RFR: 8295078: TextField blurry when inside an TitledPane -> AnchorPane [v3]

[Kevin Rushforth]

On Tue, 8 Nov 2022 21:13:27 GMT, Kevin Rushforth <kcr at openjdk.org> wrote:

>> I think the idea is this (and it only applies when snapToPixels=true).  We only need to use snapped coordinates/sizes when placing components.  In order to avoid accumulating errors, which can be seen during gradual resizing for example, we should avoid snapping of intermediary results, UNLESS there is a possibility of introducing visual artifacts.
>> 
>> What I mean by this is imagine a container that aligns its children in a table-like layout (similar to https://github.com/andy-goryachev/FxDock/blob/master/doc/CPane.md).  Depending on constraints, there might be a situation where rounding might shift certain children in relation to the vertical guide lines - we don't want that.
>> 
>> So in this case we need to snap the guide lines as an intermediate step (i.e. compute the first guide line position, then compute the next column, snap, next column, etc.)
>> 
>> Whereas in a simple case (one child node), we can simply use snapped*Inset() - we don't have intermediate computations.
>> 
>> In the case of AnchorPane, I think, we should first sum insets and anchor, then snap - because developers might want to use or not to use snapToPixels, and might set a fractional anchor.
>
> I initially had the same thought that Andy had, but I want to take a closer look -- especially at what similar layout panes do.
> 
> As for the point about doing this only when `snapPixels == true`, yes, but you don't need to worry about that if you call the `snapXXX` methods in Region. All of them check the `snapToPixel` attribute.

I looked at the other layout panes and they already do something similar to what this PR does, using the snapped insets for intermediate compuation. I also note that some of the computation is calling superclass methods that do snapping already, and expect it to be added to snapped insets (if there are insets), for example, `computeWidth()`. In this particular case -- `snappedLeftInset() + leftAnchor` -- I don't think `leftAnchor` is snapped, but it probably should be.

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PR: https://git.openjdk.org/jfx/pull/910