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, 71 insertions, 0 deletions

diff --git a/libs/preview_nif/src/NifWidget.h b/libs/preview_nif/src/NifWidget.h
new file mode 100644
index 0000000..34f2de0
--- /dev/null
+++ b/libs/preview_nif/src/NifWidget.h
@@ -0,0 +1,71 @@
+#pragma once
+
+#include "Camera.h"
+#include "OpenGLShape.h"
+#include "ShaderManager.h"
+#include "TextureManager.h"
+
+#include <QOpenGLBuffer>
+#include <QOpenGLDebugLogger>
+#include <QOpenGLShaderProgram>
+#include <QOpenGLVertexArrayObject>
+#include <QOpenGLWidget>
+#include <QSharedPointer>
+
+#include <imoinfo.h>
+#include <NifFile.hpp>
+
+#include <memory>
+
+class NifWidget : public QOpenGLWidget
+{
+    Q_OBJECT
+
+public:
+    NifWidget(
+        std::shared_ptr<nifly::NifFile> nifFile,
+        MOBase::IOrganizer* organizer,
+        bool debugContext = false,
+        QWidget* parent = nullptr,
+        Qt::WindowFlags f = {0});
+
+    ~NifWidget();
+    NifWidget(const NifWidget&) = delete;
+    NifWidget(NifWidget&&) = delete;
+    NifWidget& operator=(const NifWidget&) = delete;
+    NifWidget& operator=(NifWidget&&) = delete;
+
+protected:
+    void mousePressEvent(QMouseEvent* event) override;
+    void mouseMoveEvent(QMouseEvent* event) override;
+    void wheelEvent(QWheelEvent* event) override;
+
+    void initializeGL() override;
+    void paintGL() override;
+    void resizeGL(int w, int h) override;
+
+private:
+    void cleanup();
+    void updateCamera();
+
+    inline static QWeakPointer<Camera> SharedCamera;
+
+    std::shared_ptr<nifly::NifFile> m_NifFile;
+    MOBase::IOrganizer* m_MOInfo = nullptr;
+
+    std::unique_ptr<TextureManager> m_TextureManager;
+    std::unique_ptr<ShaderManager> m_ShaderManager;
+
+    QOpenGLDebugLogger* m_Logger = nullptr;
+
+    std::vector<OpenGLShape> m_GLShapes;
+
+    QSharedPointer<Camera> m_Camera;
+
+    QMatrix4x4 m_ViewMatrix;
+    QMatrix4x4 m_ProjectionMatrix;
+
+    int m_ViewportWidth;
+    int m_ViewportHeight;
+    QPoint m_MousePos;
+};