- Change parameter order in \providelength to match \setlength.

- Remove Part name from appendix and back matter headers.

packages/Boxout.sty

@@ -4,7 +4,7 @@
 \RequirePackage{PrimeTeX/packages/Layout}
 \RequirePackage{PrimeTeX/packages/Color}
 
-\providelength[0.5em]{\boxoutpadding}
+\providelength{\boxoutpadding}[0.5em]
 
 \colorlet{boxoutbgcolor}{PrimePaleBlue}
 \colorlet{boxoutfgcolor}{PrimeBlue}

packages/Color.sty

@@ -49,7 +49,7 @@
 	}%
 }
 
-\providelength[12.3599pt]{\warningboxsizeoffset}
+\providelength{\warningboxsizeoffset}[12.3599pt]
 
 \NewDocumentCommand{\warningbox}{O{\textwidth-\warningboxsizeoffset} +m}{%
 	\noindent%

packages/Graphics.sty

@@ -7,8 +7,8 @@
 
 \RequirePackage{wrapfig2}
 
-\providelength[0.25in]{\iconsize}
-\providelength[10pt]{\igh} % igh = Inline Graphics Height.
+\providelength{\iconsize}[0.25in]
+\providelength{\igh}[10pt] % igh = Inline Graphics Height.
 
 % Shorthand command for \includegraphics.
 \NewDocumentCommand{\ig}{O{width=0.5in} m}{%
@@ -51,10 +51,10 @@
 
 \RequirePackage{tabularray}
 
-\providelength[3pt]{\twinfigspace}
-\providelength[
+\providelength{\twinfigspace}[3pt]
+\providelength{\twinfigwidth}[
 	\textwidth / 2 + \bigfloatoverhang - \twinfigspace
-]{\twinfigwidth}
+]
 
 \NewDocumentCommand{\twinfig}{%
 	O{\bigfloatoverhang} m >{\TrimSpaces}m m m >{\TrimSpaces}m m%

packages/Header.sty

@@ -17,14 +17,17 @@
 \setlength{\outsideheaderoffset}{1.0in}
 
 \NewDocumentCommand{\chapappname}{}{Chapter \thechapter{}: }
+\NewDocumentCommand{\partlabel}{}{\partname{} \thepart{}: \parttitle}
 
 \NewDocumentCommand{\Appendix}{}{
 	\appendix
 	\RenewDocumentCommand{\chapappname}{}{Appendix \thechapter{}: }
+	\RenewDocumentCommand{\partlabel}{}{}
 }
 
 \NewDocumentCommand{\BackMatter}{}{
 	\RenewDocumentCommand{\chapappname}{}{}
+	\RenewDocumentCommand{\partlabel}{}{}
 }
 
 \NewDocumentCommand{\parttitle}{}{}
@@ -35,13 +38,13 @@
 	\ifthenelse{\boolean{isElectronic}}{
 		\fancyhfoffset[L]{\insideheaderoffset}
 		\fancyhfoffset[R]{\outsideheaderoffset}
-		\fancyhead[L]{\partname{} \thepart{}: \parttitle}
+		\fancyhead[L]{\partlabel}
 		\fancyhead[R]{\chapappname{}\leftmark}
 
 		\fancyfoot[R]{\thepage}
 	}{
 		\fancyhfoffset[LE,RO]{\outsideheaderoffset}
-		\fancyhead[LE]{\partname{} \thepart{}: \parttitle}
+		\fancyhead[LE]{\partlabel}
 		\fancyhead[RO]{\chapappname\leftmark}
 
 		\fancyfoot[LE,RO]{\thepage}

packages/Layout.sty

@@ -9,12 +9,12 @@
 \hfuzz = 6.0pt
 \vfuzz = 0.0pt
 
-\providecommand{\providelength}[2][0pt]{%
+\NewDocumentCommand{\providelength}{m O{0pt}}{%
 	\ifdeflength{#2}{% It is already defined!
 	}{% Not defined, so define it!
-		\newlength{#2}%
+		\newlength{#1}%
 	}%
-	\setlength{#2}{#1}%
+	\setlength{#1}{#2}%
 }
 
 \RequirePackage{microtype}
@@ -47,8 +47,9 @@
 \RequirePackage{calc}
 \RequirePackage[strict]{changepage}
 
-\newlength{\contentwidth}
-\setlength{\contentwidth}{\textwidth + \marginparsep + \marginparwidth}
+%\newlength{\contentwidth}
+\providelength{\marparwidth}[\marginparsep + \marginparwidth]
+\providelength{\contentwidth}[\textwidth + \marparwidth]
 
 \RequirePackage[balanced]{lua-widow-control}
 \ifthenelse{\boolean{isDraft}}{