Set proper MIME type for PPTX presentation

[StefanBrand]

When I save() a presentation and manually remove the ".pptx" at the end of the file name, I get a file that doesn't automatically open with Powerpoint. This is confusing to my users because they like to rename their output presentations (and Powerpoint adds the file extension after pressing the save button).

I suspect that this depends on the MIME type -- if it is not set properly, a file will have no extension unless manually appended. According to this SO answer the MIME type of PPTX presentations is

application/vnd.openxmlformats-officedocument.presentationml.presentation

Can the library support saving with the correct MIME type? A quick try with setting mimeType in zip.generateAsync(...) did not work for me.

PS.: I'm using Electron to build an app and I'm not sure about the implications. It's both a browser and Node.js in some way... All I could find out is that it executes the statement on line 1823.

[StefanBrand]

I think what I want to accomplish is related to #277. In order to be able to use the proper Electron methods PptxGenJs would have to give me access to fs.

[gitbrent]

Hi @StefanBrand

Same here. I tried adding a MIME type to the zip call, but it just creates a file that PowerPoint complains abut being corrupt.

The JSZip docs says MIME-type is only for blob files, so it may be that we use nodebuffer for fs calls... i'm not sure.

I'd encourage you to play around with the code and see what you can find.

[gitbrent]

Hi @StefanBrand

This is now fixed in the current branch and in 3.0