[clang] [clang-format][NFC] Improve KeepFormFeed option decription (PR #176654)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang-format

Author: Baranov Victor (vbvictor)

<details>
<summary>Changes</summary>

It was not clear from the description what this option does.
Added small example to demostrate its behavior.

---
Full diff: https://github.com/llvm/llvm-project/pull/176654.diff


2 Files Affected:

- (modified) clang/docs/ClangFormatStyleOptions.rst (+12-4) 
- (modified) clang/include/clang/Format/Format.h (+11-4) 


``````````diff
diff --git a/clang/docs/ClangFormatStyleOptions.rst b/clang/docs/ClangFormatStyleOptions.rst
index 4f81a084dd65b..74cbc040659a9 100644
--- a/clang/docs/ClangFormatStyleOptions.rst
+++ b/clang/docs/ClangFormatStyleOptions.rst
@@ -5012,10 +5012,18 @@ the configuration (without a prefix: ``Auto``).
 .. _KeepFormFeed:
 
 **KeepFormFeed** (``Boolean``) :versionbadge:`clang-format 20` :ref:`¶ <KeepFormFeed>`
-  Keep the form feed character if it's immediately preceded and followed by
-  a newline. Multiple form feeds and newlines within a whitespace range are
-  replaced with a single newline and form feed followed by the remaining
-  newlines.
+  Keep the form feed character (``\f``) if it's immediately preceded and
+  followed by a newline. Multiple form feeds and newlines within a
+  whitespace range are replaced with a single newline and form feed
+  followed by the remaining newlines.
+
+  .. code-block:: c++
+
+    false:          true:
+
+    "int i;\n"      "int i;\n"
+    "\n"            "\f\n"
+    "void f();"     "void f();"
 
 .. _LambdaBodyIndentation:
 
diff --git a/clang/include/clang/Format/Format.h b/clang/include/clang/Format/Format.h
index c7e57d47f9ed1..2c8b7b5c2c0be 100644
--- a/clang/include/clang/Format/Format.h
+++ b/clang/include/clang/Format/Format.h
@@ -3517,10 +3517,17 @@ struct FormatStyle {
   /// \version 3.7
   // bool KeepEmptyLinesAtTheStartOfBlocks;
 
-  /// Keep the form feed character if it's immediately preceded and followed by
-  /// a newline. Multiple form feeds and newlines within a whitespace range are
-  /// replaced with a single newline and form feed followed by the remaining
-  /// newlines.
+  /// Keep the form feed character (``\f``) if it's immediately preceded and
+  /// followed by a newline. Multiple form feeds and newlines within a
+  /// whitespace range are replaced with a single newline and form feed
+  /// followed by the remaining newlines.
+  /// \code
+  ///   false:          true:
+  ///
+  ///   "int i;\n"      "int i;\n"
+  ///   "\n"            "\f\n"
+  ///   "void f();"     "void f();"
+  /// \endcode
   /// \version 20
   bool KeepFormFeed;
 

``````````

</details>


https://github.com/llvm/llvm-project/pull/176654