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Fix phantom positive implicit track for auto-start/definite-end placements #1169

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Merged
nicoburns merged 3 commits into from
Aug 26, 2026
+189 −1
Merged

Fix phantom positive implicit track for auto-start/definite-end placements #1169

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2bdf203
Fix phantom positive implicit track for auto-start/definite-end place…
nicoburns Aug 26, 2026
12eacd3
Add changelog entry
nicoburns Aug 26, 2026
efb46fb
Port implicit-track serialization tests to gentests
nicoburns Aug 26, 2026
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1 change: 1 addition & 0 deletions CHANGELOG.md
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Expand Up @@ -4,6 +4,7 @@

### Fixed

- Grid: items with an `auto` start line and a definite end line (e.g. `grid-column: auto / 1`) no longer cause a phantom zero-sized positive implicit track to be created. This previously caused `grid_template_columns()`/`grid_template_rows()` to serialize an extra `0px` track (e.g. `10px 0px` instead of `10px`)
- Grid: fixed `DetailedGridTracksInfo::resolve_absolute_grid_area` edge cases: placements are now normalized (lines sorted, named lines resolved) *before* out-of-range lines are treated as `auto`, and axes with no tracks resolve against the axis' single content-aligned grid line instead of falling back to the padding edge
- Block/float: absorb `f32` rounding errors in horizontal fit checks, preventing floats from spuriously wrapping when percentage widths and margins sum to exactly 100% of the container (#1161).
- Flexbox: main-axis margins are no longer dropped from an item's intrinsic main-size contribution when the contribution is floored by the item's flex basis (column containers). This fixes negative margins being ignored on flex items with `flex-grow` (#1162) and on descendants containing an `overflow: hidden` grid item (#1163).
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3 changes: 2 additions & 1 deletion src/compute/grid/implicit_grid.rs
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Expand Up @@ -127,7 +127,8 @@ fn child_min_line_max_line_span<S: CheapCloneStr>(
(Line(track), Span(_)) => track,

// End track specified
(Auto, Line(track)) => track,
// An auto start with a definite end resolves to a span of 1 ending at that line
(Auto, Line(track)) => track - 1,
(Span(span), Line(track)) => track - span,

// Only spans or autos
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17 changes: 17 additions & 0 deletions test_fixtures/grid/grid_template_serialization_negative_implicit_column.html
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<!DOCTYPE html>
<html lang="en">
<head>
<script src="../../scripts/gentest/test_helper.js"></script>
<link rel="stylesheet" type="text/css" href="../../scripts/gentest/test_base_style.css">
<title>
Test description
</title>
</head>
<body>

<div id="test-root" style="display: grid; width: 10px; height: 10px;">
<div style="grid-column: auto / 1; width: 10px; height: 10px;"></div>
</div>

</body>
</html>
17 changes: 17 additions & 0 deletions test_fixtures/grid/grid_template_serialization_negative_implicit_row.html
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<!DOCTYPE html>
<html lang="en">
<head>
<script src="../../scripts/gentest/test_helper.js"></script>
<link rel="stylesheet" type="text/css" href="../../scripts/gentest/test_base_style.css">
<title>
Test description
</title>
</head>
<body>

<div id="test-root" style="display: grid; width: 10px; height: 10px;">
<div style="grid-row: auto / 1; width: 10px; height: 10px;"></div>
</div>

</body>
</html>
13 changes: 13 additions & 0 deletions tests/xml/grid/grid_template_serialization_negative_implicit_column__border_box_ltr.xml
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<test name="grid_template_serialization_negative_implicit_column__border_box_ltr" use-rounding="true">
<viewport width="max-content" height="max-content"/>
<input>
<div display="grid" direction="ltr" width="10px" height="10px">
<div direction="ltr" width="10px" height="10px" grid-column-end="1"/>
</div>
</input>
<expectations>
<node x="0" y="0" width="10" height="10" resolved-rows="10px" resolved-columns="10px">
<node x="0" y="0" width="10" height="10"/>
</node>
</expectations>
</test>
13 changes: 13 additions & 0 deletions tests/xml/grid/grid_template_serialization_negative_implicit_column__border_box_rtl.xml
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<test name="grid_template_serialization_negative_implicit_column__border_box_rtl" use-rounding="true">
<viewport width="max-content" height="max-content"/>
<input>
<div display="grid" direction="rtl" width="10px" height="10px">
<div direction="rtl" width="10px" height="10px" grid-column-end="1"/>
</div>
</input>
<expectations>
<node x="0" y="0" width="10" height="10" resolved-rows="10px" resolved-columns="10px">
<node x="0" y="0" width="10" height="10"/>
</node>
</expectations>
</test>
13 changes: 13 additions & 0 deletions tests/xml/grid/grid_template_serialization_negative_implicit_column__content_box_ltr.xml
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<test name="grid_template_serialization_negative_implicit_column__content_box_ltr" use-rounding="true">
<viewport width="max-content" height="max-content"/>
<input>
<div display="grid" box-sizing="content-box" direction="ltr" width="10px" height="10px">
<div box-sizing="content-box" direction="ltr" width="10px" height="10px" grid-column-end="1"/>
</div>
</input>
<expectations>
<node x="0" y="0" width="10" height="10" resolved-rows="10px" resolved-columns="10px">
<node x="0" y="0" width="10" height="10"/>
</node>
</expectations>
</test>
13 changes: 13 additions & 0 deletions tests/xml/grid/grid_template_serialization_negative_implicit_column__content_box_rtl.xml
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<test name="grid_template_serialization_negative_implicit_column__content_box_rtl" use-rounding="true">
<viewport width="max-content" height="max-content"/>
<input>
<div display="grid" box-sizing="content-box" direction="rtl" width="10px" height="10px">
<div box-sizing="content-box" direction="rtl" width="10px" height="10px" grid-column-end="1"/>
</div>
</input>
<expectations>
<node x="0" y="0" width="10" height="10" resolved-rows="10px" resolved-columns="10px">
<node x="0" y="0" width="10" height="10"/>
</node>
</expectations>
</test>
13 changes: 13 additions & 0 deletions tests/xml/grid/grid_template_serialization_negative_implicit_row__border_box_ltr.xml
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<test name="grid_template_serialization_negative_implicit_row__border_box_ltr" use-rounding="true">
<viewport width="max-content" height="max-content"/>
<input>
<div display="grid" direction="ltr" width="10px" height="10px">
<div direction="ltr" width="10px" height="10px" grid-row-end="1"/>
</div>
</input>
<expectations>
<node x="0" y="0" width="10" height="10" resolved-rows="10px" resolved-columns="10px">
<node x="0" y="0" width="10" height="10"/>
</node>
</expectations>
</test>
13 changes: 13 additions & 0 deletions tests/xml/grid/grid_template_serialization_negative_implicit_row__border_box_rtl.xml
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<test name="grid_template_serialization_negative_implicit_row__border_box_rtl" use-rounding="true">
<viewport width="max-content" height="max-content"/>
<input>
<div display="grid" direction="rtl" width="10px" height="10px">
<div direction="rtl" width="10px" height="10px" grid-row-end="1"/>
</div>
</input>
<expectations>
<node x="0" y="0" width="10" height="10" resolved-rows="10px" resolved-columns="10px">
<node x="0" y="0" width="10" height="10"/>
</node>
</expectations>
</test>
13 changes: 13 additions & 0 deletions tests/xml/grid/grid_template_serialization_negative_implicit_row__content_box_ltr.xml
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<test name="grid_template_serialization_negative_implicit_row__content_box_ltr" use-rounding="true">
<viewport width="max-content" height="max-content"/>
<input>
<div display="grid" box-sizing="content-box" direction="ltr" width="10px" height="10px">
<div box-sizing="content-box" direction="ltr" width="10px" height="10px" grid-row-end="1"/>
</div>
</input>
<expectations>
<node x="0" y="0" width="10" height="10" resolved-rows="10px" resolved-columns="10px">
<node x="0" y="0" width="10" height="10"/>
</node>
</expectations>
</test>
13 changes: 13 additions & 0 deletions tests/xml/grid/grid_template_serialization_negative_implicit_row__content_box_rtl.xml
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<test name="grid_template_serialization_negative_implicit_row__content_box_rtl" use-rounding="true">
<viewport width="max-content" height="max-content"/>
<input>
<div display="grid" box-sizing="content-box" direction="rtl" width="10px" height="10px">
<div box-sizing="content-box" direction="rtl" width="10px" height="10px" grid-row-end="1"/>
</div>
</input>
<expectations>
<node x="0" y="0" width="10" height="10" resolved-rows="10px" resolved-columns="10px">
<node x="0" y="0" width="10" height="10"/>
</node>
</expectations>
</test>
48 changes: 48 additions & 0 deletions tests/xml/mod.rs
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Expand Up @@ -33515,6 +33515,54 @@ mod grid {
crate::run_xml_test("grid", "grid_template_serialization_named_lines__content_box_rtl");
}

#[cfg(feature = "grid")]
#[test]
fn grid_template_serialization_negative_implicit_column__border_box_ltr() {
crate::run_xml_test("grid", "grid_template_serialization_negative_implicit_column__border_box_ltr");
}

#[cfg(feature = "grid")]
#[test]
fn grid_template_serialization_negative_implicit_column__content_box_ltr() {
crate::run_xml_test("grid", "grid_template_serialization_negative_implicit_column__content_box_ltr");
}

#[cfg(feature = "grid")]
#[test]
fn grid_template_serialization_negative_implicit_column__border_box_rtl() {
crate::run_xml_test("grid", "grid_template_serialization_negative_implicit_column__border_box_rtl");
}

#[cfg(feature = "grid")]
#[test]
fn grid_template_serialization_negative_implicit_column__content_box_rtl() {
crate::run_xml_test("grid", "grid_template_serialization_negative_implicit_column__content_box_rtl");
}

#[cfg(feature = "grid")]
#[test]
fn grid_template_serialization_negative_implicit_row__border_box_ltr() {
crate::run_xml_test("grid", "grid_template_serialization_negative_implicit_row__border_box_ltr");
}

#[cfg(feature = "grid")]
#[test]
fn grid_template_serialization_negative_implicit_row__content_box_ltr() {
crate::run_xml_test("grid", "grid_template_serialization_negative_implicit_row__content_box_ltr");
}

#[cfg(feature = "grid")]
#[test]
fn grid_template_serialization_negative_implicit_row__border_box_rtl() {
crate::run_xml_test("grid", "grid_template_serialization_negative_implicit_row__border_box_rtl");
}

#[cfg(feature = "grid")]
#[test]
fn grid_template_serialization_negative_implicit_row__content_box_rtl() {
crate::run_xml_test("grid", "grid_template_serialization_negative_implicit_row__content_box_rtl");
}

#[cfg(feature = "grid")]
#[test]
fn grid_template_serialization_none__border_box_ltr() {
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