Demo Application

[marbetschar]

This PR adds a demo application which should allow us to easily test portal implementations. To begin with, this demo app supports the AppChooser portal.

[danirabbit]

I don't think there's any meaningful difference between the way the API is used for text, image, or PDF files so I'm not sure we really need to have different tests for those

[marbetschar]

My intention was to be able to test different files - but yeah, we can just keep one.

[marbetschar]

@danrabbit anything we should address or can this be merged? Would love to build upon this in #20

[jeremypw]

When installed (see comment about yml path in README.md) this launched the text file in the default app when the button was clicked and only one applicable app was installed (expected). On installing another text editor a choice dialog was shown (expected). However, on closing that text editor and clicking "Open Text" button again, no dialog appeared - it was hidden below the demo window. Need to make sure the dialog is always presented.

Otherwise looking good,

[marbetschar]

any ideas why the dialog appears behind the second time? I mean, the demo app just fires off the portal - but has no clue about it otherwise. So I'm tempted to claim the error lies somewhere else?

Regarding the path to the yml file: The basic idea was to force the user to cd into the demo subfolder, to avoid accidents - but I'm fine with either way.

[Marukesu]

I believe we should be using libportal here, so we can have more control of the parameters passed to the portal.

[marbetschar]

@Marukesu don't have any experience with libportal yet - but sound like a great idea! Not sure, if we should address this in a subsequent PR though. Is there any documentation and/or Vala bindings available for libportal?

[danirabbit]

Speaking of libportal, it looks like they already provide a test app for gtk3 and gtk4: https://github.com/flatpak/libportal

Does it make sense to have our own portal test app when one exists?

[marbetschar]

@danirabbit the motivation to build a test app was primarily #20, because I need a way for testing the credentials portal during development.

So I'd claim it makes sense to roll our own test app - but probably only for custom portals such as this "Online Accounts Credentials Provider Portal" thingy...?