Description

Fixes issue #474 where symbol fonts like Webdings and Wingdings display rectangles instead of the correct symbols.

Root Cause

1. Matplotlib exclusion: Matplotlib intentionally excludes symbol fonts from its font list
2. Encoding mismatch: Symbol fonts use Microsoft Symbol encoding (platformID=3, platEncID=0) but PIL defaults to Unicode encoding

Solution

1. Font discovery: Use fc-match to find symbol font paths that matplotlib skips
2. Manual registration: Use matplotlib.font_manager.fontManager.addfont() to add symbol fonts to matplotlib's font list
3. Proper encoding: Detect symbol fonts via cmap table and use encoding="symb" when loading with PIL

Changes

• Added _ensure_symbol_fonts() function to dynamically find and register symbol fonts
• Added _is_symbol_font() with @lru_cache to detect symbol encoding efficiently
• Modified get_font_path() to ensure symbol fonts are available before lookup
• Modified get_font() to use proper encoding for symbol fonts

Testing

• Webdings now renders correct symbols instead of rectangles
• Wingdings now renders correct symbols instead of rectangles
• Regular fonts continue to work normally
• Performance impact minimal due to caching

Files Changed

• src/backend/DeckManagement/Subclasses/KeyLabel.py