Preserve trailing space in last paragraph segment by converting to nbsp (#3235)

[BryanValverdeU]

When the last text segment in a paragraph ends with a regular space, browsers collapse it during rendering. This change detects that case in handleText and replaces the trailing space with a non-breaking space (\u00A0) so it is preserved in the output.

To support this, a new ModelToDomSegmentContext interface is introduced that extends ModelToDomContext with an isLastSegment flag. handleParagraph sets this flag for each segment before dispatching, and ContentModelSegmentHandler is updated to use ModelToDomSegmentContext as its context type, eliminating the need for type casts in the handlers.

import this model:

{
    "blockGroupType": "Document",
    "blocks": [
        {
            "blockType": "Paragraph",
            "segments": [
                {
                    "segmentType": "Text",
                    "text": "Could you please provide more information ",
                    "format": {
                        "fontFamily": "Corbel, Skia, sans-serif",
                        "fontSize": "12pt",
                        "textColor": "rgb(94, 50, 124)"
                    }
                }
            ],
            "format": {
                "isProofing": true
            },
            "segmentFormat": {
                "fontFamily": "Corbel, Skia, sans-serif",
                "fontSize": "12pt",
                "textColor": "rgb(94, 50, 124)"
            }
        },
        {
            "blockType": "Paragraph",
            "segments": [
                {
                    "segmentType": "SelectionMarker",
                    "isSelected": true,
                    "format": {
                        "fontFamily": "Corbel, Skia, sans-serif",
                        "fontSize": "12pt",
                        "textColor": "rgb(94, 50, 124)"
                    }
                }
            ],
            "format": {
                "isProofing": true
            },
            "segmentFormat": {
                "fontFamily": "Corbel, Skia, sans-serif",
                "fontSize": "12pt",
                "textColor": "rgb(94, 50, 124)"
            }
        }
    ],
    "format": {
        "fontFamily": "'Corbel', 'Skia', sans-serif",
        "fontSize": "12pt",
        "textColor": "#5e327c"
    }
}

Before

After

[Copilot]

Pull request overview

This PR updates the content-model-to-DOM conversion pipeline to preserve a trailing space at the end of the last text segment in a paragraph by converting that final space to a non-breaking space (\u00A0). To enable this, it introduces a segment-scoped conversion context that can carry an isLastSegment flag.

Changes:

• Add ModelToDomSegmentContext (extends ModelToDomContext) and update segment handler typing to use it.
• Set/clear an isLastSegment flag while iterating paragraph segments, and use it in handleText to convert a trailing space to NBSP.
• Add unit tests for handleText covering the NBSP conversion behavior.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
packages/roosterjs-content-model-types/lib/index.ts	Re-export new ModelToDomSegmentContext type.
packages/roosterjs-content-model-types/lib/context/ModelToDomContext.ts	Introduce ModelToDomSegmentContext with optional isLastSegment.
packages/roosterjs-content-model-types/lib/context/ContentModelHandler.ts	Update ContentModelSegmentHandler to take ModelToDomSegmentContext.
packages/roosterjs-content-model-dom/lib/modelToDom/handlers/handleText.ts	Convert trailing space to NBSP when isLastSegment is true.
packages/roosterjs-content-model-dom/lib/modelToDom/handlers/handleParagraph.ts	Set isLastSegment while dispatching segment handlers.
packages/roosterjs-content-model-dom/test/modelToDom/handlers/handleTextTest.ts	Add tests validating NBSP conversion behavior.

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