Canvas size is hard-coded in pixels, so it can't work at the same time on bigger and smaller screens
Open a page on mobile device, or use device simulation mode - field doesn't fit the screen
Use the solution suggested in https://github.com/szimek/signature_pad/issues/268 and set the canvas size in signature.js
This also would make configuration parameters width and height optional
Right the patch
Signature field displayed correctly on both small and big screens
Configuration parameters width and height become optional
Active
1.0
Code
Giving the canvas a width of 100% would result in signature images of various widths (since the image is as wide as the canvas).
This may give some unwanted side effects, so I'd propose to allow an admin to specify the width in % and thus explicitly enable this behavior. I'd keep the height as a required and fixed value, not sure why you suggest it would become optional?