UI: image with Absolute position don't render correctly

[mockersf]

Bevy version

main since #10690

What you did

Run example game_manu or overflow_debug

What went wrong

Images that have position_type: PositionType::Absolute in their style are not displayed correctly

[mockersf]

@nicoburns any idea?

[nicoburns]

Hmm... no that's weird. It looks like it's about the right size in the x axis but it's getting stretched by about a factor of 2 in the y axis :/

[bugsweeper]

That because width is set, but height isn't. If you remove width from style, you'll see big icons with correct proportions.

[bugsweeper]

@mockersf I set height same as width and got

correct result. Is this change good enough solution, or someone should dig deeper and figure out why taffy changed behaviour?

[bugsweeper]

For overflow_debug same thing: height is set, but width isn't. If add width: Val::Px(400.0),, then result

looks correct

[bugsweeper]

But if this solution gets approve, then I think we should add some notes to Migration guide, because such things could be in bevy users code

[bugsweeper]

Or better add some check/warning in bevy_ui::layout::convert::from_style(...) -> taffy::style::Style

[mockersf]

Is this change good enough solution, or someone should dig deeper and figure out why taffy changed behaviour?

No, images should keep their ratio when you set only one of their dimension

[nicoburns]

Yeah, this definitely ought to be fixed in Taffy and/or bevy_ui (wherever the bug is)

[bugsweeper]

@mockersf The problem hides in taffy, because at some point size fills None by measured_size which is done componentwise. So there Size(Some(45), None) becomes Size(Some(45), Some(100)) which has no correct ratio. Looks like there is no issue in taffy for such case.

[nicoburns]

I think the issue here is with the image measure function. It ought to read the image node's Style and use the size, min_size and max_size as part of it's computation. For most (all?) other "leaf" nodes this is automatically applied by Taffy, but that doesn't work for images because of their inherent aspect ratio.