PDF Viewer

Read-only PDF viewer tabs using the hayro crate for pure-Rust, CPU-based rendering.

Architecture

Follows the same viewer infrastructure pattern as the Image Viewer (Task 39):

Component	Location	Purpose
FileType::Pdf	src/state.rs	Extension detection (.pdf, case-insensitive)
PdfViewerState	src/state.rs	Per-tab state: current page, zoom, page count, error
TabKind::PdfViewer	src/state.rs	Tab kind variant carrying PdfViewerState
open_pdf_tab()	src/state.rs	Opens PDF, reads page count, creates tab
render_pdf_viewer_tab()	src/app/central_panel.rs	Page rendering, navigation, zoom UI
PdfPageTexture	src/app/central_panel.rs	Cached rendered page texture
render_pdf_page()	src/app/central_panel.rs	Renders a single page via hayro to egui texture

File Opening Flow

1. open_file_with_focus() checks FileType::from_path() — PDF intercepted before binary detection
2. open_pdf_tab() reads the file, creates hayro_syntax::Pdf, extracts page count
3. If PDF parsing fails (corrupted/encrypted), stores error in PdfViewerState::error
4. Creates TabKind::PdfViewer(PdfViewerState) tab

Rendering Pipeline

PDF bytes → hayro_syntax::Pdf → page[i] → hayro::render(page, settings) → Pixmap
→ RGBA u8 slice → egui::ColorImage → egui::TextureHandle → egui::Image

• Pixmap data is premultiplied RGBA8, loaded via from_rgba_premultiplied
• Texture cached in egui temp data, keyed by (path, page_index, zoom)
• Cache automatically invalidated when page or zoom changes

Page Navigation

Action	Trigger
Previous page	◀ button, ArrowLeft, PageUp
Next page	▶ button, ArrowRight, PageDown
Zoom	Ctrl+Scroll (0.5x–4.0x range)

Metadata Bar

Bottom bar shows: ◀ 1 / N ▶ | PDF | 1.2 MB | 100%

Error Handling

• Corrupted PDF → error message overlay (no crash)
• Encrypted/password-protected → graceful error via LoadPdfError
• Page out of range → descriptive error
• File read failure → error overlay

Performance

• Page rendered once per (page, zoom) combination; texture cached in egui temp storage
• Fit-to-window on first render (no upscale beyond 1:1)
• Re-render only on page change or zoom change

Limitations

• hayro does not support encrypted/password-protected PDFs
• No text selection or search within PDF content
• Rendering is synchronous (blocking); large/complex pages may cause brief UI stalls