Pluggable exporters (to support potx theming)

[lukebrowell]

Being able to quickly author outline presentations in markdown is brilliant.

Sometimes the rough decks we outline in Marp/VsCode, we want to refine in other tools, like Powerpoint without having to copy and paste the content text in, one frame at a time. We may wish to apply our house-style to decks or tweak layouts on a per-slide basis.

This is an idea for extensions pattern for Marp, which currently flattens content to high quality images (for good reasons in the default usage).

The current implementation for exporting Powerpoint slides uses PptxGenJs.

If exporters could be made pluggable, with access to the content of the marp document model (and not just the rendered raster output), then the community could contribute custom template exporters for formats such as PowerPoint which can leverage the template features of tools like PptxGenJs.

I'm interested:

• To the user community - is there demand for this?
• To the development community - does this fit within your vision and roadmap for the project?

thanks

[yhatt]

There is already a tool Pandoc for exactly that purpose, so Marp team does not have focused to export editable slides. See also: #82

And we have not pluggable architecture of exporters for now because Marp official toolset should keep reliable and well-maintained outputs.

Having said that, thinking about more pluggability is good one :)

Currently "Pluggable architecture" that is advertised Marp is meaning a plugin for markdown-it compatible converter, Marpit/Marp Core. To interpose to output process, we must make pluggable Marp CLI and would need to rewrite current CLI drastically. (may break current workflow used by several users!)

Thus, beginning from new concept of the conversion architecture by Marp developer community may become a good first action.

Appendix: Current architecture

flowchart TD
    subgraph User input
    CSS([Custom theme CSS])
    MD([Markdown])
    MPP([Marp/Marpit/markdown-it plugins])
    end

    CSS-.->MPC
    MD==>MPC
    MPP-.->MPC

    AST-.->OUTDEV
    SNP-.->OUTDEV
    MPC[Marp Core]


    MPC==Transform Markdown==>AST
    MPC==Process styles==>CSSS
    AST[markdown-it compatible AST]==Render==>HTMLS

    subgraph SNP[Snippets]
    HTMLS[Slide HTML snippets]
    CSSS[Rendered CSS]
    end

    SNP==Render with template==>TMPHTML[HTML generated from selected template]

    subgraph CLI[Marp CLI]
    TMPHTML-.Open in.->PUPPETEER[Headless Chromium-based browser]
    PUPPETEER==Transform==>PDFOUT[PDF]
    PUPPETEER==Transform==>IMGOUT["Images (JPG/PNG)"]
    IMGOUT==Convert==>PPTXOUT[PowerPoint document]
    end

    TMPHTML==HTML output==>OUT
    PDFOUT==>OUT
    IMGOUT==>OUT
    PPTXOUT==>OUT
    OUT([Output])
    OUTDEV([Output for developers])

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Developers can try to build a custom output in a own format from Output for developers, HTML snippets, rendered CSS, and parsed AST generated from Marp Core (or custom Marpit instance). For example, may be able to convert directly from markdown-it AST for Marp to PowerPoint document, powered by PptxGenJS.