ENH: add capability to set font and size in fields

docs/modules/constants.rst

@@ -20,3 +20,9 @@ Constants
     :members:
     :undoc-members:
     :show-inheritance:
+
+.. autoclass:: pypdf.constants.FieldDictionaryAttributes
+       :members:
+       :undoc-members:
+       :exclude-members: FT, Parent, Kids, T, TU, TM, V, DV, AA, Opt, attributes, attributes_dict
+       :show-inheritance:

pypdf/_writer.py

@@ -70,7 +70,6 @@
 from .constants import CatalogAttributes as CA
 from .constants import (
     CatalogDictionary,
-    FieldFlag,
     FileSpecificationDictionaryEntries,
     GoToActionArguments,
     ImageType,
@@ -123,8 +122,8 @@
 )
 from .xmp import XmpInformation
 
-OPTIONAL_READ_WRITE_FIELD = FieldFlag(0)
 ALL_DOCUMENT_PERMISSIONS = UserAccessPermissions.all()
+DEFAULT_FONT_HEIGHT_IN_MULTILINE = 12
 
 
 class ObjectDeletionFlag(enum.IntFlag):
@@ -780,7 +779,11 @@ def append_pages_from_reader(
                 after_page_append(writer_page)
 
     def _update_field_annotation(
-        self, field: DictionaryObject, anno: DictionaryObject
+        self,
+        field: DictionaryObject,
+        anno: DictionaryObject,
+        font_name: str = "",
+        font_size: float = -1,
     ) -> None:
         # Calculate rectangle dimensions
         _rct = cast(RectangleObject, anno[AA.Rect])
@@ -799,12 +802,22 @@ def _update_field_annotation(
             da = da.get_object()
         font_properties = da.replace("\n", " ").replace("\r", " ").split(" ")
         font_properties = [x for x in font_properties if x != ""]
-        font_name = font_properties[font_properties.index("Tf") - 2]
-        font_height = float(font_properties[font_properties.index("Tf") - 1])
+        if font_name:
+            font_properties[font_properties.index("Tf") - 2] = font_name
+        else:
+            font_name = font_properties[font_properties.index("Tf") - 2]
+        font_height = (
+            font_size
+            if font_size >= 0
+            else float(font_properties[font_properties.index("Tf") - 1])
+        )
         if font_height == 0:
-            font_height = rct.height - 2
-            font_properties[font_properties.index("Tf") - 1] = str(font_height)
-            da = " ".join(font_properties)
+            if field.get(FA.Ff, 0) & FA.FfBits.Multiline:
+                font_height = DEFAULT_FONT_HEIGHT_IN_MULTILINE
+            else:
+                font_height = rct.height - 2
+        font_properties[font_properties.index("Tf") - 1] = str(font_height)
+        da = " ".join(font_properties)
         y_offset = rct.height - 1 - font_height
 
         # Retrieve font information from local DR ...
@@ -926,11 +939,13 @@ def _update_field_annotation(
             self._objects[n - 1] = dct
             dct.indirect_reference = IndirectObject(n, 0, self)
 
+    FFBITS_NUL = FA.FfBits(0)
+
     def update_page_form_field_values(
         self,
         page: Union[PageObject, List[PageObject], None],
         fields: Dict[str, Any],
-        flags: FieldFlag = OPTIONAL_READ_WRITE_FIELD,
+        flags: FA.FfBits = FFBITS_NUL,
         auto_regenerate: Optional[bool] = True,
     ) -> None:
         """
@@ -944,12 +959,18 @@ def update_page_form_field_values(
                 annotations and field data will be updated.
                 `List[Pageobject]` - provides list of pages to be processed.
                 `None` - all pages.
-            fields: a Python dictionary of field names (/T) and text
-                values (/V).
-            flags: An integer (0 to 7). The first bit sets ReadOnly, the
-                second bit sets Required, the third bit sets NoExport. See
-                PDF Reference Table 8.70 for details.
-            auto_regenerate: set/unset the need_appearances flag ;
+            fields: a Python dictionary of:
+
+                * field names (/T) as keys and text values (/V) as value
+                * field names (/T) as keys and list of text values (/V) for multiple choice list
+                * field names (/T) as keys and tuple of:
+                    * text values (/V)
+                    * font id (e.g. /F1, the font id must exist)
+                    * font size (0 for autosize)
+
+            flags: A set of flags from :class:`~pypdf.constants.FieldDictionaryAttributes.FfBits`.
+
+            auto_regenerate: Set/unset the need_appearances flag;
                 the flag is unchanged if auto_regenerate is None.
         """
         if CatalogDictionary.ACRO_FORM not in self._root_object:
@@ -997,6 +1018,10 @@ def update_page_form_field_values(
                 if isinstance(value, list):
                     lst = ArrayObject(TextStringObject(v) for v in value)
                     writer_parent_annot[NameObject(FA.V)] = lst
+                elif isinstance(value, tuple):
+                    writer_annot[NameObject(FA.V)] = TextStringObject(
+                        value[0],
+                    )
                 else:
                     writer_parent_annot[NameObject(FA.V)] = TextStringObject(value)
                 if writer_parent_annot.get(FA.FT) in ("/Btn"):
@@ -1011,7 +1036,12 @@ def update_page_form_field_values(
                     or writer_parent_annot.get(FA.FT) == "/Ch"
                 ):
                     # textbox
-                    self._update_field_annotation(writer_parent_annot, writer_annot)
+                    if isinstance(value, tuple):
+                        self._update_field_annotation(
+                            writer_parent_annot, writer_annot, value[1], value[2]
+                        )
+                    else:
+                        self._update_field_annotation(writer_parent_annot, writer_annot)
                 elif (
                     writer_annot.get(FA.FT) == "/Sig"
                 ):  # deprecated  # not implemented yet

pypdf/constants.py

@@ -427,7 +427,12 @@ class InteractiveFormDictEntries:
 
 
 class FieldDictionaryAttributes:
-    """Table 8.69 Entries common to all field dictionaries (PDF 1.7 reference)."""
+    """
+    Entries common to all field dictionaries (Table 8.69 PDF 1.7 reference)
+    (*very partially documented here*).
+
+    FFBits provides the constants used for `/Ff` from Table 8.70/8.75/8.77/8.79
+    """
 
     FT = "/FT"  # name, required for terminal fields
     Parent = "/Parent"  # dictionary, required for children
@@ -441,34 +446,63 @@ class FieldDictionaryAttributes:
     AA = "/AA"  # dictionary, optional
     Opt = "/Opt"
 
-    class FfBits:
+    class FfBits(IntFlag):
+        """
+        Ease building /Ff flags
+        Some entries may be specific to:
+
+        * Text(Tx) (Table 8.75 PDF 1.7 reference)
+        * Buttons(Btn) (Table 8.77 PDF 1.7 reference)
+        * List(Ch) (Table 8.79 PDF 1.7 reference)
+        """
+
         ReadOnly = 1 << 0
+        """common to Tx/Btn/Ch in Table 8.70"""
         Required = 1 << 1
+        """common to Tx/Btn/Ch in Table 8.70"""
         NoExport = 1 << 2
-        Multiline = 1 << 12  # Tx Table 8.77
-        Password = 1 << 13  # Tx
-
-        NoToggleToOff = 1 << 14  # Btn table 8.75
-        Radio = 1 << 15  # Btn
-        Pushbutton = 1 << 16  # Btn
-
-        Combo = 1 << 17  # Ch table 8.79
-        Edit = 1 << 18  # Ch
-        Sort = 1 << 19  # Ch
-
-        FileSelect = 1 << 20  # Tx
-
-        MultiSelect = 1 << 21  # Ch
-
-        DoNotSpellCheck = 1 << 22  # Tx / Ch
-        DoNotScroll = 1 << 23  # Tx
-        Comb = 1 << 24  # Tx
-
-        RadiosInUnison = 1 << 25  # Btn
-
-        RichText = 1 << 25  # Tx
-
-        CommitOnSelChange = 1 << 26  # Ch
+        """common to Tx/Btn/Ch in Table 8.70"""
+
+        Multiline = 1 << 12
+        """Tx"""
+        Password = 1 << 13
+        """Tx"""
+
+        NoToggleToOff = 1 << 14
+        """Btn"""
+        Radio = 1 << 15
+        """Btn"""
+        Pushbutton = 1 << 16
+        """Btn"""
+
+        Combo = 1 << 17
+        """Ch"""
+        Edit = 1 << 18
+        """Ch"""
+        Sort = 1 << 19
+        """Ch"""
+
+        FileSelect = 1 << 20
+        """Tx"""
+
+        MultiSelect = 1 << 21
+        """Tx"""
+
+        DoNotSpellCheck = 1 << 22
+        """Tx/Ch"""
+        DoNotScroll = 1 << 23
+        """Tx"""
+        Comb = 1 << 24
+        """Tx"""
+
+        RadiosInUnison = 1 << 25
+        """Btn"""
+
+        RichText = 1 << 25
+        """Tx"""
+
+        CommitOnSelChange = 1 << 26
+        """Ch"""
 
     @classmethod
     def attributes(cls) -> Tuple[str, ...]:

tests/test_writer.py

@@ -2230,3 +2230,26 @@ def test_i_in_choice_fields():
         writer.pages[0], {"State": "NY"}, auto_regenerate=False
     )
     assert "/I" not in writer.get_fields()["State"].indirect_reference.get_object()
+
+
+def test_selfont():
+    writer = PdfWriter(clone_from=RESOURCE_ROOT / "FormTestFromOo.pdf")
+    writer.update_page_form_field_values(
+        writer.pages[0],
+        {"Text1": ("Text_1", "", 5), "Text2": ("Text_2", "/F3", 0)},
+        auto_regenerate=False,
+    )
+    assert (
+        b"/F3 5 Tf"
+        in writer.pages[0]["/Annots"][1].get_object()["/AP"]["/N"].get_data()
+    )
+    assert (
+        b"Text_1" in writer.pages[0]["/Annots"][1].get_object()["/AP"]["/N"].get_data()
+    )
+    assert (
+        b"/F3 12 Tf"
+        in writer.pages[0]["/Annots"][2].get_object()["/AP"]["/N"].get_data()
+    )
+    assert (
+        b"Text_2" in writer.pages[0]["/Annots"][2].get_object()["/AP"]["/N"].get_data()
+    )