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, 39 insertions, 0 deletions

diff --git a/libs/preview_nif/src/PreviewNif.h b/libs/preview_nif/src/PreviewNif.h
new file mode 100644
index 0000000..cd5175d
--- /dev/null
+++ b/libs/preview_nif/src/PreviewNif.h
@@ -0,0 +1,39 @@
+#pragma once
+
+#include <ipluginpreview.h>
+#include <QLabel>
+#include <NifFile.hpp>
+
+class PreviewNif : public MOBase::IPluginPreview
+{
+    Q_OBJECT
+    Q_INTERFACES(MOBase::IPlugin MOBase::IPluginPreview)
+    Q_PLUGIN_METADATA(IID "org.tannin.PreviewNif" FILE "previewnif.json")
+
+public:
+    PreviewNif() = default;
+
+    // IPlugin Interface
+
+    bool init(MOBase::IOrganizer* moInfo) override;
+    QString name() const override;
+    QString author() const override;
+    QString description() const override;
+    MOBase::VersionInfo version() const override;
+    QList<MOBase::PluginSetting> settings() const override;
+    bool enabledByDefault() const override;
+
+    // IPluginPreview interface
+
+    std::set<QString> supportedExtensions() const override;
+    bool supportsArchives() const override { return true; }
+    QWidget* genFilePreview(const QString& fileName, const QSize& maxSize) const override;
+    QWidget* genDataPreview(const QByteArray& fileData, const QString& fileName,
+                            const QSize& maxSize) const override;
+
+private:
+    QWidget* makeWidget(std::shared_ptr<nifly::NifFile> nifFile) const;
+    QLabel* makeLabel(nifly::NifFile* nifFile) const;
+
+    MOBase::IOrganizer* m_MOInfo;
+};