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

I want to use TikZ page anchors to draw a sheet with a mix of text and graphics. So I started with a simple rectangle that would cover the entire page:

\fill[red] (current page.north west) rectangle (current page.south east);


Except it doesn't, there's a white space on the left of the pdf.

Here is my MWE:

\documentclass[oneside]{scrartcl}
\usepackage{tikz}
\usepackage[margin=0cm]{geometry}

\begin{document}
\tikz
\fill[red] (current page.north west) rectangle (current page.south east);
\end{document}


The result is a red rectangle shifted horizontally by a small distance to the right.

My research to a solution led me to this seemingly similar issue on TeX: TikZ current page.north west shifted ~4pts?

But it doesn't seem to apply (I've tried blindly something like, and then with stuff like inner sep=-4pts):

\fill[red] (current page.north west)[inner sep=0pt] rectangle (current page.south east);


A lot of the suggested link also seemed promising but I found no answer after going through them.

So my question is:

Why don't I have a nice red rectangle covering the whole page?

Optional question: Can I fix it to keep a somewhat natural syntax (I want (current page.north west) rectangle (current page.south east); to be the whole page) ?

There is a paragraph indentation. The white space is gone with \noindent:

\documentclass[oneside]{scrartcl}
\usepackage{tikz}
\usepackage[margin=0cm]{geometry}

\begin{document}
\noindent
\tikz
\fill[red] (current page.north west) rectangle (current page.south east);
\end{document}


Use the overlay and remember picture key:

\documentclass[oneside]{scrartcl}
\usepackage{tikz}
\usepackage[margin=0cm]{geometry}

\begin{document}
\tikz[remember picture,overlay]
\fill[red] (current page.north west) rectangle (current page.south east);
\end{document}