set_font/set_stretching: also reject NaN and infinity

CHANGELOG.md

@@ -29,6 +29,7 @@ This can also be enabled programmatically with `warnings.simplefilter('default',
 * `FPDF.set_margins()`, `FPDF.set_left_margin()`, `FPDF.set_top_margin()` and `FPDF.set_right_margin()` raise a clear `ValueError` for a negative margin, like `FPDF.set_auto_page_break()` does for the bottom one, instead of writing text off the page - thanks to @RavSinghChandan
 * `FPDF.text_columns()` raises a clear `ValueError` for a negative `gutter`, like it does for `ncols` below 1, instead of silently laying out overlapping columns whose text is printed on top of each other - thanks to @RavSinghChandan
 * `FPDF.table()` raises a clear `ValueError` for a `width` or a single `col_widths` that is zero or negative, or a negative value in `col_widths`, instead of failing with an unrelated "Not enough horizontal space to render a single character" error - thanks to @RavSinghChandan
+* `FPDF.set_font()`, `FPDF.set_font_size()` and `FPDF.set_stretching()` also raise their `ValueError` for NaN or infinity, instead of writing `nan Tz` or an infinite font size into the page, which is not a valid PDF number; `FPDF.write_html()` ignores an infinite `<font size>`, like a negative one - thanks to @RavSinghChandan
 * `FPDF.set_line_width()` and `FPDF.set_dash_pattern()` also raise their `ValueError` for NaN or infinity, instead of writing `nan w` or an infinite dash length into the page, which is not a valid PDF number - thanks to @RavSinghChandan
 * `FPDF.set_page_background()` raises a clear `ValueError` for a color tuple with a component outside [0, 255] or with neither 1 nor 3 values, like `FPDF.set_fill_color()` does, instead of failing only on the next `add_page()` (with a misleading `color component -1` message for 2 values, or a `TypeError` for 4) - thanks to @RavSinghChandan
 

fpdf/fpdf.py

@@ -2815,7 +2815,7 @@ def set_font(
             size (float): in points. The default value is the current size.
                 Must be zero or a positive number.
         """
-        if size < 0:
+        if not math.isfinite(size) or size < 0:
             raise ValueError(f"Font size must be zero or a positive number: {size}")
         if not family:
             family = self.font_family
@@ -2898,7 +2898,7 @@ def set_font_size(self, size: float) -> None:
         Args:
             size (float): font size in points. Must be zero or a positive number.
         """
-        if size < 0:
+        if not math.isfinite(size) or size < 0:
             raise ValueError(f"Font size must be zero or a positive number: {size}")
         if FloatTolerance.equal(self.font_size_pt, size):
             return
@@ -2946,7 +2946,7 @@ def set_stretching(self, stretching: float) -> None:
         Args:
             stretching (float): horizontal stretching (scaling) in percents. Must be a positive number.
         """
-        if stretching <= 0:
+        if not math.isfinite(stretching) or stretching <= 0:
             raise ValueError(f"Stretching must be a positive number: {stretching}")
         if self.font_stretching == stretching:
             return

fpdf/html.py

@@ -11,6 +11,7 @@
 # pyright: reportPrivateUsage=false
 
 import logging
+import math
 import re
 import warnings
 from dataclasses import replace
@@ -1230,16 +1231,16 @@ def handle_starttag(self, tag: str, attrs: list[tuple[str, str | None]]) -> None
                     # like browsers, a CSS length such as "14pt" or "12px";
                     # a number without a unit is still read as points
                     font_size = resolve_length(font_size_str)
-                    # like browsers, a negative font size is ignored
-                    if font_size >= 0:
+                    # like browsers, a negative or infinite font size is ignored
+                    if math.isfinite(font_size) and font_size >= 0:
                         self.font_size_pt = font_size
                 except ValueError:
                     pass
             elif "size" in attrs_dict:
                 font_size_str = attrs_dict.get("size") or ""
                 try:
                     font_size = float(font_size_str)
-                    if font_size >= 0:
+                    if math.isfinite(font_size) and font_size >= 0:
                         self.font_size_pt = font_size
                 except ValueError:
                     pass

test/fonts/test_set_font.py

@@ -66,6 +66,18 @@ def test_set_font_negative_size(size):
     assert pdf.font_size_pt == 12
 
 
+@pytest.mark.parametrize("size", [float("nan"), float("inf")])
+def test_set_font_not_finite_size(size):
+    pdf = FPDF()
+    pdf.add_page()
+    pdf.set_font("Times", size=12)
+    with pytest.raises(ValueError, match="Font size must be zero or a positive number"):
+        pdf.set_font("Times", size=size)
+    with pytest.raises(ValueError, match="Font size must be zero or a positive number"):
+        pdf.set_font_size(size)
+    assert pdf.font_size_pt == 12
+
+
 def test_set_builtin_font(tmp_path):
     pdf = FPDF()
     pdf.add_page()

test/html/test_html.py

@@ -795,10 +795,11 @@ def test_html_font_css_font_size(tmp_path, html, equivalent):
     [
         '<font size="-3">text</font>',
         '<font style="font-size: -5px">text</font>',
+        '<font size="inf">text</font>',
     ],
 )
 def test_html_font_negative_size_is_ignored(tmp_path, html):
-    "Like browsers, a negative font size is ignored: the current size is kept."
+    "Like browsers, a negative or infinite font size is ignored: the current size is kept."
     pdf = FPDF()
     pdf.add_page()
     pdf.write_html(html)

test/text/test_text.py

@@ -56,7 +56,7 @@ def test_text_stretch_spacing(tmp_path):
     assert_pdf_equal(doc, HERE / "text_stretch_spacing.pdf", tmp_path)
 
 
-@pytest.mark.parametrize("stretching", [0, -50])
+@pytest.mark.parametrize("stretching", [0, -50, float("nan"), float("inf")])
 def test_text_stretching_not_positive(stretching):
     doc = FPDF()
     doc.add_page()