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Fixup hack for flex line size calculation #39433

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Summary:
Back when rolling out flex gap, we encountered a bug where gap was added to the end of the main axis when a size was not specified.

During flex line justification/sizing, we calculate the amount of space that should be in between children. We erroneously add this, even after the last child element.

For justify-content, this space between children is derived from free space along the axis. The only time we have free space is if we had a dimension/dimension constraint already set on the parent. In this case, the extra space added to the end of the flex line is never noticed, becasue we bound maxLineMainDim to container dimension constraints at the end of layout, and the error doesn't effect how any children are positioned or sized.

betweenMainDim may still be set for gap even if we don't have a sized parent, which makes the extra space propagated to maxLineMainDim effect parent size.

Because we were in a code freeze, I opted to have us go with a solution just effecting flex gap, instead of the right one, in case there were any side effects. This cleans up the code to use the right calculation everywhere, and fixes a separate bug, where endOfLineIndex and startOfLineIndex may not be the last/first in the line if they are out of the layout flow (absolutely positioned, or display: none_

See the original conversation on facebook/yoga#1188

Differential Revision: D49260049

@facebook-github-bot facebook-github-bot added CLA Signed This label is managed by the Facebook bot. Authors need to sign the CLA before a PR can be reviewed. p: Facebook Partner: Facebook Partner fb-exported labels Sep 14, 2023
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This pull request was exported from Phabricator. Differential Revision: D49260049

NickGerleman added a commit to NickGerleman/yoga that referenced this pull request Sep 14, 2023
Summary:
X-link: facebook/react-native#39433

Back when rolling out flex gap, we encountered a bug where gap was added to the end of the main axis when a size was not specified.

During flex line justification/sizing, we calculate the amount of space that should be in between children. We erroneously add this, even after the last child element.

For `justify-content`, this space between children is derived from free space along the axis. The only time we have free space is if we had a dimension/dimension constraint already set on the parent. In this case, the extra space added to the end of the flex line is never noticed, becasue we bound `maxLineMainDim` to container dimension constraints at the end of layout, and the error doesn't effect how any children are positioned or sized.

`betweenMainDim` may still be set for `gap` even if we don't have a sized parent, which makes the extra space propagated to `maxLineMainDim` effect parent size.

Because we were in a code freeze, I opted to have us go with a solution just effecting flex gap, instead of the right one, in case there were any side effects. This cleans up the code to use the right calculation everywhere, and fixes a separate bug, where `endOfLineIndex` and `startOfLineIndex` may not be the last/first in the line if they are out of the layout flow (absolutely positioned, or display: none_

See the original conversation on facebook#1188

Differential Revision: D49260049
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analysis-bot commented Sep 14, 2023

Platform Engine Arch Size (bytes) Diff
android hermes arm64-v8a 8,329,199 -24
android hermes armeabi-v7a n/a --
android hermes x86 n/a --
android hermes x86_64 n/a --
android jsc arm64-v8a 9,567,997 +19
android jsc armeabi-v7a n/a --
android jsc x86 n/a --
android jsc x86_64 n/a --

Base commit: 196d9f9
Branch: main

NickGerleman added a commit to NickGerleman/yoga that referenced this pull request Sep 14, 2023
Summary:

X-link: facebook/react-native#39433

Back when rolling out flex gap, we encountered a bug where gap was added to the end of the main axis when a size was not specified.

During flex line justification/sizing, we calculate the amount of space that should be in between children. We erroneously add this, even after the last child element.

For `justify-content`, this space between children is derived from free space along the axis. The only time we have free space is if we had a dimension/dimension constraint already set on the parent. In this case, the extra space added to the end of the flex line is never noticed, becasue we bound `maxLineMainDim` to container dimension constraints at the end of layout, and the error doesn't effect how any children are positioned or sized.

`betweenMainDim` may still be set for `gap` even if we don't have a sized parent, which makes the extra space propagated to `maxLineMainDim` effect parent size.

Because we were in a code freeze, I opted to have us go with a solution just effecting flex gap, instead of the right one, in case there were any side effects. This cleans up the code to use the right calculation everywhere, and fixes a separate bug, where `endOfLineIndex` and `startOfLineIndex` may not be the last/first in the line if they are out of the layout flow (absolutely positioned, or display: none_

See the original conversation on facebook#1188

Reviewed By: javache

Differential Revision: D49260049
NickGerleman added a commit to NickGerleman/react-native that referenced this pull request Sep 14, 2023
Summary:
X-link: facebook/yoga#1380


Back when rolling out flex gap, we encountered a bug where gap was added to the end of the main axis when a size was not specified.

During flex line justification/sizing, we calculate the amount of space that should be in between children. We erroneously add this, even after the last child element.

For `justify-content`, this space between children is derived from free space along the axis. The only time we have free space is if we had a dimension/dimension constraint already set on the parent. In this case, the extra space added to the end of the flex line is never noticed, becasue we bound `maxLineMainDim` to container dimension constraints at the end of layout, and the error doesn't effect how any children are positioned or sized.

`betweenMainDim` may still be set for `gap` even if we don't have a sized parent, which makes the extra space propagated to `maxLineMainDim` effect parent size.

Because we were in a code freeze, I opted to have us go with a solution just effecting flex gap, instead of the right one, in case there were any side effects. This cleans up the code to use the right calculation everywhere, and fixes a separate bug, where `endOfLineIndex` and `startOfLineIndex` may not be the last/first in the line if they are out of the layout flow (absolutely positioned, or display: none_

See the original conversation on facebook/yoga#1188

Reviewed By: javache

Differential Revision: D49260049
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This pull request was exported from Phabricator. Differential Revision: D49260049

NickGerleman added a commit to NickGerleman/yoga that referenced this pull request Sep 14, 2023
Summary:

X-link: facebook/react-native#39433

Back when rolling out flex gap, we encountered a bug where gap was added to the end of the main axis when a size was not specified.

During flex line justification/sizing, we calculate the amount of space that should be in between children. We erroneously add this, even after the last child element.

For `justify-content`, this space between children is derived from free space along the axis. The only time we have free space is if we had a dimension/dimension constraint already set on the parent. In this case, the extra space added to the end of the flex line is never noticed, becasue we bound `maxLineMainDim` to container dimension constraints at the end of layout, and the error doesn't effect how any children are positioned or sized.

`betweenMainDim` may still be set for `gap` even if we don't have a sized parent, which makes the extra space propagated to `maxLineMainDim` effect parent size.

Because we were in a code freeze, I opted to have us go with a solution just effecting flex gap, instead of the right one, in case there were any side effects. This cleans up the code to use the right calculation everywhere, and fixes a separate bug, where `endOfLineIndex` and `startOfLineIndex` may not be the last/first in the line if they are out of the layout flow (absolutely positioned, or display: none_

See the original conversation on facebook#1188

Reviewed By: javache

Differential Revision: D49260049
NickGerleman added a commit to NickGerleman/react-native that referenced this pull request Sep 14, 2023
Summary:
X-link: facebook/yoga#1380


Back when rolling out flex gap, we encountered a bug where gap was added to the end of the main axis when a size was not specified.

During flex line justification/sizing, we calculate the amount of space that should be in between children. We erroneously add this, even after the last child element.

For `justify-content`, this space between children is derived from free space along the axis. The only time we have free space is if we had a dimension/dimension constraint already set on the parent. In this case, the extra space added to the end of the flex line is never noticed, becasue we bound `maxLineMainDim` to container dimension constraints at the end of layout, and the error doesn't effect how any children are positioned or sized.

`betweenMainDim` may still be set for `gap` even if we don't have a sized parent, which makes the extra space propagated to `maxLineMainDim` effect parent size.

Because we were in a code freeze, I opted to have us go with a solution just effecting flex gap, instead of the right one, in case there were any side effects. This cleans up the code to use the right calculation everywhere, and fixes a separate bug, where `endOfLineIndex` and `startOfLineIndex` may not be the last/first in the line if they are out of the layout flow (absolutely positioned, or display: none_

See the original conversation on facebook/yoga#1188

Reviewed By: javache

Differential Revision: D49260049
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This pull request was exported from Phabricator. Differential Revision: D49260049

NickGerleman added a commit to NickGerleman/react-native that referenced this pull request Sep 15, 2023
Summary:
X-link: facebook/yoga#1380


Back when rolling out flex gap, we encountered a bug where gap was added to the end of the main axis when a size was not specified.

During flex line justification/sizing, we calculate the amount of space that should be in between children. We erroneously add this, even after the last child element.

For `justify-content`, this space between children is derived from free space along the axis. The only time we have free space is if we had a dimension/dimension constraint already set on the parent. In this case, the extra space added to the end of the flex line is usually never noticed, because we bound `maxLineMainDim` to container dimension constraints at the end of layout, and the error doesn't effect how any children are positioned or sized.

There was at least one screenshot test where this issue showed up though, and I was able to add a slightly different repro where we may have free space without a definite dimension by enforcing a min dimension and not stretching.

{F1091401183}

The new reference is correct, and looking back at diffs, is what this seemed to originally look like when added three years ago. Seems like there may have been a potential regression, but I didn't spot anything suspicious when I looked around the code history.


`betweenMainDim` may still be set for `gap` even if we don't have a sized parent, which makes the extra space propagated to `maxLineMainDim` effect parent size.

Because we were in a code freeze, I opted to have us go with a solution just effecting flex gap, instead of the right one, in case there were any side effects. This cleans up the code to use the right calculation everywhere, and fixes a separate bug, where `endOfLineIndex` and `startOfLineIndex` may not be the last/first in the line if they are out of the layout flow (absolutely positioned, or display: none_

See the original conversation on facebook/yoga#1188

Reviewed By: javache

Differential Revision: D49260049
@facebook-github-bot
Copy link
Contributor

This pull request was exported from Phabricator. Differential Revision: D49260049

NickGerleman added a commit to NickGerleman/yoga that referenced this pull request Sep 15, 2023
Summary:

X-link: facebook/react-native#39433

Back when rolling out flex gap, we encountered a bug where gap was added to the end of the main axis when a size was not specified.

During flex line justification/sizing, we calculate the amount of space that should be in between children. We erroneously add this, even after the last child element.

For `justify-content`, this space between children is derived from free space along the axis. The only time we have free space is if we had a dimension/dimension constraint already set on the parent. In this case, the extra space added to the end of the flex line is usually never noticed, because we bound `maxLineMainDim` to container dimension constraints at the end of layout, and the error doesn't effect how any children are positioned or sized.

There was at least one screenshot test where this issue showed up though, and I was able to add a slightly different repro where we may have free space without a definite dimension by enforcing a min dimension and not stretching.

{F1091401183}

The new reference is correct, and looking back at diffs, is what this seemed to originally look like when added three years ago. Seems like there may have been a potential regression, but I didn't spot anything suspicious when I looked around the code history.


`betweenMainDim` may still be set for `gap` even if we don't have a sized parent, which makes the extra space propagated to `maxLineMainDim` effect parent size.

Because we were in a code freeze, I opted to have us go with a solution just effecting flex gap, instead of the right one, in case there were any side effects. This cleans up the code to use the right calculation everywhere, and fixes a separate bug, where `endOfLineIndex` and `startOfLineIndex` may not be the last/first in the line if they are out of the layout flow (absolutely positioned, or display: none_

See the original conversation on facebook#1188

Reviewed By: javache

Differential Revision: D49260049
NickGerleman added a commit to NickGerleman/yoga that referenced this pull request Sep 15, 2023
Summary:

X-link: facebook/react-native#39433

Back when rolling out flex gap, we encountered a bug where gap was added to the end of the main axis when a size was not specified.

During flex line justification/sizing, we calculate the amount of space that should be in between children. We erroneously add this, even after the last child element.

For `justify-content`, this space between children is derived from free space along the axis. The only time we have free space is if we had a dimension/dimension constraint already set on the parent. In this case, the extra space added to the end of the flex line is usually never noticed, because we bound `maxLineMainDim` to container dimension constraints at the end of layout, and the error doesn't effect how any children are positioned or sized.

There was at least one screenshot test where this issue showed up though, and I was able to add a slightly different repro where we may have free space without a definite dimension by enforcing a min dimension and not stretching.

{F1091401183}

The new reference is correct, and looking back at diffs, is what this seemed to originally look like when added three years ago. Seems like there may have been a potential regression, but I didn't spot anything suspicious when I looked around the code history.


`betweenMainDim` may still be set for `gap` even if we don't have a sized parent, which makes the extra space propagated to `maxLineMainDim` effect parent size.

Because we were in a code freeze, I opted to have us go with a solution just effecting flex gap, instead of the right one, in case there were any side effects. This cleans up the code to use the right calculation everywhere, and fixes a separate bug, where `endOfLineIndex` and `startOfLineIndex` may not be the last/first in the line if they are out of the layout flow (absolutely positioned, or display: none_

See the original conversation on facebook#1188

Reviewed By: javache

Differential Revision: D49260049
NickGerleman added a commit to NickGerleman/react-native that referenced this pull request Sep 15, 2023
Summary:
X-link: facebook/yoga#1380


Back when rolling out flex gap, we encountered a bug where gap was added to the end of the main axis when a size was not specified.

During flex line justification/sizing, we calculate the amount of space that should be in between children. We erroneously add this, even after the last child element.

For `justify-content`, this space between children is derived from free space along the axis. The only time we have free space is if we had a dimension/dimension constraint already set on the parent. In this case, the extra space added to the end of the flex line is usually never noticed, because we bound `maxLineMainDim` to container dimension constraints at the end of layout, and the error doesn't effect how any children are positioned or sized.

There was at least one screenshot test where this issue showed up though, and I was able to add a slightly different repro where we may have free space without a definite dimension by enforcing a min dimension and not stretching.

{F1091401183}

The new reference is correct, and looking back at diffs, is what this seemed to originally look like when added three years ago. Seems like there may have been a potential regression, but I didn't spot anything suspicious when I looked around the code history.


`betweenMainDim` may still be set for `gap` even if we don't have a sized parent, which makes the extra space propagated to `maxLineMainDim` effect parent size.

Because we were in a code freeze, I opted to have us go with a solution just effecting flex gap, instead of the right one, in case there were any side effects. This cleans up the code to use the right calculation everywhere, and fixes a separate bug, where `endOfLineIndex` and `startOfLineIndex` may not be the last/first in the line if they are out of the layout flow (absolutely positioned, or display: none_

See the original conversation on facebook/yoga#1188

Reviewed By: javache

Differential Revision: D49260049
@facebook-github-bot
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This pull request was exported from Phabricator. Differential Revision: D49260049

NickGerleman added a commit to NickGerleman/yoga that referenced this pull request Sep 15, 2023
Summary:

X-link: facebook/react-native#39433

Back when rolling out flex gap, we encountered a bug where gap was added to the end of the main axis when a size was not specified.

During flex line justification/sizing, we calculate the amount of space that should be in between children. We erroneously add this, even after the last child element.

For `justify-content`, this space between children is derived from free space along the axis. The only time we have free space is if we had a dimension/dimension constraint already set on the parent. In this case, the extra space added to the end of the flex line is usually never noticed, because we bound `maxLineMainDim` to container dimension constraints at the end of layout, and the error doesn't effect how any children are positioned or sized.

There was at least one screenshot test where this issue showed up though, and I was able to add a slightly different repro where we may have free space without a definite dimension by enforcing a min dimension and not stretching.

{F1091401183}

The new reference is correct, and looking back at diffs, is what this seemed to originally look like when added three years ago. Seems like there may have been a potential regression, but I didn't spot anything suspicious when I looked around the code history.


`betweenMainDim` may still be set for `gap` even if we don't have a sized parent, which makes the extra space propagated to `maxLineMainDim` effect parent size.

Because we were in a code freeze, I opted to have us go with a solution just effecting flex gap, instead of the right one, in case there were any side effects. This cleans up the code to use the right calculation everywhere, and fixes a separate bug, where `endOfLineIndex` and `startOfLineIndex` may not be the last/first in the line if they are out of the layout flow (absolutely positioned, or display: none_

See the original conversation on facebook#1188

Reviewed By: javache

Differential Revision: D49260049
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This pull request was exported from Phabricator. Differential Revision: D49260049

NickGerleman added a commit to NickGerleman/react-native that referenced this pull request Sep 15, 2023
Summary:
X-link: facebook/yoga#1380


Back when rolling out flex gap, we encountered a bug where gap was added to the end of the main axis when a size was not specified.

During flex line justification/sizing, we calculate the amount of space that should be in between children. We erroneously add this, even after the last child element.

For `justify-content`, this space between children is derived from free space along the axis. The only time we have free space is if we had a dimension/dimension constraint already set on the parent. In this case, the extra space added to the end of the flex line is usually never noticed, because we bound `maxLineMainDim` to container dimension constraints at the end of layout, and the error doesn't effect how any children are positioned or sized.

There was at least one screenshot test where this issue showed up though, and I was able to add a slightly different repro where we may have free space without a definite dimension by enforcing a min dimension and not stretching.

{F1091401183}

The new reference is correct, and looking back at diffs, is what this seemed to originally look like when added three years ago. Seems like there may have been a potential regression, but I didn't spot anything suspicious when I looked around the code history.


`betweenMainDim` may still be set for `gap` even if we don't have a sized parent, which makes the extra space propagated to `maxLineMainDim` effect parent size.

Because we were in a code freeze, I opted to have us go with a solution just effecting flex gap, instead of the right one, in case there were any side effects. This cleans up the code to use the right calculation everywhere, and fixes a separate bug, where `endOfLineIndex` and `startOfLineIndex` may not be the last/first in the line if they are out of the layout flow (absolutely positioned, or display: none_

See the original conversation on facebook/yoga#1188

Reviewed By: javache

Differential Revision: D49260049
NickGerleman added a commit to NickGerleman/yoga that referenced this pull request Sep 15, 2023
Summary:

X-link: facebook/react-native#39433

Back when rolling out flex gap, we encountered a bug where gap was added to the end of the main axis when a size was not specified.

During flex line justification/sizing, we calculate the amount of space that should be in between children. We erroneously add this, even after the last child element.

For `justify-content`, this space between children is derived from free space along the axis. The only time we have free space is if we had a dimension/dimension constraint already set on the parent. In this case, the extra space added to the end of the flex line is usually never noticed, because we bound `maxLineMainDim` to container dimension constraints at the end of layout, and the error doesn't effect how any children are positioned or sized.

There was at least one screenshot test where this issue showed up though, and I was able to add a slightly different repro where we may have free space without a definite dimension by enforcing a min dimension and not stretching.

{F1091401183}

The new reference is correct, and looking back at diffs, is what this seemed to originally look like when added three years ago. Seems like there may have been a potential regression, but I didn't spot anything suspicious when I looked around the code history.


`betweenMainDim` may still be set for `gap` even if we don't have a sized parent, which makes the extra space propagated to `maxLineMainDim` effect parent size.

Because we were in a code freeze, I opted to have us go with a solution just effecting flex gap, instead of the right one, in case there were any side effects. This cleans up the code to use the right calculation everywhere, and fixes a separate bug, where `endOfLineIndex` and `startOfLineIndex` may not be the last/first in the line if they are out of the layout flow (absolutely positioned, or display: none_

See the original conversation on facebook#1188

Reviewed By: javache

Differential Revision: D49260049
@facebook-github-bot
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This pull request was exported from Phabricator. Differential Revision: D49260049

NickGerleman added a commit to NickGerleman/react-native that referenced this pull request Sep 15, 2023
Summary:
X-link: facebook/yoga#1380


Back when rolling out flex gap, we encountered a bug where gap was added to the end of the main axis when a size was not specified.

During flex line justification/sizing, we calculate the amount of space that should be in between children. We erroneously add this, even after the last child element.

For `justify-content`, this space between children is derived from free space along the axis. The only time we have free space is if we had a dimension/dimension constraint already set on the parent. In this case, the extra space added to the end of the flex line is usually never noticed, because we bound `maxLineMainDim` to container dimension constraints at the end of layout, and the error doesn't effect how any children are positioned or sized.

There was at least one screenshot test where this issue showed up though, and I was able to add a slightly different repro where we may have free space without a definite dimension by enforcing a min dimension and not stretching.

{F1091401183}

The new reference is correct, and looking back at diffs, is what this seemed to originally look like when added three years ago. Seems like there may have been a potential regression, but I didn't spot anything suspicious when I looked around the code history.


`betweenMainDim` may still be set for `gap` even if we don't have a sized parent, which makes the extra space propagated to `maxLineMainDim` effect parent size.

Because we were in a code freeze, I opted to have us go with a solution just effecting flex gap, instead of the right one, in case there were any side effects. This cleans up the code to use the right calculation everywhere, and fixes a separate bug, where `endOfLineIndex` and `startOfLineIndex` may not be the last/first in the line if they are out of the layout flow (absolutely positioned, or display: none_

See the original conversation on facebook/yoga#1188

Reviewed By: javache

Differential Revision: D49260049
Summary:
X-link: facebook/yoga#1380


Back when rolling out flex gap, we encountered a bug where gap was added to the end of the main axis when a size was not specified.

During flex line justification/sizing, we calculate the amount of space that should be in between children. We erroneously add this, even after the last child element.

For `justify-content`, this space between children is derived from free space along the axis. The only time we have free space is if we had a dimension/dimension constraint already set on the parent. In this case, the extra space added to the end of the flex line is usually never noticed, because we bound `maxLineMainDim` to container dimension constraints at the end of layout, and the error doesn't effect how any children are positioned or sized.

There was at least one screenshot test where this issue showed up though, and I was able to add a slightly different repro where we may have free space without a definite dimension by enforcing a min dimension and not stretching.

{F1091401183}

The new reference is correct, and looking back at diffs, is what this seemed to originally look like when added three years ago. Seems like there may have been a potential regression, but I didn't spot anything suspicious when I looked around the code history.


`betweenMainDim` may still be set for `gap` even if we don't have a sized parent, which makes the extra space propagated to `maxLineMainDim` effect parent size.

Because we were in a code freeze, I opted to have us go with a solution just effecting flex gap, instead of the right one, in case there were any side effects. This cleans up the code to use the right calculation everywhere, and fixes a separate bug, where `endOfLineIndex` and `startOfLineIndex` may not be the last/first in the line if they are out of the layout flow (absolutely positioned, or display: none_

See the original conversation on facebook/yoga#1188

Reviewed By: javache

Differential Revision: D49260049
NickGerleman added a commit to NickGerleman/yoga that referenced this pull request Sep 15, 2023
Summary:

X-link: facebook/react-native#39433

Back when rolling out flex gap, we encountered a bug where gap was added to the end of the main axis when a size was not specified.

During flex line justification/sizing, we calculate the amount of space that should be in between children. We erroneously add this, even after the last child element.

For `justify-content`, this space between children is derived from free space along the axis. The only time we have free space is if we had a dimension/dimension constraint already set on the parent. In this case, the extra space added to the end of the flex line is usually never noticed, because we bound `maxLineMainDim` to container dimension constraints at the end of layout, and the error doesn't effect how any children are positioned or sized.

There was at least one screenshot test where this issue showed up though, and I was able to add a slightly different repro where we may have free space without a definite dimension by enforcing a min dimension and not stretching.

{F1091401183}

The new reference is correct, and looking back at diffs, is what this seemed to originally look like when added three years ago. Seems like there may have been a potential regression, but I didn't spot anything suspicious when I looked around the code history.


`betweenMainDim` may still be set for `gap` even if we don't have a sized parent, which makes the extra space propagated to `maxLineMainDim` effect parent size.

Because we were in a code freeze, I opted to have us go with a solution just effecting flex gap, instead of the right one, in case there were any side effects. This cleans up the code to use the right calculation everywhere, and fixes a separate bug, where `endOfLineIndex` and `startOfLineIndex` may not be the last/first in the line if they are out of the layout flow (absolutely positioned, or display: none_

See the original conversation on facebook#1188

Reviewed By: javache

Differential Revision: D49260049
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This pull request was exported from Phabricator. Differential Revision: D49260049

facebook-github-bot pushed a commit to facebook/litho that referenced this pull request Sep 15, 2023
Summary:
X-link: facebook/yoga#1380

X-link: facebook/react-native#39433

Back when rolling out flex gap, we encountered a bug where gap was added to the end of the main axis when a size was not specified.

During flex line justification/sizing, we calculate the amount of space that should be in between children. We erroneously add this, even after the last child element.

For `justify-content`, this space between children is derived from free space along the axis. The only time we have free space is if we had a dimension/dimension constraint already set on the parent. In this case, the extra space added to the end of the flex line is usually never noticed, because we bound `maxLineMainDim` to container dimension constraints at the end of layout, and the error doesn't effect how any children are positioned or sized.

There was at least one screenshot test where this issue showed up though, and I was able to add a slightly different repro where we may have free space without a definite dimension by enforcing a min dimension and not stretching.

{F1091401183}

The new reference is correct, and looking back at diffs, is what this seemed to originally look like when added three years ago. Seems like there may have been a potential regression, but I didn't spot anything suspicious when I looked around the code history.

`betweenMainDim` may still be set for `gap` even if we don't have a sized parent, which makes the extra space propagated to `maxLineMainDim` effect parent size.

Because we were in a code freeze, I opted to have us go with a solution just effecting flex gap, instead of the right one, in case there were any side effects. This cleans up the code to use the right calculation everywhere, and fixes a separate bug, where `endOfLineIndex` and `startOfLineIndex` may not be the last/first in the line if they are out of the layout flow (absolutely positioned, or display: none_

See the original conversation on facebook/yoga#1188

Reviewed By: javache

Differential Revision: D49260049

fbshipit-source-id: 218552c5ff938668b9f257df7a1493e13ded4d0d
facebook-github-bot pushed a commit to facebook/yoga that referenced this pull request Sep 15, 2023
Summary:
Pull Request resolved: #1380

X-link: facebook/react-native#39433

Back when rolling out flex gap, we encountered a bug where gap was added to the end of the main axis when a size was not specified.

During flex line justification/sizing, we calculate the amount of space that should be in between children. We erroneously add this, even after the last child element.

For `justify-content`, this space between children is derived from free space along the axis. The only time we have free space is if we had a dimension/dimension constraint already set on the parent. In this case, the extra space added to the end of the flex line is usually never noticed, because we bound `maxLineMainDim` to container dimension constraints at the end of layout, and the error doesn't effect how any children are positioned or sized.

There was at least one screenshot test where this issue showed up though, and I was able to add a slightly different repro where we may have free space without a definite dimension by enforcing a min dimension and not stretching.

{F1091401183}

The new reference is correct, and looking back at diffs, is what this seemed to originally look like when added three years ago. Seems like there may have been a potential regression, but I didn't spot anything suspicious when I looked around the code history.

`betweenMainDim` may still be set for `gap` even if we don't have a sized parent, which makes the extra space propagated to `maxLineMainDim` effect parent size.

Because we were in a code freeze, I opted to have us go with a solution just effecting flex gap, instead of the right one, in case there were any side effects. This cleans up the code to use the right calculation everywhere, and fixes a separate bug, where `endOfLineIndex` and `startOfLineIndex` may not be the last/first in the line if they are out of the layout flow (absolutely positioned, or display: none_

See the original conversation on #1188

Reviewed By: javache

Differential Revision: D49260049

fbshipit-source-id: 218552c5ff938668b9f257df7a1493e13ded4d0d
@facebook-github-bot facebook-github-bot added the Merged This PR has been merged. label Sep 15, 2023
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This pull request has been merged in 598b7ed.

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