[QGIS-Developer] QGIS and WebAssembly

[Martin Dobias]

Hi Andreas!

On Tue, Mar 22, 2022 at 9:49 AM Andreas Neumann <a.neumann at carto.net> wrote:

>
> Would any part of the current QGIS Desktop part be re-usable in a "web
> assembly" QGIS? Or would the GUI part have to be re-developed?
>

In theory, we could try to run QGIS Desktop as it is in WebAssembly
environment in the browser, Qt generally supports that. There are many
question marks though, among some I can think of:
- dealing with files / data sources - this would need many changes to
accept the fact that we are not dealing with a local file system and that
access to raw data over network will be generally much slower. Also
persistence of data - you will probably want to have some server backend
anyway to store the data.
- Qt Widgets-based apps can be run on WebAssembly, but I have a feeling
that the performance would not be great, due to the way how the get
rendered on screen (all work done on CPU) - I would expect that an
optimized OpenGL / WebGL based GUI would have much better performance in
browsers - probably based on Qt Quick module (like Input / QField)


> I would also assume that access to local files would be very restricted -
> right? Network based resources (DB access and web services) would probably
> work fine?
>
Indeed, access to local files from browser would not be possible at all -
data would need to come from the server. Network based resources would work
fine, but with various limitations - for example, you are normally not
allowed to request resources from other servers unless the servers allow
that [1], and you can't directly access services like PostgreSQL that are
not HTTP servers (although of course this could be handled by tunneling
through WebSockets, or using HTTP-based protocols like Postgrest).

Cheers
Martin

[1] https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS
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