GH 821: PowerPoint Export

[ejulio-ts]

This fixes #821

PowerPoint (.pptx) files are just a bunch of XML files following the Office Open XML (OOXML) standard and then zipped.
This adds a pptx lib that wraps all the logic to create these files around a Presentation. There's a base template with the files that don't change and then the slides and some other required metadata are generated on the fly. The XML content was based on the content of an exported presentation. The intent here wasn't to create pptx library.

Important in pptx/pptx.go I tested 3 different approaches to generate the XML files.

• long template string (getRelsSlideXml)
• string builder with long templates (getPresentationXmlRels)
• string builder with a single tag per line (getAppXml)

I don't have any strong preference. The first one is quite complicated to update, as finding the template tags can be hard. The last one spans over many lines with long functions. So, open for ideas here and then I can use a single standard after this review. Just made it this way to see if there was some preference to keep.

Tested the resulting `.pptx. file on:

• MS PowerPoint on Mac and Windows
• Open Office on Ubuntu
• KeyNote on Mac
• OneDrive
• Google Drive

ToDo:

• add links and appendix: this can be a separate PR with just linking, to keep this one small..

Below is the result for

mobile -> backend

backend: {
    link: layers.backend
}

mobile: {
    link: layers.mobile
}

layers: {
    backend: {
        api -> mongodb
        worker <-> kafka
        worker -> mongodb

        kafka.shape: queue
        mongodb.shape: cylinder
    }
    mobile: {
        a button
        b button
        c button
        steps: {
            1: {
                user clicks -> a button
            }
            2: {
                a button -> authorized?
                authorized? -> return: no    
            }
            3: {
                authorized? -> save data: yes
            }
        }
    }
}

scenarios: {
    offline: {
        backend.style.opacity: 0.1
        mobile -> local db
        local db.shape: cylinder
        mobile -> backend: try to reconnect every 1s
    }
}

app-flow.pptx

About the metadata, here's a screenshot

[gavin-ts]

I think the builder option makes sense, it doesn't need to be long templates, or a single tag each, just what makes sense for each call. builder is also used for svg rendering and the giant template option is hard to use

[ejulio-ts]

I think the builder option makes sense, it doesn't need to be long templates, or a single tag each, just what makes sense for each call. builder is also used for svg rendering and the giant template option is hard to use

Yeah, I prefer the builder for sure, just not sure about what style. So leaving open for a discussion

[alixander]

why is it so small?

Kapture.2023-04-06.at.13.07.10.mp4

[ejulio-ts]

Let me check it..
Also, just checked that adding the links doesn't seem that hard, so I'll add it here..
Finally, I was talking to @gavin-ts and I'll see to use sections to group layers/scenarios/steps as in https://support.microsoft.com/en-us/office/organize-your-powerpoint-slides-into-sections-de4bf162-e9cc-4f58-b64a-7ab09443b9f8

[alixander]

oh what in the fuck, cool lol

[ejulio-ts]

About the image size, it was an issue with integer division in IMAGE_WIDTH. I changed it to a hard coded constant instead of calculating it there.
Also, it had an issue with resizing that was only considering the largest side, but not the aspect ratio that would result in a better fit.

[ejulio-ts]

It turns out that adding the links is a bit more complicated than I expected.
From what I can tell I'm missing some tag/property and the link is not showing up in Keynote/PowerPoint.

So, I don't want to keep this one hanging because of links/sections as they can be separate PRs. Can you review this one then while I keep looking that?

[alixander]

didn't review much of the voodoo going on in the construction, mostly just wanna make sure the interfacing with cli and tests are good

[ejulio-ts]

• Changed to use templates instead of raw XML strings

CI is failing with playwright (not sure if I'm missing something)

[alixander]

@ejulio-ts nah, it's a known issue, just add a skip_ci like we do for pdfs.

[alixander]

add changelog plz