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Fix null check crash in MultiscriptsLayoutDelegate intrinsic layout #132

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Fix null check crash in MultiscriptsLayoutDelegate intrinsic layout #132

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14 changes: 11 additions & 3 deletions lib/src/render/layout/multiscripts.dart
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Original file line number Diff line number Diff line change
Expand Up @@ -133,7 +133,13 @@ class MultiscriptsLayoutDelegate extends IntrinsicLayoutDelegate<_ScriptPos> {
required Map<_ScriptPos, double> childrenWidths,
bool isComputingIntrinsics = false,
}) {
final baseSize = childrenWidths[_ScriptPos.base]!;
// `_ScriptPos.base` can be absent from `childrenWidths` for certain
// subscript/superscript expressions during intrinsic-width layout
// (e.g. `\mathrm{CL_r = CL_{tot} \times f_e}`), which made the previous
// `!` throw a "Null check operator used on a null value" exception and
// freeze the whole UI (see issue #1). Fall back to 0 so layout can
// continue; this only affects intrinsic-size probing, not final paint.
final baseSize = childrenWidths[_ScriptPos.base] ?? 0.0;
final subSize = childrenWidths[_ScriptPos.sub];
final supSize = childrenWidths[_ScriptPos.sup];
final presubSize = childrenWidths[_ScriptPos.presub];
Expand Down Expand Up @@ -175,13 +181,15 @@ class MultiscriptsLayoutDelegate extends IntrinsicLayoutDelegate<_ScriptPos> {
required Map<_ScriptPos, double> childrenBaselines,
bool isComputingIntrinsics = false,
}) {
final baseSize = childrenHeights[_ScriptPos.base]!;
// Same rationale as performHorizontalIntrinsicLayout above: guard
// against `_ScriptPos.base` being absent during intrinsic layout.
final baseSize = childrenHeights[_ScriptPos.base] ?? 0.0;
final subSize = childrenHeights[_ScriptPos.sub];
final supSize = childrenHeights[_ScriptPos.sup];
final presubSize = childrenHeights[_ScriptPos.presub];
final presupSize = childrenHeights[_ScriptPos.presup];

final baseHeight = childrenBaselines[_ScriptPos.base]!;
final baseHeight = childrenBaselines[_ScriptPos.base] ?? 0.0;
final subHeight = childrenBaselines[_ScriptPos.sub];
final supHeight = childrenBaselines[_ScriptPos.sup];
final presubHeight = childrenBaselines[_ScriptPos.presub];
Expand Down