Flip fantastichdr headrule ainda estranho

Question

Estou tentando conseguir um breve desbotamento \headrulenos números das páginas. Mas não consigo descobrir como "inverter" nas páginas pares/ímpares. Alguém sabe como gerenciar isso?

Também recebo um aviso dizendo que headheighté muito pequeno. Isso é causado pelo tikzpicture, mas como posso consertar isso? Não quero aumentar headheighttanto...

\documentclass[11pt, titlepage, openright]{book}

\usepackage[textwidth=13cm, left=2.5cm, bottom=2cm, top=2.5cm, paperwidth=20cm, paperheight=27cm, layoutwidth=19cm, layoutheight=26cm, layouthoffset=0.5cm, layoutvoffset=0.5cm, showcrop, asymmetric]{geometry}
\usepackage{fancyhdr}
\usepackage{tikz}
\usepackage{lipsum}

\pagestyle{fancy}
\renewcommand{\chaptermark}[1]{\markboth{#1}{}}
\fancyhead{}
\fancyfoot{}

\definecolor{grey}{rgb}{0.6,0.6,0.6}
\definecolor{darkgrey}{rgb}{0.4,0.4,0.4}

\setlength{\headheight}{24pt}
\fancyhead[RO]{\sffamily\bfseries\textcolor{grey}\leftmark\hspace{0.3cm}\sffamily\textcolor{darkgrey}\thepage}
\fancyhead[LE]{\sffamily\bfseries\textcolor{darkgrey}\thepage\hspace{0.3cm}\sffamily\textcolor{grey}\leftmark}
\renewcommand{\headrulewidth}{0.6pt}
\renewcommand{\footrulewidth}{0pt}
\renewcommand{\headrule}{
\begin{tikzpicture}
    \shade[white] (0,0) rectangle (8,0);
    \shade[left color=white, right color=black, dashed] (8,1) rectangle (12.98,1.01);
\end{tikzpicture}}

\begin{document}

\chapter{Test chapter}
\lipsum
\lipsum

\end{document}

Answer 1

No LaTeX padrão, a verificação dos cabeçalhos esquerdo/direito é realizada no valor de \count0via \ifodd. Você pode usar isso em seu \headrulecomando para definir imagens diferentes nas duas páginas.

Adicionar uma headheightopção à sua geometryespecificação dará mais espaço. Use o valor relatado no arquivo de log.

No entanto, você diz em sua pergunta que não quer fazer isso. A razão pela qual seu cabeçalho é tão alto é que você tenta movê-lo para cima desenhando algo em branco na altura 0e a regra na altura 1. Mais fácil é apenas desenhar a régua e certificar-se de que ela está posicionada corretamente usando alguns saltos verticais.

\documentclass[11pt, titlepage, openright]{book}

\usepackage[textwidth=13cm, left=2.5cm, bottom=2cm, top=2.5cm,
paperwidth=20cm, paperheight=27cm, layoutwidth=19cm,
layoutheight=26cm, layouthoffset=0.5cm, layoutvoffset=0.5cm,
showcrop, asymmetric]{geometry}
\usepackage{fancyhdr}
\usepackage{tikz}
\usepackage{lipsum}

\pagestyle{fancy}
\renewcommand{\chaptermark}[1]{\markboth{#1}{}}
\fancyhead{}
\fancyfoot{}

\definecolor{grey}{rgb}{0.6,0.6,0.6}
\definecolor{darkgrey}{rgb}{0.4,0.4,0.4}

\setlength{\headheight}{24pt}
\fancyhead[RO]{\sffamily\bfseries\textcolor{grey}\leftmark\hspace{0.3cm}\sffamily\textcolor{darkgrey}\thepage}
\fancyhead[LE]{\sffamily\bfseries\textcolor{darkgrey}\thepage\hspace{0.3cm}\sffamily\textcolor{grey}\leftmark}
\renewcommand{\headrulewidth}{0.6pt}
\renewcommand{\footrulewidth}{0pt}

\renewcommand{\headrule}{%
\vskip-\baselineskip\vskip4pt
\ifodd\count0\hfill\begin{tikzpicture}
    \shade[left color=white, right color=black, dashed] (0,0) rectangle (4.98,0.01);
\end{tikzpicture}\else\begin{tikzpicture}
    \shade[left color=black, right color=white, dashed] (0,0) rectangle (4.98,.01);
\end{tikzpicture}\fi}

\begin{document}

\chapter{Test chapter}
\lipsum
\lipsum

\end{document}

Answer 2

Você pode fazer isso com o etoolboxpacote:

\documentclass[11pt, titlepage, openright]{book}

\usepackage[textwidth=13cm, left=2.5cm, bottom=2cm, top=2.5cm, paperwidth=20cm, paperheight=27cm, layoutwidth=19cm, layoutheight=26cm, layouthoffset=0.5cm, layoutvoffset=0.5cm, showcrop, asymmetric]{geometry}
\usepackage{fancyhdr}
\usepackage{tikz}
\usepackage{lipsum}

\pagestyle{fancy}
\renewcommand{\chaptermark}[1]{\markboth{#1}{}}
\fancyhead{}
\fancyfoot{}

\definecolor{grey}{rgb}{0.6,0.6,0.6}
\definecolor{darkgrey}{rgb}{0.4,0.4,0.4}%
\usepackage{etoolbox}
\setlength{\headheight}{24pt}
\fancyhead[RO]{\sffamily\bfseries\textcolor{grey}\leftmark\hspace{0.3cm}\sffamily\textcolor{darkgrey}\thepage}
\fancyhead[LE]{\sffamily\bfseries\textcolor{darkgrey}\thepage\hspace{0.3cm}\sffamily\textcolor{grey}\leftmark}
\renewcommand{\headrulewidth}{0.6pt}
\renewcommand{\footrulewidth}{0pt}

\renewcommand{\headrule}{%
\begin{tikzpicture}%
\ifnumodd{\value{page}}{%
 \shade[white] (0,0) rectangle (8,0);
    \shade[left color=white, right color=black, dashed] (8,1) rectangle (12.98,1.01);
}%
{%
 \shade[white] (0,0) rectangle (5,0);
 \shade[left color=black, right color=white, dashed] (0,1) rectangle (4.98,1.02);
 }
\end{tikzpicture}
}%

\begin{document}

\chapter{Test chapter}
\lipsum
\lipsum

\end{document} 

Answer 3

Você pode colocar seu \fancyheadconteúdo dentro de um nodee desenhar fica fácil.

\fancyhead[RO]{%
  \begin{tikzpicture}
    \node[inner xsep=0pt, align=right,text width=5cm] (a) {\sffamily\bfseries\textcolor{grey}
             {\leftmark}\hspace{0.3cm}\sffamily\textcolor{darkgrey}{\thepage}};
    \shade[left color=white, right color=black, dashed] (a.south west) rectangle
            ([yshift=0.01cm]a.south east);
  \end{tikzpicture}%
  }
\fancyhead[LE]{%
  \begin{tikzpicture}
    \node[inner xsep=0pt, align=left,text width=5cm](a){\sffamily\bfseries\textcolor{darkgrey}
     {\thepage}\hspace{0.3cm}\sffamily\textcolor{grey}{\leftmark}};
    \shade[right color=white, left color=black, dashed] (a.south west) rectangle
            ([yshift=0.01cm]a.south east);
  \end{tikzpicture}%
  }

Código:

\documentclass[11pt, titlepage, openright]{book}

\usepackage[textwidth=13cm, left=2.5cm, bottom=2cm, top=2.5cm, paperwidth=20cm, paperheight=27cm, layoutwidth=19cm, layoutheight=26cm, layouthoffset=0.5cm, layoutvoffset=0.5cm, showcrop, asymmetric,headheight=24pt]{geometry}
\usepackage{fancyhdr}
\usepackage{tikz}
\usepackage{lipsum}

\pagestyle{fancy}
\renewcommand{\chaptermark}[1]{\markboth{#1}{}}
\fancyhead{}
\fancyfoot{}

\definecolor{grey}{rgb}{0.6,0.6,0.6}
\definecolor{darkgrey}{rgb}{0.4,0.4,0.4}

%\setlength{\headheight}{24pt}
\fancyhead[RO]{%
  \begin{tikzpicture}
    \node[inner xsep=0pt, align=right,text width=5cm] (a) {\sffamily\bfseries\textcolor{grey}
             {\leftmark}\hspace{0.3cm}\sffamily\textcolor{darkgrey}{\thepage}};
    \shade[left color=white, right color=black, dashed] (a.south west) rectangle
            ([yshift=0.01cm]a.south east);
  \end{tikzpicture}%
  }
\fancyhead[LE]{%
  \begin{tikzpicture}
    \node[inner xsep=0pt, align=left,text width=5cm](a){\sffamily\bfseries\textcolor{darkgrey}
     {\thepage}\hspace{0.3cm}\sffamily\textcolor{grey}{\leftmark}};
    \shade[right color=white, left color=black, dashed] (a.south west) rectangle
            ([yshift=0.01cm]a.south east);
  \end{tikzpicture}%
  }
\renewcommand{\headrulewidth}{0pt}
\renewcommand{\footrulewidth}{0pt}


\begin{document}

\chapter{Test chapter}
\lipsum
\lipsum

\end{document}