VFS perf fixes, icon/stylesheet compat, download filename fix

VFS:
- Open backing fd at mo2_open time for read-only handles so mo2_read can
  splice without re-opening the file on every read call.
- Bump RLIMIT_NOFILE at mount time to fit the resulting fd pressure when
  the game keeps hundreds of BSAs open.
- Dedicated node_cache_mutex so resolveByInode / mo2_lookup stop racing
  unordered_map writes while multiple tree_mutex readers are active.
- max_read=1MB + matching conn->max_read and raised max_readahead/max_write
  so the kernel merges Wine's small sequential reads into bigger FUSE
  requests.
- Per-op wall-clock counters in mo2_init() logs so we can distinguish VFS
  latency from game-side work.

Proton launch:
- Write dxvk.conf to the prefix and set DXVK_CONFIG_FILE to force
  dxvk.enableGraphicsPipelineLibrary=False, avoiding long GPL compile
  stalls on first run.

UI / plugin compat:
- Clamp IconDelegate's per-icon width to [8, 16] so narrow content
  columns don't trigger QIcon::pixmap(0,0) returning null and logging
  "failed to load icon" every repaint.
- Pre-create lowercase symlinks in the stylesheet directory so QSS files
  authored on Windows resolve url(foo.svg) when on-disk files are Foo.svg.
- Flip content icons empty-chessboard.png and facegen.png to 8-bit RGBA
  so Qt's built-in PNG reader loads them uniformly.
- Add mobase.Version.canonicalString shim for legacy Python plugins that
  still call the old VersionInfo method on appVersion()'s return.
- BSPluginList: compare normalized plugin name lists instead of byte
  hashes so the post-run case-fix refresh stops spuriously firing the
  "load order changed" dialog.
- BSPluginList disabled by default.

Download manager:
- Parse CDN URL with QUrl + QUrlQuery and read the filename from the
  response-content-disposition query param (RFC 6266 quoted / unquoted /
  ext-value forms), not QFileInfo on the raw URL.
- When the API or URL gives us a CDN object key (no archive extension),
  prefer the actual Content-Disposition header from the live response in
  metaDataChanged and downloadFinished.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

4 files changed, 674 insertions, 0 deletions

diff --git a/libs/installer_bsplugins/src/TESFile/Reader.h b/libs/installer_bsplugins/src/TESFile/Reader.h
new file mode 100644
index 0000000..0479842
--- /dev/null
+++ b/libs/installer_bsplugins/src/TESFile/Reader.h
@@ -0,0 +1,67 @@
+#ifndef TESFILE_READER_H
+#define TESFILE_READER_H
+
+#include "Stream.h"
+
+#include <concepts>
+#include <cstdint>
+#include <filesystem>
+#include <istream>
+#include <utility>
+
+namespace TESFile
+{
+
+template <typename Handler>
+concept ReaderHandler = requires(Handler& handler) {
+  {
+    handler.Group(std::declval<GroupData>())
+  } -> std::convertible_to<bool>;
+  {
+    handler.Form(std::declval<FormData>())
+  } -> std::convertible_to<bool>;
+  {
+    handler.Chunk(std::declval<Type>())
+  } -> std::convertible_to<bool>;
+  {
+    handler.Data(std::declval<std::istream&>())
+  };
+};
+
+template <ReaderHandler Handler>
+class Reader
+{
+public:
+  void parse(const std::filesystem::path& path, Handler& handler);
+
+  void parse(std::istream& stream, Handler& handler);
+
+private:
+  enum HeaderSize
+  {
+    HeaderSize_Standard  = sizeof(RecordHeader),
+    HeaderSize_Oblivion  = 20,
+    HeaderSize_Morrowind = 16,
+  };
+
+  std::uint32_t parsePluginInfo(std::istream& stream, Handler& handler);
+
+  std::uint32_t parseRecord(std::istream& stream, Handler& handler);
+
+  std::uint32_t handleForm(std::istream& stream, const RecordHeader& header,
+                           Handler& handler);
+
+  std::uint32_t handleGroup(std::istream& stream, const RecordHeader& header,
+                            Handler& handler);
+
+  std::uint32_t parseChunk(std::istream& stream, Handler& handler);
+
+  TESFormat chunkFormat_;
+  int headerSize_;
+};
+
+}  // namespace TESFile
+
+#include "Reader.inl"
+
+#endif  // TESFILE_READER_H
diff --git a/libs/installer_bsplugins/src/TESFile/Reader.inl b/libs/installer_bsplugins/src/TESFile/Reader.inl
new file mode 100644
index 0000000..3324a15
--- /dev/null
+++ b/libs/installer_bsplugins/src/TESFile/Reader.inl
@@ -0,0 +1,238 @@
+#include "Reader.h"
+
+#include <zlib.h>
+
+#include <cstring>
+#include <format>
+#include <fstream>
+#include <stdexcept>
+
+namespace TESFile
+{
+
+template <ReaderHandler Handler>
+inline void Reader<Handler>::parse(const std::filesystem::path& path, Handler& handler)
+{
+  std::ifstream stream;
+  stream.open(path, std::ios_base::binary | std::ios_base::in);
+  if (!stream.good()) {
+    throw std::runtime_error(std::strerror(errno));
+  }
+  parse(stream, handler);
+}
+
+template <ReaderHandler Handler>
+inline void Reader<Handler>::parse(std::istream& stream, Handler& handler)
+{
+  parsePluginInfo(stream, handler);
+  while (stream.good() && stream.peek() != std::char_traits<char>::eof()) {
+    parseRecord(stream, handler);
+  }
+}
+
+template <ReaderHandler Handler>
+inline std::uint32_t Reader<Handler>::parsePluginInfo(std::istream& stream,
+                                                      Handler& handler)
+{
+  const RecordHeader header = readType<RecordHeader>(stream);
+  if (stream.fail()) {
+    throw std::runtime_error("record incomplete");
+  }
+
+  if (header.type == "TES4"_ts) {
+    if (header.old.firstChunk == "HEDR"_ts) {
+      chunkFormat_ = TESFormat::Oblivion;
+      headerSize_  = HeaderSize_Oblivion;
+      stream.seekg(HeaderSize_Oblivion - sizeof(RecordHeader), std::istream::cur);
+    } else {
+      chunkFormat_ = TESFormat::Standard;
+      headerSize_  = sizeof(RecordHeader);
+    }
+  } else if (header.type == "TES3"_ts) {
+    chunkFormat_ = TESFormat::Morrowind;
+    headerSize_  = HeaderSize_Morrowind;
+    stream.seekg(HeaderSize_Morrowind - sizeof(RecordHeader), std::istream::cur);
+  } else {
+    throw std::runtime_error(
+        std::format("Unrecognized plugin info type: '{}'", header.type.value));
+  }
+
+  return handleForm(stream, header, handler);
+}
+
+template <ReaderHandler Handler>
+inline std::uint32_t Reader<Handler>::parseRecord(std::istream& stream,
+                                                  Handler& handler)
+{
+  RecordHeader header;
+  stream.read(reinterpret_cast<char*>(&header), headerSize_);
+  if (stream.fail()) {
+    throw std::runtime_error("record incomplete");
+  }
+
+  if (header.type == "GRUP"_ts) {
+    return handleGroup(stream, header, handler);
+  } else {
+    return handleForm(stream, header, handler);
+  }
+}
+
+template <ReaderHandler Handler>
+inline std::uint32_t Reader<Handler>::handleForm(std::istream& stream,
+                                                 const RecordHeader& header,
+                                                 Handler& handler)
+{
+  std::uint32_t dataSize = header.dataSize;
+  const bool compressed  = header.formData.flags & RecordFlags::Compressed;
+  // Check for Oblivion plugin data
+  uint16_t version       = 0;
+  if (header.old.firstChunk.string() != "HEDR") {
+    version = header.version;
+  }
+  if (handler.Form(
+          FormData(header.type, header.formData.flags, header.formData.formId, version))) {
+
+    std::string data;
+    data.resize(dataSize);
+    stream.read(data.data(), dataSize);
+    if (stream.fail()) {
+      throw std::runtime_error("chunk incomplete");
+    }
+
+    std::istringstream chunkstream;
+    if (!compressed) {
+      chunkstream.str(std::move(data));
+    } else {
+      if (data.size() < 4) {
+        throw std::runtime_error("chunk incomplete");
+      }
+
+      std::memcpy(&dataSize, data.data(), sizeof(dataSize));
+
+      std::string inflated;
+      inflated.resize(dataSize);
+
+      int zret;
+      ::z_stream zstreambuf{
+          .next_in = reinterpret_cast<z_const ::Bytef*>(data.data() + sizeof(dataSize)),
+          .avail_in  = static_cast<::uInt>(data.size() - sizeof(dataSize)),
+          .next_out  = reinterpret_cast<::Bytef*>(inflated.data()),
+          .avail_out = static_cast<::uInt>(inflated.size()),
+          .zalloc    = Z_NULL,
+          .zfree     = Z_NULL,
+          .opaque    = Z_NULL,
+      };
+      zret = ::inflateInit(&zstreambuf);
+      if (zret != Z_OK) {
+        throw std::runtime_error("zlib failed to init");
+      }
+
+      zret = ::inflate(&zstreambuf, Z_FINISH);
+      if (zret != Z_STREAM_END) {
+        throw std::runtime_error("zlib failed to read data");
+      }
+      zret = ::inflateEnd(&zstreambuf);
+
+      chunkstream.str(std::move(inflated));
+    }
+
+    while (dataSize != 0) {
+      const std::uint32_t fieldSize = parseChunk(chunkstream, handler);
+
+      if (fieldSize > dataSize) {
+        throw std::runtime_error(
+            std::format("Subrecord exceeded record size ({}-{})", dataSize, fieldSize));
+      }
+
+      dataSize -= fieldSize;
+    }
+
+    if constexpr (requires { handler.EndForm(); }) {
+      handler.EndForm();
+    }
+  } else {
+    stream.seekg(dataSize, std::istream::cur);
+    if (stream.fail()) {
+      throw std::runtime_error("record incomplete");
+    }
+  }
+
+  return headerSize_ + header.dataSize;
+}
+
+template <ReaderHandler Handler>
+inline std::uint32_t Reader<Handler>::handleGroup(std::istream& stream,
+                                                  const RecordHeader& header,
+                                                  Handler& handler)
+{
+  std::uint32_t dataSize = header.dataSize - headerSize_;
+
+  if (handler.Group(GroupData(header.groupData.label, header.groupData.groupType))) {
+
+    while (dataSize != 0) {
+      const std::uint32_t recordSize = parseRecord(stream, handler);
+
+      if (recordSize > dataSize) {
+        throw std::runtime_error(
+            std::format("Record exceeded group size ({}-{})", dataSize, recordSize));
+      }
+
+      dataSize -= recordSize;
+    }
+
+    if constexpr (requires { handler.EndGroup(); }) {
+      handler.EndGroup();
+    }
+  } else {
+    stream.seekg(dataSize, std::istream::cur);
+    if (stream.fail()) {
+      throw std::runtime_error("group incomplete");
+    }
+  }
+
+  return header.dataSize;
+}
+
+template <ReaderHandler Handler>
+inline std::uint32_t Reader<Handler>::parseChunk(std::istream& stream, Handler& handler)
+{
+  ChunkHeader header = readType<ChunkHeader>(stream);
+  if (stream.fail()) {
+    throw std::runtime_error("chunk header incomplete");
+  }
+  std::uint32_t readSize = sizeof(ChunkHeader) + header.dataSize;
+
+  std::uint32_t dataSize = header.dataSize;
+  if (header.type == "XXXX"_ts) {
+    if (dataSize != 4) {
+      throw std::runtime_error("XXXX field has invalid size");
+    }
+    dataSize = readType<std::uint32_t>(stream);
+    header   = readType<ChunkHeader>(stream);
+    if (stream.fail()) {
+      throw std::runtime_error("chunk size incomplete");
+    }
+    readSize += sizeof(ChunkHeader) + dataSize;
+  }
+
+  if (handler.Chunk(header.type)) {
+    std::string field;
+    field.resize(dataSize);
+    stream.read(field.data(), dataSize);
+    if (stream.fail()) {
+      throw std::runtime_error("chunk data incomplete");
+    }
+    std::istringstream data(std::move(field));
+    data.exceptions(std::ios_base::failbit);
+    handler.Data(data);
+  } else {
+    stream.seekg(dataSize, std::istream::cur);
+    if (stream.fail()) {
+      throw std::runtime_error("chunk incomplete");
+    }
+  }
+
+  return readSize;
+}
+
+}  // namespace TESFile
diff --git a/libs/installer_bsplugins/src/TESFile/Stream.h b/libs/installer_bsplugins/src/TESFile/Stream.h
new file mode 100644
index 0000000..db22580
--- /dev/null
+++ b/libs/installer_bsplugins/src/TESFile/Stream.h
@@ -0,0 +1,291 @@
+#ifndef TESFILE_STREAM_H
+#define TESFILE_STREAM_H
+
+#include "Type.h"
+
+#include <algorithm>
+#include <cctype>
+#include <cstdint>
+#include <cstring>
+#include <istream>
+#include <ranges>
+#include <utility>
+
+namespace TESFile
+{
+
+template <typename T>
+inline T readType(std::istream& stream)
+{
+  union
+  {
+    char buffer[sizeof(T)];
+    T value;
+  };
+  std::memset(buffer, 0x42, sizeof(T));
+  stream.read(buffer, sizeof(T));
+  return value;
+}
+
+inline std::string readZstring(std::istream& stream)
+{
+  std::string value;
+  std::getline(stream, value, '\0');
+  return value;
+}
+
+inline int icompare(const std::string& a, const std::string& b)
+{
+  const std::size_t n = std::min(a.size(), b.size());
+  for (std::size_t i = 0; i < n; ++i) {
+    const unsigned char ca =
+        static_cast<unsigned char>(std::tolower(static_cast<unsigned char>(a[i])));
+    const unsigned char cb =
+        static_cast<unsigned char>(std::tolower(static_cast<unsigned char>(b[i])));
+    if (ca != cb)
+      return ca < cb ? -1 : 1;
+  }
+  if (a.size() == b.size())
+    return 0;
+  return a.size() < b.size() ? -1 : 1;
+}
+
+inline bool iequals(const std::string& a, const std::string& b)
+{
+  return icompare(a, b) == 0;
+}
+
+template <std::ranges::input_range R, typename Proj = std::identity>
+inline auto find(R&& r, const std::string& value, Proj proj = {})
+{
+  return std::ranges::find_if(
+      r,
+      [&](auto&& val) {
+        return iequals(val, value);
+      },
+      proj);
+}
+
+struct less
+{
+  bool operator()(const std::string& a, const std::string& b) const
+  {
+    return icompare(a, b) < 0;
+  }
+};
+
+enum class TESFormat
+{
+  Standard,
+  Oblivion,
+  Morrowind,
+};
+
+enum class GroupType : std::int32_t
+{
+  Top,
+  WorldChildren,
+  InteriorCellBlock,
+  InteriorCellSubBlock,
+  ExteriorCellBlock,
+  ExteriorCellSubBlock,
+  CellChildren,
+  TopicChildren,
+  CellPersistentChildren,
+  CellTemporaryChildren,
+  QuestChildren,
+  CellVisibleDistantChildren = 10,
+};
+
+struct RecordFlags
+{
+  enum TES4Flag : std::uint32_t
+  {
+    Master    = 0x1,
+    Optimized = 0x10,
+    Localized = 0x80,
+    SmallNew  = 0x100,
+    SmallOld  = 0x200,
+    Update    = 0x200,
+    Medium    = 0x400,
+    Blueprint = 0x800,
+  };
+
+  enum Flag : std::uint32_t
+  {
+    Compressed = 0x40000,
+  };
+};
+
+struct RecordHeader
+{
+  Type type;
+  std::uint32_t dataSize;
+  union
+  {
+    struct
+    {
+      std::uint32_t flags;
+      std::uint32_t formId;
+    } formData;
+    struct
+    {
+      std::uint32_t label;
+      GroupType groupType;
+    } groupData;
+  };
+  union
+  {
+    struct
+    {
+      std::uint32_t revision;
+      Type firstChunk;
+    } old;
+    struct
+    {
+      std::uint16_t timestamp;
+      std::uint16_t revision;
+      std::uint16_t version;
+      std::uint16_t unknown1;
+    };
+  };
+};
+static_assert(sizeof(RecordHeader) == 24);
+
+struct ChunkHeader
+{
+  Type type;
+  std::uint16_t dataSize;
+};
+static_assert(sizeof(ChunkHeader) == 6);
+
+class GroupData final
+{
+public:
+  constexpr GroupData() : formId_{0}, groupType_{GroupType::Top} {}
+
+  constexpr GroupData(std::uint32_t label, GroupType type)
+      : formId_{label}, groupType_{type}
+  {}
+
+  constexpr auto operator<=>(const GroupData& other) const
+  {
+    if (groupType_ != other.groupType_) {
+      return groupType_ <=> other.groupType_;
+    } else {
+      if (hasFormType()) {
+        return formType() <=> other.formType();
+      } else if (hasBlock()) {
+        return block() <=> other.block();
+      } else if (hasGridCell()) {
+        return gridCell() <=> other.gridCell();
+      } else {
+        return formId_ <=> other.formId_;
+      }
+    }
+  }
+
+  constexpr bool operator==(const GroupData& other) const
+  {
+    return groupType_ == other.groupType_ && formId_ == other.formId_;
+  }
+
+  [[nodiscard]] constexpr GroupType type() const { return groupType_; }
+
+  [[nodiscard]] constexpr bool hasFormType() const
+  {
+    return groupType_ == GroupType::Top;
+  }
+
+  [[nodiscard]] constexpr bool hasParent() const
+  {
+    return groupType_ == GroupType::WorldChildren ||
+           groupType_ == GroupType::CellChildren ||
+           groupType_ == GroupType::TopicChildren ||
+           groupType_ == GroupType::CellPersistentChildren ||
+           groupType_ == GroupType::CellTemporaryChildren ||
+           groupType_ == GroupType::QuestChildren;
+  }
+
+  [[nodiscard]] constexpr bool hasDirectParent() const
+  {
+    return groupType_ == GroupType::WorldChildren ||
+           groupType_ == GroupType::CellChildren ||
+           groupType_ == GroupType::TopicChildren ||
+           groupType_ == GroupType::QuestChildren;
+  }
+
+  [[nodiscard]] constexpr bool hasBlock() const
+  {
+    return groupType_ == GroupType::InteriorCellBlock ||
+           groupType_ == GroupType::InteriorCellSubBlock;
+  }
+
+  [[nodiscard]] constexpr bool hasGridCell() const
+  {
+    return groupType_ == GroupType::ExteriorCellBlock ||
+           groupType_ == GroupType::ExteriorCellSubBlock;
+  }
+
+  [[nodiscard]] constexpr Type formType() const { return formType_; }
+
+  [[nodiscard]] constexpr std::uint32_t parent() const { return formId_; }
+
+  [[nodiscard]] constexpr std::int32_t block() const { return number_; }
+
+  [[nodiscard]] constexpr std::pair<std::int16_t, std::int16_t> gridCell() const
+  {
+    return {cell_.x, cell_.y};
+  }
+
+  constexpr void setLocalIndex(std::uint8_t index)
+  {
+    if (hasParent()) {
+      formId_ = (formId_ & 0xFFFFFFU) | (index << 24U);
+    }
+  }
+
+private:
+  GroupType groupType_;
+  union
+  {
+    Type formType_;
+    std::uint32_t formId_;
+    std::int32_t number_;
+    struct
+    {
+      std::int16_t y;
+      std::int16_t x;
+    } cell_;
+  };
+};
+
+class FormData final
+{
+public:
+  constexpr FormData(Type type, std::uint32_t flags, std::uint32_t formId, std::uint16_t formVersion)
+      : type_{type}, flags_{flags}, formId_{formId}, formVersion_{formVersion}
+  {}
+
+  [[nodiscard]] constexpr Type type() const { return type_; }
+
+  [[nodiscard]] constexpr std::uint32_t flags() const { return flags_; }
+
+  [[nodiscard]] constexpr std::uint32_t formId() const { return formId_; }
+
+  [[nodiscard]] constexpr std::uint16_t formVersion() const { return formVersion_; }
+
+  [[nodiscard]] constexpr std::uint8_t localModIndex() const { return formId_ >> 24; }
+
+private:
+  Type type_;
+  std::uint32_t flags_;
+  std::uint32_t formId_;
+  std::uint16_t formVersion_;
+};
+
+}  // namespace TESFile
+
+using namespace TESFile::literals;
+
+#endif  // TESFILE_STREAM_H
diff --git a/libs/installer_bsplugins/src/TESFile/Type.h b/libs/installer_bsplugins/src/TESFile/Type.h
new file mode 100644
index 0000000..3b93b20
--- /dev/null
+++ b/libs/installer_bsplugins/src/TESFile/Type.h
@@ -0,0 +1,78 @@
+#ifndef TESFILE_TYPE_H
+#define TESFILE_TYPE_H
+
+#include <bit>
+#include <concepts>
+#include <cstddef>
+#include <cstdint>
+#include <string>
+#include <string_view>
+#include <type_traits>
+#include <utility>
+
+namespace TESFile
+{
+
+template <std::integral T>
+constexpr std::make_unsigned_t<T> bswap(T i)
+{
+  return []<std::size_t... N>(std::make_unsigned_t<T> i, std::index_sequence<N...>) {
+    return ((((i >> (N * 8)) & 0xFF) << ((sizeof(T) - 1 - N) * 8)) | ...);
+  }(i, std::make_index_sequence<sizeof(T)>());
+}
+
+#pragma pack(push, 1)
+struct Type
+{
+  std::uint32_t value;
+
+  constexpr Type() = default;
+
+  template <std::size_t N>
+  constexpr Type(const char (&str)[N])
+      : value{[&]<std::size_t... Is>(std::index_sequence<Is...>) {
+          return ((static_cast<std::uint32_t>(str[Is]) << Is * 8U) | ...);
+        }(std::make_index_sequence<N - 1>())}
+  {}
+
+  constexpr operator std::uint32_t() const { return value; }
+
+  constexpr auto operator<=>(const Type& other) const
+  {
+    return bswap(value) <=> bswap(other.value);
+  }
+
+  [[nodiscard]] std::string string() const { return std::string(view()); }
+
+  [[nodiscard]] std::string_view view() const
+  {
+    return std::string_view(reinterpret_cast<const char*>(&value), sizeof(value));
+  }
+
+  [[nodiscard]] const char* data() const
+  {
+    return reinterpret_cast<const char*>(&value);
+  }
+
+  [[nodiscard]] static constexpr std::size_t size() { return sizeof(value); }
+};
+static_assert(sizeof(Type) == 4);
+static_assert(alignof(Type) == 1);
+static_assert(Type().value == 0);
+#pragma pack(pop)
+
+namespace literals
+{
+  template <Type T>
+  consteval Type operator""_ts()
+  {
+    return T;
+  }
+  static_assert("TES4"_ts.value == '4SET');
+  static_assert("AMMO"_ts < "BOOK"_ts);
+}  // namespace literals
+}  // namespace TESFile
+
+using namespace TESFile::literals;
+
+#endif  // TESFILE_TYPE_H