Fixed FPDF.local_context() style leak during page breaks - Fix #1204

CHANGELOG.md

@@ -24,18 +24,19 @@ This can also be enabled programmatically with `warnings.simplefilter('default',
 * feature to identify the Unicode script of the input text and break it into fragments when different scripts are used, improving text shaping results
 * [`FPDF.image()`](https://py-pdf.github.io/fpdf2/fpdf/fpdf.html#fpdf.fpdf.FPDF.image): now handles `keep_aspect_ratio` in combination with an enum value provided to `x`
 * file names are mentioned in errors when `fpdf2` fails to parse a SVG image
-* * feature to adjust spacing before lists via the `HTML2FPDF.list_vertical_margin` attribute
+* [`FPDF.write_html()`](https://py-pdf.github.io/fpdf2/fpdf/fpdf.html#fpdf.fpdf.FPDF.write_html): spacing before lists can now be adjusted via the `HTML2FPDF.list_vertical_margin` attribute
 ### Fixed
+* [`FPDF.local_context()`](https://py-pdf.github.io/fpdf2/fpdf/fpdf.html#fpdf.fpdf.FPDF.local_context) used to leak styling during page breaks, when rendering `footer()` & `header()`
 * [`fpdf.drawing.DeviceCMYK`](https://py-pdf.github.io/fpdf2/fpdf/drawing.html#fpdf.drawing.DeviceCMYK) objects can now be passed to [`FPDF.set_draw_color()`](https://py-pdf.github.io/fpdf2/fpdf/fpdf.html#fpdf.fpdf.FPDF.set_draw_color), [`FPDF.set_fill_color()`](https://py-pdf.github.io/fpdf2/fpdf/fpdf.html#fpdf.fpdf.FPDF.set_fill_color) and [`FPDF.set_text_color()`](https://py-pdf.github.io/fpdf2/fpdf/fpdf.html#fpdf.fpdf.FPDF.set_text_color) without raising a `ValueError`: [documentation](https://py-pdf.github.io/fpdf2/Text.html#text-formatting).
 * individual `/Resources` directories are now properly created for each document page. This change ensures better compliance with the PDF specification but results in a slight increase in the size of PDF documents. You can still use the old behavior by setting `FPDF().single_resources_object = True`
 * line size calculation for fragments when text shaping is used
 * fixed incoherent indentation of long list entries - _cf._ [issue #1073](https://github.com/py-pdf/fpdf2/issues/1073)
 * default values for `top_margin` and `bottom_margin` in `HTML2FPDF._new_paragraph()` calls are now correctly converted into chosen document units.
+### Removed
+* an obscure and undocumented [feature](https://github.com/py-pdf/fpdf2/issues/1198) of [`FPDF.write_html()`](https://py-pdf.github.io/fpdf2/fpdf/fpdf.html#fpdf.fpdf.FPDF.write_html), which used to magically pass local variables as arguments.
 ### Changed
-* Removed an obscure and undocumented [feature](https://github.com/py-pdf/fpdf2/issues/1198) of [`FPDF.write_html()`](https://py-pdf.github.io/fpdf2/fpdf/fpdf.html#fpdf.fpdf.FPDF.write_html), which used to magically pass local variables as arguments.
 * [`FPDF.table()`](https://py-pdf.github.io/fpdf2/Tables.html) now raises an error when a single row is too high to be rendered on a single page
-* `HTML2FPDF.tag_indents` can now be non-integer. Indentation of HTML elements is now independent of font size and bullet strings.
-* No spacing controlled by `HTML2FPDF.list_vertical_margin` is created for nested HTML `<li>` elements in contrast with prior respect for `Paragraph.top_margin` when handling `Paragraph`s created when handling `<ul>` and `<ol>` start tags.
+* [`FPDF.write_html()`](https://py-pdf.github.io/fpdf2/fpdf/fpdf.html#fpdf.fpdf.FPDF.write_html): `tag_indents` can now be non-integer. Indentation of HTML elements is now independent of font size and bullet strings.
 
 ## [2.7.9] - 2024-05-17
 ### Added

fpdf/fpdf.py

@@ -2746,18 +2746,7 @@ def mirror(self, origin, angle):
 
     @check_page
     @contextmanager
-    def local_context(
-        self,
-        font_family=None,
-        font_style=None,
-        font_size=None,
-        line_width=None,
-        draw_color=None,
-        fill_color=None,
-        text_color=None,
-        dash_pattern=None,
-        **kwargs,
-    ):
+    def local_context(self, **kwargs):
         """
         Creates a local graphics state, which won't affect the surrounding code.
         This method must be used as a context manager using `with`:
@@ -2770,7 +2759,11 @@ def local_context(
             allow_transparency
             auto_close
             blend_mode
+            char_vpos
+            char_spacing
             dash_pattern
+            denom_lift
+            denom_scale
             draw_color
             fill_color
             fill_opacity
@@ -2780,15 +2773,21 @@ def local_context(
             font_stretching
             intersection_rule
             line_width
+            nom_lift
+            nom_scale
             paint_rule
             stroke_cap_style
             stroke_join_style
             stroke_miter_limit
             stroke_opacity
+            sub_lift
+            sub_scale
+            sup_lift
+            sup_scale
             text_color
             text_mode
+            text_shaping
             underline
-            char_vpos
 
         Args:
             **kwargs: key-values settings to set at the beggining of this context.
@@ -2798,6 +2797,32 @@ def local_context(
                 "cannot create a local context inside an unbreakable() code block"
             )
         self._push_local_stack()
+        self._init_local_context(**kwargs)  # write "q" in the output stream
+        yield
+        self._out("Q")
+        self._pop_local_stack()
+
+    def _init_local_context(
+        self,
+        font_family=None,
+        font_style=None,
+        font_size=None,
+        line_width=None,
+        draw_color=None,
+        fill_color=None,
+        text_color=None,
+        dash_pattern=None,
+        **kwargs,
+    ):
+        """
+        This method starts a "q" context in the output stream,
+        and inserts operators in it to initialize all the PDF settings specified.
+        """
+        if "font_size_pt" in kwargs:
+            if font_size is not None:
+                raise ValueError("font_size & font_size_pt cannot be both provided")
+            font_size = kwargs["font_size_pt"] / self.k
+            del kwargs["font_size_pt"]
         gs = None
         for key, value in kwargs.items():
             if key in (
@@ -2815,7 +2840,23 @@ def local_context(
                 setattr(gs, key, value)
                 if key == "blend_mode":
                     self._set_min_pdf_version("1.4")
-            elif key in ("font_stretching", "text_mode", "underline", "char_vpos"):
+            elif key in (
+                "char_vpos",
+                "char_spacing",
+                "current_font",
+                "denom_lift",
+                "denom_scale",
+                "font_stretching",
+                "nom_lift",
+                "nom_scale",
+                "sub_lift",
+                "sub_scale",
+                "sup_lift",
+                "sup_scale",
+                "text_mode",
+                "text_shaping",
+                "underline",
+            ):
                 setattr(self, key, value)
             else:
                 raise ValueError(f"Unsupported setting: {key}")
@@ -2842,9 +2883,6 @@ def local_context(
             self.set_text_color(text_color)
         if dash_pattern is not None:
             self.set_dash_pattern(**dash_pattern)
-        yield
-        self._out("Q")
-        self._pop_local_stack()
 
     @property
     def accept_page_break(self):
@@ -3537,7 +3575,14 @@ def _perform_page_break_if_need_be(self, h):
 
     def _perform_page_break(self):
         x = self.x
+        gs_stack = []
+        while self._is_current_graphics_state_nested():
+            self._out("Q")
+            gs_stack.append(self._pop_local_stack())
         self.add_page(same=True)
+        for prev_gs in reversed(gs_stack):
+            self._push_local_stack(prev_gs)
+            self._init_local_context(**prev_gs)
         self.x = x  # restore x but not y after drawing header
 
     def _has_next_page(self):
@@ -3813,9 +3858,7 @@ def multi_cell(
             page_break_required = self.will_page_break(h + padding.bottom)
             if page_break_required:
                 page_break_triggered = True
-                x = self.x
-                self.add_page(same=True)
-                self.x = x
+                self._perform_page_break()
                 self.y += padding.top
 
             if box_required and (text_line_index == 0 or page_break_required):
@@ -5070,6 +5113,9 @@ def use_font_face(self, font_face: FontFace):
 
             with pdf.use_font_face(FontFace(emphasis="BOLD", color=255, size_pt=42)):
                 put_some_text()
+
+        Known limitation: in case of a page jump in this local context,
+        the temporary style may "leak" in the header() & footer().
         """
         if not font_face:
             yield

fpdf/graphics_state.py

@@ -28,35 +28,44 @@ class GraphicsStateMixin:
     DEFAULT_DRAW_COLOR = DeviceGray(0)
     DEFAULT_FILL_COLOR = DeviceGray(0)
     DEFAULT_TEXT_COLOR = DeviceGray(0)
+    DEFAULT_STATE = dict(
+        draw_color=DEFAULT_DRAW_COLOR,
+        fill_color=DEFAULT_FILL_COLOR,
+        text_color=DEFAULT_TEXT_COLOR,
+        underline=False,
+        font_style="",
+        font_stretching=100,
+        char_spacing=0,
+        font_family="",
+        font_size_pt=0,
+        current_font={},
+        dash_pattern=dict(dash=0, gap=0, phase=0),
+        line_width=0,
+        text_mode=TextMode.FILL,
+        char_vpos=CharVPos.LINE,
+        sub_scale=0.7,
+        sup_scale=0.7,
+        nom_scale=0.75,
+        denom_scale=0.75,
+        sub_lift=-0.15,
+        sup_lift=0.4,
+        nom_lift=0.2,
+        denom_lift=0.0,
+        text_shaping=None,
+    )
+
+    @staticmethod
+    def _copy_graphics_state(gs):
+        # "current_font" must be shallow copied
+        # "text_shaping" must be deep copied (different fragments may have different languages/direction)
+        # Doing a whole copy and then creating a copy of text_shaping to achieve this result
+        gs = copy(gs)
+        if "text_shaping" in gs:
+            gs["text_shaping"] = copy(gs["text_shaping"])
+        return gs
 
     def __init__(self, *args, **kwargs):
-        self.__statestack = [
-            dict(
-                draw_color=self.DEFAULT_DRAW_COLOR,
-                fill_color=self.DEFAULT_FILL_COLOR,
-                text_color=self.DEFAULT_TEXT_COLOR,
-                underline=False,
-                font_style="",
-                font_stretching=100,
-                char_spacing=0,
-                font_family="",
-                font_size_pt=0,
-                current_font={},
-                dash_pattern=dict(dash=0, gap=0, phase=0),
-                line_width=0,
-                text_mode=TextMode.FILL,
-                char_vpos=CharVPos.LINE,
-                sub_scale=0.7,
-                sup_scale=0.7,
-                nom_scale=0.75,
-                denom_scale=0.75,
-                sub_lift=-0.15,
-                sup_lift=0.4,
-                nom_lift=0.2,
-                denom_lift=0.0,
-                text_shaping=None,
-            ),
-        ]
+        self.__statestack = [self.DEFAULT_STATE]
         super().__init__(*args, **kwargs)
 
     def _push_local_stack(self, new=None):
@@ -69,12 +78,10 @@ def _pop_local_stack(self):
         return self.__statestack.pop()
 
     def _get_current_graphics_state(self):
-        # "current_font" must be shallow copied
-        # "text_shaping" must be deep copied (different fragments may have different languages/direction)
-        # Doing a whole copy and then creating a copy of text_shaping to achieve this result
-        gs = copy(self.__statestack[-1])
-        gs["text_shaping"] = copy(gs["text_shaping"])
-        return gs
+        return self._copy_graphics_state(self.__statestack[-1])
+
+    def _is_current_graphics_state_nested(self):
+        return len(self.__statestack) > 1
 
     @property
     def draw_color(self):

test/text/test_cell.py

@@ -325,6 +325,27 @@ def test_cell_deprecated_txt_arg():
         pdf.cell(txt="Lorem ipsum Ut nostrud irure")
 
 
+def test_header_footer_and_local_context_font_size(tmp_path):  # issue 1204
+    class PDF(FPDF):
+        def header(self):
+            self.cell(text=f"Header {self.page_no()}")
+            self.ln()
+
+        def footer(self):
+            self.set_y(-15)
+            self.cell(text=f"Footer {self.page_no()}")
+
+    pdf = PDF()
+    pdf.set_font(family="helvetica", size=12)
+    pdf.add_page()
+    with pdf.local_context(font_size=36):  # LABEL C
+        pdf.multi_cell(w=0, text="\n".join(f"Line {i + 1}" for i in range(21)))
+    assert pdf.font_size_pt == 12
+    assert_pdf_equal(
+        pdf, HERE / "header_footer_and_local_context_font_size.pdf", tmp_path
+    )
+
+
 @ensure_exec_time_below(seconds=24)
 @ensure_rss_memory_below(mib=1)
 def test_cell_speed_with_long_text():  # issue #907

test/text/test_use_font_face.py

@@ -0,0 +1,28 @@
+from pathlib import Path
+
+from fpdf import FPDF, FontFace
+
+from test.conftest import assert_pdf_equal
+
+HERE = Path(__file__).resolve().parent
+
+
+def test_header_footer_and_use_font_face(tmp_path):  # issue 1204
+    class PDF(FPDF):
+        def header(self):
+            with self.use_font_face(FontFace(color="#00ff00", size_pt=12)):  # LABEL A
+                self.cell(text=f"Header {self.page_no()}")
+            self.ln()
+
+        def footer(self):
+            self.set_y(-15)
+            with self.use_font_face(FontFace(color="#0000ff", size_pt=12)):  # LABEL B
+                self.cell(text=f"Footer {self.page_no()}")
+
+    pdf = PDF()
+    pdf.set_font(family="helvetica", size=12)
+    pdf.add_page()
+    with pdf.use_font_face(FontFace(size_pt=36)):  # LABEL C
+        pdf.multi_cell(w=0, text="\n".join(f"Line {i + 1}" for i in range(21)))
+    assert pdf.font_size_pt == 12
+    assert_pdf_equal(pdf, HERE / "header_footer_and_use_font_face.pdf", tmp_path)