Csdrhrt

When we use the macro title{Some Title}, the macro just assign the Some Text to another internal one @title as defined in latex.ltx:

deftitle#1{gdef@title{#1}}

We can use the @title in various places of document, for example, in hypersetup{pdftitle={@title}} for pdf-meta, or in some another places of an document. For example, if title looks like

title{The World Big Idea: with small corrections}.

The some places need to be shown as The World Big Idea: line break here with small corrections. But in some another places it should stand still in a single line.

How to redefine title or possible, any other good ideas?

documentclass{article}



title{Some Title}



    begin{document}



    makeatletter

        @title % One can use @title in different places

    makeatother



    makeatletter 

        %@title Here one need to use the same text, but with line breack between "Same" and "Tile"

        Some\Title

    makeatother

end{document}

Here is a naive idea.

Use a placeholder in the definition of @title via title and redefine that placeholder variable as required by the context.

documentclass{article}



newcommand*{mypossiblenewline}{newline}

title{Some mypossiblenewline Title}



begin{document}

makeatletter

  @title

makeatother



makeatletter 

  begingroup

  renewcommand*{mypossiblenewline}{}

  @title

  endgroup

makeatother

end{document}

You could wrap that up in one command, for example

makeatletter

DeclareRobustCommand*{sergiotitlenobreak}{%

  begingroup

  renewcommand*{mypossiblenewline}{}%

  @title

  endgroup

}

DeclareRobustCommand*{sergiotitlewithbreak}{%

  begingroup

  renewcommand*{mypossiblenewline}{newline}%

  @title

  endgroup

}

makeatother

but that would not be expandable (which could be a problem depending on the context).

Save two more variables, for lack of creativity I named them realtitle and inlinetitle. In the second one, \ tokens are substituted with spaces, first removing spaces at either side of \. Thus it is immaterial if you input any of

title{Some Title \ with line breaks}

title{Some Title\ with line breaks}

title{Some Title\with line breaks}

Here's the code.

documentclass{article}

usepackage{xparse}

usepackage{hyperref}



ExplSyntaxOn

RenewDocumentCommand{title}{m}

 {

  tl_gset:cn { @title } { #1 } % needed by maketitle

  tl_gset:Nn { realtitle } { #1 }

  seq_set_split:Nnn l_tmpa_seq { \ } { #1 }

  tl_gset:Nx inlinetitle { seq_use:Nn l_tmpa_seq { ~ } }

 }

ExplSyntaxOff



author{author}

title{Some Title \ with line breaks}



hypersetup{

  pdftitle=inlinetitle

}





begin{document}



maketitle



The title of this document is ``inlinetitle''.



begin{center}

realtitle

end{center}



end{document}

You can also cope with \[<dimen>]:

documentclass{article}

usepackage{xparse}

usepackage{hyperref}



ExplSyntaxOn

RenewDocumentCommand{title}{m}

 {

  tl_gset:cn { @title } { #1 } % needed by maketitle

  tl_gset:Nn { realtitle } { #1 }

  tl_set:Nn inlinetitle { #1 }

  regex_replace_all:nnN { s* c{\}([[^]]*])+ s* } {   } inlinetitle

 }

ExplSyntaxOff



author{author}

title{Some Title \[1ex] with line breaks \[1ex] and added spacing}



hypersetup{

  pdftitle=inlinetitle

}





begin{document}



maketitle



The title of this document is ``inlinetitle''.



begin{center}

realtitle

end{center}



end{document}

Different approach: instead of redefining @title, you can use texorpdfstring to specify two versions, one without linebreaks which will be used in the pdf meta data and one with linebreak to be displayed in the pdf

documentclass{article}



usepackage{hyperref}



title{texorpdfstring{Somenewline Title}{Some title}}



    begin{document}



    makeatletter

        @title % One can use @title in different places

    makeatother



end{document}