Cfrgtkky

I would like to locate the exact position of the north west corner of the text area. Using layout (see image in Notes section), it seems that the required offset from current page.north west is

xshift=1.0in+hoffset+oddsidemargin,

yshift=-1.0in-voffset-headsep,

Using showframe package: (as in MWE)

The image below is the north west corner of the text area at 6400% zoom where I have placed a gray + and a filled in circle. This visually looks like it is pretty close to the correct location. However, to get to this position required an additional tweak of

(-0.35pt,2.35pt)%% Required shift to obtain image below (see MWE)

from the above parameters.

The somewhat related questions listed in the References section mention an issue with inner sep and parindent, both of which have been accounted for. (They are actually not needed here, but added them anyway).

Why is this additional tweak required?

Using showframe option to geometry package:

IF instead of using the showframe package, I instead use

usepackage[showframe]{geometry}

The tweak required is slightly different:

(-0.1pt,1.8pt)

which yields:

References:

• 
  TikZ: Anchor current page north west isn't where expected.


• 
  TikZ current page.north west shifted ~4pts?.

Notes:

• 
  

  Using layout, we obtain the following picture from which I obtained the parameters to compute the exact location of the north west of the text area.

  
  
  

  

  
  
  

  

  
  

Code:

documentclass{article}

usepackage{showframe}

usepackage{tikz}



usepackage{layout}

usepackage{geometry}



newcommand*{ShowNorthWestOfTextArea}{%

begin{tikzpicture}[remember picture, overlay]

    coordinate (X) at ([

            xshift=1.0in+hoffset+oddsidemargin-0.35pt,

            yshift=-1.0in-voffset-headsep+2.35pt,

        ]current page.north west);



    draw [draw=red, fill=yellow, text=gray] (X) circle (1pt)

        node [inner sep=0pt] {+};

end{tikzpicture}%

}%





begin{document}%layout% <-- uncomment to obtain the layout parameters

noindentShowNorthWestOfTextArea%

end{document}

Position of the text area relative to the page corner

The top of the layout image generally looks like the image below, but in your case the dashed line appears to coincide with the bottom of the header because ④ (topmargin = -13pt) and ⑤ (headheight = 12pt) nearly cancel out.

You can read off that the horizontal/vertical distance between the top left corner of the text with respect to the top left corner of the page are

horizontal distance = 1in+hoffset+oddsidemargin or 1in+hoffset+evensidemargin,

vertical distance = 1in+voffset+topmargin+headheight+headsep

(oddsidemargin is for single-sided documents and odd pages of double-sided documents, and evensidemargin for even pages of double-sided documents.)

Position of the text area relative to current page.north west

For TikZ, the coordinates of the top left corner of the text area are (w.r.t. current page.north west)

(1in+oddsidemargin, -1in-2voffset-topmargin-headheight-headsep)

for a single-sided document and odd pages of double-sided documents (and the same with evensidemargin for even pages of a double-sided document).

Note: I have no clue why you would need to add -2voffset to the y coordinate, but it seems like a bug.
Perhaps a sign error was made somewhere in the code when correcting for voffset?

Usually hoffset and voffset are both equal to zero, however, so this won't matter.

Here is a version of your MWE with the right parameters:

documentclass{article}

usepackage{showframe}

usepackage{tikz}



usepackage{geometry}



newcommand*{ShowNorthWestOfTextArea}{%

begin{tikzpicture}[remember picture, overlay]

    coordinate (X) at ([

            xshift=1.0in+oddsidemargin,

            yshift=-1.0in-2voffset-topmargin-headheight-headsep,

        ]current page.north west);



    draw [draw=red, fill=yellow, text=gray] (X) circle (1pt)

        node [inner sep=0pt] {+};

end{tikzpicture}%

}%



begin{document}



noindentShowNorthWestOfTextArea%



end{document}

Note that showframe draws a border around the text area.

The package tikzpagenodes provides a useful set of tikz coordinates for:

• current page text area


• current page marginpar area


• current page header area


• current page footer area

So, if tikzpagenodes is loaded then you can get the "north west corner of the text area" using
(current page text area.north west) from inside a tikzpicture environment. You will need to use remember picture,overlay for this to work.

Adapting the MWE from the question, we can use:

documentclass{article}

usepackage{showframe}

usepackage{tikz}

usepackage{tikzpagenodes}

usepackage{layout}

usepackage{geometry}



newcommand*{ShowNorthWestOfTextArea}{%

begin{tikzpicture}[remember picture, overlay]

  coordinate (X) at (current page text area.north west);



  draw [draw=red, fill=yellow, text=gray] (X) circle (1pt)

      node [inner sep=0pt] {+};

end{tikzpicture}%

}%





begin{document}%layout% <-- uncomment to obtain the layout parameters

  ShowNorthWestOfTextArea%

end{document}

With this code, the north west corner of the text area looks like: