ENH: Wrap and align text in flattened PDF forms (#3465)

Author: PJBrs

CONTRIBUTORS.md

@@ -13,6 +13,7 @@ history and [GitHub's 'Contributors' feature](https://github.com/py-pdf/pypdf/gr
 
 * [abyesilyurt](https://github.com/abyesilyurt)
 * [ArkieCoder](https://github.com/ArkieCoder)
+* [Beers, PJ](https://github.com/PJBrs)
 * [Clauss, Christian](https://github.com/cclauss)
 * [DL6ER](https://github.com/DL6ER)
 * [Duy, Phan Thanh](https://github.com/zuypt)

docs/user/forms.md

@@ -46,6 +46,13 @@ parameter is `True` by default for legacy compatibility, but this flags the PDF
 processor to recompute the field's rendering, and may trigger a "save changes"
 dialog for users who open the generated PDF.
 
+If you want to flatten your form, that is, keeping all form field contents while
+removing the form fields themselves, you can set the `flatten` parameter in
+{func}`~pypdf.PdfWriter.update_page_form_field_values` to `True`. This
+will convert form field  contents to regular PDF content. Afterwards, use
+{func}`~pypdf.PdfWriter.remove_annotations` with `subtypes="/Widget"`
+to remove all form fields to get an actual flattened PDF.
+
 ## Some notes about form fields and annotations
 
 PDF forms have a dual-nature approach to the fields:

pypdf/_font.py

@@ -1,5 +1,4 @@
 from dataclasses import dataclass, field
-from typing import Optional
 
 from pypdf.generic import DictionaryObject
 
@@ -29,10 +28,16 @@ class FontDescriptor:
     character_widths: dict[str, int] = field(default_factory=dict)
 
     @classmethod
-    def from_font_resource(cls, pdf_font_dict: DictionaryObject) -> "Optional[FontDescriptor]":
+    def from_font_resource(cls, pdf_font_dict: DictionaryObject) -> "FontDescriptor":
         from pypdf._codecs.core_fontmetrics import CORE_FONT_METRICS  # noqa: PLC0415
         # Prioritize information from the PDF font dictionary
-        font_name = pdf_font_dict.get("/BaseFont", "Unknown")
-        if font_name[1:] in CORE_FONT_METRICS:
-            return CORE_FONT_METRICS.get(font_name[1:])
+        font_name = pdf_font_dict.get("/BaseFont", "Unknown").removeprefix("/")
+        if font_name in CORE_FONT_METRICS:
+            return CORE_FONT_METRICS[font_name]
         return cls(name=font_name)
+
+    def text_width(self, text: str) -> float:
+        """Sum of character widths specified in PDF font for the supplied text."""
+        return sum(
+            [self.character_widths.get(char, self.character_widths.get("default", 0)) for char in text], 0.0
+        )