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fix: rebuild fragment on geometry change #2842

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fix: rebuild fragment on geometry change #2842

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12 changes: 9 additions & 3 deletions packages/layout-engine/painters/dom/src/index.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -3029,7 +3029,7 @@ describe('DomPainter', () => {
expect(appliedWordSpacing).toBeCloseTo(expectedWordSpacing, 5);
});

it('reuses fragment DOM nodes when layout geometry changes', () => {
it('rebuilds fragment DOM nodes when layout geometry changes to keep line epochs in sync', () => {
const painter = createTestPainter({ blocks: [block], measures: [measure] });
painter.paint(layout, mount);

Expand All @@ -3051,9 +3051,12 @@ describe('DomPainter', () => {

painter.paint(movedLayout, mount);
const fragmentAfter = mount.querySelector('.superdoc-fragment') as HTMLElement;
const lineAfter = fragmentAfter.querySelector('.superdoc-line') as HTMLElement;

expect(fragmentAfter).toBe(fragmentBefore);
expect(fragmentAfter).not.toBe(fragmentBefore);
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@chittolinag chittolinag Apr 17, 2026 •
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@artem-harbour I think it makes more sense to use toEqual here. I know that the old code was already using toBe, but toBe does a strict comparison using ===. This means that the objects could be semantically the same, but toBe would still result in false.

Jest's doc:

Image

expect(fragmentAfter.style.left).toBe('60px');
expect(fragmentAfter.dataset.layoutEpoch).toBeTruthy();
expect(lineAfter.dataset.layoutEpoch).toBe(fragmentAfter.dataset.layoutEpoch);
});

it('rebuilds fragment DOM when block content changes via setData', () => {
Expand Down Expand Up @@ -5016,10 +5019,13 @@ describe('DomPainter', () => {
painter.paint(updatedLayout, mount);

const updatedWrapper = mount.querySelector('.superdoc-fragment-list-item') as HTMLElement;
expect(updatedWrapper).toBe(initialWrapper);
const updatedLine = updatedWrapper.querySelector('.superdoc-line') as HTMLElement;
expect(updatedWrapper).not.toBe(initialWrapper);
expect(updatedWrapper.style.left).toBe('90px');
expect(updatedWrapper.style.top).toBe('55px');
expect(updatedWrapper.style.width).toBe('310px');
expect(updatedWrapper.dataset.layoutEpoch).toBeTruthy();
expect(updatedLine.dataset.layoutEpoch).toBe(updatedWrapper.dataset.layoutEpoch);
});

it('applies resolved zIndex only to anchored media fragments', () => {
Expand Down
12 changes: 12 additions & 0 deletions packages/layout-engine/painters/dom/src/renderer.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -2714,6 +2714,7 @@ export class DomPainter {

if (current) {
existing.delete(key);
const geometryChanged = hasFragmentGeometryChanged(current.fragment, fragment);
const sdtBoundaryMismatch = shouldRebuildForSdtBoundary(current.element, sdtBoundary);
// Detect mismatch in any between-border property
const betweenBorderMismatch =
Expand All @@ -2730,6 +2731,7 @@ export class DomPainter {
current.element.dataset.pmStart != null &&
this.currentMapping.map(Number(current.element.dataset.pmStart)) !== newPmStart;
const needsRebuild =
geometryChanged ||
this.changedBlocks.has(fragment.blockId) ||
current.signature !== fragmentSignature(fragment, this.blockLookup) ||
sdtBoundaryMismatch ||
Expand Down Expand Up @@ -7288,6 +7290,16 @@ const fragmentSignature = (fragment: Fragment, lookup: BlockLookup): string => {
return base;
};

const hasFragmentGeometryChanged = (previous: Fragment, next: Fragment): boolean =>
previous.x !== next.x ||
previous.y !== next.y ||
previous.width !== next.width ||
('height' in previous &&
'height' in next &&
typeof previous.height === 'number' &&
typeof next.height === 'number' &&
previous.height !== next.height);

const getSdtMetadataId = (metadata: SdtMetadata | null | undefined): string => {
if (!metadata) return '';
if ('id' in metadata && metadata.id != null) {
Expand Down
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