[libcamera-devel] "cam" utility is quite confusing

[Laurent Pinchart]

On Sat, Jul 30, 2022 at 02:14:31PM +0300, Laurent Pinchart wrote:
> Hello,
> 
> On Sat, Jul 30, 2022 at 10:26:11AM +0100, Kieran Bingham wrote:
> > Quoting Pavel Machek via libcamera-devel (2022-07-29 20:56:20)
> > > Hi!
> > > 
> > > I just spent quite some time debugging C++... when problem was in my
> > > commnad line.
> > 
> > I'm sorry to hear that. cam is just a test tool, so indeed it possibly
> > doesn't have the friendliest CLI - but it should still be expected to be
> > usable, so I think you've hit a very valid bug.
> > 
> > > First, --sdl needs to come up after -c. Okay, documentation warns
> > > about that "Options valid in the context of --camera:".
> > > 
> > > Second, AFAICT, you can not have file output and sdl viewfinder at the
> > > same time.
> > 
> > That's an internal limitation at the moment I think that each buffer is
> > only processed by one output. It could be extended to support more I
> > believe.
> > 
> > > Third, and most confusing... --sdl will not actually display anything
> > > unless you also pass -C. I don't think help text is really clear about
> > > that.
> > > 
> > > I believe command line interface could be improved (automatically
> > > assume -C when --sdl is passed? allow --sdl before -c?), or at least
> > > documenation should be clear about these limitations.
> > 
> > This sounds good to me - --sdl doesn't make sense if it's not actually
> > capturing, so I think an implicit -C is fine. Would you like to submit a
> > patch for this?
> > 
> > I think the --sdl still needs to be within the context of a camera
> > though. But I do wonder if we could default the first context to be the
> > first camera? (Removing the need to explicitly set a -c ?
> 
> I'm not a big fan of implicit options. I'd rather turn the three options
> related to sinks (-F, -D, -S) into a single sink option, as they're
> mutually exclusive. Maybe "-S sdl", or "-o sdl" ? It could then later be
> extended to support multiple sinks if needed, maybe along the line of
> "-o sdl,file".

And I forgot to mention maybe printing an error if a sink if specified
without the capture option.

-- 
Regards,

Laurent Pinchart