Android correct way to draw vector with stroke width

Imagine the drawable as a coordinate system with the point p(0,0) being on the top-left corner. Your x-axis goes from top-left to top-right and your y-axis goes from top-left to bottom-left.

When you're creating a path, it goes from one point to another point in the coordinate system. When you're stroking this path, the drawn line has some strokeWidth which is 1 by default. But when you set the width to, lets say 10, then the line is much thicker in your coordinate-system, but where should this "Thickness" go if your path is, for example already at y=0 ? The drawable won't display any negativate coordinates. That's why your drawable got cut-off.

The solution: add the strokeWidth to the coordinates, that are smaller than strokeWidth + subtract the strokeWidth from the coordinates, that are greater than your viewportWidth-strokeWidth and/or viewportHeight-strokeWidth + give spacing for edges that are at the borders of your viewport (in this example a extra spacing of 3 is fine)

So your code should look like this:

<?xml version="1.0" encoding="utf-8"?>
<vector xmlns:android="http://schemas.android.com/apk/res/android"
    android:width="1024dp"
    android:height="1024dp"
    android:viewportWidth="1024"
    android:viewportHeight="1024">
    <path
        android:pathData="M 13,13 L 50,13 L 50,50 z"
        android:strokeColor="#000000"
        android:strokeWidth="10"/>
</vector>