Drawing vs. canvas alignment

[HanzPetrov]

Hi Ollie,

Although only really noticeable when working with small drawing sizes, the drawing and canvas appear to be misaligned. I suspect that this has something to do with stroke coordinates vs. pixel coordinates (corner vs. centre of pixel) - and it may be desired behaviour - but my WYSIWYG expectation would be to have stroke start and end points aligned with pixel centres.

Observed:

Expected:

I have kluged a fix (based on the idea that the misalignment is always equal to one-half pixel), but will hold off on a PR, since this might throw off GCode expections, or have other unintended consequences. Any thoughts welcome.

PS. Brilliant work refactoring Scott’s code, developing an elegant GUI, and adding loads of great new features and PFMs!

[SonarSonic]

Hello!
Thanks for your work and for spotting this!
I added some thoughts to your commits :)