Fix timeline title wrapping issue (#6393)

[nourhenta]

📑 Summary

This pull request resolves the issue where timeline titles do not wrap correctly when the text is too long. The problem caused layout issues, such as overflowing or shrinking diagrams, making them unreadable. The fix ensures that timeline titles break into multiple lines and maintain consistent diagram layouts.

Resolves ##6393

📏 Design Decisions

1. Identified the Problem

• Found that the title was rendered using an SVG element, which does not support automatic text wrapping.

2.Introduced for Wrapping

Replaced the element with to enable proper wrapping using HTML/CSS.
Updated Code:

if (title) {
  const foreignObject = svg
    .append('foreignObject')
    .attr('x', LEFT_MARGIN) // Adjust position as needed
    .attr('y', TOP_MARGIN) // Adjust vertical position as needed
    .attr('width', diagramWidth - LEFT_MARGIN * 2) // Set width
    .attr('height', WRAPPING_HEIGHT); // Define height for wrapping

  foreignObject
    .append('xhtml:div') // Use xhtml namespace for HTML inside SVG
    .style('font-size', `${conf.fontSize || '16px'}`)
    .style('word-wrap', 'break-word')
    .style('white-space', 'normal')
    .style('text-align', 'center')
    .text(title);
}

3. Applied CSS Styling for Wrapping

• word-wrap: break-word; Ensures long words break into multiple lines.
• white-space: normal; Allows natural line breaks.
• text-align: center; Centers the title for better readability.

4. Tested with Long Titles

📋 Tasks

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• 📖 have read the contribution guidelines
• 💻 have added necessary unit/e2e tests.
• 📓 have added documentation. Make sure MERMAID_RELEASE_VERSION is used for all new features.
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npm i https://pkg.pr.new/mermaid-js/mermaid@6394

npm i https://pkg.pr.new/mermaid-js/mermaid/@mermaid-js/layout-elk@6394

npm i https://pkg.pr.new/mermaid-js/mermaid/@mermaid-js/mermaid-zenuml@6394

npm i https://pkg.pr.new/mermaid-js/mermaid/@mermaid-js/parser@6394

commit: 130762b

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 57 lines in your changes missing coverage. Please review.

Project coverage is 3.85%. Comparing base (d602240) to head (130762b).

Files with missing lines	Patch %	Lines
packages/mermaid/src/diagrams/timeline/svgDraw.js	0.00%	43 Missing ⚠️
.../mermaid/src/diagrams/timeline/timelineRenderer.ts	0.00%	14 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           develop   #6394      +/-   ##
==========================================
- Coverage     3.86%   3.85%   -0.01%     
==========================================
  Files          402     401       -1     
  Lines        42682   42706      +24     
  Branches       644     644              
==========================================
  Hits          1648    1648              
- Misses       41034   41058      +24     

Flag	Coverage Δ
unit	3.85% <0.00%> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
.../mermaid/src/diagrams/timeline/timelineRenderer.ts	0.39% <0.00%> (-0.02%)	⬇️
packages/mermaid/src/diagrams/timeline/svgDraw.js	0.00% <0.00%> (ø)

... and 1 file with indirect coverage changes

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