fix(layout.logo): add font fallback, use bold monospace

tinyticker/layouts.py

@@ -6,15 +6,15 @@
 import dataclasses as dc
 import io
 import logging
-from typing import Callable, Optional, Tuple
+from typing import Callable, Optional, Tuple, Union
 
 import matplotlib.pyplot as plt
 import mplfinance as mpf
 import numpy as np
 from matplotlib.axes import Axes
 from matplotlib.figure import Figure
 from matplotlib.ticker import FormatStrFormatter
-from PIL import Image, ImageFont, ImageDraw
+from PIL import Image, ImageDraw, ImageFont
 
 from .config import LayoutConfig
 from .tickers._base import TickerBase, TickerResponse
@@ -345,8 +345,17 @@ def logo(size: Size, ticker: TickerBase, resp: TickerResponse) -> Image.Image:
     logo_height = int(size[0] * 0.4) - 2 * padding
     logo_width = logo_height
 
-    monospace_font = ImageFont.truetype("DejaVuSansMono.ttf", size=12)
-    regular_font = ImageFont.truetype("DejaVuSans.ttf")
+    def ttf_font_or_default(
+        font: str, size: int = 10
+    ) -> Union[ImageFont.FreeTypeFont, ImageFont.ImageFont]:
+        try:
+            return ImageFont.truetype(font, size)
+        except OSError:
+            return ImageFont.load_default(size)
+
+    # DejaVuSans seems to be installed by default on RPis
+    monospace_font = ttf_font_or_default("DejaVuSansMono.ttf", 12)
+    regular_font = ttf_font_or_default("DejaVuSans-Bold.ttf")
 
     range_text = f"{len(resp.historical)}x{ticker.config.interval} {_perc_change(ticker, resp):+.2f}%"
     range_text_bbox = monospace_font.getbbox(range_text)