The HTML to PDF module in Adobe LiveCycle PDF Generator ES2 uses Webkit for HTML content rendering. In using Webkit, we had to make code changes to enable Webkit to render the HTML content over PDFPort (a native canvas-like object) so that the rendered content can then be converted to PDF.
Normally, Webkit renders the HTML on the native canvas that the underlying operating system provides. This way, any browser (for example Safari) can use Webkit to render HTML content for on-screen display.
Therefore, the only thing that has changed here is the canvas on which the content is being rendered. No changes have been made to the HTML parsing / rendering logic inside Webkit.