options - Increasing notebook magnification pushes output onto a new line

When I increase the notebook magnification beyond a certain level, it pushes the output of a command onto a newline.

It does this normally when you enter something like foo // FullForm, because Out[n]= gets replaced by Out[n]//FullForm=, which is so much wider that it has to start a newline for the output. But it's a shame that once n enters double-digits that at a certain magnification, the usual Out[n]= is just barely too wide, and this behavior occurs. Setting the magnification with

SetOptions[EvaluationNotebook[], Magnification -> 1.65]

is enough to get this behavior, but a magnification of 1.6 is still fine. Is there an easy way to avoid this behavior? Can we slightly increase the size of the margin where In[n]:= and Out[n]= live to avoid this issue?

I'm running Mathematica 11.0 in Linux x86 (64-bit), and apparently this is an issue on OS X too, but not on Windows.

Answer

You can increase the CellMargins for the styles "Input" and "Output" in your style sheet to accommodate the increased size of the cell labels. For example, the following setting:

CellMargins -> {{80, 10}, {10, 5}}

fixes the issue for me with a Magnification of 2.

---

If you don't want to mess around with editing the style sheet, you could evaluate the following instead:

SetOptions[
    EvaluationNotebook[],

    StyleDefinitions -> Notebook[{
        Cell[StyleData[StyleDefinitions->"Default.nb"]],
        Cell[StyleData["Input"],CellMargins->{{80,10},{10,5}}],
        Cell[StyleData["Output"],CellMargins->{{80,10},{10,5}}]
    }]
]