R C-R

Understood, but 6 months ago you were just being asked if you could upload a sample file to the Dropbox account Serif is paying for.

My point was simply that as @Fixx said, it is unlikely it would work with Affinity Photo & thus its purchase price would offer no value if that is the app one intended to use it with.

They don't "always" focus on any one thing, nor was my reply you quoted in any sense 'darker' than the one by @v_kyr I was replying to. Besides, there are always hurdles & barriers worth considering in any development process; it does not make much sense to ignore them.

It certainly was bulbous compared to the 2 seat coupe & the back seat was really only suitable for kids ... but considering the era & the price it still would have been a reasonably affordable & very stylish way to haul around a family of 4.

And only about twice the price of Affinity Photo, too.

I am not casting a dark cloud over anything, just pointing out a few of the things they have to consider that @v_kyr did not explicitly mention in the post I replied to. The OP seems to think both posts were worthy of a "Like" so I am not sure why you would consider either one particularly dark.

In addition to all that, the Affinity developers (& management) have to consider the relative merits of making any changes that would affect the native file format shared by all the Affinity apps or the original design goals like for (almost) realtime adjustments, panning, & zooming.

Beauty is in the eye of the beholder & all that, but I never thought the XJ-S was an ugly car. Its biggest stylistic 'sin' was that it was widely considered to be a unworthy successor to the iconic E-Type ... but there were people who thought that various versions of the E-Type were ugly too, like the 2+2 coupe or anything that departed even slightly from the original series one design, like the switch to headlights without covers to meet U.S. design regulations, etc.

In the very first Beginners Series tutorial ("Opening & Saving") watch carefully what the presenter selects at around the 0:55 mark & note its file extension. Does that answer your question?

Has Jaguar ever made one that wasn't?

FWIW, at least with macOS 10.13 you can access the Assistant Manager & from that the Develop Assistant without having to open a file if the toolbar includes the Assistant Options button. It may be necessary to customize it for that button to appear on the toolbar, but you can also do that without opening a file by right-clicking on the toolbar & choosing "Customize Toolbar ..." from the menu that pops up. Since I have not upgraded to 10.14, I don't know if this still works in that version, but I would like to know from someone running 10.14 if it does. TIA

But in practical terms, what can? That's what my next to last bullet point was about. One way or another, any practical implementation should at least render correctly for all zoom levels the app can support, be compatible with the native Affinity file format, not adversely affect performance, & ideally export to supported vector file formats without loss of accuracy.

I mentioned earlier that they have already said they would like to "do more" with circles, but that almost certainly requires replacing the Affinity bezier approximation of circular (& more generally elliptical) shapes with something that can be calculated more precisely. I think that in turn would require increasing the internal precision of the app's calculations, which I believe they have said is something on the order of 8 decimal points. From what I can tell from online calculators like this one, that would require increasing the internal precision substantially, but I don't have a clue about how much would be enough for fitting circles to 3 points & such. To get some idea about that, I made the assumption that whatever I paste into the Transform panel will be calculated to the equivalent of ~8 decimal points regardless of the display precision preference setting, & used the center point & radius values below from the online calculator to create the "Approx. circle" ellipse in the attached 3 point Circle fit.afdesign file. Assuming my methodology is sound (& my iMac & app are working correctly), at first it looks like a good fit. However, when I start to zoom in on a point in Outline View mode, it becomes increasingly obvious that somewhat greater internal precision would be required for a fit that would be visually accurate all the way down to the extreme zoom levels the Affinity apps are capable of. At 6000% the misfit is already clearly visible: At really extreme zoom levels like 2 million % the point & where the circle should touch it can't even be displayed on the screen at the same time. So I think this boils down to three things: How much more precision is enough to satisfy most users' needs? Is there a better way to provide it for these shapes that does not require increasing the internal precision for all calculations? Whatever the method, would it reduce the responsiveness of the Affinity apps to unacceptable levels? Any thoughts on that?

When you do that, the screenshot is pasted as an "(Image)" layer type (more about that here). To copy only the 'marching ants' selection (rectangular or otherwise) to paste that into some other document, you need to first rasterize the Image layer, which you can do with the Layer > Rasterize menu command or by right clicking on the Image layer in the Layers panel & selecting Rasterize from there.