libcamera build instructions may have some holes?

[njhollinghurst]

Building libcamera

• The list of dependencies to be installed before building libcamera doesn't mention cmake. It seems to be needed.
• The recommended configuration (for meson) doesn't mention the -Dpycamera option, needed for picamera2 integration.

libepoxy vs. libcamera-apps

• It's mentioned near the top of libcamera and libcamera-apps packages that libepoxy-dev is required "only ... if you want support for the X11/GLES preview window". Since most users will want this, could it be better emphasized, perhaps with a reminder in the Building libcamera-apps section?
• Is the libegl1-mesa-dev dependency also required even when libepoxy is not rebuilt from scratch?

[aallan]

ping @davidplowman

[davidplowman]

Thanks, Nick.

Is cmake really needed for libcamera? I'm sure it was not the case some time ago, but maybe things have changed...

Yes, we should list -Dpycamera (and perhaps add that you can omit it if you don't want Python bindings).

libepoxy-dev - yes, maybe we could emphasise that the other way round.

libegl1-mesa-dev... no idea. Possibly. Anyone fancy trying it??!

[njhollinghurst]

cmake is definitely needed now; I think for the Yaml parser.
I'll have to try different combinations of libepoxy-dev and libegl1-mesa-dev to see what's really needed for libcamera-apps to build with viewfinder.
I am happy to draft and PR a revised version.

[njhollinghurst]

Before documenting -Dpycamera I ought first to figure out the proper way to get its installation onto Python's path (picamera2 currently fails to load it).

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[aallan]

Still valid.

[njhollinghurst]

Yeah I could not bring myself to document adding the build tree (rather than an installation point) to PYTHONPATH.
I might have a go at seeing if the local installation can be made to install it to a sensible place, as the apt version does.

[lurch]

FYI the -Dpycamera part has been done in #2921