Missing footer on first page of each chapter in LaTeX

In the doxygen pdf manual we see that on the first page of each chapter the footer is missing, the same occurs in the "normal" documentation generated by doxygen.
References:
- https://tex.stackexchange.com/questions/566034/footer-ruler-on-first-page-in-fancyhdr-with-book
- https://tex.stackexchange.com/questions/566056/footer-ruler-on-first-page-in-fancyhdr-with-book-but-not-in-part-part/

Code changes ("normal" documentation):
- latexgen.cpp changes required for the "normal" documentation

Code changes (doxygen manual)
- doxygen_manual.sty, remove word "Part" for the Appendices.
- manual.sty changes like for "normal" documentation plus patching part in case of the `\part` (here we don't want the footer or header)

2 files changed, 23 insertions, 13 deletions

diff --git a/doc/doxygen_manual.tex b/doc/doxygen_manual.tex
index 0148379..aacb573 100644
--- a/doc/doxygen_manual.tex
+++ b/doc/doxygen_manual.tex
@@ -171,6 +171,7 @@ Written by Dimitri van Heesch\\[2ex]
 \chapter{Perl Module Output}\label{perlmod}\hypertarget{perlmod}{}\input{perlmod}
 \chapter{Doxygen's internals}\label{arch}\hypertarget{arch}{}\input{arch}
 \renewcommand{\thepart}{}
+\renewcommand{\partname}{}
 \part{Appendices}
 \appendix
 %mean that subinputfrom requires a / at the end of the path
diff --git a/doc/manual.sty b/doc/manual.sty
index 643bd40..fd9fd0e 100644
--- a/doc/manual.sty
+++ b/doc/manual.sty
@@ -8,7 +8,6 @@
 
 % Setup fancy headings
 \RequirePackage{fancyhdr}
-\pagestyle{fancyplain}
 \newcommand{\clearemptydoublepage}{%
   \newpage{\pagestyle{empty}\cleardoublepage}%
 }
@@ -18,18 +17,28 @@
 \renewcommand{\sectionmark}[1]{%
   \markright{\thesection\ #1}%
 }
-\fancyhead[LE]{\fancyplain{}{\bfseries\thepage}}
-\fancyhead[CE]{\fancyplain{}{}}
-\fancyhead[RE]{\fancyplain{}{\bfseries\leftmark}}
-\fancyhead[LO]{\fancyplain{}{\bfseries\rightmark}}
-\fancyhead[CO]{\fancyplain{}{}}
-\fancyhead[RO]{\fancyplain{}{\bfseries\thepage}}
-\fancyfoot[LE]{\fancyplain{}{}}
-\fancyfoot[CE]{\fancyplain{}{}}
-\fancyfoot[RE]{\fancyplain{}{\bfseries\scriptsize Generated by Doxygen @VERSION@ }}
-\fancyfoot[LO]{\fancyplain{}{\bfseries\scriptsize Generated by Doxygen @VERSION@ }}
-\fancyfoot[CO]{\fancyplain{}{}}
-\fancyfoot[RO]{\fancyplain{}{}}
+
+% Headers & footers
+\pagestyle{fancyplain}
+\renewcommand{\footrulewidth}{0.4pt}
+%
+\fancypagestyle{fancyplain}{
+\fancyhf{}
+\fancyhead[LE, RO]{\bfseries\thepage}
+\fancyhead[LO]{\bfseries\rightmark}
+\fancyhead[RE]{\bfseries\leftmark}
+\fancyfoot[LO, RE]{\bfseries\scriptsize Generated by Doxygen @VERSION@ }
+}
+%
+\fancypagestyle{plain}{
+\fancyhf{}
+\fancyfoot[LO, RE]{\bfseries\scriptsize Generated by Doxygen @VERSION@ }
+\renewcommand{\headrulewidth}{0pt}}
+%
+\pagestyle{fancyplain}
+%
+\usepackage{xpatch}
+\xpatchcmd{\part}{plain}{empty}{}{}
 
 % Define caption that is also suitable in a table
 \makeatletter