Fall back to integrating topmost desktop file

[probonopd]

Some AppImages currently fail to integrate and are hence missing from the applications menu.

Examples:

• https://github.com/prusa3d/PrusaSlicer/issues/1431
• https://github.com/AppImage/appimage.github.io/pull/1614
• https://github.com/AppImage/appimage.github.io/pull/1615 (at this point I fear that all electron-builder based AppImages are affected)

A usr/ structure is not strictly required in an AppDir, nor in an AppImage (although it has become common practice these days). In accordance with the AppImageSpec, we may fall back to integrating topmost desktop file (there should be exactly one in the root directory of an AppImage) in case usr/share/applications does not exist in the AppImage.

[azubieta]

According to: https://github.com/AppImage/libappimage/blob/4e251dfeffa8548791a5f2ae9ab49f7148ebd65a/src/libappimage/utils/resources_extractor/ResourcesExtractor.cpp#L37-L40

Using the desktop in the root of the AppDir is the default and only behavior to perform desktop integration. Also tested the latest PrusaSlicer AppImage and the desktop entry was created.

[probonopd]

That is interesting, did I give the wrong answer in https://github.com/prusa3d/PrusaSlicer/issues/1431 then? Can we even reproduce that issue with appimaged and/or AppImageLauncher?

[azubieta]

I tried it using appimaged and the only issue I had was firejail preventing it from running. Maybe that's the same issue they are having

[azubieta]

Will close the issue as it's already implemented. Fell free to reopen it if required.