Make sure 'lift' is reset if Fragment changes lift in _render_styled_…

…text_line (#862)

CHANGELOG.md

@@ -29,6 +29,7 @@ This can also be enabled programmatically with `warnings.simplefilter('default',
 - [`FPDF.image()`](https://pyfpdf.github.io/fpdf2/fpdf/fpdf.html#fpdf.fpdf.FPDF.image): allowing images path starting with `data` to be passed as input
 - text overflow is better handled by `FPDF.write()` & `FPDF.write_html()` - _cf._ [issue #847](https://github.com/PyFPDF/fpdf2/issues/847)
 - the initial text color is preserved when using `FPDF.write_html()` - _cf._ [issue #846](https://github.com/PyFPDF/fpdf2/issues/846)
+- handle superscript and subscript correctly when rendering `TextLine`- [Pull Request #862](https://github.com/PyFPDF/fpdf2/pull/862) 
 ### Deprecated
 - the `center` optional parameter of [`FPDF.cell()`](https://pyfpdf.github.io/fpdf2/fpdf/fpdf.html#fpdf.fpdf.FPDF.cell) is **no more** deprecated, as it allows for horizontal positioning, which is different from text alignment control with `align="C"`
 

fpdf/fpdf.py

@@ -2845,6 +2845,7 @@ def _render_styled_text_line(
         s_width, underlines = 0, []
         # We try to avoid modifying global settings for temporary changes.
         current_ws = frag_ws = 0.0
+        current_lift = 0.0
         current_char_vpos = CharVPos.LINE
         current_font = self.current_font
         current_text_mode = self.text_mode
@@ -2894,9 +2895,10 @@ def _render_styled_text_line(
                     current_font = frag.font
                     sl.append(f"/F{frag.font.i} {frag.font_size_pt:.2f} Tf")
                 lift = frag.lift
-                if lift != 0.0:
+                if lift != current_lift:
                     # Use text rise operator:
                     sl.append(f"{lift:.2f} Ts")
+                    current_lift = lift
                 if (
                     frag.text_mode != TextMode.FILL
                     or frag.text_mode != current_text_mode
@@ -2983,6 +2985,7 @@ def _render_styled_text_line(
             # pylint: disable=too-many-boolean-expressions
             if (
                 current_ws != 0.0
+                or current_lift != 0.0
                 or current_char_vpos != CharVPos.LINE
                 or current_font != self.current_font
                 or current_text_mode != self.text_mode

test/text/test_varied_fragments.py

@@ -192,3 +192,35 @@ def test_varfrags_text_mode(tmp_path):
     pdf.ln()
     pdf.write_fragments(frags, align=Align.C)
     assert_pdf_equal(pdf, HERE / "varfrags_text_mode.pdf", tmp_path)
+
+
+def test_varfrags_char_vpos(tmp_path):
+    pdf = FxFPDF()
+    pdf.add_page()
+    pdf.line(pdf.l_margin, pdf.t_margin, pdf.l_margin, pdf.h - pdf.b_margin)
+    pdf.line(
+        pdf.l_margin + pdf.epw,
+        pdf.t_margin,
+        pdf.l_margin + pdf.epw,
+        pdf.h - pdf.b_margin,
+    )
+    pdf.set_font("helvetica", "", 14)
+    f1 = Fragment(TEXT_1, pdf._get_current_graphics_state(), pdf.k)
+    pdf.char_vpos = "SUB"
+    f2 = Fragment(TEXT_2, pdf._get_current_graphics_state(), pdf.k)
+    f3 = Fragment(TEXT_3, f1.graphics_state, pdf.k)
+    pdf.char_vpos = "SUP"
+    f4 = Fragment(TEXT_4, pdf._get_current_graphics_state(), pdf.k)
+    f5 = Fragment(TEXT_5, f1.graphics_state, pdf.k)
+    frags = [f1, f2, f3, f4, f5]
+    pdf.write_fragments(frags)
+    pdf.ln()
+    pdf.ln()
+    pdf.write_fragments(frags, align=Align.J)
+    pdf.ln()
+    pdf.ln()
+    pdf.write_fragments(frags, align=Align.R)
+    pdf.ln()
+    pdf.ln()
+    pdf.write_fragments(frags, align=Align.C)
+    assert_pdf_equal(pdf, HERE / "varfrags_char_vpos.pdf", tmp_path)