Add RenderSliver.getMaxPaintRect by zemanux · Pull Request #180074 · flutter/flutter

zemanux · 2025-12-18T16:32:52Z

This PR extracts the getMaxPaintRect logic into a shared method in RenderSliver. This helper is required for upcoming changes in #179003 and #179802 to avoid code duplication.

Cc @Piinks

Pre-launch Checklist

I read the [Contributor Guide] and followed the process outlined there for submitting PRs.
I read the [Tree Hygiene] wiki page, which explains my responsibilities.
I read and followed the [Flutter Style Guide], including [Features we expect every widget to implement].
I signed the [CLA].
I listed at least one issue that this PR fixes in the description above.
I updated/added relevant documentation (doc comments with ///).
I added new tests to check the change I am making, or this PR is [test-exempt].
I followed the [breaking change policy] and added [Data Driven Fixes] where supported.
All existing and new tests are passing.

gemini-code-assist

Code Review

This pull request extracts a shared method RenderSliver.getMaxPaintRect and adds comprehensive tests for it. The implementation appears correct and the tests cover various scenarios. I have one suggestion to improve code style and readability by renaming a local variable to avoid shadowing an instance member.

Piinks · 2026-01-07T21:31:04Z

+  @protected
+  Rect getMaxPaintRect() {
+    final SliverGeometry? sliverGeometry = geometry;
+    if (sliverGeometry == null) {


Suggested change

if (sliverGeometry == null) {

if (sliverGeometry == null || sliverGeometry == SliverGeometry.zero) {

Should we short circuit the zero case here as well?

Piinks · 2026-01-07T21:31:54Z

+          constraints.scrollOffset + sliverGeometry.cacheExtent + constraints.cacheOrigin;
+    }
+    final double paintExtent = sliverGeometry.paintExtent;
+    // If sliver is pinned, the scroll offset is sticked to the edge.


Suggested change

// If sliver is pinned, the scroll offset is sticked to the edge.

// If sliver is pinned, the scroll offset is stuck to the edge.

I think? Can you explain this a bit more?

Done.
I've tried to make it clearer. I also renamed the variable to leadingOffset.

Piinks · 2026-01-07T21:35:17Z

+        -clampedScrollOffset,
+        0.0,
+        maxPaintExtent,
+        constraints.crossAxisExtent,


Could this potentially be incorrect in the case of SliverCrossAxisGroup? The rect may not go from 0 --> crossAxisExtent if there are multiple slivers in the cross axis grouping.

This would make for some good test cases as well.

Could this potentially be incorrect in the case of SliverCrossAxisGroup? The rect may not go from 0 --> crossAxisExtent if there are multiple slivers in the cross axis grouping.

This is a good catch! Done!

Piinks · 2026-01-07T21:37:07Z

+    sliver.layout(
+      const SliverConstraints(
+        axisDirection: AxisDirection.down,
+        growthDirection: GrowthDirection.forward,


Should there be test cases that cover when GrowthDirection.reverse is used?

Piinks · 2026-01-07T21:38:09Z

    }
  }

+  /// Returns the [Rect] that covers the total paint extent of the sliver.


I might add to the docs clarity about what coordinate space this rect is, local to the viewport, global to the screen?

I might add to the docs clarity about what coordinate space this rect is, local to the viewport, global to the screen?

Done. Let me know if that's okay.

Actually, the resulting coordinates match the ones used in paint (via the offset parameter). So I tried to use the same terminology in the explanation.

Piinks

This LGTM! Thank you!

Renzo-Olivares

LGTM, thank you for your patience and contribution!

auto-submit · 2026-01-20T23:23:19Z

autosubmit label was removed for flutter/flutter/180074, because The base commit of the PR is older than 7 days and can not be merged. Please merge the latest changes from the main into this branch and resubmit the PR.

Piinks · 2026-01-20T23:40:29Z

Rebasing to pass the check. :)

@Piinks

This PR extracts the `getMaxPaintRect` logic into a shared method in `RenderSliver`. This helper is required for upcoming changes in flutter#179003 and flutter#179802 to avoid code duplication. Cc @Piinks ## Pre-launch Checklist - [X] I read the [Contributor Guide] and followed the process outlined there for submitting PRs. - [X] I read the [Tree Hygiene] wiki page, which explains my responsibilities. - [X] I read and followed the [Flutter Style Guide], including [Features we expect every widget to implement]. - [X] I signed the [CLA]. - [X] I listed at least one issue that this PR fixes in the description above. - [X] I updated/added relevant documentation (doc comments with `///`). - [X] I added new tests to check the change I am making, or this PR is [test-exempt]. - [X] I followed the [breaking change policy] and added [Data Driven Fixes] where supported. - [X] All existing and new tests are passing.

github-actions Bot added framework flutter/packages/flutter repository. See also f: labels. f: scrolling Viewports, list views, slivers, etc. labels Dec 18, 2025

gemini-code-assist Bot reviewed Dec 18, 2025

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Comment thread packages/flutter/lib/src/rendering/sliver.dart Outdated

zemanux mentioned this pull request Dec 18, 2025

Fix decorated box #179802

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zemanux force-pushed the get_max_paint_rect branch from 5fe6903 to 03277be Compare December 18, 2025 18:59

zemanux mentioned this pull request Dec 19, 2025

Add SliverClipRect and SliverClipRRect #179003

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zemanux force-pushed the get_max_paint_rect branch from 03277be to 8fad906 Compare December 29, 2025 09:18

justinmc requested review from Piinks and Renzo-Olivares December 30, 2025 23:15

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zemanux force-pushed the get_max_paint_rect branch from 8fad906 to 58c2388 Compare January 8, 2026 12:04

justinmc requested a review from Piinks January 13, 2026 23:17

Piinks approved these changes Jan 14, 2026

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Renzo-Olivares approved these changes Jan 20, 2026

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zemanux added 2 commits January 20, 2026 17:40

Add RenderSliver.getMaxPaintRect

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Piinks force-pushed the get_max_paint_rect branch from 986357d to 084e702 Compare January 20, 2026 23:40

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Merged via the queue into flutter:master with commit d20a814 Jan 21, 2026
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zemanux deleted the get_max_paint_rect branch January 21, 2026 06:41

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d20a814fc Add RenderSliver.getMaxPaintRect (flutter/flutter#180074)

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d20a814fc Add RenderSliver.getMaxPaintRect (flutter/flutter#180074)

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Piinks mentioned this pull request Jan 24, 2026

Flutter Notable Commits - 2026 #181433

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	if (sliverGeometry == null) {
	if (sliverGeometry == null \|\| sliverGeometry == SliverGeometry.zero) {

	// If sliver is pinned, the scroll offset is sticked to the edge.
	// If sliver is pinned, the scroll offset is stuck to the edge.

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zemanux commented Dec 18, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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zemanux commented Dec 18, 2025 •

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