Auto cross axis margins are ignored in wrapping containers and baseline rows

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Evaluación

Dificultad
4/5
Tiempo estimado
3-5 días
Aptitud para principiantes
56/100
Tipo de issue
Error
Claridad
Bastante claro
Estado de actividad
Activo
Stack tecnológico
cpp
Área
backend

Línea de trabajo

Start in CalculateLayout.cpp at STEP 8, which the report identifies as overwriting cross-axis positions set by STEP 7 when items have auto margins. Read the related Flexbox steps cited in the issue and compare the reported wrap and baseline cases. Add the described cases as gentest fixtures and verify their cross positions and sizes match the expected values.

Escrito por el modelo de indexación a partir del texto del issue.

Descripción

Report

Issues and Steps to Reproduce

With flexWrap: 'wrap' or 'wrap-reverse', or in a row where any item uses baseline alignment, cross axis auto margins are ignored.

Take a row 200 wide with children 50x50 and 50x10, the second with marginTop: 'auto', and read the second child's top under each alignItems. For the baseline column there is no wrap and the first child has alignSelf: 'baseline'.

Expected Behavior

Top 40 in every case, as without wrap. Following CSS Flexbox 1 (9.4 steps 8 and 11, 9.6 steps 13 and 14), auto margins take the line's free space, and such an item is not stretched, baseline aligned or aligned by align-self.

Actual Behavior

alignItems no wrap wrap baseline expected
flex-start 40 0 0 40
center 40 20 20 40
flex-end 40 40 40 40
stretch 40 0 0 40

With wrap, marginBottom: 'auto' or both margins auto give the same column (expected 0 and 20), and under stretch a second child with no height gets top 0 and height 50 (expected top 50, height 0). alignItems: 'baseline' with marginBottom: 'auto' gives 40 (expected 0). YGErrataAll and YGErrataNone agree.

The cause is STEP 8 in CalculateLayout.cpp, which runs in both cases. It sets each item's cross position from its alignment with auto margins as 0, overwriting STEP 7's offset. Found in #2045.

Link to Code

The trees above use only the public C API, and I can add them as gentest fixtures with a fix.

Lenguaje dominante
C++
Estrellas
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Forks
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Merge medio
2 d 5 h
PR fusionados (30 d)
12

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