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Fix markdown character escaping bug (issue #1236) #1741

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3b2ed77
Bug #1236 has been fixed
Feb 4, 2026
8870842
Merge branch 'master' into CHANGELOG.md
andersonhc Feb 5, 2026
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1 change: 1 addition & 0 deletions CHANGELOG.md
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Expand Up @@ -29,6 +29,7 @@ This can also be enabled programmatically with `warnings.simplefilter('default',
* the `A5` value that could be specified as page `format` to the `FPDF` constructor was slightly incorrect, and the corresponding page dimensions have been fixed. This could lead to a minor change in your documents dimensions if you used this `A5` page format. - _cf._ [issue #1699](https://github.com/py-pdf/fpdf2/issues/1699)
* a bug when rendering empty tables with `INTERNAL` layout, that caused an extra border to be rendered due to an erroneous use of `list.index()` - _cf._ [issue #1669](https://github.com/py-pdf/fpdf2/issues/1669)
* edge cases where tiny floating-point drift could trigger incorrect behaviour like [issue #1393](https://github.com/py-pdf/fpdf2/issues/1393)
* the bug “Escape character escaping multiple consecutive markdown characters” (https://github.com/py-pdf/fpdf2/issues/1236) has been fixed.
* parentheses are now escaped in more places. This fixes embedding a file with a single parenthesis in the filename, but might also have impacts on e.g. section names.
### Changed
* improved performance when rendering paths, SVGs, and opaque raster images with an alpha channel - _cf._ [PR #1675](https://github.com/py-pdf/fpdf2/pull/1675)
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61 changes: 37 additions & 24 deletions fpdf/fpdf.py
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Expand Up @@ -4464,9 +4464,32 @@ def frag() -> Fragment:
font_glyphs = self.current_font.cmap # type: ignore[union-attr]
else:
font_glyphs = []
num_escape_chars = 0

while text:
tlt = text[:3] ## get triples to check for escape character
if self.MARKDOWN_ESCAPE_CHARACTER == tlt[0] and tlt[1:] in [
"**",
"__",
"~~",
"--",
]:
Comment on lines +4470 to +4475
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@andersonhc andersonhc Feb 5, 2026

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Suggested change
if self.MARKDOWN_ESCAPE_CHARACTER == tlt[0] and tlt[1:] in [
"**",
"__",
"~~",
"--",
]:
if tlt.startswith(self.MARKDOWN_ESCAPE_CHARACTER) and tlt[1:] in (
self.MARKDOWN_BOLD_MARKER,
self.MARKDOWN_ITALICS_MARKER,
self.MARKDOWN_STRIKETHROUGH_MARKER,
self.MARKDOWN_UNDERLINE_MARKER,
):

This change would make it easier to read - less 'magic values' across the code.

## remove the escape character
txt_frag.append(text[1])
txt_frag.append(text[2])
yield frag()
text = text[3:]
continue

if self.MARKDOWN_ESCAPE_CHARACTER == tlt[0:1] and \
self.MARKDOWN_ESCAPE_CHARACTER == tlt[1:2]:
# double-escape, juste produce it
txt_frag.append(text[0])
txt_frag.append(text[1])
yield frag()
text = text[2:]
continue


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@andersonhc andersonhc Feb 5, 2026

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You are removing characters from the input text even when markdown=False. This portion of code should be inside an if markdown: block

is_marker = text[:2] in (
self.MARKDOWN_BOLD_MARKER,
self.MARKDOWN_ITALICS_MARKER,
Expand Down Expand Up @@ -4509,29 +4532,19 @@ def frag() -> Fragment:
and (not txt_frag or txt_frag[-1] != half_marker)
and (len(text) < 3 or text[2] != half_marker)
):
txt_frag = (
txt_frag[: -((num_escape_chars + 1) // 2)]
if num_escape_chars > 0
else txt_frag
)
if num_escape_chars % 2 == 0:
if txt_frag:
yield frag()
if text[:2] == self.MARKDOWN_BOLD_MARKER:
in_bold = not in_bold
if text[:2] == self.MARKDOWN_ITALICS_MARKER:
in_italics = not in_italics
if text[:2] == self.MARKDOWN_STRIKETHROUGH_MARKER:
in_strikethrough = not in_strikethrough
if text[:2] == self.MARKDOWN_UNDERLINE_MARKER:
in_underline = not in_underline
text = text[2:]
continue
num_escape_chars = (
num_escape_chars + 1
if text[0] == self.MARKDOWN_ESCAPE_CHARACTER
else 0
)
if txt_frag:
yield frag()
if text[:2] == self.MARKDOWN_BOLD_MARKER:
in_bold = not in_bold
if text[:2] == self.MARKDOWN_ITALICS_MARKER:
in_italics = not in_italics
if text[:2] == self.MARKDOWN_STRIKETHROUGH_MARKER:
in_strikethrough = not in_strikethrough
if text[:2] == self.MARKDOWN_UNDERLINE_MARKER:
in_underline = not in_underline
text = text[2:]
continue

is_link = self.MARKDOWN_LINK_REGEX.match(text)
if is_link:
link_text, link_dest, text = is_link.groups()
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2 changes: 2 additions & 0 deletions test/text/test_cell.py
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Expand Up @@ -179,6 +179,8 @@ def test_cell_markdown_escaped(tmp_path):
pdf.add_page()
pdf.set_font("Times", size=40)
pdf.cell(text="**Lo\\rem** \\__Ipsum\\__ \\\\--dolor\\\\--", markdown=True)
pdf.write(text="\n")
pdf.cell(text="\\****BOLD**\\**", markdown=True)
assert_pdf_equal(pdf, HERE / "cell_markdown_escaped.pdf", tmp_path)


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124 changes: 90 additions & 34 deletions test/text/test_markdown_parse.py
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Expand Up @@ -15,6 +15,40 @@
GSTATE_BI = GSTATE.copy()
GSTATE_BI.font_style = "BI"

def merge_fragments(fragments):
"""
Helper function for testing the escaping chracters
Will merge fragments that have different characters but same fragment.graphics_state
and same fragment.k and same fragment.link.
Example Input:
(
Fragment(characters=['a'], graphics_state={000}, k=1, link=None),
Fragment(characters=['b'], graphics_state={000}, k=1, link=None)
)
Example Output:
(Fragment(characters=['a', 'b'], graphics_state={000}, k=1, link=None))
"""
if not fragments:
return []

merged_fragments = []
current_fragment = fragments[0]

for fragment in fragments[1:]:
if (
fragment.graphics_state == current_fragment.graphics_state
and fragment.k == current_fragment.k
and fragment.link == current_fragment.link
):
current_fragment.characters.extend(fragment.characters)
else:
merged_fragments.append(current_fragment)
current_fragment = fragment

merged_fragments.append(current_fragment)

return tuple(merged_fragments)


def test_markdown_parse_simple_ok():
frags = tuple(
Expand All @@ -35,63 +69,75 @@ def test_markdown_parse_simple_ok():


def test_markdown_parse_simple_ok_escaped():
frags = tuple(
FPDF()._parse_chars(
"\\**bold\\**, \\__italics\\__ and \\--underlined\\-- escaped", True
frags = merge_fragments(
tuple(
FPDF()._parse_chars(
"\\**bold\\**, \\__italics\\__ and \\--underlined\\-- escaped", True)
)
)
expected = (
Fragment("**bold**, __italics__ and --underlined-- escaped", GSTATE, k=PDF.k),
Fragment("**bold**, __italics__ and --underlined-- escaped", GSTATE, k=PDF.k),
)
assert frags == expected
frags = tuple(
frags = merge_fragments (tuple(
FPDF()._parse_chars(
r"raw \**bold\**, \__italics\__ and \--underlined\-- escaped", True
)
)
))
expected = (
Fragment(
"raw **bold**, __italics__ and --underlined-- escaped", GSTATE, k=PDF.k
),
)
assert frags == expected
frags = tuple(FPDF()._parse_chars("escape *\\*between marker*\\*", True))
frags =(
tuple(FPDF()._parse_chars("escape *\\*between marker*\\*", True))
)
expected = (Fragment("escape *\\*between marker*\\*", GSTATE, k=PDF.k),)
assert frags == expected
frags = tuple(FPDF()._parse_chars("escape **\\after marker**\\", True))
frags = merge_fragments(
tuple(FPDF()._parse_chars("escape **\\after marker**\\", True))
)
expected = (
Fragment("escape ", GSTATE, k=PDF.k),
Fragment("\\after marker", GSTATE_B, k=PDF.k),
Fragment("\\", GSTATE, k=PDF.k),
)


def test_markdown_unrelated_escape():
frags = tuple(FPDF()._parse_chars("unrelated \\ escape \\**bold\\**", True))
frags = merge_fragments(
tuple(FPDF()._parse_chars("unrelated \\ escape \\**bold\\**", True))
)
expected = (Fragment("unrelated \\ escape **bold**", GSTATE, k=PDF.k),)
assert frags == expected
frags = tuple(
FPDF()._parse_chars("unrelated \\\\ double escape \\**bold\\**", True)
frags = merge_fragments(
tuple(FPDF()._parse_chars("unrelated \\\\ double escape \\**bold\\**", True))
)
expected = (Fragment("unrelated \\\\ double escape **bold**", GSTATE, k=PDF.k),)
assert frags == expected


def test_markdown_parse_multiple_escape():
frags = tuple(FPDF()._parse_chars("\\\\**bold\\\\** double escaped", True))
frags = merge_fragments(
tuple(FPDF()._parse_chars("\\\\**bold\\\\** double escaped", True))
)
expected = (
Fragment("\\", GSTATE, k=PDF.k),
Fragment("bold\\", GSTATE_B, k=PDF.k),
Fragment("\\\\", GSTATE, k=PDF.k),
Fragment("bold\\\\", GSTATE_B, k=PDF.k),
Fragment(" double escaped", GSTATE, k=PDF.k),
)

assert frags == expected
frags = tuple(FPDF()._parse_chars("\\\\\\**triple bold\\\\\\** escaped", True))
expected = (Fragment("\\**triple bold\\** escaped", GSTATE, k=PDF.k),)
frags = merge_fragments(
tuple(FPDF()._parse_chars("\\\\\\**triple bold\\\\\\** escaped", True))
)
expected = (Fragment("\\\\**triple bold\\\\** escaped", GSTATE, k=PDF.k),)
assert frags == expected


def test_markdown_parse_overlapping():
frags = tuple(FPDF()._parse_chars("**bold __italics__**", True))
frags = merge_fragments(
tuple(FPDF()._parse_chars("**bold __italics__**", True))
)
expected = (
Fragment("bold ", GSTATE_B, k=PDF.k),
Fragment("italics", GSTATE_BI, k=PDF.k),
Expand All @@ -100,13 +146,14 @@ def test_markdown_parse_overlapping():


def test_markdown_parse_overlapping_escaped():
frags = tuple(FPDF()._parse_chars("**bold \\__italics\\__**", True))
frags = merge_fragments(
tuple(FPDF()._parse_chars("**bold \\__italics\\__**", True))
)
expected = (Fragment("bold __italics__", GSTATE_B, k=PDF.k),)
assert frags == expected


def test_markdown_parse_crossing_markers():
frags = tuple(FPDF()._parse_chars("**bold __and** italics__", True))
frags = merge_fragments (tuple(FPDF()._parse_chars("**bold __and** italics__", True)))
expected = (
Fragment("bold ", GSTATE_B, k=PDF.k),
Fragment("and", GSTATE_BI, k=PDF.k),
Expand All @@ -116,7 +163,7 @@ def test_markdown_parse_crossing_markers():


def test_markdown_parse_crossing_markers_escaped():
frags = tuple(FPDF()._parse_chars("**bold __and\\** italics__", True))
frags =merge_fragments (tuple(FPDF()._parse_chars("**bold __and\\** italics__", True)))
expected = (
Fragment("bold ", GSTATE_B, k=PDF.k),
Fragment("and** italics", GSTATE_BI, k=PDF.k),
Expand All @@ -125,7 +172,7 @@ def test_markdown_parse_crossing_markers_escaped():


def test_markdown_parse_unterminated():
frags = tuple(FPDF()._parse_chars("**bold __italics__", True))
frags = merge_fragments (tuple(FPDF()._parse_chars("**bold __italics__", True)))
expected = (
Fragment("bold ", GSTATE_B, k=PDF.k),
Fragment("italics", GSTATE_BI, k=PDF.k),
Expand All @@ -134,7 +181,7 @@ def test_markdown_parse_unterminated():


def test_markdown_parse_unterminated_escaped():
frags = tuple(FPDF()._parse_chars("**bold\\** __italics__", True))
frags = merge_fragments(tuple(FPDF()._parse_chars("**bold\\** __italics__", True)))
expected = (
Fragment("bold** ", GSTATE_B, k=PDF.k),
Fragment("italics", GSTATE_BI, k=PDF.k),
Expand All @@ -143,16 +190,22 @@ def test_markdown_parse_unterminated_escaped():


def test_markdown_parse_line_of_markers():
frags = tuple(FPDF()._parse_chars("*** woops", True))
frags = merge_fragments (tuple(FPDF()._parse_chars("*** woops", True)))
expected = (Fragment("*** woops", GSTATE, k=PDF.k),)
assert frags == expected
frags = tuple(FPDF()._parse_chars("----------", True))
frags = merge_fragments (tuple(FPDF()._parse_chars("----------", True)))
expected = (Fragment("----------", GSTATE, k=PDF.k),)
assert frags == expected
frags = tuple(FPDF()._parse_chars("****BOLD**", True))
expected = (Fragment("****BOLD", GSTATE, k=PDF.k),)
expected = (Fragment("**BOLD", GSTATE_B, k=PDF.k),)
frags = merge_fragments(tuple(FPDF()._parse_chars("\\****BOLD**\\**", True)))
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I guess you missing an assert after line 200

expected = (
Fragment("**", GSTATE, k=PDF.k),
Fragment("BOLD", GSTATE_B, k=PDF.k),
Fragment("**", GSTATE, k=PDF.k),)

assert frags == expected
frags = tuple(FPDF()._parse_chars("* **BOLD**", True))
frags = merge_fragments (tuple(FPDF()._parse_chars("* **BOLD**", True)))
expected = (
Fragment("* ", GSTATE, k=PDF.k),
Fragment("BOLD", GSTATE_B, k=PDF.k),
Expand All @@ -161,17 +214,20 @@ def test_markdown_parse_line_of_markers():


def test_markdown_parse_line_of_markers_escaped():
frags = tuple(FPDF()._parse_chars("\\****BOLD**", True))
expected = (Fragment("\\****BOLD", GSTATE, k=PDF.k),)
frags = merge_fragments(tuple(FPDF()._parse_chars("\\****BOLD**", True)))
expected = (
Fragment("**", GSTATE, k=PDF.k),
Fragment("BOLD", GSTATE_B, k=PDF.k),
)
assert frags == expected
frags = tuple(FPDF()._parse_chars("*\\***BOLD**", True))
expected = (Fragment("*\\***BOLD", GSTATE, k=PDF.k),)
frags = merge_fragments(tuple(FPDF()._parse_chars("*\\***BOLD**", True)))
expected = (Fragment("****BOLD", GSTATE, k=PDF.k),)
assert frags == expected


def test_markdown_parse_newline_after_markdown_link(): # issue 916
text = "[fpdf2](https://py-pdf.github.io/fpdf2/)\nGo visit it!"
frags = tuple(FPDF()._parse_chars(text, True))
frags = merge_fragments(tuple(FPDF()._parse_chars(text, True)))
gstate_link = GSTATE.copy()
gstate_link.underline = True
expected = (
Expand Down
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