[CMake] cmake-gui's separation between configuration & generation

[David Cole]

On Thu, Aug 23, 2012 at 2:24 PM, Robert Dailey <rcdailey.lists at gmail.com>wrote:

> On Thu, Aug 23, 2012 at 1:03 PM, David Cole <david.cole at kitware.com>
> wrote:
> > On Thu, Aug 23, 2012 at 11:50 AM, Robert Dailey <
> rcdailey.lists at gmail.com>
> > wrote:
> >>
> >> On Thu, Aug 23, 2012 at 10:48 AM, Robert Dailey
> >> <rcdailey.lists at gmail.com> wrote:
> >> > On Thu, Aug 23, 2012 at 10:43 AM, John Drescher <drescherjm at gmail.com
> >
> >> > wrote:
> >> >>> Is the separation between configuration & generation really
> necessary
> >> >>> for cmake-gui? I ask because several of my co-workers are confused
> >> >>> between the differences in the two, even though I explain it.
> >> >>>
> >> >>> Honestly there isn't really a reason that I can think of to do a
> >> >>> configure without a generate, unless you're testing the integrity of
> >> >>> your CMake script changes maybe, but even then, if its broken
> >> >>> generation won't take place.
> >> >>>
> >> >>> The command line program does not separate the two, so I simply
> think
> >> >>> cmake-gui should eliminate the configure button, and simply have a
> >> >>> generate button. Does this seem fair? Is there a reason why they are
> >> >>> separated?
> >> >>
> >> >> I can think of one use case that I use that the separation is a good
> >> >> thing. What about when you have options and variables that are
> >> >> conditional depending on other CMake variables so that setting the
> >> >> variables / options may take more than 1 configure.
> >> >
> >> > Well, think of this from the perspective of Linux users. They don't
> >> > get to configure seperately, so only Windows users get special
> >> > treatment here (and maybe Mac too, since it's using Qt). Basically, if
> >> > two configures are necessary, you simply just hit the "generate"
> >> > button twice, and the wait may be slightly longer because of the
> >> > generation. However, usually it's the configure step that takes 99% of
> >> > the time and generation is quick since it's just spitting out files to
> >> > disk it seems.
> >> >
> >> > I would also argue that any CMake project should have appropriate
> >> > defaults OR logic to calculate the defaults for you, so that even if a
> >> > user decides to not modify any cache variables, generation should
> >> > always succeed. CMake can't assume that 2 passes will be necessary
> >> > (and it really shouldn't).
> >>
> >> Oh and also, if two configures are necessary (say that, a library or
> >> package can't be found intelligently), then the configuration step
> >> would fail and be interrupted, so you get a chance to correct any
> >> errors and adjust appropriate cache variables. So, in this case it
> >> doesn't really matter if you've hit configure or generate.
> >> --
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> >
> >
> >
> > Iterative configuring through the gui is useful for some people/projects,
> > and generating is time-consuming too on some larger projects with some
> > generators.
> >
> > So we probably won't be eliminating the Configure button anytime soon. On
> > the other hand, you can just click "Generate" if that's what you want and
> > ignore the configure button altogether nowadays. "Generate" will
> > configure-first if necessary, and then generate.
> >
> > Here are some related issues indicating some people want the exact
> opposite
> > (i.e., separate configure and generate steps for the command line cmake)
> >   http://public.kitware.com/Bug/view.php?id=13359
> >
> > And a request for a "build" button in cmake-gui:
> >   http://public.kitware.com/Bug/view.php?id=8260
>
> I definitely hear your point, and I realize not everyone has my
> specific workflow, but usually I only hit configure to see if there
> are any failures that do NOT stop the generation process (such as
> status messages that print in red, but do not indicate an actual
> error). In that case, I do not want generation to proceed but instead
> I want to address the alert / error in the logs. However, if
> configuration succeeds I only end up hitting generate right after that
> anyway.
>
> I am only bringing this up since I was surprised to see how my team
> struggled to understand the differences between the two, and when to
> use one or the other. Most of the time I just say "Ignore the
> configure button, just always hit generate". If it wasn't there, it
> would be more clear to people that are new to CMake. I'm trying to
> migrate my company to CMake, so I thought this might be valuable
> feedback, as it was one of the surprising little things we got hung up
> on that you just never really think about.
>


We hear you, too. But there are lots of people who like the separate
buttons, so we're keeping them.
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