Should Force Pixel Alignment override Snap to Spread Mid Points?

[GarryP]

See attached video for an example.
With Force Pixel Alignment set to ON and Snap to Spread Mid Points set to OFF all is okay.
However, switching Snap to Spread Mid Points to ON allows me to move the layer to where the pixel alignment is not being forced.
Is this what most people would expect, or does it seem ‘wrong’ in some way?

Note: I've only checked this in the current commercial release of Photo.

[firstdefence]

I get Force Pixel Alignment override with this combo...

Turning off Snap To Grid gets Force Pixel Alignment back, I wish Snapping had a panel instead of or as well as a dropdown menu.

[firstdefence]

With this snapping combo I still retain Force Pixel Alignment.

[Alfred]

I’ve long complained about ‘Force pixel alignment’ being overridden by the ‘Move by whole pixels’ child option, but I think there’s a good argument for having it take precedence over everything else.

[Pšenda]

2 hours ago, Alfred said:

I’ve long complained about ‘Force pixel alignment’ being overridden by the ‘Move by whole pixels’ child option, but I think there’s a good argument for having it take precedence over everything else.

I think it's a shame and it's very confusing for users that the criteria for snapping do not respect the "stack ordering" in which they are listed on the Snapping panel. For example, the mentioned "Force pixel alignment" is visually clearly superior to "Move by whole pixels", but in reality it works differently. This also applies to "Spread Mid Points", which is visually below "Force pixel alignment".

In order for some parameters and criteria to be truly universal and to suit everyone, it would be necessary to be able to define their priority, because some options are complementary, but some are excluded.

[GarryP]

Without wanting to get into the “does Force Pixel Alignment actually force pixel alignment” issue, I’m hoping that one of the team will see this and chip in with an official opinion.
Whether this is expected behaviour or not, it would be nice to know what the priorities of forcing/snapping are so we can have some idea of what should be happening.

[MEB]

Hi GarryP,
You have built an edge case on purpose to show two conflicting settings clash in specific circumstances. What's the purpose of the the project/work? If you want to work with pixel aligned stuff then align to spread's middle points is a bit irrelevant. If you still wanted to enforce the spread middle point alignment (for whatever reason) and force pixel alignment simultaneously then you could have picked a proper/more adequate canvas size (21x21px rather than 20x20). The only actual use case where these settings collide (with object bounding box mid points more than spreads) is when aligning stuff for web/UI interfaces where the object you are trying to align to doesn't have an even width or height (for example one object with 11px and another with 6px) - but in those cases, to what side the object you are trying to align to should the app mismatch/go? Left or right? Currently we leave up to you to decide rather than picking one automatically just to enforce the pixel alignment setting.

[GarryP]

I didn’t create this on purpose, I found it entirely by accident while trying to answer someone else’s question on a slightly unrelated subject (the ‘age-old’ subject of blurred pixels on layers which are not on pixel boundaries).
I realise that it’s quite obvious what’s happening in this case as the document has such small dimensions but a worry I had was when the user has the same ‘issue’ in a document with much larger dimensions where the snap isn’t as obvious. They might think that the layer they are moving is being forced to pixel boundaries when it might actually not be. The number of cases where this would be a problem are probably very small but I thought it was worth asking the question and seeing what the general consensus (and official line) was.
I can understand your points about giving the user control (responsibility) over what they want to do rather than ignoring their choices.
If all is working as expected then that’s fine with me, and there’s always the “Pixel Work” preset (but I can’t remember if I added that myself or not).