[PATCH setup] Add view mode "Unneeded"

[Jon Turney]

On 02/08/2022 13:17, Christian Franke wrote:
> In long standing cygwin installations, many no longer needed 
> automatically installed packages (e.g. libicuNN) accumulate. This patch 
> adds a new view which is possibly helpful to cleanup packages manually.
> 
> Some possible later enhancements:
> - automatically refresh this view (a few seconds) after the user changed 
> a package status as this may add or remove entries.
> - add a keyboard shortcut (^U) to the list view for "Uninstall this 
> package and then select next package"
> 

Thanks.  This looks good.

I think perhaps a better approach would be a view showing all packages 
which aren't user_picked, or a dependency of a user_picked package.

(If I've read the code correctly your implementation has the weakness 
that if e.g. appA -> libbB -> libC, which is then changed to appA -> 
libD -> libE, it will only show libC as unneeded, then libB on the next 
run?)

> +// Scan installed or desired packages and collect the names of packages
> +// which provide the dependencies of other packages or are member of
> +// category "Base".
> +static void FindNeededPackages (const packagedb & db, std::set<std::string> & needed)
> +{
> +  std::map<std::string, std::string> providedBy;
> +  for (const auto & p : db.packages)
> +    {
> +      const packagemeta & pkg = *p.second;
> +      if (!pkg.isBinary ())
> +        continue;
> +      if (!(pkg.desired && (pkg.installed || pkg.picked ())))
> +        continue;

This seems redundant.  Why can't this be just !pkg.desired?

This should also update the tooltip for the view dropdown 
(IDS_VIEWBUTTON_TOOLTIP) to describe the new view.