PDF Rendering in browsers
Why was the certificate blank? A user sent me a screenshot of a signed document. The signature was there. The certificate page behind it was empty. Not broken, not garbled. Just a clean white page with nothing on it, like the PDF gave up halfway through. Worked fine on my machine, obviously. It always does. How the preview works You can't hand a browser a raw PDF and call it a day (not when the…
A user reported a signed document with an empty certificate page, which appeared as a blank white page when viewed in a browser. This issue arose because the PDF rendering process in the Alpine container, used by the application, did not have the necessary fonts installed. Alpine containers are lightweight and minimal, often lacking fonts, which led to the pdf rendering tool pdftoppm failing to find a substitute font and rendering a blank page instead.
The cause of this was the Alpine distribution, which is designed to have minimal dependencies and come with very few fonts by default. When the pdftoppm tool tried to render the document, it could not locate any fonts to use, resulting in a blank page. The solution was to add Liberation fonts to the Dockerfile, as they are a drop-in replacement for the original 14 base fonts and maintain the document's layout and appearance.
Additionally, the application displayed typed signatures in a handwriting-like font called Dancing Script, but the generated PDF displayed these signatures in Helvetica Oblique, a completely different font. This discrepancy between what users saw on the screen and what was stored in the PDF led to confusion and potential legal issues, as the document was not what the users expected.
To address this, the developers included Dancing Script within the PDF itself, effectively embedding the font directly into the file. This fix ensured that the document displayed exactly what users saw on the screen, maintaining the integrity of the document as described by the application's pitch of "the document is exactly what you saw."
This experience underscored the importance of considering font dependencies when building and deploying applications, especially those that generate PDF documents.
Written by urgent.news from Dev.to's reporting — not their text. Machine-written — may contain errors; check the original before relying on it.