fix: subtract trailing padding in editor intrinsic size computations - #2749
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fix: subtract trailing padding in editor intrinsic size computations#2749ndelanou wants to merge 1 commit into
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RenderEditableContainerBox's computeMin/MaxIntrinsicWidth and computeMin/MaxIntrinsicHeight computed the child extent as 'extent - padding.leading + padding.trailing' (missing parentheses), so with symmetric padding children were measured at the undeflated extent while performLayout deflates both sides. Under IntrinsicHeight this made the editor's reported height one line short at the exact moment a line wraps, overflowing composer-style layouts. Fixes singerdmx#2748 Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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July 7, 2026 16:09
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Description
RenderEditableContainerBox's four intrinsic size computations resolve the child's cross extent as:i.e. the leading padding is subtracted but the trailing padding is added (missing parentheses). With symmetric padding the children are measured at the full, undeflated extent, while
performLayoutcorrectly deflates both sides.Concretely, for a
QuillEditorwithpadding: EdgeInsets.symmetric(horizontal: 12)placed underIntrinsicHeight(a typical message-composer layout), text is measured 24px wider than it is laid out: a word that wraps onto a new line at layout width still fits at measure width, so the intrinsic height is exactly one line short — aRenderFlex overflowed by <one line> pixels on the bottomright at the moment a line wraps. Typing a few more characters makes the too-wide measurement wrap too and the error "heals", until the next wrap.The fix replaces the expressions with
extent - padding.horizontal/extent - padding.verticalin all four methods (computeMin/MaxIntrinsicWidth,computeMin/MaxIntrinsicHeight).Includes a regression test in
test/bug_fix_test.dartthat lays out an editor with horizontal padding and assertsgetMin/MaxIntrinsicHeight(width)equals the laid-out height (fails before the fix, passes after), plus aCHANGELOG.mdentry.Related Issues
_getIntrinsicMainAxis, not addressed here)Type of Change
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