How do browsers calculate media print width in pixels?

Question

Android

Typesetting html with sizes in pt is not suitable.
Need 1/203 inch accuracy.
The only hope for px, but it is not clear with them, it seems that everyone thinks in their own way.
in the question, PX is a unit, the size of the smallest dot that can be drawn
. The logical assumption that the px size for printing would be 1/75 is not supported. Browsers consider
that A4 in width is something from 7xx to 8xx.
What I want is that the
layout on the printer, on the phone screen and on the computer is the same, not in physical dimensions, but in appearance (
number of letters per line and, for example, in a table cell)
In Android, canvas resolution 1pt = 1/72 inch.
Those. if we just put Point() it will be 1/72 by 1/72
The thermal printer only has 384 dots per line. The actual density is 1/203.
If we describe the media with actual density, then existing
programs will draw only 137 pixels
, resulting in sharp printing at 1/3 of the width, or blurring at the full width.
The best result is obtained when the roll is described at 72dpi and 1/2 inch margins.
Unit of measure is millis 1/1000 of an inch field
formula calculation
+ 1000 * dots_in_the_printer_matrix / 72
1000 + 1000 * 384 / 72 is converted to type integer . Alas, we lose a few points for rounding.
why not a constant, so in addition to 384, there is also 560 and in general the manufacturer can produce
a model with any number of points (a multiple of 8, if he is not a complete pervert)
This description as a result allows you to print at full resolution. There are very few points and they should all work.
Drawing by means of android becomes simple, the only amendment
is 1pt = 1dot
I took the dimensions from the canvas and you know how many points are available to you.
But how to make the WebView understand correctly?