[two_dimensional_scrollables] Fix TreeView null dereference during paint #9103
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Collapsing a node when there were other nodes offscreen was causing an unexpected null dereference during painting. This PR fixes the bug and adds a test. The bug was caused by erroneous computation of the max vertical scroll extent. Previously, the code computed this considering only scroll extent in the trailing (down) direction; it may also be the case that there is a larger scroll extent in the leading (up) direction. The miscalculation resulted in subsequent error computing the first visible row as a row that is actually offscreen, and thus does not have a render box. The row render box is asserted to be non-null during painting. Fixes flutter/flutter#149182 and flutter/flutter#164981
Piinks
reviewed
Apr 17, 2025
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Hey @tdenniston welcome! Thank you for finding and fixing this! Just a small nit to resolve the failing test below:
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@Piinks Thanks for the fast review! LMK of other changes, or if I need to squash the commits. |
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Collapsing a node when there were other nodes offscreen was causing an unexpected null dereference during painting. This PR fixes the bug and adds a test.
The bug was caused by erroneous computation of the max vertical scroll extent. Previously, the code computed this considering only scroll extent in the trailing (down) direction; it may also be the case that there is a larger scroll extent in the leading (up) direction.
The miscalculation resulted in subsequent error computing the first visible row as a row that is actually offscreen, and thus does not have a render box. The row render box is asserted to be non-null during painting.
Fixes flutter/flutter#149182 and flutter/flutter#164981
Pre-Review Checklist
[shared_preferences]pubspec.yamlwith an appropriate new version according to the pub versioning philosophy, or I have commented below to indicate which version change exemption this PR falls under1.CHANGELOG.mdto add a description of the change, following repository CHANGELOG style, or I have commented below to indicate which CHANGELOG exemption this PR falls under1.///).If you need help, consider asking for advice on the #hackers-new channel on Discord.
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