Is it possible to use a custom viewer?

[ghost]

Currently, texpresso uses MuPDF as its viewer. I have no idea how deep MuPDF is integrated into texpresso's sourcecode, but would it be possible in theory to use a custom viewer e.g. zathura with pdf-poppler, or in vscode the built-in viewer provided by the pdf extension?

[let-def]

TeXpresso really uses DVI/XDV internally. MuPDF is not that deeply integrated, any Canvas-like API with good support for drawing custom glyphs could work in theory.

But this is mucher lower-level than a PDF, so a PDF viewer would not be suitable as a replacement (unless significant work is done on this viewer, essentially implementing support for an incremental flavor of DVI).
I tried producing PDFs, but that would be the bottleneck and defeats the purpose of live rendering.

However a PDF engine is still necessary for supporting \includegraphics, and MuPDF is used for that at the moment. So there are at least three parts to a rendering engine:

• low-level control over glyph rendering on a canvas for handling TeX output
• low-level graphic operator interpretation for drawing effects (TikZ, beamer decorations, etc)
• high-level PDF (and other images) page extraction and rendering for external media