Fix visual gap after {nb} page alias when text shaping is enabled (#1090)

CHANGELOG.md

@@ -23,6 +23,7 @@ This can also be enabled programmatically with `warnings.simplefilter('default',
 * `resource_access_policy` and [Security considerations](https://py-pdf.github.io/fpdf2/Security.html) documentation
 * [`FPDF.optional_content()`](https://py-pdf.github.io/fpdf2/OptionalContent.html) context manager to mark content as visible on screen only or in print only, using PDF Optional Content Groups - _cf._ [issue #441](https://github.com/py-pdf/fpdf2/issues/441), based on a recipe by @digidigital
 ### Fixed
+* visual gap in rendering subsequent text after `{nb}` page alias when text shaping is enabled - _cf._ [issue #1090](https://github.com/py-pdf/fpdf2/issues/1090)
 * font state (family, style, size, current font, and the page-level "font is set" flag) no longer leaks back onto the `FPDF` instance after a `text_columns()` / `text_region()` context exits, so a subsequent `pdf.cell()` / `pdf.write()` renders at the caller's font instead of the last paragraph's - _cf._ [issue #1804](https://github.com/py-pdf/fpdf2/issues/1804)
 * text rendering when the first text on a page starts with a fallback glyph - _cf._ [issue #1772](https://github.com/py-pdf/fpdf2/issues/1772)
 * preserve boundary-neutral formatting during bidirectional text preprocessing - _cf._ [issue #1779](https://github.com/py-pdf/fpdf2/issues/1779)

docs/PageBreaks.md

@@ -21,7 +21,6 @@ Simply call `.add_page()`.
 The special string `{nb}` will be substituted by the total number of pages on document closure.
 This special value can changed by calling [alias_nb_pages()](https://py-pdf.github.io/fpdf2/fpdf/fpdf.html#fpdf.fpdf.FPDF.alias_nb_pages).
 
-!!! warning "This is currently incompatible with [text shaping](./TextShaping.md).<br>_cf._ [GitHub issue #1090](https://github.com/py-pdf/fpdf2/issues/1090)"
 
 ## will_page_break ##
 

docs/TextShaping.md

@@ -2,7 +2,6 @@
 
 _New in [:octicons-tag-24: 2.7.5](https://github.com/py-pdf/fpdf2/blob/master/CHANGELOG.md)_
 
-!!! warning "This is currently incompatible with [the special `{nb}` string](./PageBreaks.md) that inserts the number of pages.<br>_cf._ [GitHub issue #1090](https://github.com/py-pdf/fpdf2/issues/1090)"
 
 ## What is text shaping? ##
 Text shaping is a fundamental process in typography and computer typesetting that influences the aesthetics and readability of text in various languages and scripts. It involves the transformation of Unicode text into glyphs, which are then positioned for display or print. 

fpdf/fpdf.py

@@ -4460,23 +4460,24 @@ def get_fallback_font(self, char: str, style: str = "") -> Optional[str]:
 
     def _parse_chars(self, text: str, markdown: bool) -> Iterator[Fragment]:
         "Split text into fragments"
-        if not markdown and not self.text_shaping and not self._fallback_font_ids:
-            if self.str_alias_nb_pages:
-                for seq, fragment_text in enumerate(
-                    text.split(self.str_alias_nb_pages)
-                ):
-                    if seq > 0:
-                        yield TotalPagesSubstitutionFragment(
-                            self.str_alias_nb_pages,
-                            self._get_current_graphics_state(),
-                            self.k,
-                        )
-                    if fragment_text:
-                        yield Fragment(
-                            fragment_text, self._get_current_graphics_state(), self.k
-                        )
-                return
+        if self.str_alias_nb_pages and self.str_alias_nb_pages in text:
+            for seq, fragment_text in enumerate(text.split(self.str_alias_nb_pages)):
+                if seq > 0:
+                    yield TotalPagesSubstitutionFragment(
+                        self.str_alias_nb_pages,
+                        self._get_current_graphics_state(),
+                        self.k,
+                        dummy_width_string=(
+                            str(self.page_no())
+                            if self.text_shaping
+                            else self.str_alias_nb_pages
+                        ),
+                    )
+                if fragment_text:
+                    yield from self._parse_chars(fragment_text, markdown)
+            return
 
+        if not markdown and not self.text_shaping and not self._fallback_font_ids:
             yield Fragment(text, self._get_current_graphics_state(), self.k)
             return
         txt_frag: list[str] = []
@@ -4577,6 +4578,11 @@ def frag() -> Fragment:
                         self.str_alias_nb_pages,
                         gstate,
                         self.k,
+                        dummy_width_string=(
+                            str(self.page_no())
+                            if self.text_shaping
+                            else self.str_alias_nb_pages
+                        ),
                     )
                     text = text[len(self.str_alias_nb_pages) :]
                     continue

fpdf/line_break.py

@@ -423,9 +423,16 @@ class TotalPagesSubstitutionFragment(Fragment):
     output is being produced.
     """
 
-    def __init__(self, *args: Any, **kwargs: Any) -> None:
+    def __init__(
+        self, *args: Any, dummy_width_string: str = "1", **kwargs: Any
+    ) -> None:
         super().__init__(*args, **kwargs)
         self.uuid = uuid4()
+        self.dummy_width_string = dummy_width_string
+        # Use dummy_width_string for layout phase width calculation if characters are not empty (non-cloned)
+        # and text shaping is active.
+        if self.characters and self.graphics_state.text_shaping:
+            self.characters = list(dummy_width_string)
 
     def get_placeholder_string(self) -> str:
         """

test/test_alias.py

@@ -131,3 +131,15 @@ def test_alias_with_shaping(tmp_path):
     pdf.write_html("<h1>{nb}</h1>")
     pdf.multi_cell(w=pdf.epw, text="Number of pages: {nb}\nAgain:{nb}")
     assert_pdf_equal(pdf, HERE / "alias_with_text_shaping.pdf", tmp_path)
+
+
+def test_alias_in_middle_with_shaping(tmp_path):
+    pdf = fpdf.FPDF()
+    pdf.add_font("Quicksand", style="", fname=HERE / "fonts" / "Quicksand-Regular.otf")
+    pdf.add_page()
+    pdf.set_font("Quicksand", size=24)
+    pdf.set_text_shaping(True)
+    pdf.write(text="Pages {nb} with shaping")
+    pdf.ln()
+    pdf.write(text="Pages {nb} with {nb} shaping")
+    assert_pdf_equal(pdf, HERE / "alias_in_middle_with_shaping.pdf", tmp_path)