Add NIF previewer plugin with Linux-specific fixes

Vendored from github.com/Parapets/mo2-preview_nif and adapted for Linux:

- BSA texture resolution via MO2 virtual tree with case-insensitive
  fallback walk (Linux FS is case-sensitive; NIFs reference textures
  with arbitrary case against files on disk)
- Process-wide cached BSA candidate list, keyed by profile path,
  priority-sorted, filtering disabled mods
- Path backslash normalization before loose-file lookup
- Polygon offset on SLSF1_Decal-flagged shapes to break z-ties with
  coincident base meshes (road decals, moss overlays)
- Opaque framebuffer via glColorMask alpha lock so alpha-blended shapes
  can't bleed the dialog background through the preview area
- QMouseEvent::globalPosition().toPoint() for Qt6 compatibility

Preview dialog behavior (organizercore.cpp):
- Switch previewFile and previewFileWithAlternatives from stack-allocated
  exec() to heap + ApplicationModal + show() + WA_DeleteOnClose.
- Parent passed as nullptr so preview lifetime is decoupled from the
  stack-allocated ModInfoDialog that spawns it. Nested exec() inside
  the enclosing dialog's exec() was softlocking on close.

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

1 files changed, 114 insertions, 0 deletions

diff --git a/libs/preview_nif/src/PreviewNif.cpp b/libs/preview_nif/src/PreviewNif.cpp
new file mode 100644
index 0000000..8e7e03a
--- /dev/null
+++ b/libs/preview_nif/src/PreviewNif.cpp
@@ -0,0 +1,114 @@
+#include <NifFile.hpp>
+
+#include "PreviewNif.h"
+#include "NifExtensions.h"
+#include "NifWidget.h"
+
+#include <QGridLayout>
+#include <filesystem>
+#include <sstream>
+#include <string>
+
+bool PreviewNif::init(MOBase::IOrganizer* moInfo)
+{
+    m_MOInfo = moInfo;
+    return true;
+}
+
+QString PreviewNif::name() const
+{
+    return "Preview NIF";
+}
+
+QString PreviewNif::author() const
+{
+    return "Parapets";
+}
+
+QString PreviewNif::description() const
+{
+    return "Supports previewing NIF files";
+}
+
+MOBase::VersionInfo PreviewNif::version() const
+{
+    return MOBase::VersionInfo(0, 2, 0, 0, MOBase::VersionInfo::RELEASE_BETA);
+}
+
+QList<MOBase::PluginSetting> PreviewNif::settings() const
+{
+    return QList<MOBase::PluginSetting>();
+}
+
+bool PreviewNif::enabledByDefault() const
+{
+    return true;
+}
+
+std::set<QString> PreviewNif::supportedExtensions() const
+{
+    return { "bto", "btr", "nif" };
+}
+
+QWidget* PreviewNif::genFilePreview(const QString& fileName, const QSize&) const
+{
+    auto path    = std::filesystem::path(fileName.toStdString());
+    auto nifFile = std::make_shared<nifly::NifFile>(path);
+
+    if (!nifFile->IsValid()) {
+        qWarning(qUtf8Printable(tr("Failed to load file: %1").arg(fileName)));
+        return nullptr;
+    }
+
+    return makeWidget(nifFile);
+}
+
+QWidget* PreviewNif::genDataPreview(const QByteArray& fileData,
+                                    const QString& fileName, const QSize&) const
+{
+    std::string data(fileData.constData(), fileData.size());
+    std::istringstream stream(std::move(data), std::ios::binary);
+
+    auto nifFile = std::make_shared<nifly::NifFile>();
+    if (nifFile->Load(stream) != 0 || !nifFile->IsValid()) {
+        qWarning(qUtf8Printable(tr("Failed to load file: %1").arg(fileName)));
+        return nullptr;
+    }
+
+    return makeWidget(nifFile);
+}
+
+QWidget* PreviewNif::makeWidget(std::shared_ptr<nifly::NifFile> nifFile) const
+{
+    auto layout = new QGridLayout();
+    layout->setRowStretch(0, 1);
+    layout->setColumnStretch(0, 1);
+
+    layout->addWidget(makeLabel(nifFile.get()), 1, 0, 1, 1);
+
+    auto nifWidget = new NifWidget(nifFile, m_MOInfo);
+    layout->addWidget(nifWidget, 0, 0, 1, 1);
+
+    auto widget = new QWidget();
+    widget->setLayout(layout);
+    return widget;
+}
+
+QLabel* PreviewNif::makeLabel(nifly::NifFile* nifFile) const
+{
+    int shapes = 0;
+    int faces = 0;
+    int verts = 0;
+
+    for (auto& shape : nifFile->GetShapes()) {
+        shapes++;
+        faces += shape->GetNumTriangles();
+        verts += shape->GetNumVertices();
+    }
+
+    auto text = tr("Verts: %1 | Faces: %2 | Shapes: %3").arg(verts).arg(faces).arg(shapes);
+    auto label = new QLabel(text);
+    label->setWordWrap(true);
+    label->setTextInteractionFlags(Qt::TextSelectableByMouse);
+    return label;
+}