX
// state — a cost that scales with the project's plugin count rather than with
// what the switch changed. FX is OR'd back in per apply, only when I_FXEN or a
// per-FX offline state really moved (TrackApplyResult::fxMoved).
// [verify — DAW] INFERRED, not documented: UNDO_STATE_TRACKCFG reads
// "track/master vol/pan/routing" (reaper_plugin.h:1541) and names neither
// B_SHOWINTCP/B_SHOWINMIXER nor the fixed-lane properties (assumed to ride
// UNDO_STATE_ITEMS, :1543). Wrong ⇒ a Ctrl-Z restores less than the switch did.
constexpr int kApplyUndoMask = UNDO_STATE_TRACKCFG | UNDO_STATE_ITEMS | UNDO_STATE_MISCCFG;

// Holds REAPER's UI refresh off for the write phase; the deliberate rebuild
// (TrackList_AdjustWindows + UpdateArrange) runs after it releases. RAII because
// an unbalanced pair leaves the user's UI frozen with no way back — the SDK's
// own warning at reaper_plugin_functions.h:5581.
struct UiRefreshHold {
    UiRefreshHold() { PreventUIRefresh(1); }
    ~UiRefreshHold() { PreventUIRefresh(-1); }
    UiRefreshHold(const UiRefreshHold&) = delete;
    UiRefreshHold& operator=(const UiRefreshHold&) = delete;
};

// applyMode is reachable from the load tick, the actions and render_in_place, and its
// TrackFX_SetOffline calls are assumed to pump the message loop — so any of them can
// re-enter it mid-apply, planning against the same model the outer loop is iterating.
// An inner restoreTrack consuming a snapshot the outer sits mid-park over leaves that
// track flags-restored, chain-offline and snapshotless: refused forever. Fail closed.
bool g_applying = false;
struct ApplyLatch {
    ApplyLatch() { g_applying = true; }
    ~ApplyLatch() { g_applying = false; }
    ApplyLatch(const ApplyLatch&) = delete;
    ApplyLatch& operator=(const ApplyLatch&) = delete;
};

// C_LANESCOLLAPSED=2: render a tool-split track like a normal single-lane
// track showing only the playing lane (SDK: 1=collapsed, 2=hidden-lanes-exist
// but displays as non-fixed-lane).
constexpr int kLanesDisplayAsNormal = 2;

// C_LANESETTINGS &32 = hide per-lane buttons; OR'd in, never clobbering the
// mask. Deliberately NOT setting &1 (auto-remove empty lanes): the lazy-mint
// decision never mints an empty lane, so &1 buys nothing and risks REAPER
// silently removing a managed lane out from under the ownership index.
constexpr int kLaneSettingsHideButtons = 32;

// Makes a tool-split track's display read as an ordinary track. Gated by every
// caller on the tool-driven transition INTO fixed lanes (freeMode != 2 before
// the flip) — a track already in fixed-lane mode (the user's own) never
// reaches this, so a user's comp-lane display prefs are never stomped.
void applyTransparentLaneDisplay(MediaTrack* tr) {
    SetMediaTrackInfo_Value(tr, "C_LANESCOLLAPSED",
                            static_cast<double>(kLanesDisplayAsNormal));
    const int settings = static_cast<int>(GetMediaTrackInfo_Value(tr, "C_LANESETTINGS"));
    SetMediaTrackInfo_Value(tr, "C_LANESETTINGS",
                            static_cast<double>(settings | kLaneSettingsHideButtons));
}

// The master track is not enumerated by GetTrack (index space excludes it),
// so it can never enter the tree — the master-untouched invariant holds by
// construction.
std::vector<TrackFolderEntry> readFolderEntries(
        ReaProject* proj,
        TrackHandles& handleByGuid) {
    std::vector<TrackFolderEntry> entries;
    int count = CountTracks(proj);
    entries.reserve(static_cast<std::size_t>(count));
    handleByGuid.reserve(static_cast<std::size_t>(count));
    for (int i = 0; i < count; ++i) {
        MediaTrack* tr = GetTrack(proj, i);
        if (!tr) continue;
        std::string guid = guidString(tr);
        if (guid.empty()) continue;
        int depth = static_cast<int>(GetMediaTrackInfo_Value(tr, "I_FOLDERDEPTH"));
        entries.push_back(TrackFolderEntry{guid, depth});
        handleByGuid.emplace_back(guid, tr);
    }
    return entries;
}

// Every park, restore, parent and lane op resolves its GUID; a linear scan made
// that O(T²) on the one path whose cost the user waits on. The vector form
// survives beside it because view_solo's writers take one pass over it.
using TrackByGuid = std::unordered_map<std::string, MediaTrack*>;

TrackByGuid indexHandles(const TrackHandles& handleByGuid) {
    TrackByGuid byGuid;
    byGuid.reserve(handleByGuid.size());
    for (const auto& kv : handleByGuid) byGuid.emplace(kv.first, kv.second);
    return byGuid;
}

MediaTrack* resolve(const TrackByGuid& byGuid, const std::string& guid) {
    auto it = byGuid.find(guid);
    return it == byGuid.end() ? nullptr : it->second;  // stale/deleted GUID — pruned by being skipped
}

// Lane `laneIdx`'s durable name (P_LANENAME:n) on `tr`, or empty if unnamed /
// unavailable (non-fixed-lane track).
std::string laneName(MediaTrack* tr, int laneIdx) {
    char parm[32];
    std::snprintf(parm, sizeof(parm), "P_LANENAME:%d", laneIdx);
    char buf[512] = {0};
    if (!GetSetMediaTrackInfo_String(tr, parm, buf, false)) return {};
    return std::string(buf);
}

// Managed lane durable key -> current ordinal on `tr`. Manual lanes are
// omitted, so a key absent from the map must not be driven.
std::map<std::string, int> managedLaneOrdinals(MediaTrack* tr) {
    std::map<std::string, int> byKey;
    const int numLanes = static_cast<int>(GetMediaTrackInfo_Value(tr, "I_NUMFIXEDLANES"));
    for (int lane = 0; lane < numLanes; ++lane) {
        std::optional<std::string> key = managedLaneKey(laneName(tr, lane));
        if (key) byKey.emplace(*key, lane);  // first ordinal wins if names collide
    }
    return byKey;
}

// Track-side C_LANEPLAYS:N alone hides+silences every item on lane N (SDK:
// item-side C_LANEPLAYS is read-only, so no per-item write exists or is
// needed). B_FIXEDLANE_HIDDEN is also read-only — hide/show follows from
// C_LANEPLAYS=0/1, never written directly.
bool applyLanePlays(MediaTrack* tr, int laneIdx, int lanePlays) {
    char parm[32];
    std::snprintf(parm, sizeof(parm), "C_LANEPLAYS:%d", laneIdx);
    return writeIfChanged(tr, parm, static_cast<double>(lanePlays));
}

// `freeMode` alone decides whether UpdateTimeline is owed; `wrote` is any project
// write at all, which is what the apply's undo-point decision reads.
struct LaneApplyResult {
    bool freeMode = false;
    bool wrote    = false;
};

// Groups ops by track, reconciles each op's durable laneKey to the track's
// current ordinal (a stale/renamed/deleted key is pruned, never mis-driven),
// enables fixed-lane mode on any track carrying a managed lane, and drives
// C_LANEPLAYS. UpdateTimeline() is the caller's job when `freeMode` comes back
// true (SDK: required after an I_FREEMODE change).
LaneApplyResult applyLaneOps(const TrackByGuid& handleByGuid,
                             const std::vector<LanePlayOp>& lanes) {
    LaneApplyResult out;
    if (lanes.empty()) return out;

    std::map<std::string, std::vector<const LanePlayOp*>> byTrack;
    for (const LanePlayOp& op : lanes) byTrack[op.trackGuid].push_back(&op);

    for (const auto& [guid, ops] : byTrack) {
        MediaTrack* tr = resolve(handleByGuid, guid);
        if (!tr) continue;  // stale GUID — prune

        // Every track reaching here already owns a managed lane (planToggle
        // only emits ops for managed lanes), so re-asserting fixed-lane mode
        // is always a tool-driven (re)split — never a user's untouched
        // manual-fixed-lane track — and gets the same transparent display.
        const int freeMode = static_cast<int>(GetMediaTrackInfo_Value(tr, "I_FREEMODE"));
        if (freeMode != kFreeModeFixedLanes) {
            SetMediaTrackInfo_Value(tr, "I_FREEMODE",
                                    static_cast<double>(kFreeModeFixedLanes));
            applyTransparentLaneDisplay(tr);
            out.freeMode = true;
            out.wrote    = true;
        }

        const std::map<std::string, int> ordinals = managedLaneOrdinals(tr);
        for (const LanePlayOp* op : ops) {
            auto it = ordinals.find(op->laneKey);
            if (it == ordinals.end()) continue;  // key not live on this track — prune
            if (applyLanePlays(tr, it->second, op->lanePlays)) out.wrote = true;
        }
    }
    return out;
}

// One pass, so the assign loop needs no per-item re-scan.
std::map<std::string, MediaItem*> itemHandlesByGuid(MediaTrack* tr) {
    std::map<std::string, MediaItem*> byGuid;
    const int itemCount = CountTrackMediaItems(tr);
    for (int i = 0; i < itemCount; ++i) {
        MediaItem* it = GetTrackMediaItem(tr, i);
        if (!it) continue;
        std::string ig = itemGuid(it);
        if (!ig.empty()) byGuid.emplace(std::move(ig), it);
    }
    return byGuid;
}

// An untagged item is Arrange by default (mirrors leafBelongsToMode). A
// show-both/multi-mode item resolves to its first mode id — unusual for lane
// content, and any one mode is sufficient for the decision.
std::string itemModeFromMembership(const ViewModeModel& model, const std::string& itemGuid) {
    const std::set<std::string> modes = model.membership().modesOf(itemGuid);
    if (modes.empty()) return kArrangeModeId;
    return *modes.begin();
}

// The per-track LaneItem picture the pure decision consumes. Manual-lane reads
// are skipped on a non-fixed-lane track (isOnManualLane is false there anyway).
std::vector<LaneTrack> readLaneTracks(
        const ViewModeModel& model,
        const TrackHandles& handleByGuid) {
    std::vector<LaneTrack> tracks;
    tracks.reserve(handleByGuid.size());
    for (const auto& [guid, tr] : handleByGuid) {
        if (!tr) continue;  // TrackHandles legally carries nulls post-validation (view.cpp)
        LaneTrack lt;
        lt.trackGuid = guid;

        const bool fixedLane =
            static_cast<int>(GetMediaTrackInfo_Value(tr, "I_FREEMODE")) == kFreeModeFixedLanes;

        const int itemCount = CountTrackMediaItems(tr);
        lt.items.reserve(static_cast<std::size_t>(itemCount));
        for (int i = 0; i < itemCount; ++i) {
            MediaItem* it = GetTrackMediaItem(tr, i);
            if (!it) continue;
            const std::string ig = itemGuid(it);
            if (ig.empty()) continue;
            LaneItem li;
            li.guid = ig;
            li.modeId = itemModeFromMembership(model, ig);
            const std::string ln = fixedLane ? itemLaneName(tr, it) : std::string{};
            li.onManualLane = isOnManualLane(fixedLane, ln);
            lt.items.push_back(std::move(li));
        }
        tracks.push_back(std::move(lt));
    }
    return tracks;
}

// Idempotent, and non-destructive: only this reversible flag is written, never
// a move in time or across tracks.
bool assignItemToLane(MediaTrack* tr, MediaItem* it, int laneOrdinal) {
    const int current = static_cast<int>(GetMediaItemInfo_Value(it, "I_FIXEDLANE"));
    if (current == laneOrdinal) return false;  // already there — no-op
    SetMediaItemInfo_Value(it, "I_FIXEDLANE", static_cast<double>(laneOrdinal));
    return true;
}

// Applies the pure LaneMintPlan. Returns true if any project write actually
// changed state (⇒ caller keeps the Undo block and refreshes the timeline).
//
// The plan only ever names managed-prefixed lanes and only ever assigns
// managed-eligible items; I_NUMFIXEDLANES is only ever GROWN, never shrunk,
// so a user's existing manual lanes are never renamed or reassigned.
bool applyMintPlan(ViewModeModel& model, const LaneMintPlan& plan,
                   const TrackByGuid& handleByGuid) {
    bool changed = false;

    std::map<std::string, std::vector<const LaneMint*>> mintsByTrack;
    for (const LaneMint& m : plan.mints) mintsByTrack[m.trackGuid].push_back(&m);
    std::map<std::string, std::vector<const LaneAssign*>> assignsByTrack;
    for (const LaneAssign& a : plan.assigns) assignsByTrack[a.trackGuid].push_back(&a);

    for (const LaneMintPlan::TrackSplit& split : plan.splits) {
        MediaTrack* tr = resolve(handleByGuid, split.trackGuid);
        if (!tr) continue;  // stale GUID — prune

        // A track not already in fixed-lane mode is one the tool is splitting
        // now, so it owns the display; a track already at I_FREEMODE==2 (the
        // user's own, or a prior tool run) skips this and keeps its display prefs.
        const int freeMode = static_cast<int>(GetMediaTrackInfo_Value(tr, "I_FREEMODE"));
        if (freeMode != kFreeModeFixedLanes) {
            SetMediaTrackInfo_Value(tr, "I_FREEMODE", static_cast<double>(kFreeModeFixedLanes));
            applyTransparentLaneDisplay(tr);
            changed = true;
        }

        // Grow-only: a track may already carry the user's manual lanes, so the
        // lane count only ever increases; managed lanes occupy the tail ordinals.
        int laneCount = static_cast<int>(GetMediaTrackInfo_Value(tr, "I_NUMFIXEDLANES"));

        std::map<std::string, int> present = managedLaneOrdinals(tr);

        for (const LaneMint* m : mintsByTrack[split.trackGuid]) {
            model.lanes().setManaged(m->trackGuid, m->laneKey, m->modeId);  // ownership
            if (present.count(m->laneKey)) continue;  // already minted — idempotent

            const int laneIdx = laneCount++;
            SetMediaTrackInfo_Value(tr, "I_NUMFIXEDLANES", static_cast<double>(laneCount));
            char parm[32];
            std::snprintf(parm, sizeof(parm), "P_LANENAME:%d", laneIdx);
            std::vector<char> name(m->laneKey.begin(), m->laneKey.end());
            name.push_back('\0');
            GetSetMediaTrackInfo_String(tr, parm, name.data(), true);
            present.emplace(m->laneKey, laneIdx);  // now resolvable for the assign pass
            changed = true;
        }

        const std::map<std::string, int> ordinals = managedLaneOrdinals(tr);
        const std::map<std::string, MediaItem*> itemsByGuid = itemHandlesByGuid(tr);
        for (const LaneAssign* a : assignsByTrack[split.trackGuid]) {
            auto ord = ordinals.find(a->laneKey);
            if (ord == ordinals.end()) continue;  // key not live — prune, never mis-assign
            auto handle = itemsByGuid.find(a->itemGuid);
            if (handle == itemsByGuid.end()) continue;  // stale item GUID — prune
            if (assignItemToLane(tr, handle->second, ord->second)) changed = true;
        }
    }
    return changed;
}

} // namespace

bool transportBlocksModeSwitch(ReaProject* proj) {
    return (GetPlayStateEx(proj) & kTransportMoving) != 0;
}

bool modeApplyInProgress() { return g_applying; }

bool applyMode(ViewModeModel& model, const std::string& targetModeId, ReaProject* proj) {
    if (g_applying) return false;  // see ApplyLatch; same fail-closed shape as the guards below
    ApplyLatch latch;

    if (!model.modes().contains(targetModeId)) {
        return false;  // reject before touching the project — no partial apply
    }

    // Pinned ONCE: begin and end sit a whole apply apart with the pump premise between
    // them, so resolving "current project" independently at each would let a tab switch
    // mid-apply open the block on one project and close it on another.
    ReaProject* const project = proj ? proj : EnumProjects(-1, nullptr, 0);
    if (!ValidatePtr2(nullptr, project, "ReaProject*")) return false;

    // The discriminator behind both halves of the contract in view.h. A gate placed
    // unconditionally here would break tagging and the project-load reapply during
    // playback; a solo round on every reapply would flicker the user's solo on every
    // membership edit.
    const std::string outgoingModeId = model.activeModeId();
    const bool realSwitch = targetModeId != outgoingModeId;

    if (realSwitch && transportBlocksModeSwitch(project)) {
        return false;  // same fail-closed shape as the mode-exists guard above
    }

    TrackHandles handleByGuid;
    std::vector<TrackFolderEntry> entries = readFolderEntries(project, handleByGuid);
    TrackByGuid trackByGuid = indexHandles(handleByGuid);
    FolderTree tree = buildFolderTree(entries);

    // Prune snapshots for tracks no longer in the live enumeration before
    // planning (membership is intentionally left alone — see model.reconcile).
    // Because reapply-on-load routes through applyMode, this also reconciles
    // on project open.
    std::set<std::string> liveGuids;
    for (const auto& kv : handleByGuid) liveGuids.insert(kv.first);
    model.reconcile(liveGuids);

    // Read before any write, and while activeModeId() still names the mode being left.
    const std::map<std::string, int> outgoingSolo =
        realSwitch ? view::soloedTracks(readTrackSolos(handleByGuid))
                   : std::map<std::string, int>{};

    TogglePlan plan = model.planToggle(tree, targetModeId);

    // Target is guaranteed registered (checked at entry); fall back to the id
    // defensively if that ever changes.
    const Mode* targetMode = model.modes().query(targetModeId);
    const std::string undoLabel =
        "ReaSampler: activate " +
        (targetMode ? targetMode->displayName : targetModeId) + " view";

    int undoMask = kApplyUndoMask;
    bool laneModeChanged = false;
    bool wrote = false;  // anything at all this apply changed — see applyMintsUndoPoint
    std::vector<std::string> refusedParkNames;
    FxRestoreDrops fxDrops;
    int fxDropTracks = 0;

    Undo_BeginBlock2(project);
    {
        UiRefreshHold uiHold;  // every write below lands with the TCP/MCP frozen

        // DISJOIN THE SOLO SURFACES. Both this clear and the replay after
        // setActiveMode ride the existing undo block — one mode toggle stays one Ctrl-Z.
        if (realSwitch) {
            model.soloCache().store(outgoingModeId, outgoingSolo);
            clearTrackSolos(handleByGuid, outgoingSolo);
        }

        // PARK / RESTORE: view_fx_park owns one track's whole move, flags and
        // per-FX offline together. A refusal is named HERE, while the handle is
        // fresh — never held past Undo_EndBlock2/TrackList_AdjustWindows.
        for (const TrackPlan& tp : plan.park) {
            if (tp.flags.empty()) continue;  // every op in a TrackPlan targets one track
            const std::string& guid = tp.flags.front().guid;
            MediaTrack* tr = resolve(trackByGuid, guid);
            // Re-validated per track, not once at resolve: offlining a plugin is
            // ASSUMED to pump the message loop, so a track deleted during an
            // earlier iteration's FX writes would leave this handle dangling.
            if (!tr || !trackStillLive(project, tr)) continue;  // stale/deleted GUID — prune

            const TrackApplyResult r = parkTrack(model, guid, tr, tp.flags);
            if (r.refused) { refusedParkNames.push_back(trackDisplayName(tr)); continue; }
            if (r.wrote) wrote = true;
            if (r.fxMoved) undoMask |= UNDO_STATE_FX;
        }

        for (const TrackPlan& tp : plan.restore) {
            if (tp.flags.empty()) continue;
            const std::string& guid = tp.flags.front().guid;
            MediaTrack* tr = resolve(trackByGuid, guid);
            if (!tr || !trackStillLive(project, tr)) continue;  // stale/deleted GUID — prune

            const TrackApplyResult r = restoreTrack(model, guid, tr, tp.fxOffline, tp.flags);
            if (r.wrote) wrote = true;
            if (r.fxMoved) undoMask |= UNDO_STATE_FX;
            if (r.drops.total() > 0) { fxDrops.add(r.drops); ++fxDropTracks; }
        }

        // The FX writes above are the only thing here assumed to pump the message
        // loop, so this is the one point a handle taken before them can have died.
        // Re-validated for the whole enumeration rather than per consumer: lane ops,
        // parent visibility and the solo replay all write through pre-FX handles.
        for (auto& kv : handleByGuid) {
            if (trackStillLive(project, kv.second)) continue;
            trackByGuid.erase(kv.first);
            kv.second = nullptr;  // view_solo's writers already skip a null handle
        }

        // MANAGED LANES: the active mode's lane plays+shows, every other managed
        // lane is silenced+hidden. Empty on a D1-only project — byte-identical there.
        const LaneApplyResult lanes = applyLaneOps(trackByGuid, plan.lanes);
        laneModeChanged = lanes.freeMode;
        if (lanes.wrote) wrote = true;

        // PARENT VISIBILITY (never parked): recomputed every toggle, never
        // snapshotted. Only the two visibility flags — never mainSend/FX on a parent.
        std::set<std::string> visible = model.visibleTracks(tree, targetModeId);
        for (const FolderNode& node : tree.nodes) {
            if (!node.isParent) continue;
            MediaTrack* tr = resolve(trackByGuid, node.guid);
            if (!tr) continue;  // stale GUID — prune
            const double show = visible.count(node.guid) ? 1.0 : 0.0;
            if (writeIfChanged(tr, "B_SHOWINTCP", show)) wrote = true;
            if (writeIfChanged(tr, "B_SHOWINMIXER", show)) wrote = true;
        }

        model.setActiveMode(targetModeId);

        // Replay + consume, before the single relayout below picks the change up.
        // Dropped against `visible` (computed above for parent visibility), not the
        // park plan: a folder parent can be hidden without being parked, and a
        // hidden track must not receive a replayed solo it carries no visible
        // control to undo.
        if (realSwitch) {
            if (const std::map<std::string, int>* cached = model.soloCache().query(targetModeId)) {
                restoreTrackSolos(handleByGuid, *cached, liveGuids, visible);
                model.soloCache().clear(targetModeId);
            }
        }
    }

    // Force REAPER to rebuild the TCP/MCP now rather than on the next user
    // interaction — AdjustWindows(false) is the full relayout tracks appearing
    // and disappearing owes.
    TrackList_AdjustWindows(false);
    UpdateArrange();

    // UpdateTimeline() is owed only when a track was actually toggled into
    // fixed lanes this apply (SDK requirement for I_FREEMODE changes).
    if (laneModeChanged) UpdateTimeline();

    const bool mint = applyMintsUndoPoint(realSwitch, wrote);
    Undo_EndBlock2(project, mint ? undoLabel.c_str() : "", mint ? undoMask : 0);

    // After the undo block and the UI hold: a report is not a project write, and
    // it must not join what a Ctrl-Z rolls back.
    reportRefusedParks(project, refusedParkNames);
    reportFxRestoreDrops(fxDrops, fxDropTracks);
    return true;
}

bool mintManagedLanes(ViewModeModel& model, ReaProject* proj) {
    TrackHandles handleByGuid;
    std::vector<TrackFolderEntry> entries = readFolderEntries(proj, handleByGuid);
    // The tree is needed to detect a content-bearing folder derived-visible in
    // >1 mode, exactly as applyMode builds it.
    const FolderTree tree = buildFolderTree(entries);

    const std::vector<LaneTrack> tracks = readLaneTracks(model, handleByGuid);
    const LaneMintPlan plan = planLaneMinting(model, tree, tracks);
    if (plan.empty()) return false;  // nothing to mint — no Undo point for a no-op tick

    const TrackByGuid trackByGuid = indexHandles(handleByGuid);

    // `proj` deliberately NOT pinned the way applyMode pins it: nothing between this
    // begin and its end pumps the message loop, so no tab switch can land between them.
    Undo_BeginBlock2(proj);
    const bool changed = applyMintPlan(model, plan, trackByGuid);

    if (!changed) {
        // Plan was non-empty but every write was already satisfied — discard
        // the empty undo point rather than flooding history every detect tick.
        Undo_EndBlock2(proj, "", 0);

        // The arrange still needs a redraw: this no-op path is reached when a
        // freshly-inserted item already landed on the active mode's playing
        // lane (REAPER places new items on the playing lane), so
        // assignItemToLane wrote nothing even though the item needs to appear
        // there now. UpdateArrange() alone (no I_FREEMODE change happened, so
        // UpdateTimeline isn't owed) is a repaint, not a mutation — stays
        // outside the undo block.
        UpdateArrange();
        return false;
    }

    // Reapply the active mode's lane visibility so freshly-minted lanes take
    // their play/show state immediately. applyMode is deliberately NOT reused
    // here — it would re-park/restore whole tracks and recompute parent
    // visibility, which a lane-only mint must not touch.
    const TogglePlan togglePlan = model.planToggle(FolderTree{}, model.activeModeId());
    applyLaneOps(trackByGuid, togglePlan.lanes);

    UpdateTimeline();  // a split happened this call — refresh is owed
    UpdateArrange();

    // Lane minting writes track lane config and item lane assignment and nothing
    // else — never an FX state — so it takes the same honest mask applyMode does
    // (kApplyUndoMask, whose [verify — DAW] on lane-property domain binds here too).
    Undo_EndBlock2(proj, "ReaSampler: separate cross-mode content into lanes", kApplyUndoMask);
    return true;
}

void reconcileManagedLanes(ViewModeModel& model, ReaProject* proj) {
    TrackHandles handleByGuid;
    readFolderEntries(proj, handleByGuid);  // populates handleByGuid (tree unused here)

    // Pure read of REAPER state (no lane created, no I_FREEMODE/I_NUMFIXEDLANES/
    // I_FIXEDLANE written) plus an ownership-index write, recovering managed
    // classification from the durable name. An unprefixed lane is left alone.
    for (const auto& [guid, tr] : handleByGuid) {
        const int freeMode = static_cast<int>(GetMediaTrackInfo_Value(tr, "I_FREEMODE"));
        if (freeMode != kFreeModeFixedLanes) continue;  // no fixed lanes ⇒ nothing managed

        const int numLanes = static_cast<int>(GetMediaTrackInfo_Value(tr, "I_NUMFIXEDLANES"));
        for (int lane = 0; lane < numLanes; ++lane) {
            const std::string name = laneName(tr, lane);
            std::optional<std::string> key = managedLaneKey(name);
            if (!key) continue;  // manual/unnamed lane — leave off the index
            std::optional<std::string> mode = modeIdFromLaneName(name);
            if (!mode) continue;  // prefix-only/illegal name — skip defensively

            // A mode id encoded in the name may no longer be registered (e.g.
            // removed since the project was saved). Recording it managed would
            // make the toggle planner drive a lane keyed to a mode that can
            // never be active — permanently silenced, orphaning its items. So
            // skip: the lane stays off the index (manual-by-default) but keeps
            // its name, so a later re-registration of the mode heals cleanly.
            if (!model.modes().contains(*mode)) continue;
            model.lanes().setManaged(guid, *key, *mode);
        }
    }
}

} // namespace reasampler